1

Helwan University

Faculty of Science

Chemistry Department

Introduction of Biochemistry

Dr

Mohamed Mostafa Omran

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Biochemistry is the study of life including cell biology, genetics,

immunology, microbiology, pharmacology, and physiology. Biochemical

processes are controlled genetically. Although it overlaps other disciplines,

including cell biology, genetics, immunology, microbiology, pharmacology,

and physiology.

Four major classes of biomolecules serve as building blocks for larger

macromolecules:

1. Carbohydrates: e.g. glucose, fructose, sucrose, mainly used as sources of

car energy.

2. Lipids: commonly known as fats

- organic compounds that are not very water soluble

- used as sources of cellular energy

- components of cell membranes

3. Amino Acids:

- 20 natural amino acids in total

- Used as building blocks for proteins

4. Nucleotides:

- 5 in total

- Used as building blocks for DNA and RNA precursors

5. Other:

- Vitamins: organic compounds necessary for proper growth and

development

- Heme: Organometallic compound containing iron; important for

transporting oxygen in your blood stream.

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Carbohydrates

General Information:

1. Carbohydrates are the most abundant class of organic compounds found

in living organisms.

2. They originate as products of photosynthesis, an endothermic reductive

condensation of carbon dioxide requiring light energy and the pigment

chlorophyll.

n H2O + Energy CnH2nOn + n O2

3. The formulas of many carbohydrates can be written as carbon hydrates,

Cn (H2O) n, hence their name.

4. The carbohydrates are a major source of metabolic energy, both for

plants and for animals that depend on plants for food.

5. Aside from the sugars and starches that meet this vital nutritional role,

carbohydrates also serve as a structural material (cellulose), a component of

the energy transport compound ATP, recognition sites on cell surfaces, and

one of three essential components of DNA and RNA.

6. Carbohydrates are called saccharides or, if they are relatively small,

sugars.

A- Simple Sugars

1 Contain the elements carbon, hydrogen, and oxygen.

2 The name carbohydrate literally means water compounds of carbon.

3 The general formula for simple sugars is Cn(H2O)n.

4 This class of compounds is better described as Polyhydroxy aldehydes and

ketones.

5 The simplest carbohydrates are glyceraldehyde and dihydroxyacetone.

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HC

C

CH2OHH

O

HO

glyceraldehyde

C CH2OH

O

HOH2C

dihydroxyacetone

A - Methods of Classification:

Several methods are used to classify carbohydrates.

1-One method of classification is based on whether the carbohydrate

can be broken down into smaller units.

Monosaccharides: simple sugars cannot be broken down into smaller units

by hydrolysis.

1. Disaccharides: can be broken down into two monosaccharide units.

2. Oligosaccharides: can be broken into three to six monosaccharide units.

3. Polysaccharides: composed of 7 or more monosaccharide units.

2-Another method is based on the number of carbons found in a simple

sugar.

If it has 3 carbons it is called a triose.

If it has 4 carbons it is called a tetrose.

If it has 5 carbons it is called a pentose.

If it has 6 carbons it is called a hexose.

3-Another method uses the kind of carbonyl group.

A- Aldose: A monosaccharide with an aldehyde group.

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HCO

C

C

CH2OH

OH

OH

H

H

erythrose

B- Ketose: A monosaccharide with a ketone group.

C

C

C

CH2OH

C

CH2OH

O

H

H

H

HO

OH

OH

fructose

Usually combine the carbonyl classification and the number classification

together.

COH

C OHH

CH2OH

glyceraldehyde

aldotriose

COH

C OHH

C HHO

C OHH

C OHH

CH2OH

CH2OH

C O

C HHO

C OHH

C OHH

CH2OH

glucose fructose

aldohexose ketohexose

B-Stereoconfigurations of simple sugars

Carbohydrates contain many stereocenters. If the OH group is found

on the right side of the carbon chain, the sugar is designated as a D sugar

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(i.e., the -OH at C5 of D-glucose is on the right in a Fischer projection). If

the OH group is found on the left side of the chain of carbons, the sugar is

designated as an L sugar (The L sugars are the mirror images of their D

counterparts). Sugars that differ only by the configuration around one C

atom are known as epimers of one another. e.g, D-glucose and D-mannose

are epimers with respect to C2.

The most common ketoses are those with their ketone function at C2.

The position of their carbonyl group gives ketoses one less asymmetric

center than their isomeric aldoses, so a ketohexose has only 23 = 8 possible

stereoisomers (4 D sugars and 4 L sugars).

C

C OHH

CH2OH

OH

D-glyceraldehyde

D-aldotriose

C

C HHO

CH2OH

OH

L-glyceraldehyde

L-aldotriose

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B- Stereoconfigurations of simple sugars

C

C

C

C

CHO

H

H

H

OH

OH

OH

HO

H

CH2OH

C

C

C

C

CHO

H

H

H

OH

OH

HO

HO

H

CH2OH

C

C

C

C

CHO

OH

H

OH

OH

H

OH

H

H

CH2OH

C

C

C

C

CHO

OH

OH

OH

HO

H

H

H

H

CH2OH

C

C

C

C

CHO

H

H

H

OH

HO

OH

HO

H

CH2OH

C OHH

CH2OH

CHO

C

C

H

OH

HO

H

CH2OH

CHO

C

C

C

C

CHO

H

OH

OH

HO

HO H

H

H

CH2OH

C

C

OH

OH

H

H

CH2OH

CHO

C

C

C

H

H

OH

OH

HO

H

CH2OH

CHO

C

C

C

H

H

OH

HO

HO

H

CH2OH

CHO

C

C

C

OH

OH

HO H

H

H

CH2OH

CHO

C

C

C

OH

OH

H OH

H

H

CH2OH

CHO

C

C

C

C

CHO

HO

H

H

OH

H

HO

HO

H

CH2OH

C

C

C

C

CHO

H

H

OH

OH

HO

OH

H

H

CH2OH

D-glyceraldehyde

D-erythrose D-threose

D-arabinose D-ribose D-xyloseD-lyxose

D-glucoseD-mannose D-alloseD-altrose D-tallose D-galactose D-idose D-gulose

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D -s o r b o s eD -ta g a to s e D -fr u c to s e D -p s ic o s e

C H 2 O H

C

C

O

O HH

C O HH

C

C H 2 O H

O HH

C H 2 O H

C

C

O

HH O

C O HH

C

C H 2 O H

O HH

C H 2 O H

C

C

O

O HH

C HH O

C

C H 2 O H

O HH

C H 2 O H

C

C

O

HH O

C HH O

C

C H 2 O H

O HH

D -r ib u lo s eD -x y lu lo s e

C H 2 O H

C

C

O

O HH

C O HH

C H 2 O H

C H 2 O H

C

C

O

HH O

C O HH

C H 2 O H

D -e r y th r u l o s e

C H 2 O H

C

C

O

O HH

C H 2 O H

d ih yd r o x y a c e to n e

C H 2 O H

C

C H 2 O H

O

Cyclic Structures: Five membered sugar rings are known as furanose rings.

-D-ribofuranose -D-ribofuranose

O

OH

H

H

H

OH

CH2HO

OH

H

O

OH

H

H

OH

CH2HO

H

H

OH

+

C

C

C

C

CH2OH

H

H

OH

H

OH

OH

OH

D-ribose

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Six membered sugar rings are known as pyranose rings.

-D-glucopyranose-D-glucopyranose

+

O

H

OH

OHH

OH

H

CH2HO

HO

HO

OH

H

OHH

OH

H

CH2HO

HO

H

D-glucose

C

C

C

C

C

OH

OH

OH

HO

H

H

H

H

CH2OH

OH

Carbohydrate Anomers: Formation of either of the cyclic form has

created a new stereocenter. These stereoisomeric ring forms of

carbohydrates are called Anomers.

Anomers:

Anomers are carbohydrates that differ by the stereo-configuration of the

carbon involved in ring formation. (the carbonyl carbon, called the

anomeric carbon, becomes a chiral center with two possible

configurations.). The greek letters α and β are used to describe these

configurations about the ring forming carbon. The α anomer always has the

OH group oriented in a downward fashion on the anomeric carbon of a D-

sugar. The β anomer always has the OH group oriented in an upward

fashion on the anomeric carbon of a D-sugar.

The two anomers of D-sugar have slightly different physical and

chemical properties, including different optical rotations The anomers freely

interconvert in aqueous solution, so at equilibrium, D-glucose is a mixture of

the β anomer (63.6%) and the α anomer (36.4%). The linear form is

normally present in only minute amounts.

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Important Carbohydrates

Monosaccharides: composed of three to seven carbon atoms.

1- Glucose

1 The most abundant hexose in our diet.

2 The building block of complex carbohydrates.

3 Component of the disaccharides: sucrose, maltose and lactose.

4 Found in the polysaccharides: starch, cellulose and glycogen.

C

C

C

C

CHO

OH

OH

OH

HO

H

H

H

H

CH2OH

O

H

H

H

OH

OH

CH2OH

HOH H,OH

2. Galactose

Found in the disaccharide, lactose.Found in the cellular membranes of the

brain and nervous system. Galactose is the C-4 epimer of glucose.

C

C

C

C

CHO

OH

H

OH

HO

H

H

HO

H

CH2OH

H,OH

O

H

H

OH

CH2OH

HOH

HO

H

3. Fructose

Sweetest of the carbohydrates. Component of the disaccharide sucrose.

Fructose is a keto sugar.

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C

C

C

C

CHO

OH

H

OH

HO

H

H

HO

H

CH2OH

H,OH

O

H

H

OH

CH2OH

HOH

HO

H

Disaccharides: composed of 2 monosaccharide units.

1. Maltose - malt sugar. Used in cereals, candies and the brewing of

beverages.Composed of two D-glucose sugars joined by an α-1,4 linkage.

