CHAPTER 5The Structure and Function of

Macromolecules

“You are what you eat!”

What does it mean to be a MACROmolecule?

You must be a Large molecule You have a complex structure

“little” moleculeMacromolecule

I. Most macromolecules are polymers, built from monomers

What is a polymer?• Poly = many; mer = part. • A long molecule made of monomers

bonded together What is a monomer?

• A monomer is a sub-unit of a polymer.

Three of the classes of life’s organic molecules are polymers• Carbohydrates, Proteins, Nucleic acids

A. Making and Breaking Polymers

How do monomers bind to form polymers?• condensation reactions called

dehydration synthesis (removal of water)

How can polymers break down when monomers are needed?

Hydrolysis reaction• Hydro = water; lysis = break• Water is added and the lysis of the

polymer occurs.

Hydrolysis

II. Classes of Organic Molecules:

• Carbohydrates• Lipids• Proteins• Nucleic Acids

A. CARBOHYDRATES

What are Carbohydrates?• Sugars and their polymers• Carbo = carbon, hydrate = water;

carbohydrates have the molecular formula (CH2O)n

Functions of Carbohydrates in living things:• Major fuel/energy source• Can be used as raw materials for other

Macromolecules• Complex sugars = building material in

plants What is the Carbohydrate Monomer?

• Monosaccharide (“mono” = one; “saccharide” = sugar)

1. Structure of Monosaccharides Contain only C, H, O Hydroxyl group is attached to each carbon One carbon contains a carbonyl group

• Classified according to the size of their carbon chains and location of Carbonyl group

In aqueous solutions many monosaccharides form rings:

2. Structure of Disaccharides

Consist of two monosaccharides Are joined by a glycosidic linkage What reaction forms the glycosidic linkage?

• Dehydration synthesis

3. Polysaccharides

Structure: Polymers of a few hundred or a few thousand monosaccharides.

Functions: energy storage molecules or for structural support:

Starch is a plant storage form of energy, easily hydrolyzed to glucose units

Cellulose is a fiber-like structural material made of glucose monomers used in plant cell walls

Why is Cellulose so strong? Glucose monomers are flipped to expose equal

Hydroxyl groups on either side of the chain When Cellulose chains are lined up next to each other,

they Hydrogen Bond making a strong material that’s difficult to break!

Glycogen is the animal short-term storage form of energy

Glucose monomers

Chitin is a polysaccharide used as a structural material in arthropod exoskeleton and fungal cell walls.

B. LIPIDS What are Lipids?• Fats, phospholipids, steroids, waxes, pigments• Hydrophobic (“hydro”=water; “phobic” = fearing)• Consist mostly of hydrocarbons• Do NOT consist of polymers

Functions of Lipids in living things:• Energy storage • membrane structure• Protecting against desiccation

(drying out). • Insulating against cold.• Absorbing shocks. • Regulating cell activities by

hormone actions.

1. Structure of Fats (Triglycerides) Consist of a single glycerol and usually three

fatty acids Glycerol – an alcohol with three carbons Fatty Acid - Long Hydrocarbon chains with a

Carboxyl group at one end.

Saturated and Unsaturated Fats

Unsaturated fats :• one or more double bonds

between carbons in the fatty acids allows for “kinks” in the tails

• liquid at room temp• most plant fats

Saturated fats:• No double bonds in fatty

acid tails• solid at room temp• most animal fats

(a) Saturated fat and fatty acid

Stearic acid

(b) Unsaturated fat and fatty acidcis double bondcauses bending

Oleic acid

Saturated fatty acid

Saturated fatty acid

Unsaturated fatty acid

Why are Unsaturated Fats better for you than Saturated Fats?

3. Phospholipids Structure: Glycerol + 2 fatty acids +

phosphate group. Function: Main structural component of

membranes, where they arrange in bilayers.

Phospholipids in Water

4. Waxes

Function:• Lipids that serve as coatings for

plant parts and as animal coverings.

5. Steroids Structure: Four carbon rings with no fatty acid

tails Functions:

• Component of animal cell membranes (Ex: Cholesterol)

• Modified to form sex hormones

PROTEINS

C. Proteins

What are Proteins?• Chains of amino acid monomers connected

by peptide bonds• Have a 3 dimensional globular shape

Examples of Protein Functions Immune System

• Binding of antibodies (proteins) to foreign substances

Transport• Membrane transport proteins that move substances

across cell membranes• Hemoglobin carries oxygen, iron, and other

substances through the body. Muscle Contraction

• actin and myosin fibers that interact in muscle tissue.

Signaling• Hormones such as insulin regulate sugar levels in

blood.

