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LECTURE PRESENTATIONSFor CAMPBELL BIOLOGY, NINTH EDITION

Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson

© 2011 Pearson Education, Inc.

Lectures byErin Barley

Kathleen Fitzpatrick

The Structure and Function of Large Biological Molecules

Chapter 5

Overview: The Molecules of Lifefour classes of large biological molecules:

carbohydrates - polymer

lipids proteins - polymer

nucleic acids - polymer

Polymer: made of many small parts

each part is a monomer

Many biological molecules are polymers

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Figure 5.UN02

Overview: The Molecules of Life

• Macromolecules = big molecules

usually a polymer

• Molecular structure and function are linked

» Change the structure or shape of a molecule and you will destroy it’s function

» “denature” = changing shape of molecule (protein) so that it doesn’t work anymore

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• dehydration reaction: making bonds (synthesizing a molecule) by taking away water

The Synthesis and Breakdown of Polymers

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Animation: Polymers

• Breaking a polymer apart hydrolysis, a reaction that is essentially the reverse of the dehydration reaction

The Synthesis and Breakdown of Polymers

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Animation: Polymers

The Diversity of Polymers

• Macromolecules – many thousands of kinds– Species differences– Individual differences– Cell differences within organism

• small set of monomers can make MANY kinds of monomers– A small set of letter make MANY different words

HO

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Concept 5.2: Carbohydrates serve as fuel and building material

• Carbohydrates - sugars and their polymers• “saccharides” – sugars• monosaccharides

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Concept 5.2: Carbohydrates serve as fuel and building material

• Carbohydrates - sugars and their polymers• “saccharides” – sugars• Monosaccharides – 1 sugar• Disaccharide – molecule made of 2 sugars

• Polysaccharides – long chains of sugar monomers

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Sugars

• Monosaccharides - CH2O-like formula

• Glucose (C6H12O6) is the most common

• Monosaccharides are classified by – The number of carbons in the carbon skeleton

– The location of the carbonyl group (as aldose or ketose)

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

• Monosaccharides (especially glucose) serve as a major fuel for cells and as raw material for building molecules

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• A disaccharide is formed when a dehydration reaction joins two monosaccharides

• This covalent bond is called a glycosidic linkage

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Animation: Disaccharide

Polysaccharides

• Polysaccharides - storage and structural roles

• Polysaccharide structure and function

which sugar monomers

position of glycosidic linkages

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Storage Polysaccharides• Starch, a storage polysaccharide of plants, consists

entirely of glucose monomers

• Plants store surplus starch as granules within chloroplasts and other plastids

• The simplest form of starch is amylose

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• Glycogen is a storage polysaccharide in animals

• Humans and other vertebrates store glycogen mainly in liver and muscle cells

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Structural Polysaccharides

• The polysaccharide cellulose is a major component of the tough wall of plant cells

• Like starch but the glycosidic linkages differ– Why we can’t digest cellulose

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Animation: Polysaccharides

Cell wall

Microfibril

Cellulosemicrofibrils in aplant cell wall

Cellulosemolecules

Glucosemonomer

10 m

0.5 m

Figure 5.8

• Enzymes that digest starch by hydrolyzing linkages can’t hydrolyze linkages in cellulose

• Cellulose in human food passes through the digestive tract as insoluble fiber

• Some microbes use enzymes to digest cellulose

• Many herbivores, from cows to termites, have symbiotic relationships with these microbes

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• Chitin: structural polysaccharide of animals– exoskeleton of arthropods– cell walls of many fungi

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Concept 5.3: Lipids are a diverse group of hydrophobic molecules

• Lipids – NOT A POLYMER• hydrophobic (non-polar covalent bonds)• 3 kinds of lipids in biology

– fats, phospholipids, and steroids

• Water dissolves things it can make polar bonds with. Has trouble bonding with lipids.