O OHH

H

HH

H

O

H

OHOH H H

OH OH

OH

OH

CH2OH CH2OH

H

2. Lactose - milk sugar. Found in milk and milk products. Composed of

one galactose and one glucose unit joined by a β-1,4 linkage.

OH

H

H

OH H

OH

OH

CH2OH

HO

CH2OH

OH

HOH

H

H

OH

H

O

3. Sucrose - table sugar. Product of sugar cane and sugar beets. Composed

of one glucose and one fructose unit. Linkage is at both anomeric carbons.

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OO

OH

H

OH

H

H

O

HH

H

OH H

HOH

CH2OHOH

CH2OH

CH2OH

Polysaccharides: composed of many (more than 10) monosaccharide units.

classified as homopolysaccharides(if they consist of one type of

monosaccharide) or heteropolysaccharides ( consist of more than one type

of monosaccharide). Polysaccharides in contrast to proteins and nucleic

acids, form branched as well as linear polymers. This is because glycosidic

linkages can be made to any of the hydroxyl groups of a monosaccharide.

1- Cellulose: Major structural material of plant cells. Consists of many

glucose units joined by β-1,4 linkages. ( a linear polymer of up to 15,000 D-

glucose residues linked by β (1-4) glycosidic bonds).

2. Starch: Storage form of glucose found in rice wheat, potatoes, grains and

cereals. Consists of many glucose units joined by α-1,4 linkages. Maltose is

the disaccharide starting material. is deposited in the chloroplasts of plant

cells as insoluble granules composed of α-amylose and

amylopectin. α-Amylose is a linear polymer of several thousand glucose

residues linked by α

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3. Glycogen: Animal starch. Storage form of glucose found in the liver and

muscle of animals. Contains many highly branched glucose units.

1 Joined by α-1,4 linkages and branched by α-1,6 linkages.

4. Chitin: is the principal structural component of the exoskeletons of

invertebrates such as crustaceans, insects, and spiders and is also present in

the cell walls of most fungi and many algae. Chitin is a homopolymer of

-linked Nacetyl- D-glucosamine residues.

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Conclusion

1- Carbohydrates are wide group of bio molecules that represents the

first row of energy sources in our bodies.

2- Carbohydrates are carbon hydrate molecules that can be simple or

multiple from two (disaccharide) or more (poly saccharides)

monomeric units of (monosaccharides).

3- Carbohydrates are stereochemical active molecules.

4- general formula of simple sugar is Cn (H2O)n like glucose C6(H2O)6.

5- Disaccharides like succrose, poly saccharides like starch which is

linear or branched polymers.

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Amino Acids

Amino Acids are the building units of proteins. Proteins are polymers of

amino acids linked together by what is called ― Peptide bond‖ (see latter).

There are about 300 amino acids occur in nature. Only 20 of them occur in

proteins.

Structure of amino acids:

Each amino acid has 4 different groups attached to α- carbon (which is

C-atom next to COOH). So the common amino acids are known as α-amino

acids, These 4 groups are: amino group, COOH group, hydrogen atom and

side Chain (R). The 20 standard amino acids differ in the structures of their

side chains (R groups).

Amino Acids Are Dipolar Ions

At physiological PH (7.4), -COOH gp is dissociated forming a

negatively charged carboxylate ion (COO-) and amino gp is protonated

forming positively charged ion (NH3+) forming Zwitter ion (dipolar ions :

act as both an acid and a base). Amino acids, like other ionic compounds, are

more soluble in polar solvents than in nonpolar solvents.

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Peptide Bonds Link Amino Acids

Amino acids can be polymerized to form chains. This process can be

represented as a condensation reaction (bond formation with the

elimination of a water molecule). The resulting CO-NH linkage, an amide

linkage, is known as a peptide bond. Polymers composed of two, three, a

few (3–10), and many amino acid units are known, respectively, as

dipeptides, tripeptides, oligopeptides, and polypeptides. These

substances, however, are often referred to simply as peptides. After they are

incorporated into a peptide, the individual amino acids (the monomeric

units) are referred to as amino acid residues. Polypeptides are linear

polymers rather than branched chains; that is, each amino acid residue

participates in two peptide bonds and is linked to its neighbors in a head-to-

tail fashion. The residues at the two ends of the polypeptide each participate

in just one peptide bond. The residue with a free amino group is called the

amino terminus or N-terminus. The residue with a free carboxylate group

(at the right) is called the carboxyl terminus or C-terminus.

Classification of amino acids

I- Chemical classification: According to number of COOH and NH2

groups i.e. according to net charge on amino acid.

A- Monobasic, monocarboxylic amino acids i.e. neutral or uncharged

(glycine, alanine, valine)

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B- Basic amino acids:

Contain two or more NH2 groups or nitrogen atoms that act as base i.e. can

bind proton. At physiological pH, basic amino acids will be positively

charged. e.g.

a- Lysine

b- Arginine: contains guanido group

c- Histidine: is an example on basic heterocyclic amino acids

C- Acidic Amino acids: at physiological pH will carry negative charge. e.g.

Aspartic acid (aspartate) and Glutamic acid (glutamate).

see structures in hand out. Aspargine and Glutamine: They are amide

forms of aspartate and glutamate in which side chain COOH groups are

amidated. They are classified as neutral amino acids.

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II- Classification according to polarity of side chain (R):

The amino acid side chains in globular proteins are spatially distributed

according to their polarities:

A- Polar amino acids: in which R contains polar hydrophilic group so can

forms hydrogen bond with H2O.

In those amino acids, R may contain:

1- OH group: as in serine, threonine and tyrosine

2- SH group: as in cysteine

3- amide group: as in glutamine and aspargine.

4- NH2 group or nitrogen act as a base (basic amino acids): as lysine,

arginine and histidine.

5- COOH group ( acidic amino acids): as aspartic and glutamic .

-The charged polar residues Arg, His, Lys, Asp, and Glu are usually located

on the surface of a protein in contact with the aqueous solvent. This is

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because immersing an ion in the virtually anhydrous interior of a protein is

energetically unfavorable.

-The uncharged polar groups Ser, Thr, Asn, Gln, and Tyr are usually on the

protein surface but also occur in the interior of the molecule. When buried in

the protein, these residues are almost always hydrogen bonded to other

groups, the formation of a hydrogen bond neutralizes their polarity.

B- Non polar amino acids:

R is alkyl hydrophobic group which can’t enter in hydrogen bond

formation. 9 amino acids are non polar (glycine, alanine, valine, leucine,

isoleucine, phenyl alanine, tryptophan, proline and methionine).

The nonpolar residues Val, Leu, Ile, Met, and Phe occur mostly in the

interior of a protein, out of contact with the aqueous solvent. The

hydrophobic effects that promote this distribution are largely responsible for

the three-dimensional structure of native proteins.

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III- Nutritional classification:

1- Essential amino acids: These amino acids can’t be formed in the body

and so, it is essential to be taken in diet. Their deficiency affects growth,

health and protein synthesis.

2- Semiessential amino acids: These are formed in the body but not in

sufficient amount for body requirements especially in children.

3- Non essential amino acids: These are the rest of amino acids that are

formed in the body in amount enough for adults and children. They are

the remaining 10 amino acids.

IV- Metabolic classification: according to metabolic or degradation

products of amino acids they may be:

1- Ketogenic amino acids: which give ketone bodies.Lysine and Leucine

are the only pure ketogenic amino acids.

2- Mixed ketogenic and glucogenic amino acids: which give both

ketonbodies and glucose.These are: isoleucine, phenyl alanine, tyrosine

and tryptophan.

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3- Glucogenic amino acids: Which give glucose. They include the rest of

amino acids. These amino acids by catabolism yields products that enter

in glycogen and glucose formation.

Properties of Amino Acid

A. Physical properties:

1. Solubility: most of the amino acids are soluble in water and insoluble in

inorganic solvent:

2. Melting point: amino acids are generally melt at higher temperature ,

often above 200°C

3. Taste: amino acids may be sweet (Gly, Ala, Val), tasteless (Leu) or bitter

(Arg, ILe).Monosodium Glutamate (Ajinomoto) is used as flavouring agent

in food industry, chinese foood to increase taste and flavour.

Zwitterions or dipolar ion: The name Zwitter derived from the

German word which mean hybrid. Zwitter ion is a hybrid molecule

containing positive and negative ionic group. The amino acids rarely exists

in a neutral form with free carboxylic (-COOH ) and free amino (-NH2)

groups. In strongly acidic pH the amino acid are positively charged, while

in strongly alkaline pH it is negatively charged. Each amino acid has a

characteristics pH at which it carries both positive and negative charge and

Exist as Zwitterions.

Isoelectric pH: pH at which amino acids exist as the zwitterion

(neutral) and carries no net charge. Thus molecule is electrically neutral.

The pl value can be calculated by taking the average pKa values

corresponding to the ionizable groups. For example leucine has two

ionizable groups, and its pl value can be calculated as follows.

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B. Chemical properties

3 Reaction due to –COOH group

1. Amino acid form salts (-COONa) with base, and Ester (-COOR) with

alcohol.

2. Decarboxylation: Amino acid undergo deacarboxylation to produce

amines: this reaction assumes significance in the living cell due to the

formation of many biologically important amine. These include histamine,

tyramine, γ-amino butyric acid from the amino acid histidine, tyrosine and

glutamate respectively.

3. Reaction with ammonia: the carboxyl group of dicarboxylic amino acid

reacts with NH3 to form amide.

Aspartic acid + NH3 Aspargine

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4. Reaction due to NH2

The amino acid behave as bases and combine with acids to form salts.