Amino Acids

Monomers of polypeptides• Molecules with carboxyl and amino

groups• Differ in their properties due to differing

side chains, called R groups

20 different amino

acids existThe sequence of amino acids and the interactions of the different amino acids determine a proteins shape

Peptide bonds connect amino acids to form polypeptide chains

One or more polypeptide chains make up a protein

Proteins are very complex! Their specific structure determines their

function.

HEMOGLOBIN: Transport of gases and iron in blood ACTIN: Filament involved in

muscle contraction

Four Levels of Protein Structure

Primary structure• Is the unique

sequence of amino acids in a polypeptide

Figure 5.20–

Amino acid subunits

+H3NAmino end

oCarboxyl end

oc

GlyProThrGlyThr

Gly

GluSeuLysCysProLeu

MetVal

Lys

ValLeu

AspAlaVal ArgGly

SerPro

Ala

Gly

lle

SerProPheHisGluHis

Ala

GluVal

ValPheThrAlaAsn

AspSer

GlyProArg

ArgTyrThr

lleAla

Ala

Leu

LeuSer

ProTyrSerTyrSerThr

Thr

Ala

ValVal

ThrAsnProLysGlu

ThrLys

SerTyrTrpLysAlaLeu

GluLle Asp

O C α helix

β pleated sheet

Amino acidsubunits NC

H

C

O

C NH

CO

H

R

C N

H

C

O H

C

R

NH

H

R C

O

R

C

H

N

H

C

OHN

CO

R

C

H

N

H

HC

R

C

O

C

O

C

N

HH

R

C

C

O

NH

H

C

R

C

O

N

H

R

C

HC

ONH

H

C

R

C

O

N

H

R

C

H C

ONH

H

C

R

C

O

N H

H C R

N H O

O C N

C

RC

HO

CH R

N H

O C

RC H

N H

O C

H C R

N H

CC

N

RH

O C

H C R

N H

O C

RC H

HC

RNH

CO

C

N

H

R

C

HC

O

NH

C

Secondary structure• Is the folding or coiling of the polypeptide

into a repeating configuration resulting from hydrogen bonding of amino with carboxyl groups

• Includes the α helix and the β pleated sheet

H H

Figure 5.20

Tertiary structure• Is the overall three-dimensional shape

of a polypeptide• Results from interactions between

amino acids and R groups

CH2CH

OH

O

CHO

CH2

CH2 NH3+ C-O CH2

O

CH2SSCH2

CH

CH3

CH3

H3C

H3C

Hydrophobic interactions and van der Waalsinteractions

Polypeptidebackbone

Hydrogenbond

Ionic bond

CH2

Disulfide bridge

Quaternary structure• Is the overall protein structure that results

from the aggregation of two or more polypeptide subunits

Chaperonins• Are protein molecules that assist in the

proper folding of other proteins

Hollowcylinder

Cap

Chaperonin(fully assembled)

Steps of ChaperoninAction: An unfolded poly- peptide enters the cylinder from one end.

The cap attaches, causing the cylinder to change shape insuch a way that it creates a hydrophilic environment for the folding of the polypeptide.

The cap comesoff, and the properlyfolded protein is released.

Correctlyfoldedprotein

Polypeptide

2

1

3

Figure 5.23

Sickle Cell Disease: A simple change in Primary Structure

Enzymes Are a type of protein that acts as a catalyst,

speeding up chemical reactions up to 10 billion times faster than they would spontaneously occur.

Environmental Factors That Determine Protein Conformation

Change in environment may lead to denaturation of protein (pH, temperature, salinity, etc.)

Denatured protein is biologically inactive Can renature if primary structure is not lost

NUCLEIC ACIDS

D. Nucleic Acids : The stuff of Genes

Nucleic acids store and transmit hereditary information

Genes• Are the units of inheritance• Program the amino acid sequence of

polypeptides• Are made of nucleic acids

Two Kinds of Nucleic Acids DNA (Deoxyribonucleic acid)

• double stranded• can self replicate• makes up genes which code for

proteins is passed from one generation to another

RNA (Ribonucleic acid)

• single stranded • functions in actual synthesis of

proteins coded for by DNA• is made from the DNA template

molecule

1. Nucleotide Monomer Structure

Both DNA and RNA are composed of nucleotide monomers.

Nucleotide = 5 carbon sugar, phosphate, and nitrogenous base

Deoxyribose in DNA Ribose in RNA

2. Building the Polymer Phosphate group of one nucleotide forms

strong covalent bond with the #3 carbon of the sugar of the other nucleotide.

DNA:

• Double helix

• 2 polynucleotide chains wound into the double helix

• Base pairing between chains with H bonds

• A - T

• C - G

Summary of the Organic Molecules: