Chapter 1 Biomolecules

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SBK1013Introduction to Biochemistry

CHAPTER 1: BIOMOLECULES

Learning Outcomes

State the common functional groups of

organic biomolecules

Describe major classes of biological molecules

Draw the general molecular structure of

biomolecules


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What is organic molecules?

Organic molecule is one that containsatoms of carbon and hydrogen

Organic molecules make up portions

of cells, tissues and organs

What is inorganic molecules?

Inorganic molecules does not contain carbon.

Water (H2O) and salt (NaCl) are examples of

inorganic molecule


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Carbon Atom and CarbonSkeleton

Carbon, with total of six electrons, has four electron

in the outer shell

To complete outer shell carbon atoms shares

electron with CHNOPS elements

Carbon chain of an organic molecule is called its

skeleton or backbone

Functional Groups

A functional group is a specific combination of

bonded atoms that always has the same chemical

properties

Therefore always react in the same way, regardless

of the particular carbon skeleton to which it is

attached

Functional group of organic molecule help to

determine its chemical properties


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Common Functional Groups

Functional Groups Found in

Hydroxyl Alcohol, sugars

Carboxyl Amino acids, fatty acid

Carbonyl Aldehydes, ketones

Amino Amino acids, proteins

Phosphate ATP, nucleic acids

Sulfhydryl Amino acids, cystein,

proteins


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Aldehydes: the carbonyl is placed at the end of a

carbon skeleton

Ketones: the carbonyl is placed between two carbon

atoms

Aldehydes vs Ketones

Carbonyl vs Carboxyl

Carbonyl: A carbon atom double bonded to an oxygen

atom

Carboxyl: A carbonyl (RR'C=O) and a hydroxyl (R-O-H),

which has the formula -C(=O)OH, usually written as -

COOH

CarbonylCarboxyl


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Major Classes of BiologicalMolecules

Carbohydrates

Lipids

Proteins

Nucleic Acids

Carbohydrates

Universally used as an immediate energy source

Carbohydrate can be found in the form of:

Monosaccharide a monomer of the carbohydrate

which is a single sugar molecule i.e glucose

Disaccharide two bonded sugar molecules

Polysaccharide- many sugar molecules bondedtogether


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Monosaccharide

All have the formula (CH2O)n,where n is between 3 and 7.

The most common & important

monosaccharide is glucose, which

is a six-carbon sugar.

It's formula is C6H12O6

Glucose forms a six-sided ring. The

six carbon atoms are numbered as

shown.

Glucose Isomers

There are many monosaccharides, with the same chemical

formula (C6H12O6), but different structural formulae. These

include fructose and galactose.

Glucose (C6H12O6)

(anan aldehydealdehyde)Fructose (C6H12O6)

(aa ketoneketone))

Galactose (C6H12O6)

(anan aldehydealdehyde)


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Glucose Isomers

Common five-carbon sugars (where n = 5, C5H10O5) include

ribose and deoxyribose (found in nucleic acids and ATP).


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Disaccharide

Disaccharides areformed when two

monosaccharides

are joined together

by a glycosidic

bond.

The reaction

involves the

formation of a

molecule of water(H2O)

Disaccharide

Two monosaccharide

bonded together

Sucrose derived from sugar

beet and sugar cane

Lactose found in milk

Maltose derived from barley


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Polysaccharide

Polysaccharides are long chains of many monosaccharides joinedtogether by glycosidic bonds.

There are three important polysaccharides:

i. Starch

Plant storage polysaccharide.

Consist of amylose and amylopectin.

Ii. Glycogen

Contain similar structure to amylopectin.

It is made by animals as their storage polysaccharide, and is found

mainly in muscle and liver. Iii. Cellulose

Only found in plants, where it is the main component of cell walls

Starch

amylose

amylopectin

Glycogen

Cellulose


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Lipids Lipids contain fats and oils (fats are solid at room

temperature, whereas oils are liquid)

Triglycerides

Triglycerides are commonly called fats or oils.

They are made of glycerol and fatty acids.

Glycerol is a small, 3-carbon molecule with three hydroxyl

groups.

Fatty acids are long molecules with a polar, hydrophilic end

and a non-polar, hydrophobic "tail"


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Triglyceride molecule

Insoluble in water

The structure can pack a lot of energy into one molecule

Long term energy storage

Saturated vs Unsaturated Fatty Acids Saturated fatty acid

No C=C double bonds in the hydrocarbon chain,

These fatty acids form straight chains, and have a high melting

point.

Unsaturated fatty acid

There are C=C double bonds in the hydrocarbon chain

These fatty acids form bent chains, and have a low melting point.

Fatty acids with more than one double bond are called poly-

unsaturated fatty acids


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Proteins

Proteins are made of amino

acids.

Amino acids are made of the

five elements C H O N S.

The general structure of an

amino acid consists of:

hydrogen atom

amino group

carboxyl group

a variable "R" group (or side

chain)

Amino Acids There are 20 different R groups, and so 20 different amino

acids.

Since each R group is slightly different, each amino acid has

different properties.

Example:


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Polypetides

Amino acids are joined together by peptide bonds When two amino acids join together a dipeptide is formed.

Three amino acids form a tripeptide.

Many amino acids form a polypeptide.

Nucleic Acids

Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are the

nucleic acids in cells.

Nucleic acids are polymer in which the monomer is called a

nucleotide.

DNA or RNA, both consists of:

A phosphate

A 5-carbon sugar

Nitrogen containing base


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DNA vs RNA

DNA RNA

Sugar Deoxyribose Ribose

Bases A, G, C, T A, G, C, U

Strand Double

stranded

Single

stranded

Helix Yes No

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Chapter 1 Biomolecules