Chapter 5: Macromolecules

Macromolecules

• A large molecule in a living organism– Proteins, Carbohydrates, Nucleic Acids

• Polymer- long molecules built by linking repeating building blocks in a chain

• Monomer- units that serve as building blocks of polymer

Dehydration Synthesis- How cells link together monomers- Monomers have H atoms and hydroxyl groups- Add a monomer to a chain, a water molecule is released

Hydrolysis

- Opposite of dehydration synthesis- Bond in a polymer are broken by addition of water

1. Carbohydrates

Carbohydrates: include sugars and polymers of sugar

Monosaccharides: the simplest carbohydrate, made of a single sugar

Monosaccharides • The simplest carbohydrate made of a

single sugar

• Have molecular formulas multiple of CH20 (Most common sugar is glucose C6H1206)

• Have a hydroxyl group (OH) and a carbonyl group (C=0)

• OH group make it an alcohol and the C=0 make it an aldehyde or ketone

Fig. 5-3

Dihydroxyacetone

Ribulose

Ket

ose

sA

ldo

ses

Fructose

Glyceraldehyde

Ribose

Glucose Galactose

Hexoses (C6H12O6)Pentoses (C5H10O5)Trioses (C3H6O3)

• Though often drawn as linear skeletons, in aqueous solutions many sugars form rings

• Monosaccharides serve as a major fuel for cells (glucose)

• Most sugars end in -oseMonosaccharides (cont’d)

Disaccharide • A double sugar created when dehydration

synthesis joins

Ex: 2 glucose -> maltose (malt sugar makes beer)

• Glycosidic linkage: covalent bond between 2 sugars of a disaccharide

(b) Dehydration reaction in the synthesis of sucrose

Glucose Fructose Sucrose

MaltoseGlucoseGlucose

(a) Dehydration reaction in the synthesis of maltose

1–4glycosidic

linkage

1–2glycosidic

linkage

• Many act as storage molecules of sugar, that cells break down for energy

• Hundreds or thousands of monosaccharides joined together (glycosidic links)

Polysaccharide

Polysaccharide- Starch • Made of all glucose and found in plants

• Plants store starch and break into glucose when needed for energy

• Humans and animals hydrolyze starch when they eat it (found in wheat, corn, rice, potatoes)

• Glycogen is hydrolyzed to release glucose when needed

• Excess sugar in animals is stored as glycogen in liver and muscles

Polysaccharide- Glycogen

• A component of a plant’s cell wall, gives them structure

Polysaccharide- Cellulose

• Cellulose molecules connected by hydrogen bonds and form fiber

Fig. 5-9

• Chitin, another structural polysaccharide, is found in the exoskeleton of arthropods

• Chitin also provides structural support for the cell walls of many fungi

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig. 5-10

The structureof the chitinmonomer.

(a) (b) (c)Chitin forms theexoskeleton ofarthropods.

Chitin is used to makea strong and flexiblesurgical thread.

What does this say about their solubility?

• Compounds that consist mainly of C and H atoms linked by nonpolar covalent bonds

Lipid

• Ex: fats, oils, cholesterol, waxes

- a 3 carbon alcohol with hydroxyl group

• A large lipid made of glycerol and fatty acids

Fats

• Ex: fats, oils, waxes• 1 fat molecule = 1 glycerol and 3 fatty acids

• Function is energy storage (1 g of fat stores more than 2x as much energy as 1 g of starch)

Fig. 5-11

Fatty acid(palmitic acid)

Glycerol

(a) Dehydration reaction in the synthesis of a fat

Ester linkage

(b) Fat molecule (triacylglycerol)

• No double bond in fatty acid• Solids (lard, butter- animal fats)• Leads to heart disease, plaque in blood vessels

Saturated Fats

• the fatty acid contains double bonds, preventing the skeleton from having the max # of hydrogen’s.

• Molecules can’t pack together tightly and form liquids at room temp (oils and plant fats)

Unsaturated Fats

The Curious Case of Olestra

• A diet rich in saturated fats may contribute to cardiovascular disease through plaque deposits

• Hydrogenation is the process of converting unsaturated fats to saturated fats by adding hydrogen

• Hydrogenating vegetable oils also creates unsaturated fats with trans double bonds

• These trans fats may contribute more than saturated fats to cardiovascular disease

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

• Major component of cell membranes• Similar to fat, but contain phosphorus and have 2 fatty acid (not 3)

Phospholipids

Cholesterol

• Stabilizes cell membrane

• Helps resist temperature changes

• 1 fatty acid and an alcohol• More hydrophobic than fats• Natural coating on fruit• Insects have to keep from drying out

Waxes

• lipids whose carbon skeleton is bent to form 4 fused rings

• all steroids have 3-6 sided rings and 1-5 sided ring

• Ex: cholesterol found in animal cell membranes and animal cells use it to make other steroids (estrogen and testosterone)

Steroids

Fig. 5-15

Chapter 5: Macromolecules

http://www.youtube.com/watch?v=lijQ3a8yUYQ

Proteins

• Proteins account for more than 50% of the dry mass of most cells

• Protein functions include structural support, storage, transport, cellular communications, movement, and defense against foreign substances