Reaction with ninhydrine: the α- Amino acidreact with ninhydrine to form a

purple , blue or pink color complex (Ruhemann’s purple)

Amino acid + ninhydrine keto acid+NH3+ CO2+ Hydrindantin

Hydrindantin+ NH3+Ninhydrine Ruhemann’s purple

5. Colour reaction

6. Transamination

7. Oxidative deamination: Ninhydrine can react with imino acids as proline

and hydroxy proline but gives yellow color.

3- Reactions due to side chain (R):

1- Millon reaction: for tyrosine gives red colored mass

2- Rosenheim reaction: for trptophan and gives violet ring.

3- Pauly reaction: for imidazole ring of histidine: gives yellow to reddish

product

4- Sakagushi test: for guanido group of arginine andgives red color.

5- Lead sulfide test (sulfur test): for sulfur containing amino acids as

cysteine give brown color.

Peptides and Proteins

20 amino acids are commonly found in protein. These 20 amino acids

are linked together through ―peptide bond forming peptides and proteins

(what’s the difference). The chains containing less than 50 amino acids are

called ―peptides‖ while those containing greater than 50 amino acids are

called ―proteins‖.

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Peptide bond formation:

α-carboxyl group of one amino acid (with side chain R1) forms a

covalent peptide bond with α-amino group of another amino acid ( with the

side chain R2) by removal of a molecule of water. The result is Dipeptide (

i.e. Two amino acids linked by one peptide bond). By the same way, the

dipeptide can then forms a second peptide bond with a third amino acid

(with side chain R3) to give Tripeptide. Repetition of this process generates

a polypeptide or protein of specific amino acid sequence.

Peptide bond formation:

Each polypeptide chain starts on the left side by free amino group of the

first amino acid enter in chain formation . It is termed (N- terminus).

- Each polypeptide chain ends on the right side by free COOH group of the

last amino acid and termed (C-terminus).

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Examples on Peptides:

1- Dipeptide (tow amino acids joined by one peptide bond):

Example: Aspartame which acts as sweetening agent being used in

replacement of cane sugar. It is composed of aspartic acid and phenyl

alanine.

2- Tripeptides: 3 amino acids linked by two peptide bonds. Example:

glutathione which is formed from 3 amino acids: glutamic acid, cysteine

and glycine. It helps in absorption of amino acids, protects against hemolysis

of RBC by breaking H2O2 which causes cell damage.

3- Octapeptides: 8 amino acids, for examples: two hormones; oxytocine

and vasopressin (ADH).

4- Polypeptides: 10- 50 amino acids: e.g. Insulin hormone

Protein structure:

There are four levels of protein structure (primary, secondary, tertiary

and quaternary).

1. Primary structure: The primary structure of a protein is its linear

sequence of amino acids and the location of covalent linkages such as

disulfide bonds between amino acids. Lysozyme, an enzyme that attacks

bacteria, consists of a polypeptide chain of 129 amino acids. The precise

primary structure of a protein is determined by inherited genetic information.

At one end is an amino acid with a free amino group the (the N-terminus)

and at the other is an amino acid with a free carboxyl group the (the C-

terminus).

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High orders of Protein structure

A functional protein is not just a polypeptide chain, but one or more

polypeptides precisely twisted, folded and coiled into a molecule of unique

shape (conformation). This conformation is essential for some protein

function e.g. Enables a protein to recognize and bind specifically to another

molecule e.g. hormone/receptor; enzyme/substrate and antibody/antigen.

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2- Secondary structure: areas of folding or coiling within a protein;

Results from hydrogen bond formation between hydrogen of –NH group of

peptide bond and the carbonyl oxygen of another peptide bond. According

to H-bonding there are two main forms of secondary structure:

α-helix: It is a spiral structure resulting from hydrogen bonding between one

peptide bond and the fourth one

β-sheets: is another form of secondary structure in which two or more

polypeptides (or segments of the same peptide chain) are linked together by

hydrogen bond between H- of NH- of one chain and carbonyl oxygen of

adjacent chain (or segment).

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Hydrogen bonding in α-helix: In the α-helix CO of the one amino acid

residue forms H-bond with NH of the forth one.

Supersecondary structure or Motifs: occurs by combining secondary

structure. The combination may be: α-helix- turn- α-helix- turn…..etc

Or: β-sheet -turn- β-sheet-turn………etc

Or: α-helix- turn- β-sheet-turn- α-helix

Turn (or bend): is short segment of polypeptides (3-4 amino acids) that

connects successive secondary structures.

e.g. β-turn: is small polypeptide that connects successive strands of β-

sheets.

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3. Tertiary structure is determined by a variety of non-covalent

interactions (bond formation) among R groups and between R groups and

the polypeptide backbone forming three-dimensional structure of a protein

a. The weak interactions include:

Hydrogen bonds among polar side chains. Ionic bonds between

charged R groups (basic and acidic amino acid). Hydrophobic interactions

among hydrophobic (nonpolar) R groups.

b. Strong covalent bonds include disulfide bridges, that form between

the sulfhydryl groups (SH) of cysteine monomers, stabilize the

structure.

4. Quaternary structure: results from the aggregation (combination) of

two or more polypeptide subunits held together by non-covalent interaction

like H-bonds, ionic or hydrophobic interactions. Examples on protein

having quaternary structure:

Insulin: two polypeptide chains (dimeric)

Collagen is a fibrous protein of three polypeptides (trimeric) that are

supercoiled like a rope. This provides the structural strength for their role in

connective tissue.

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Hemoglobin is a globular protein with four polypeptide chains (tetrameric

Classification of proteins

I- Simple proteins: i.e. on hydrolysis gives only amino acids

Examples:

1- Albumin and globulins: present in egg, milk and blood. They are

proteins of high biological value i.e. contain all essential amino acids

and easily digested.

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Types of globulins:

α1 globulin: e.g. antitrypsin.

α2 globulin: e.g. hepatoglobin: protein that binds hemoglobin to prevent its

excretion by the kidney

β-globulin: e.g. transferrin: protein that transport iron

γ-globulins e.g Immunoglobulins (antibodies) : responsible for immunity.

Conjugated proteins: i.e. On hydrolysis, give protein part and non protein

part and subclassified into:

1- Phosphoproteins: These are proteins conjugated with phosphate group.

Phosphorus is attached to oh group of serine or threonine. e.g. Casein of

milk and vitellin of yolk.

2- Lipoproteins:

These are proteins conjugated with lipids.

Functions: a- help lipids to transport in blood. b- Enter in cell membrane

structure helping lipid soluble substances to pass through cell membranes.

3- Glycoproteins: proteins conjugated with sugar (carbohydrate)

e.g. Mucin

Some hormones such as erythropoeitin

Present in cell membrane structure

Blood groups.

4- Nucleoproteins: These are basic proteins ( e.g. histones) conjugated with

nucleic acid (DNA or RNA).

e.g. a- chromosomes: are proteins conjugated with DNA

b- Ribosomes: are proteins conjugated with RNA

5- Metalloproteins: These are proteins conjugated with metal like iron,

copper, zinc.

33

a- Iron-containing proteins:Iron may present in heme such as in

- hemoglobin (Hb), myoglobin (protein of skeletal muscles and

cardiacmuscle), cytochromes, catalase, peroxidases (destroy H2O2). Iron

may be present in free state (not in heme) as in three forms:

Ferritin: main store of iron in the body, present in liver, spleen and bone

marrow.

Hemosidrin: another iron store.

Transferrin: is the iron carrier protein in plasma.

b- Copper containing proteins:

e.g. - Ceruloplasmin which oxidizes ferrous ions into ferric ions.

- Oxidase enzymes such as cytochrome oxidase.

c- Zn containing proteins: e.g. Insulin and carbonic anhydrase

d- Mg containing proteins:e.g. Kinases and phosphatases.

6-Chromoproteins: These are proteins conjugated with pigment. e.g.

- All proteins containing heme (Hb, myoglobin)

- Melanoprotein:e.g proteins of hair or iris which contain melanin.

Derived proteins

Produced from hydrolysis of simple proteins.

e.g. - Gelatin: from hydrolysis of collagen

- Peptone: from hydrolysis of albumin

34

Conclusion

1. Amino Acids are the building units of proteins

2. Each amino acid has 4 different groups attached to α- carbon

are: amino group, COOH group, hydrogen atom and side Chain (R).

3. Amino Acids are classified chemically to neutral or uncharged e.g: (

glycine, alanine, valine). Basic amino acids: Lysine

- Acidic Amino acids :-Aspargine and Glutamine

4. Classified according to polarity of side chain (R) to:( Polar amino

acids- Non polar amino acids)

5. Nutritional classification (Essential amino acids, Semi essential amino

acids -Non essential amino acids).

6. Metabolic classification (Ketogenic amino acids, mixed ketogenic and

glucogenic amino acids and Glucogenic amino acids)

7. amino acids are bonded to each other by peptide bonds forming

peptides or proteins

8. Proteins structures are primary, secondary, tertiary and quaternary.

9. proteins can be simple or conjugated (containing non protein part )

35

Lipids

1 Lipids are diverse in form and are defined by solubility in non-polar

solvents (and insolubility in water)

2 Lipids are used for efficient energy storage, as structural components

of cell membranes, as chemical messengers and as fat-soluble

vitamins with a variety of functions

3 We consume many lipids from a variety of plant and animal sources

4 Our cells can also biosynthesize most lipids.

Classification of Lipids

1. Simple lipids: Esters of fatty acids with various alcohols.

a. Fats: Esters of saturated fatty acids with glycerol (animal sources).

b. Oils: Esters of unsaturated fatty acids with glycerol (plant sources).

c. Waxes: Esters of fatty acids with higher molecular weight monohydric

alcohols.

2. Complex lipids: Esters of fatty acids containing groups in addition to an

alcohol and a fatty acid.

a. Phospholipids: They frequently have nitrogen-containing bases and

other substituents, eg, in glycerophospholipids the alcohol is glycerol and

in sphingophospholipids the alcohol is sphingosine.

b. Glycolipids (glycosphingolipids): Lipids containing a fatty acid,

sphingosine, and carbohydrate.

c. Other complex lipids: Lipids such as sulfolipids and aminolipids.

