CHAPTER 5The Structure and Function

of Macromolecules

What MacromoleculesCan you see inThis picture?

What makes you- you… or any organism on Earth

what it is? What four types of molecules are cells and organisms composed of?

Big Idea 1: The process of evolution drives the diversity and unity of life.

The origin of living systems is explained by natural processes.Molecular and genetic evidence from extant and extinct organisms indicates that all organisms on Earth share a common ancestral origin of life.

1. Scientific evidence includes molecular building blocks that are common to all life forms: glucose, amino acids, nucleotides, fatty acids + glycerol, ATP> ADP

2. Scientific evidence includes a common genetic code: DNA RNA Protein

PROTEIN

Carbo-hydratesLipids

Nucleic Acids

Photons + 6CO2 + 6H20 --> C6H12O6 + 6O2

C6H12O6 + 6 02 --> 6 CO2 + 6 H20 + 38 ATP

POLYMERS (macromolecules) &

MONOMERS (building blocks)

POLYMER =

A long molecule made of identical monomers linked together with covalent bonds.

Ex.DNA, RNA, Protein, Polysaccharides

THE CONDENSATION REACTION

aka DEHYDRATION SYNTHESIS

condensation rxn dehydration synthesis rxn

• A way to connect monomers together to build a larger molecule… polymer

• H is taken off of one monomer• OH is taken off a second monomer &• the monomers form a covalent bond.• Water is produced.• Covalent bond is formed between

monomers.

HOW WOULD YOU DO THE OPPOSITE REACTION???

What is it called?

Figure 5.2 The synthesis and breakdown of polymers

THE HYDROLYSIS REACTIONdissociation

The hydrolysis rxn =

• Hydro “water” + Lysis “to cut”• Breaking C-C bonds within a

polymer using water.• Split a water & add H and OH back

to the monomers.

Big Idea 4: Biological systems interact, and these systems and their

interactions possess complex properties.

• Interactions within biological systems lead to complex properties.

• Structure and function of polymers are derived from the way their monomers are assembled.

1. Carbohydrates are composed of sugar monomers whose structures and bonding with each other by dehydration synthesis determine the properties and functions of the molecules.

Ex. cellulose versus starch.

• ✘ The molecular structure of specific carbohydrate polymers is beyond the scope of the course and the AP Exam.

CARBOHYDRATES

• Contain the elements: C, H, O• Molecular ratio of elements: 1:2:1

1. MONOSACCHARIDES =simple sugars

PROPERTIES:• Hydrocarbon chains with hydroxyl groups• Polar molecules• General formula = (CH2O)n (n=3-7)• Role = fuel for cellular work (cellular respiration)• Serves as the carbon skeleton for other types of

monomers (ex. Amino acids)• Component of nucleotides (ribose/deoxyribose)

Hexose sugars: C6H12O6

1. Glucose- straight chain ALDEHYDE

2. Galactose-straight chain ALDEHYDE

3. Fructose-Straight chain KETONE

THE 3 MOST IMPORTANT:

Question:

These were branched diagrams… but when dissolved in water all three take on what form?

Answer: Ring

Q: how are these forms different???

A: Oxygen is in the “ring”… functional grps. Notice the bond is between the carbonyl on carbon 1 and the hydroxyl on carbon 5.

what is the importance of glucose?

Main fuel source to generate

energy (ATP) via cell respiration in the mitochondria

ATP

ADP

2. DISACCHARIDES-double sugar

• Comprised of: 2 monosaccharides• Bonded together via: a condensation

rxnglycosidic

linkage

2. DISACCHARIDES-double sugar

Types:a) Sucrose =

glucose + fructoseb) Maltose =

glucose + glucosec) Lactose =

glucose + galactose

SUCROSEIllustrative examples.

Figure 5.5x Glucose monomer and disaccharides

Glucose monomer

Sucrose

Maltose

3. POLYSACCHARIDES-complex carbohydrates• Polymerizationa) STARCHES = • glucose monomers bound repeatedly; • Short term energy storage for plants

inside plastids (ex. amyloplast)1) Amylose (unbranched)2) Amylopectin (branched)

b) GLYCOGEN =• highly branched & coiled glucose

monomer chains • Short term energy storage for

animals inside liver and muscle cells.

c) CELLULOSE =• Chains of beta glucose

monomers• Every other glucose is

upside down in the polymer

• Straight chain (fibers), never branched

• Cell walls of plants- structure only.