Table 5-1

• Enzymes are a type of protein that acts as a catalyst to speed up chemical reactions

• Enzymes can perform their functions repeatedly being reused

Enzymes

Fig. 5-16

Enzyme(sucrase)

Substrate(sucrose)

Fructose

Glucose

OH

HO

H2O

Amino Acid Monomers

• Amino acids (monomers) build proteins (polymers)• Amino acids are organic molecules with carboxyl and amino groups• Amino acids differ in their properties due to differing side chains,

called R groups• THE R GROUP is the variable part of the amino acid and determines

physical and chemical properties

Fig. 5-UN1

Aminogroup

Carboxylgroup

carbon

Nonpolar

Glycine(Gly or G)

Alanine(Ala or A)

Valine(Val or V)

Leucine(Leu or L)

Isoleucine(Ile or )

Methionine(Met or M)

Phenylalanine(Phe or F)

Trypotphan(Trp or W)

Proline(Pro or P)

Polar

Serine(Ser or S)

Threonine(Thr or T)

Cysteine(Cys or C)

Tyrosine(Tyr or Y)

Asparagine(Asn or N)

Glutamine(Gln or Q)

Electricallycharged

Acidic Basic

Aspartic acid(Asp or D)

Glutamic acid(Glu or E)

Lysine(Lys or K)

Arginine(Arg or R)

Histidine(His or H)

Fig. 5-17c

Acidic

Arginine (Arg or R)

Histidine (His or H)

Aspartic acid (Asp or D)

Glutamic acid (Glu or E)

Lysine (Lys or K)

Basic

Electricallycharged

Amino Acid Polymers

• Amino acids are linked by peptide bonds between carbonyl and amino group

• A polypeptide is a polymer of amino acids

• Polypeptides range in length from a few to more than a thousand monomers

• Each polypeptide has a unique linear sequence of amino acids

Peptidebond

Fig. 5-18

Amino end(N-terminus)

Peptidebond

Side chains

Backbone

Carboxyl end(C-terminus)

(a)

(b)

Polypeptides

• Polypeptides are polymers built from the same set of 20 amino acids

• A protein consists of one or more polypeptides

Protein Structure and Function

• A functional protein consists of one or more polypeptides twisted, folded, and coiled into a unique shape

• The sequence of amino acids determines a protein’s three-dimensional structure

• A protein’s structure determines its function

• Primary structure, the sequence of amino acids in a protein, is like the order of letters in a long word

• Primary structure is determined by inherited genetic information

Primary Structure

• The coils and folds of secondary structure result from hydrogen bonds between repeating constituents of the polypeptide backbone (amino and carbonyl group

• Typical secondary structures are a coil called an alpha helix and a folded structure called a pleated sheet

Secondary Structure

• Tertiary structure is determined by interactions between R groups, rather than interactions between backbone constituents

• These interactions between R groups include hydrogen bonds, ionic bonds, hydrophobic interactions, and van der Waals interactions

• Strong covalent bonds called disulfide bridges may reinforce the protein’s structure

Tertiary Structure

Fig. 5-21e

Tertiary Structure Quaternary Structure

Fig. 5-21f

Polypeptidebackbone

Hydrophobicinteractions andvan der Waalsinteractions

Disulfide bridge

Ionic bond

Hydrogenbond

• Quaternary structure results when two or more polypeptide chains form one macromolecule

• Forms a “globular protein”

Quaternary Structure

Fig. 5-21g

Polypeptidechain

Chains

HemeIron

Chains

CollagenHemoglobin

Sickle-Cell Disease: A Change in

Primary Structure

• A slight change in primary structure can affect a protein’s structure and ability to function

• Sickle-cell disease, an inherited blood disorder, results from a single amino acid substitution in the protein hemoglobin

What Determines Protein Structure?

• In addition to primary structure, physical and chemical conditions can affect structure

• Alterations in pH, salt concentration, temperature, or other environmental factors can cause a protein to unravel

• This loss of a protein’s structure is called denaturation

• A denatured protein is biologically inactive

Fig. 5-23

Normal protein Denatured protein

Denaturation

Renaturation

The Roles of Nucleic Acids

• There are two types of nucleic acids:– Deoxyribonucleic acid (DNA)– Ribonucleic acid (RNA)

• DNA provides directions for its own replication

• DNA directs synthesis of messenger RNA (mRNA) and, through mRNA, controls protein synthesis

• Protein synthesis occurs in ribosomes

Fig. 5-26-3

mRNA

Synthesis ofmRNA in thenucleus

DNA

NUCLEUS

mRNA

CYTOPLASM

Movement ofmRNA into cytoplasmvia nuclear pore

Ribosome

AminoacidsPolypeptide

Synthesisof protein

1

2

3

The Structure of Nucleic Acids

• Nucleotides are monomers of DNA/RNA

• Each nucleotide consists of a nitrogenous base, a pentose sugar, and a phosphate group

Nucleotide Polymers

• Adjacent nucleotides are joined by covalent bonds

• These links create a backbone of sugar-phosphate units