Lipoproteins may also be placed in this category.

3) Precursor and derived lipids: These include steroids (cholesterol),

lipid-soluble vitamins, and hormones.

36

Types of Lipids

1 Following is a summary of the types of lipids we will study and their

general structures:

Fatty Acids

1 The simplest lipids are the fatty acids, which rarely exist alone in

nature, but instead are usually a component of more complex lipids

2 Fatty acids are carboxylic acids with a long hydrocarbon chain

attached

3 Although the acid end is polar, the nonpolar hydrocarbon tail makes

fatty acids insoluble (or sparingly soluble) in water

37

4 Fatty acids can be classified by how many double bonds are present in

the hydrocarbon tail:

- Saturated fatty acids have only single bonds

- Monounsaturated fatty acids have one double bond

- Polyunsaturated fatty acids have two or more double bonds

Structures and Melting Points of Saturated Fatty Acids

38

Physical Properties of Saturated Fatty Acids

Saturated fatty acids have:

1 Molecules that fit closely together in a regular pattern

2 Strong attractions (dispersion forces) between fatty acid chains

3 High melting points that makes them solids at room temperature.

Structures and Melting Points of Unsaturated Fatty Acids

39

Physical Properties of Unsaturated Fatty Acids

Unsaturated fatty acids have:

1 Nonlinear chains that do not allow molecules to pack closely

2 Weak attractions (dispersion forces) between fatty acid chains

3 Low melting points and so are liquids at room

temperature

41

Triglycerides

Triglycerides (also called Triacylglycerols) are tri-fatty acid esters of

glycerol. Triglycerides are the major form of fatty acid storage in

plants and animals. Triglycerides can be classified as fats or oils.

- fats are solid at room temperature and most come from animals

- oils are usually liquid at room temperature and come from plants

(palm and coconut oils are liquids at room temperature). Triacylglycerols

function as energy reservoirs in animals and are therefore their most

abundant class of lipids because they are not components of cellular

membranes.

41

Olive Oil

Olive oil contains mostly triolein, which has three oleic acids. Oleic acid,

a monounsaturated fatty acid, is a component of all fats and oils, but is

especially abundant in olive and peanut oils. Some studies have

shown that oleic acid may raise HDL (―good cholesterol‖) levels

while also lowering LDL (―bad cholesterol‖) levels

42

Olestra: a Fat Substitute

Olestra is: used in foods as an artificial fat. Sucrose linked by ester

bonds to several long-chain fatty chains. Not broken down in the

intestinal tract. Olestra inhibits the absorbtion of fat-soluble vitamins

(A, D, E and K) and carotenoids. There are many reports of problems

such as diarrhea and abdominal cramps with olestra use, but the

manufacturers claim there’s no proof

Reaction of fatty acids

1. Hydrogenation

2. Oxidation

3. Hydrolysis

1. Hydrogenation of Unsaturated Oils

Hydrogenation converts alkenes to alkanes. So, hydrogenation of

unsaturated oils produces saturated fats. Hydrogenation is typically

carried out by bubbling H2 gas through the heated oil, in the presence

of a metal catalyst (such as nickel or platinum). Unsaturated oils are

usually only partially hydrogenated, so that the product is not

completely saturated, giving a soft semisolid fat such as margarine

43

CH

CH2

O C

O

(CH2)7CH CH(CH2)7CH3

O C

O

(CH2)7CH CH(CH2)7CH3

CH2 O C

O

(CH2)7CH CH(CH2)7CH3

Pt

CH2 O C

O

(CH2)16CH3

CH2 O C

O

(CH2)16CH3

CH O C

O

(CH2)16CH3

+3H2

Cis and Trans Unsaturated Fatty Acids

1. Natural unsaturated fatty acids have cis double bonds

2. When unsaturated vegetable oils are hydrogenated to form more saturated

oils (as in margarine), some of the cis fatty acids are isomerized to trans

fatty acids.

3.Trans fatty acids are much more linear than cis fatty acids, so their melting

points are higher and studies have shown that trans fats may act similarly

to saturated fats and could contribute to heart disease and some cancers.

4.Due to new requirements for including amounts of trans fats on food labels,

many companies are developing hydrogenation methods that do not

produce trans fats

2. Oxidation of Unsaturated Oils

Fats and oils can become rancid in two ways:

44

- bacterial ester hydrolysis (next slide)

- air oxidation of alkenes

Oxidation of fatty acid alkenes involves cleavage of the double bonds to

form short-chain carboxylic acids. These oxidation products are foul-tasting

and smell horrible

OH

O

O2 or O3

OH

O

+

OH

O

HO

O

Hydrolysis of Fats and Oils

1. Fats and oils contain ester groups which can be hydrolyzed with aqueous

acid, aqueous base (saponification) or enzymes

2. The hydrolysis products are glycerol and three fatty acids

3. When triglycerides containing short-chain fatty acids are hydrolyzed the

carboxylic acid products (such as butanoic and hexanoic acids) are foul-

smelling and foul-tasting (rancid)

HC

H2C

H2C

O C (CH2)14CH3

O

O C

O

(CH2)14CH3

O C (CH2)14CH3

O

H3O+

orlipase

HC

H2C

H2C

OH

OH

OH

+ HO C (CH2)14CH3

O

3

45

Saponification

When a triglycerides is hydrolyzed with a strong base the process is

called saponification. The products of saponification are glycerol and fatty

acid salts (soap). NaOH is used with saturated fats to produce hard soaps.

KOH is used with unsaturated fats to produce softer, more liquid soaps

HC

H2C

H2C

O C (CH2)14CH3

O

O C

O

(CH2)14CH3

O C (CH2)14CH3

O

HC

H2C

H2C

OH

OH

OH

+ O C (CH2)14CH3

O

3

NaOHNa

(Soap)

Cholesterol

Cholesterol is soft, fat-like, waxy substance. Bloodstream and cells

needed it for cell membranes and hormones and to make vitamin D.

comes from 2 sources:

– Body produces it (mostly genetic) in liver (1000 mg day)

– Food sources (animal products not from plant sources such as meats,

poultry, fish, eggs, butter, whole milk, and cheese) (100 – 500 mg day)

– Foods with trans fats or saturated fats may cause the body to produce

more cholesterol

46

Cholesterol

Must be transported through blood. Carriers are called lipoproteins

– Low-density lipoprotein (LDL)

– High-density lipoprotein (HDL)

Lipoprotein = protein + fat

– LDL, more fat, less protein

– HDL, more protein, less fat

LDL vs. HDL

LDL = ―bad‖. Too much can clog arteries by forming plaque

Atherosclerosis can cause heart attack or stroke.

LDL vs. HDL

HDL = ―good‖. Tends to carry cholesterol away from arteries and back to

liver. May also remove excess cholesterol from plaque in arteries, slows

buildup

Triglycerides

Form of fat. Also made in body (body fat stored as triglyceride) and from

food. Help transport dietary fat, metabolism. Trigger liver to make more

cholesterol, rising LDL and total cholesterol

Synthesis of vitamin D

47

Steroids

Steroids constitute an important class of biological compounds. Steroids

are usually found in association with fat. They are derivatives of

cholesterol that is formed of steroid ring or nucleus. Biologically

important groups of substances, which contain this ring, are: Sterols,

Adrenal cortical hormones, Male and female sex hormones, Vitamin D

group, Bile acids, Cardiac glycosides.

Bile acids: They are produced from oxidation of cholesterol in the liver

producing cholic and chenodeoxycholic acids that are conjugated with

glycine or taurine to produce glycocholic, glycochenodeoxycholic,

taurocholic and taurochenodeoxycholic acids. They react with sodium or

potassium to produce sodium or potassium bile salts.

Their function is as follows: Emulsification of lipids during digestion. Help

in digestion of the other foodstuffs. Activation of pancreatic lipase. Help

digestion and absorption of fat-soluble vitamins. Solubilizing cholesterol in

bile and prevent gall stone formation. Intestinal antiseptic that prevent

putrefaction

Conclusion

1- Lipids are esters of fatty acids, alcohols, sometimes additional

groups.

2- lipids are storage forms of energy for living organisms

3- lipids are classified to simple (esters of fatty acids and alcohols)

and complex (contains additional groups e.g. protein part)

4- fatty acids are the building unites of lipids which can be saturated

or unsaturated

5- Cholesterol is soft, fat-like, waxy substance. Cells needed it for

cell membranes and hormones and to make vitamin D.

48

6- Good cholesterol (HDL), bad cholesterol (LDL) is very important

types of cholesterol used in detection of fat content abnormalities.

7- Triglycerides are Forms of fat made in body and from food. Help

transport dietary fat, metabolism. Trigger liver to make more

cholesterol, rising LDL and total cholesterol

8- Steroids are derivatives of cholesterol that is formed of steroid

ring or nucleus e.g:Adrenal cortical hormones.

9- Bile acids are produced from oxidation of cholesterol in the liver,

make Emulsification of lipids during digestion. Help in digestion

of the other foodstuffs.

49

NUCLEOTIDES

There are eight common varieties of nucleotides, each composed of a

nitrogenous base linked to a sugar to which at least one phosphate group is

also attached. The bases of nucleotides are planar, aromatic, heterocyclic

molecules that are structural derivatives of either purine or pyrimidine

(although they are not synthesized in vivo from either of these organic

compounds).

The most common purines are adenine (A) and guanine (G), and the

major pyrimidines are cytosine (C), uracil (U), and thymine (T).