Figure 5.7x Starch and cellulose molecular models

Glucose Glucose

Starch

Cellulose

Why do animals have difficulty digesting cellulose?

• Animals lack the necessary enzyme to break the Beta linkages

• Cows overcame this problem by harboring bacteria that can break down cellulose.

Figure 5.x1 Cellulose digestion: termite and Trichonympha

Termites can do it to because of a symbiotic relationship

with this kind of protazoan…. Trichonympha.

d) CHITIN• Similar to cellulose (also contains N)• Used in cell walls of fungi and in the

exoskeletons of arthropods like:- insects- spiders- scorpions- lobsters, shrimp

“chitin is excitin’! “

LIPIDSContain the elements:C, H, O

Properites:• Little or no affinity for water

(hydrophobic)• Consist mostly of hydrocarbons and

some polar bonds with oxygen.• Smaller than true macromolecules (nucleic acids, proteins, carbohydrates)

1. Fats and Oils• One molecule of

fat is made of: - glycerol - fatty acids

• Triglyceride =- three fatty acids- one glycerol

nonpolar

long hydro-carbonchains are why fatsare hydrophobic!

GLYCEROL STRUCTURE• Alcohol• 3 carbon’s • each w/ hydroxyl grp.

FATTY ACID STRUCTURE• Acid• Long carbon skeleton (16-18 C’s long)• carboxyl grp. at one end

Figure 5.11 Examples of saturated and unsaturated fats and fatty acids 

No double bonds between carbon atoms.

Hydrogen bonded as much as possible onto the carbon skeleton.

“Saturated with hydrogens” = SATURATED FAT

Figure 5.11 Examples of saturated and unsaturated fats and fatty acids 

Double bonds exist between carbon atoms.

Formed by the removal of hydrogen from the carbon skeleton.

“Not saturated with hydrogens” = UNSATURATED FAT

Saturated FatsBADSolid at room tempAnimal fats

Unsaturated FatsGOODLiquid at room tempPlant & Fish fats

WHICH IS HEALTHIER TO COOK WITH/ EAT???

Diets rich in saturated fats contribute to Atherosclerosis-

• Cardiovascular disease

• Plaques develop inside blood vessels blocking flow and making them inelastic.

- heart attack, stroke,thrombosis

why are fats perfect for storage and energy?

• They are LIGHT! Which is important for animals & seeds.

• 1 gram of fat stores more than twice as much energy as a gram of polysaccharide.

2. PHOSPHOLIPIDS• The main component of cell

membranes.• Are comprised of :

a) two fatty acidsb) glycerolc) phosphate group (negative)

& various attachments• glycerol/phosphate is the

“HEAD”• two fatty acids are the “TAILS”

Phospholipid’s Key property:

• Ambivalent towards water.

• When placed in water they self assemble into clusters that shield the hydrophobic tails from the water.- micelle- phospholipid bilayer- coacervates

3. STEROIDS

• Basic structure: four fused rings.

• Vary in the functional groups attached to the rings.

EXAMPLES: A. CHOLESTEROL1) Component of animal cell membranes.2) Precursor to other steroids

sex hormones:B. ESTROGENC. PROGESTERONED. TESTOSTERONE

stress hormone:E. Cortisol

F. ANABOLIC steroids-Ex. TESTOSTERONEpromotes muscle growth and development

End. (part 1)

PROTEINS • Contain the elements:

C,H,N,O• The building blocks are:

AMINO ACIDS.• Account for > 50% of

the dry weight of most cells.

• Proteios, “first place”Fun fact:You should eat 9 grams of protein for every 20 pounds of body weight.

Protein functions:• Structural support

– Keratin, collagen, cytoskeleton of cells

• Storage – ex. albumin of egg whites

store amino acids

• Transport of substances– Membrane tunnels

• Signaling– Hormones like insulin,

oxytocin, glucagon

• Movement– Contractile proteins like actin

and SARCOMERE functional unitof a muscle cell… made of Actin and Myosin proteins

DEFENSEEx. Antibodies

ENZYMES

• Biological molecules that catalyze (increase the rates of) chemical reactions.