The purines form bonds to a five-carbon sugar (a pentose) via their N9

atoms, whereas pyrimidines do so through their N1 atoms. In

ribonucleotides, the pentose is ribose, while in deoxyribonucleotides (or just

deoxynucleotides), the sugar is 2’-deoxyribose (i.e., the carbon at position 2’

lacks a hydroxyl group). Note that the primed numbers refer to the atoms of

the pentose; unprimed numbers refer to the atoms of the nitrogenous base.

In a ribonucleotide or a deoxyribonucleotide, one or more phosphate groups

are bonded to atom C3’ or atom C5’ of the pentose to form a 3’-nucleotide

or a 5’-nucleotide, respectively When the phosphate group is absent, the

compound is known as a nucleoside. A 5’-nucleotide can therefore be called

a nucleoside-5’-phosphate. Nucleotides most commonly contain one to three

phosphate groups at the C5’ position and are called nucleoside

monophosphates, diphosphates, and triphosphates.

51

The structures, names, and abbreviations of the common bases,

nucleosides, and nucleotides Ribonucleotides are components of RNA

(ribonucleic acid), whereas deoxynucleotides are components of DNA

(deoxyribonucleic acid). Adenine, guanine, and cytosine occur in both

ribonucleotides and deoxynucleotides (accounting for six of the eight

common nucleotides), but uracil primarily occurs in ribonucleotides and

thymine occurs in deoxynucleotides. Free nucleotides, which are anionic, are

almost always associated with the counterion Mg2+ in cells.

Nucleic Acids Are Polymers of Nucleotides

The nucleic acids are chains of nucleotides whose phosphates bridge

the 3’ and 5’ positions of neighboring ribose units. The phosphate of these

polynucleotides is acidic, so at physiological pH, nucleic acids are

polyanions. The linkage between individual nucleotides is known as a

phosphodiester bond, so named because the phosphate is esterified to two

ribose units. Each nucleotide that has been incorporated into the

polynucleotide is known as a nucleotide residue. The terminal residue whose

C5’ is not linked to another nucleotide is called the 5’ end, and the terminal

residue whose C3’ is not linked to another nucleotide is called the 3’ end. By

convention, the sequence of nucleotide residues in a nucleic acid is written,

left to right, from the 5’ end to the 3’ end. The properties of a polymer such

51

as a nucleic acid may be very different from the properties of the individual

units, or monomers.

DNA Forms a Double Helix (Watson–Crick model)

The Watson–Crick model of DNA has the following major features:

1. Two polynucleotide chains wind around a common axis to form a double

helix.

2. The two strands of DNA are antiparallel (run in opposite directions), but

Each forms aright-handed helix.

3. The bases is the core of the helix and sugar–phosphate chains are the

periphery.

4. Each base is hydrogen bonded to a base in the opposite strand to form a

planar base pair.

The Watson ــــCrick structure can accommodate only two types of

base pairs. Each adenine residue must pair with a thymine residue and vice

versa, and each guanine residue must pair with a cytosine residue and vice

versa. These hydrogen-bonding interactions, a phenomenon known as

complementary base pairing, result in the specific association of the two

hains of the double helix.

52

RNA Is a Single-Stranded Nucleic Acid

RNA occurs primarily as single strands, which usually form compact

structures rather than loose extended chains (double-stranded RNA is the

hereditary material of certain viruses). An RNA strand which is identical to a

DNA strand except for the presence of 2’-OH groups and the substitution of

uracil for thymine can base-pair with a complementary strand of RNA or

DNA. As expected, A pairs with U (or T in DNA), and G with C.

53

CONCLUSION

DNA RNA

Deoxiribose Ribose sugar

Adenine, Guanine Adenine, Guanine Purine

Thymine,Cytosine

Uracil, Cytosine pyrimidine

present present Phosphate groups

In nucleus In nucleus presence

present Absent Duble helex

Carry and save genetic

information

Protein synthesis Function

One type 3 types Types

54

Enzymes

Function of Enzymes

Biological catalysts made up of proteins. Enzymes speed up the rate

of chemical reactions in the body; both breaking down (e.g.: starch into

maltose) and building up reactions. (e.g: amino acids into proteins).

Enzymes lower the activation energy required to start a chemical reaction

Characteristics of Enzymes

Enzymes are highly specific in action. Enzymes remain chemically

unchanged at the end of the reaction. Enzymes are required in minute

amounts.

Nomenclature of Enzymes

In most cases, enzyme names end in –ase

The common name for a hydrolase is derived from the substrate

– Urea: remove -a, replace with -ase = urease

– Lactose: remove -ose, replace with -ase = lactase

Other enzymes are named for the substrate and the reaction catalyzed

– Lactate dehydrogenase

– Pyruvate decarboxylase

Some names are historical - no direct relationship to substrate or reaction

type

– Catalase, pepsin, chymotrypsin and trypsin

Nomenclature and Classification

Enzymes are often classified by placing them in categories according to the

reactions that they catalyze:

Classification Type of Reaction Catalyzed

1. Oxidoreductases Oxidation–reduction reactions

55

2. Transferases Transfer of functional groups

3. Hydrolases Hydrolysis reactions

4. Lyases Group elimination to form double bonds

5. Isomerases Isomerization

6. Ligases Bond formation coupled with ATP hydrolysis

Classification of Enzymes

Oxidoreductases catalyze redox reactions

– Reductases

– Oxidases

2.Transferases: transfer a group from one molecule to another

– Transaminases catalyze transfer of an amino group

– Kinases transfer a phosphate group

3. Hydrolases cleave bonds by adding water

– Phosphatases

– Peptidases

– Lipases

56

4. Lyases catalyze removal of groups to form double bonds or the reverse

break double bonds.eg Decarboxylases and synthases

5. Isomerases catalyze intramolecular rearrangements

– Epimerases

– Mutases

1. Ligases catalyze a reaction:

in which a C-C, C-S, C-O, or C-N bond is made or broken

57

Mode of Action

Substrate fits in the enzyme active site, just like a key fits into a lock.

An enzyme-substrate complex is formed. Chemical reactions occur at the

active site and products are formed.

1. Lock and Key Enzyme Model: In the lock-and-key model, the enzyme

is assumed to be the lock and the substrate the key. The enzyme and

substrate are made to fit exactly. This model fails to take into account

proteins conformational changes to accommodate a substrate molecule

2. Induced Fit Enzyme Model

The induced-fit model of enzyme action assumes that the enzyme active site

is more a flexible pocket whose conformation changes to accommodate the

substrate molecule

58

Specificity of the Enzyme-Substrate Complex

For enzyme and substrate to react, surfaces of each must be complementary.

Enzyme specificity: the ability of an enzyme to bind only one, or a very few,

substrates thereby catalyzing only a single reaction. Compare these 2

reactions: Urease is very specific or has a high degree of specificity.

Classes of Enzyme Specificity

Absolute: enzyme reacts with only one substrate

Group: enzyme catalyzes reaction involving any molecules with the same

functional group

Linkage: enzyme catalyzes the formation or break up of only certain

category or type of bond

Stereochemical: enzyme recognizes only one of two enantiomers

Cofactors and Coenzymes

Active enzyme / Holoenzyme:

– Polypeptide portion of enzyme (apoenzyme)

– Nonprotein prosthetic group (cofactor)

Cofactors are bound to the enzyme for it to maintain the correct

configuration of the active site

– Metal ions

– Organic compounds

– Organometallic compounds

59

Coenzymes

A coenzyme is required by some enzymes

– An organic molecule bound to the enzyme by weak interactions

/ Hydrogen bonds

– Most coenzymes carry electrons or small groups

– Many have modified vitamins in their structure

61

Factors affecting Enzyme Activity

1. Temperature

Low temperatures, at 0C cause low Kinetic Energy of enzymes and

substrates. No/very few enzyme-substrate complexes are formed. Enzymes

are inactivated. at 20 0C Increasing the temperature will lead to the increase

in kinetic energy of enzyme and substrate molecules. Enzyme and substrate

molecules move with increasing speed and collide more frequently with

each other. This increases the rate of enzyme-substrate complex formation

This increases the rate of enzyme-substrate complex formation and product

formation then rate of reaction increases. As the temperature continues to

61

increase, the rate of enzyme activity also increases until the optimal

temperature is reached. Optimal temperature is the temperature at which the

enzyme works best. Rate of product formation is highest. Beyond Optimal

Temperatures, at high temperatures (>60°C), weak bonds within the enzyme

molecule are broken. Enzyme loses its shape and its active site.Loss of shape

leads to a loss of function. Enzyme is said to have denatured. Denaturation

is the change in 3D structure of an enzyme or any other protein caused by

heat or chemicals such as acids or alkali, causing it to lose its function.

Different enzymes denature at different temperatures. Most enzymes

denature at temperatures higher than 60°C. However, there are some

enzymes that stay active even at high temperatures like 80°C (Enzymes in

the bacteria Thermus aquaticus).

2. Effect of pH on enzyme activity

Enzyme works best within a narrow pH range. Each enzyme works

best at particular pH, known as its optimum pH level. At extreme pH levels,

enzymes lose their shape and function and become denatured.

62

3. Effect of substrate concentration on enzyme activity

As substrate concentration increases, the rate of reaction increases (at

constant enzyme concentration). The enzyme eventually becomes saturated

giving maximum activity.

Uses of Enzymes in Medicine

Diagnostic enzyme levels altered with disease

Liver :Aspartate aminotransferase (AST), alanine aminotransferase (ALT)

alkaline phosphatase (ALP), gamma glutamyl tranferase (GGT)

Heart attack: Lactate dehydrogenase, Creatine phosphate, AST

63

Pancreatitis: Amylase, lipase

Analytical reagents: Enzyme used to measure another substance eg. Urea

converted to NH3 via urease.

CONCLUSION

1. Enzymes Biological highly specific catalysts made up of proteins

which speed up the rate of chemical reactions in the body.

2. Common name of an enzyme = substrate or reaction or both +ase.

3. Enzymes act according to Lock and Key Model also Induced Fit

Enzyme Model.

4. Enzyme activity affected by temperature, pH and enzyme

substrate concentration.

5. Diagnostic enzyme levels altered with disease.

64

Vitamins

Vitamins are made up of carbon, hydrogen and oxygen. Vitamins are

called micronutrients because they are needed in only very small quantities.

They all have chemicals names but they are usually referred to by letters.

Main functions

Vitamins are essential to the body:

1. To maintain health

2. To help prevent deficiency diseases such as Beriberi (weakened muscles,

heart, nerves and digestive system) and rickets (softening of the bones)

3. To regulate the repair of body cells

4. To help combat the ageing process

5. To help to process carbohydrates and release energy in the body

Vitamins are Two main categories

1. Water soluble Vitamins ( B, C)

2. Fat Soluble (A, D, E, K)

Water soluble: Cannot be stored in body - regular supply needed. Excess is

excreted in urine. No danger of toxic levels. Unstable to heat and light, leach

into cooking liquids.

Fat Soluble: Can be stored in body - regular supply not needed. Can

accumulate to toxic levels if large amounts ingested. Fairly stable at normal

cooking temperatures

Vitamin A found in two forms; Retinol and Beta-Carotene

Retinol: Named because of its concern with retina of eye, only found in

animal foods

Beta-Carotene: plant sources, present with chlorophyll in plants, converted

to Vitamin A in gut wall.

65

Functions: Regulates growth, promotes healthy skin, maintenance of

healthy tissues, helps eye adapt to dim light.

Sources: Retinol - Cod liver oil, Liver, Dairy products, Herrings, Egg yolk

Beta-Carotene: Dark green leafy, vegetables, Broccoli, Carrots, Deep

orange, fruits and vegetables

Effects of deficiency

• Retarded growth, malformed bones, long term-may lead to night

blindness, susceptibility to infection, excess beta-carotene may lead

to liver and bone damage

Vitamin D -Calciferols

Functions: Absorption and laying down of calcium and phosphorous in

bones and teeth. Regulates calcium balance between bones and blood,

Prevents rickets

Sources: Sunlight conversion, Fish liver oils, Dairy products, Oily fish,

Margarine

Effects of deficiency

1. Rickets in children and osteomalacia in adults (Conditions where bones

are soft and cannot take weight of body).

2.Osteoporosis (Bones become light, less dense and prone to fractures)

3. Dental caries

Vitamin E - Tocopherol

Functions:

1. Protects tissues against damage

2. Promotes normal growth and development

3. Helps in normal red blood cell formation

Sources: Pure vegetable oils, Wheat, wholemeal bread, Cereals, egg yolk,

nuts, sunflower seeds.

66

Effects of deficiency

Deficiency is very rare but it could affect the central nervous system

Vitamin K - Napthoquinone

Functions: Needed for blood clotting, which means it helps wounds heal

properly.There is increasing evidence that vitamin K is also needed to help

build strong bones.

Sources: Green leafy Vegetable, vegetable oil, cereals.

Effects of deficiency

Deficiency is very rare but individuals with liver damage and new born

infants are at a higher risk

Vitamin B1 - Thiamin

Functions: Essential for release of energy from carbohydrates. Necessary

for appetite and good health. Needed for normal functioning of nervous

system

Sources: Meat, Oatmeal, Breakfast cereals, Wheat, Fortified white flour

Milk, Eggs, vegetables

Deficiency:

1. Fatigue, depression, irritability

2. Beri-beri - disease of nervous system

Vitamin B2 -Riboflavin

Functions

1. Metabolism of carbohydrates, proteins and fats

2. Growth, repair, development of body tissues - healthy skin, eyes and

tongue

3. The principal growth promoting factor in the vitamin B complex

Sources: Offal, Milk, Cheese, Eggs, Yeast extracts, Green Vegetables

67

Deficiency

1. Loss of appetite

2. Swollen tongue, cracked lips, eye infection,

Vitamin B3 -Niacin

Functions

1. Metabolism of carbohydrates, proteins and fats

2. Needed for normal functioning of nervous system

Sources: Meat, Offal, Yeast extracts, Yeast, Bran, wheat, flour

Some pulses, dried fruit

Deficiency

1. Fatigue, depression, irritability

2. Beri-beri - disease of nervous system

Vitamin B9 -Folic Acid

Functions

1. Red blood cell formation

2. Development of brain, spinal cord and skeleton in foetus

3. Reduces risk of neural tube defects e.g. spina bifida

4. May play role preventing heart attacks, strokes and cancer

Sources:

fortified cereals, green leafy vegetables, potatoes, bread, milk, wheat

Deficiency

1. Fatigue in mild cases

2. Anaemia in severe cases

3. Neural tube defects

Important to take folic acid prior to conception and vital during first 3

months pregnancy

68

Vitamin C -Ascorbic Acid

Functions

1. Critical to immune system. 2. Formation of connective tissue, collagen

Helps absorption of iron. 3. Prevents scurvy. 4. Promotes healing of wounds

and healthy blood vessels.5. Acts as antioxidant, protects cholesterol

Sources: Rosehips, blackcurrants, green peppers, kiwi, citrus, fruits,

strawberries, spinach, cabbage, broccoli

Deficiency

1. Weakening of connective tissue

2. Susceptibility to infection

3. Incomplete iron absorption

4. Delayed healing of wounds

5. Prevent scurvy - pale skin with spots, bleeding, soft gums.

Conclusion

1. Vitamins are very important organic biomolecules which can be water

soluble or fat soluble

2. Water soluble: Cannot be stored in body, Unstable to heat and light, leach

into cooking liquids.e.g: ( B, C)

3. Fat Soluble: Can be stored in body. Fairly stable at normal cooking

temperatures.eg; (A, D, E, K)

4. Each type of vitamins have it's own importance and is needed daily for

healthy body.

69

MINERALS

Our body requires mineral elements for a variety of functions. They are also

known as micronutrients. Unlike vitamins, which are organic substances

minerals are inorganic and are found in rocks and soil. Vegetables absorb

minerals as they grow, while animals digest it through their diet. Minerals

can be divided into two groups those needed in larger quantities (major

minerals) and those only required in tiny amounts (trace elements).

Trace Minerals - are iron, zinc and iodine.

Major Minerals - are sodium, potassium, calcium and phosphorus.

Minerals have 4 major functions: Body building – teeth and bones. Control

of body processes, especially the nervous system. Essential part of body

fluids and cells. Form part of enzymes and other proteins necessary for the

release of energy

Iron

Functions: Production of haemoglobin in red blood cells to carry oxygen in

the blood

Deficiency: Anaemia,

Sources: Red meat, Kidney, Liver, Eggs, Bread, Green veg

Calcium

Functions: Teeth and bones, Blood clotting, Nerve and muscle contraction.

Heart regulation.

Deficiency: Stunted growth can cause rickets, osteoporosis.

Sources: Dairy products, fortified white bread, oily fish, green veg, nuts and

seeds, citrus fruits.

Phosphorus

Functions: Bones and teeth with calcium.Muscle contraction

Deficiency: Rarely deficient but could cause tiredness and depression

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Sources: Dairy products, Nuts, Meat, Fish, foods rich in calcium

Sodium

Functions: Maintains water balance in the body and controls body

temperature, helps you sweat when body temp rises.

Deficiency: Deficiency is highly unlikely

Sources: Cheese, Bacon, smoked meats, Fish, processed foods, table salt.

Government advice says on average you should be eating no more than 6g of

salt a day.

Potassium

Functions: Muscle contraction and in maintaining fluid. It is necessary for

the building of muscle and for normal body growth.

Deficiency: Dry skin, acne, Muscle spasms

Sources: Banana, Celery, Turnips

Zinc

Functions: Everything from acne to diabetes. Aids the immune system.

Needed for the senses of smell and taste.

Deficiency: Dry skin, acne, Muscle spasms

Sources: Meat (lamb), Oats, Eggs, Nuts

Iodine:

Functions: Thyroid gland function (controls how quickly the body uses

energy) and body metabolism

Deficiency: Particularly in children, fall in the production of thyroid

hormones

Sources: Animal and plat life from the sea, milk, eggs, yogurt

Conclusion

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1. Minerals are inorganic and are found in rocks and soil.

2. Major Minerals required in larger quantities are sodium, potassium,

calcium and phosphorus.

3. Trace Minerals required in tiny amounts are iron, zinc and iodine.

4. Each type of elements have it's own importance and needed for healthy

body.

MCQ

Q.1- Which of the following is a simple sugar or monosaccharide?

a) Galactose c)Maltose

b) Lactose d)Sucrose (a)

Q.2- What is the molecular formula for Glucose?

a) CH3OH c)C12H22O11

b) C6H1206 d)C6H12O5 (b)

Q.3- Maltose is composed of which two sugars?

a) Glucose and Glucose c) Glucose and Fructose

b) Glucose and Galactose d) Fructose and Galactose (a)

Q.4- In which form Glucose is stored in animals?

a) Starch c)Dextrins

b) Glycogen d)Cellulose (b)

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Q.5-All are glucosans except-

a) Glycogen c)Starch

b) Inulin d)Cellulose (b)

Q.6- Choose the Aldose sugar-

a) Sucrose c)Fructose

b) Ribulose d)Ribose (d)

Q.7- Choose the keto triose-

a) Glyceraldehyde c) Dihydroxyacetone

b)

Erythrose d)Arabinose (c)

Q.8- A pentose sugar present in the heart muscle is-

a) Xylose c)Xylulose

b)Lyxose d)Aldose (b)

Q.9- α-D Glucose and β- D glucose are-

a) Epimers c)Anomers

b) Keto- Aldose Isomers d) Optical isomers (c)

Q.10- All tests arenegative for sucrose except-

a) Benedict c)Barfoed

b)

Seliwanoff d)Osazone (b)

Q.11- Glucose canhave ————- isomers due to the presence of 4

asymmetric carbon atoms-

a) 4 c)8

b)

12 d)16 (d)

Q.12- Galactose andGlucose are-

a) Epimers c)Anomers

b) Isomers d)Ketose- Aldose isomers (a)

Q.13- The compounds having same structural formula but differing in

configuration around one carbon atom are called-

a) Optical isomers c) Anomers

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b) Stereo isomers d)

Epimers (d)

Q.14- What does the following equation represent?