• The set of enzymes made in a cell determines the metabolic pathways that will occur there.

AMINO ACID STRUCTURE

• asymmetric carbon• Amino group• Carboxyl group• Hydrogen atom• R group (variable)

- side chain- 20 different ones- Polar, nonpolar, acidic, or basic

1.Proteins are POLYPEPTIDESThe peptide bond: Covalent bond between • the carboxyl group of one amino acid and • the amino group of another• Formed by a condensation rxn.

Proteins have an amino (NH2) end and a carboxyl (COOH) end, and consist of a linear sequence of amino acids connected by the formation of peptide bonds by dehydration synthesis between the amino and carboxyl groups of adjacent monomers.

2. SHAPES OF PROTEINS The specific order of amino acids in a polypeptide (primary

structure) interacts with the environment to determine the overall shape of the protein, which also involves secondary tertiary and quaternary structure and, thus, its function.

The four levels of protein structure.

2. SHAPES OF PROTEINS

A. PRIMARY STRUCTURE- unique sequence of amino acids (like the order of letters in a very long word)

A. SECONDARY STRUCTURE- coiled and folded patterns due to hydrogen bonds. Occurs between atoms attached to the backbone- but not R group.

1) a-helix- coil held by hydrogen bonding between every 4th amino acid.

Ex) keratin2) B-pleated sheet- cross-linkage between two or more regions that lie parallel to each other.

Ex) silk

C. TERTIARY STRUCTUREirregular contortions from interactions between R-groups (side chains)

1) hydrophobic/ van der waals interactions (nonpolar R-groups)2) hydrogen bonding (polar R-groups)3) disulfide bridge (s-s, from -SH R-groups)4) ionic bonding (+ & -)

TERTIARY STRUCTURE

The R group of an amino acid can be categorized by chemical properties:

hydrophobic hydrophilic and ionic.

and the interactions of these R groups determine structure and function of that region of the protein.

D. QUATERNARY STRUCTURE1) Triple Helix- three alpha helixes

ex. Collagen… rope-like

2) Globular- two or more polypeptide chains

ex. Hemoglobin… a & B chains

Figure 5.24 Review: the four levels of protein structure

What happens when a protein becomes denatured?• It loses its native conformation.• Is thus… biologically inactive. • ENVIRONMENT: pH, salt concentration, high

temperature, can unravel the protein.• Yes, proteins can become “renatured”.

Table 5.2 Polypeptide Sequence as Evidence for Evolutionary Relationships

NUCLEIC ACIDS: DNA & RNA (S&F)

DNA molecule is comprised of a series of nucleotides that can be linked together in various sequences; the resulting polymer carries hereditary material for the cell, including information that controls cellular activities.

Q: What is a double helix?A: two polynucleotides that spiral around an

imaginary axis. Double stranded.Q: What holds the double helix

together? A: hydrogen bonds between nitrogenous

bases hold the 2 strands together.Q: What are base pairs?A: bases that are compatible w/ e/o… that

hydrogen bond to eachother.1) Adenine - Thymine (2 H bonds)

2) Guanine - Cytosine (3 H bonds)

James Watson and Francis CrickRosalind Franklin

1.DNA• Unit of heredity. Enables living things to reproduce their

components from generation to generation. • Directs protein synthesis.• NUCLEOTIDE is the chemical building block

A. 5 carbon sugar: deoxyriboseB. Phosphate groupC. Nitrogen bases

1. Adenine, Guanine (purines: 2 rings)

2. Cytosine, Thymine (pyrimidines: 1 ring)

Figure 5.29 The components of nucleic acids

Figure 5.30 The DNA double helix and its replication

DNA is self-replicating

Complementary basepairing makes the precisecopying of DNA possible.

2. RNA* Molecules that function in the

synthesis of proteins!• 5 carbon sugar: RIBOSE• Phosphate group• Nitrogenous bases

1. Adenine, Guanine2. Cytosine, URACIL

* RNA is a single stranded molecule!

W/ your Partner

Compare and contrast DNA with RNA in terms of:

1) Structure2) Function3) Evolutionary Relationships

• THE END