α-D Glucose +112ο→+52.5 ο → +19 ο β- D glucose

a) Stereoisomerism c) Opticalisomerism

b) Mutarotation d)Epimerization (b)

Q.15- Thecarbohydrate of blood group substance is-

a) Fucose c)Lyxose

b) Xylose d)Fructose (a)

Q.16- Dulcitol isa -

a) Sugar acid c) Deoxysugar

b) Amino sugar d) Sugaralcohol (d)

Q.17- Which of thefollowing is a non reducing sugar-

a) Arabinose c)Trehalose

b) Erythrose d)Ribulose (c)

Q.18- APolysaccharide formed by β1→4 Glycosidic linkages is-

a) Starch c)Glycogen

b) Dextrin d)Cellulose (d)

Q.19-Invert sugaris-

a) Starch c)Fructose

b) Glucose d)Hydrolytic product of Sucrose

(d)

Q.20- Thepolysaccharide found in the exoskeleton of insects is-

a) Hyaluronic acid c) Chitin

b) Cellulose d)Chondrosamine (c)

Q,21- Which of thefollowing is a polymer of fructose?

a) Inulin c)Cellulose

b)Dextrin d)Glycogen (a)

Q.22- Adisaccharide produced on hydrolysis of starch is called-

a) Sucrose c)Maltose

b) Lactose d)Trehalose (c)

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Q.23- The typicalcyclical structure of Glucose is α and β D-

a) Glucopyranose c)Glucofuranose

b) Glucoside d)Glucosamine (a)

Q.24- Which testcan be undertaken to differentiate between Glucose and

Fructose?

a) Benedict c)Seliwanoff

b) Molisch d)Osazone (c)

Q.25- Which of thefollowing molecules is a carbohydrate?

a) C3 H7O2N c)C6H12O6

b) C13H26O2 d)C20H40O2 (c)

Q.26- Which of the followingmonosaccharides is not an aldose?

a) Ribose c) Glucose

b) Fructose d)Glyceraldehyde (b)

Q.27-Which of following is ananomeric pair?

a) D-glucose and L-glucose c) D-glucose andD-fructose

b) α-D-glucose and β-D-glucose d) α-D-glucose and β-L-glucose

(b)

Q.28- Which of the followingmonosaccharides is not a carboxylic acid?

a) Glucuronate c) Glucose

b) Gluconate d)Muramic acid

(c)

Q.29- From the abbreviated nameof the compound Gal (β 1 →4) Glc, we

know that:

a) The glucose residue is the β anomer.

b) The galactose residue is at thenonreducing end.

c) C-4 of glucose is joined toC-1 of galactose by a glycosidic bond.

d) The compound is in its

furanoseform (c)

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1. The general formula of monosaccharides is (A) CnH2nOn (B) C2nH2On

(C) CnH2O2n (D) CnH2nO2n

2. The general formula of polysaccharides is (A) (C6H10O5)n (B) (C6H12O5)n

(C) (C6H10O6)n (D) (C6H10O6)n

3. The aldose sugar is (A) Glycerose (B) Ribulose

(C) Erythrulose (D) Dihydoxyacetone

4. A triose sugar is (A) Glycerose (B) Ribose

(C) Erythrose (D) Fructose

5. A pentose sugar is

(A) Dihydroxyacetone (B) Ribulose

(C) Erythrose (D) Glucose

6. The pentose sugar present mainly in the heart muscle is (A) Lyxose (B) Ribose

(C) Arabinose (D) Xylose

7. Polysaccharides are (A) Polymers (B) Acids

(C) Proteins (D) Oils

8. The number of isomers of glucose is

(A) 2 (B) 4

(C) 8 (D) 16

9. Two sugars which differ from one another only in configuration

around a single carbon atom are termed (A) Epimers (B) Anomers

(C) Optical isomers (D) Stereoisomers

10. Isomers differing as a result of variations in configuration of the —

OH and —H on carbon atoms 2, 3 and 4 of glucose are known as (A) Epimers (B) Anomers

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(C) Optical isomers (D) Steroisomers

11. The most important epimer of glucose is (A) Galactose (B) Fructose

(C) Arabinose (D) Xylose

12. α-D-glucose and β -D-glucose are

(A) Stereoisomers (B) Epimers

(C) Anomers (D) Keto-aldo pairs

13. α-D-glucose + 1120 → + 52.50 ← + 190 β-

D-glucose for glucose above represents (A) Optical isomerism (B) Mutarotation

(C) Epimerisation (D) D and L isomerism

14. Compounds having the same structural formula but differing in

spatial configuration are known as (A) Stereoisomers (B) Anomers

(C) Optical isomers (D) Epimers

15. In glucose the orientation of the —H and —OH groups around the

carbon atom 5 adjacent to the terminal primary alcohol carbon

determines (A) D or L series

(B) Dextro or levorotatory

(C) α and β anomers

(D) Epimers

Answer

1. A 2. A 3. A 4. A 5. B 6. A

7. A 8. D 9. A 10. A 11. A 12. C

13. B 14. A 15.

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Amino Acids Quiz

1. Which of the following is most found in protein molecule?

a. Carbon b. Hydrogen c. Oxygen d. Nitrogen

2. No of naturally occuring aminoacids is :

a. 10 b. 20 c. 30 d. 40

3. All of the following are aliphatic amino acids except :

a. Glycine b. Alanine c. Proline d. Lysine

4. One of the following is neutral amino acid :

a. Arginine b. Lysine c. Glutamine d. Valine

5. All of the following are hydroxy containing amino acids except :

a. Serine b. Threonine c. Valine d. Tyrosine

6. One of the following is optically non active amino acid

a. Valine b. Tyrosine c. Glycine d. Threonine

7. All of the following are polar amino acids except:

a. Serine b. Glutamate c. Arginine d. Alanine

8. All of the following are essential amino acids except :

a. Lysine b. Aspartate c. Tryptophan d. Hisitidine

9. Lysine:

a. Basic Only ketogenic b. Ketogenic glucogenic c. Acidic glucogenic

d. Non essential

10. All of the following are primary aminoacids except:

a. Cysteine b. Cystine c. Alanine d. Arginine

11. Which of the following is precursor of T3 and T4 :

a. GABA b. Dopa c. B- Alanine d. Di-iodotyrosine

12. Zwitter ion are:

a. Basic b. Acidic c. Neutral d. Carry both -ve & +ve charges e.

Both c and d

13. The unit of peptides is:

a. Moiety b. Residue c. Polypeptide d. Both a and b

14. Lactic acid is buffered by:

a. L.Carnosine b. Glutathione c. Casenogin d. Dopa

15. N terminal of glutathione is:

a. Glycine b. Cysteine c. Glutamate d. Aspartate

16. Which of the following is BLOOD iron carrier?

a. Haemoglobin b. Albumin c. Transferrin d. Globulin

17. Storage form of iron:

a. Transferrin b. Ferritin c. Myosin d. Actin

18. Which of the following protein is found in bone :

a. Keratin b. Ossein c. Mucin d. Actin

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19. Type of bonds between C terminal and N terminal is:

a. Covalent b. Disulphide bond c. Peptide d. Ionic e. Both a

and c

20. Type of bond between nitrogen and carbonyl group:

a. Hydrogen bonds b. Covalent bond c. Peptide bond d. Disulphide

bond

21. All of the following are non covalent except:

a. Hydrophobic interactions b. Disulphide bond

c. Hydrogen bond d. Electrostatic bond

22. Primary structure of proteins refers to:

a. Coiling and folding in form of specific structure

b. Number of amino acids in a chain

c. 3D structure d. Alpha and Beta sheets

23. Denaturation involves:

a. Peptide bonds b. Primary structure of protein c. Secondary

structure

d. Function e. Both c and d

24. Tertiary structure of proteins involves EXCEPT:

a. Domains b. Globular c. Fibrous d. Beta sheets

25. All of the following are simple proteins except :

a. Histones b. Albumin c. Keratins d. Glycoprotein

26. Which of the following is sulphur highly containing protein :

a. Collagen b. Keratin c. Ossein d. Reticulin

27. Casenogen is

a. Chromoprotein b. Phosphoprotein c. Glycoprotein d.

Lipoprotein

28. X-ray is a chemical agent for protein denaturation

a. True b. False

29. Increase viscosity of proteins is due to

a. Denaturation b. Isoelectric point c. Both d. None

30. Separation of low molecular weight protein from high one is:

a. Dialysis b. Cromotography c. Electrophoresis d.

Ultracentrifugation

31. Example of basic essential amino acids

a. Arginine b. Histidine c. Lysine d. All of the above

e. None of the above

32. Example of non-protein amino acid

79

a. Glycine b. Alanine c. Tryptophan d. All of the above e.

None of the above

33. Example of non-protein amino acid

a. Alanine b. Citrulline c. Phenylalanine d. Leucine

34. Glutathione is an example for

a. Amino acid b. Dipeptide c. Polypeptide d. Protein e.

Tripeptide

35. The active group of glutathione is

a. Amino group b. Sulfhydryl group c. Carboxylic group d. Imino

group e. Peptide linkage

36. The peptide bond is

a. Covalent bond b. Non-covalent bond c. Weak bond

37. First order of protein structure refers to

a. Bending of protein chain b. Number and sequence of amino acids

c. Three dimensional structure of protein d. Site of disulfide

bonds

e. Non-covalent bonds in protein molecule

38. Second order of protein structure refers to

a. Number and sequence of amino acids

b. Three dimensional structure of protein

c. Proteins formed of more than one monomer

d. Bending of protein molecule

e. Dependence on covalent bonds

39. Third structure of protein structure refers to

a. Number and sequence of amino acids

b. Three dimensional structure of protein

c. Proteins formed of more than one monomer

d. Bending of protein molecule

e. Dependence on covalent bonds

40. Fourth structure of protein structure refers to

a. Proteins formed of more than one monomer

b. Myoglobin is an example.

c. Depends on covalent bonds d. None of the above

e. All of the above

41. Covalent bond is a. A weak bond

b. A true chemical bond c. A hydrogen bond

d. Responsible for secondary structure of protein

81

e. Liable to be destroyed

42. Example of essential aromatic amino acids

a. Threonine b. Alanine c. Phenyl alanine d. Glycine e. Cysteine

43. Protein of high biological value

a. Contains essential amino acids b. Is poor in essential amino acids

c. Is of plant source d. Contains amino acid glycine e. Is a basic

protein

44. Albumin is

a. Insoluble in water

b. Heat coagulable protein c. A plant protein

d. A protein of low biological value

e. Poor in essential amino acids

45. Globulin is

a. A basic protein

b. A protein of low molecular weight

c. Heat coagulable protein

d. Easily soluble in water e. A fibrous protein

46. Keratin is

a. Protein of tendons b. Rich in sulfur

c. Poor in cysteine

d. Conjugated protein e. Soluble in water

47. Collagen contains high percentage of

a. Glycine b. Tryptophan c. Phenyl alanine d. Serine e. Valine

48. Caseinogen is

a. Simple protein b. Derived protein c. Phosphoprotein

d. Rich in sulfur containing amino acids e. Present in plasma

49. On electrophoresis for plasma proteins using buffer of pH 8.6

a. The proteins are neutral

b. The proteins carry negative charge

c. The proteins carry positive charge

d. The proteins are easily precipitated

e. The proteins are denaturated

50. Albumins are separated by

a. 1/2 saturated ammonium sulfate

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b. Full saturated ammonium sulfate

c. 20% saturated ammonium sulfate

d. 60% saturated ammonium sulfate

e. 10% saturated ammonium sulfate

51. Albumins and globulins are defined as:

a. Derived protein

b. Conjugated protein c. Fibrous protein

d. Globular protein e. Lipoprotein

52. Plasma proteins are separated by

a. Dialysis b. Electrophoresis c. Filtration d. Alcohol

precipitation

53. Example of essential sulphur containing amino acids

a. Lysine

b. Cysteine c. Cystine d. Alanine

e. Methionine

54. The bonds present in the primary structure of protein are

a. Peptide bonds

b. Hydrogen bonds c. Disulfide bonds d. All of these

55. A protein rich in proline and hydroxy proline is

a. Globin b. Collagen c. Casein d. Histone

56. The buffering property of proteins is due to the presence of

a. Acidic and basic groups

b. Hydrogen bonds c. Indole groups

d. Hyrophobic bonds

57. Arginine, lysine and ornithine are

a. Obtained by hydrolysis of proteins

b. Essential amino acids c. Basic amino acids

d. Derived from butyric acid

58. Glycine Is characterized by

a. Absence of an asymmeteric carbon

b. Absence of optical activity c. The shortest amino acid d. All of these

59. Ornithine is

a. A basic amino acid

b. An essential amino acid

c. Present in protein structure d. All of these

82

60. Albumin, globulin and casein are

a. Milk proteins

b. Plasma proteins c. Egg proteins

d. Meat proteins

61. Cysteine, cystine and methionine are

a. Essential amino acids

b. Present in protein structure c. Acidic amino acids

d. All of these

62. A protein that gives positive biuret test is

a. Albumin b. Globulin c. Casein d. All of these

63. A basic amino acid present in protein structure is

a. Histidine b. Citruline c. Ornithine d. All of these

64. Example of amino acid containing guanido group

a. Arginine b. Lysine

c. Histidine d. Valine e. Leucine

65. Keratin is

a. A scleroprotein b. Rich in cystine

c. A simple protein d. All of these

66. A fibrous protein is

a. Albumin b. Myosin

c. Casein d. Globulin 67. Glycine is

a. A non-optically active amino acid

b. Present in structure of glutathione

c. A neutral amino acid d. All of these

68. Proteins associated with nucleic acid in nucleo-protein are

a. Albumin b. Globulin c. Keratin d. Histones

69. ln proteins, the alpha-helix and Beta-pleated sheet are examples of

a. Primary structure

b. Secondary structure c. Tertiary structure

d. Quaternary structure

70. A tetra peptide contains the following number of preptide bonds

83

a. Two b. Three c. Four d. Five

71. A globular protein is

a. Actin b. Myosin c. Collagen d. Albumin

72. Example of branched amino acid

a. Valine b. Leucine c. Isoleucine d. All of the above e.

None of the above

73. Example of hydroxy containing amino acids

a. Serine b. Phenyl alanine c. Tryptophan d. Proline e.

Glutamic acid

74. Example of amino acids containing imino group

a. Glycine b. Valine c. Proline d. Lysine e. Phenyl alanine

75. Example of an amino acid containing sulfhydryl group

a. Alanine b. Cysteine c. Proline d. Tryptophan e. Lysine

76. Example of non-optically active amino acid

a. Proline b. Alanine c. Glycine d. Phenylalanine

77. Which of the following statements about amino acids is not true?

a. Amino acids are ampholytes

b. Amino acids are linked through peptide bonds to form proteins

c. Amino acids are not Crystalline compounds

d. Leucine is a purely ketogenic amino acid

78. The amino acids found in biological proteins are of:

a. D-Configuration and dextrorotatory

b. L-Configuration and levorotatory

c. D-Configuration and levo/dextrorotatory

d. L-Configuration and dextro/laevoratatory

79. Which amino acid doesn’t occur in proteins of biological system?

a. Ornithine b. Arginine c. Cystine d. Histidine

80. All amino adds are optically active except:

a. Serine b. Glycine c. Tryptophan d. Threonine '

81. Which of the following amino acids possesses an imino group?

a. Tryptophan b. Hydroxylysine c. Tyrosine d. Proline

82. An amino acid which contains a disulphide bond is:

a. Lysine b. Methionine c. Homocysteine d. Cystine

84

83. Chemically keratin is a:

a. Globulin b. Fibrous protein c. Tripeptide d. Conjugated protein

84. The most abundant protein in the human body is:

a. Collagen b. Keratin c. Myosin d. Albumin

85. Denaturation of proteins is often characterised by:

a. Loss of biological activity

b. Always being irreversible

c. Being greater the lower the temperature

d. Changes in primary structure

86. Decarboxylation of amino acids will result in the formation of:

a. Amines b. Imino acids

c. Basic amino acids d. Amides

87. The number of amino acid residues in one spiral of alpha- helix of

proteins is usually:

a. 2.6 b. 3.6 c. 4.6 d. 5.6

88. Which of the following is not found in proteins?

a. Citrulline b. Arginine

c. Methionine d. Cysteine

89. The only amino acid containing indole ring is:

a. Tryptophan b. Tyrosine c. Histidine d.

Phenylalanine

90. With the exception of glycine, all amino acids found in proteins are:

a. Optically active

b. Dextrorotatory

c. Of L-configuration d. Levorotatory

91. Essential amino acids are so named because:

a. They are essential for life process

b. Cannot be synthesized in the body

c. Deficiency leads to genetic diseases

d. Important in cell growth

92. Casein is a:

85

a. Lipoprotein b. Mucoprotein c. Phosphoprotein

d.Chromoprotein

93. Which is a basic amino acid?

a. Lysine b. Tyrosine c. Glycine d. Leucine

94. An amino acid containing imidazole group is:

a. lsoleucine b. Arginine c. Proline d. Histidine

95. The major linkage between amino acids in protein is the:

a. Hydrogen bond b. Ionic bond

c. Sulphide bond d. Peptide bond

96. An example of a chromoprotein is:

a. Casein b. Hemoglobin c. Peptone d. Collagen

97. When a peptide bond is formed there is removal of :

a. CO2 b. H2O c. NH3 d. H+

98. Aspartic acid is a (an):

a. Monoamino dicarboxylic acid

b. Diamino monocarboxylic acid

c. Aromatic amino acid

d. Imino acid

99. All amino acids are optically active except:

a. Glycine

b. Serine

c. Threonine

d. Tryptophan

100. Amino acid which synthesizes many hormones is:

a. Valine b. Phenylalanine c. Alanine d. Histidine

1. A 26. B 51. D 76. D

2. B 27. B 52. B 77. C

3. C 28. B 53. E 78. D

86

4. C 29. A 54. A 79. A

5. C 30. A 55. B 80. B

6. C 31. D 56. A 81. D

7. D 32. E 57. C 82. D

8. B 33. B 58. D 83. B

9. B 34. E 59. A 84. A

10. B 35. B 60. A 85. A

11. D 36. A 61. B 86. A

12. D 37. B 62. D 87. B

13. D 38. D 63. A 88. A

14. A 39. B 64. A 89. A

15. C 40. A 65. D 90. A

16. C 41. B 66. B 91. B

17. B 42. C 67. D 92. C

18. B 43. A 68. D 93. A

19. E 44. B 69. B 94. D

20. A 45. C 70. B 95. D

21. B 46. B 71. D 96. B

22. B 47. A 72. D 97. B

23. E 48. C 73. A 98. A

24. D 49. B 74. C 99. A

25. D 50. B 75. B 100.b