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Fats: glycerol + fatty acids

• water molecules bonds to water, excluding the fats

• In a fat, three fatty acids are joined to glycerol by an ester linkage, creating a triacylglycerol, or triglyceride

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• Saturated fatty acids

• maximum number of hydrogen atoms

• no double bonds

• Usually solid at room temp

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Animation: Fats

• Unsaturated fatty acids have one or more double bonds

• Each double bond causes a kink in the chain

• Usually liquid at room temp

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Animation: Fats

• Cis vs. Trans

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• Essential fatty acids– We can’t make them (must get from food; omega-3)

– Used in normal growth

– Protect against cardiovascular disease??

• Fats are used for energy storage

– Stored in adipose tissue

– Also cushion’s organs

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Phospholipids

• Glycerol + phosphate + two fatty acidsHydrophilic hydrophobic

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• The fatty acid tails are hydrophobic• The heads are hydrophilic

• Tails point away from water• The major component in membranes

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Steroids• Steroids are lipids made of four carbon rings

• Cholesterol, an important steroid, is a component in animal cell membranes

• Although cholesterol is essential in animals, high levels in the blood may contribute to cardiovascular disease

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Steroids• Steroids are lipids made of four carbon rings• Some hormones are steroids

• Cholesterol, is also a steroid– Used in animals membranes, but high levels in blood may

contribute to cardiovascular disease

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Concept 5.4: Proteins include a diversity of structures, resulting in a wide range of functions

• Used for EVERYTHING• structural support, storage, transport, cellular

communications, movement, and defense against foreign substances

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

• If you change the shape, the protein stops working.

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• Enzymes: proteins that speed up chemical reactions (acts as a catalyst)

• Enzymes can perform their functions repeatedly, functioning as workhorses that carry out the processes of life

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Animation: Enzymes

•Shape is crucial to enzyme function

•If you denature it, the enzyme stops working

Figure 5.15-a

Enzymatic proteins Defensive proteins

Storage proteins Transport proteins

Enzyme Virus

Antibodies

Bacterium

Ovalbumin Amino acidsfor embryo

Transportprotein

Cell membrane

Function: Selective acceleration of chemical reactions

Example: Digestive enzymes catalyze the hydrolysisof bonds in food molecules.

Function: Protection against disease

Example: Antibodies inactivate and help destroyviruses and bacteria.

Function: Storage of amino acids Function: Transport of substances

Examples: Casein, the protein of milk, is the majorsource of amino acids for baby mammals. Plants havestorage proteins in their seeds. Ovalbumin is theprotein of egg white, used as an amino acid sourcefor the developing embryo.

Examples: Hemoglobin, the iron-containing protein ofvertebrate blood, transports oxygen from the lungs toother parts of the body. Other proteins transportmolecules across cell membranes.

Figure 5.15-b

Hormonal proteins

Function: Coordination of an organism’s activities

Example: Insulin, a hormone secreted by thepancreas, causes other tissues to take up glucose,thus regulating blood sugar concentration

Highblood sugar

Normalblood sugar

Insulinsecreted

Signalingmolecules

Receptorprotein

Muscle tissue

Actin Myosin

100 m 60 m

Collagen

Connectivetissue

Receptor proteins

Function: Response of cell to chemical stimuli

Example: Receptors built into the membrane of anerve cell detect signaling molecules released byother nerve cells.

Contractile and motor proteins

Function: Movement

Examples: Motor proteins are responsible for theundulations of cilia and flagella. Actin and myosinproteins are responsible for the contraction ofmuscles.

Structural proteins

Function: Support

Examples: Keratin is the protein of hair, horns,feathers, and other skin appendages. Insects andspiders use silk fibers to make their cocoons and webs,respectively. Collagen and elastin proteins provide afibrous framework in animal connective tissues.

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Animation: Structural Proteins

Animation: Storage Proteins

Animation: Transport Proteins

Animation: Receptor Proteins

Animation: Contractile Proteins

Animation: Defensive Proteins

Animation: Hormonal Proteins

Animation: Sensory Proteins

Animation: Gene Regulatory Proteins

Amino Acids: protein building blocks

• Amino acids are organic molecules with carboxyl and amino groups

• Amino acids differ in their properties due to differing side chains, called R groups

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Figure 5.16Nonpolar side chains; hydrophobic

Side chain(R group)

Glycine(Gly or G)

Alanine(Ala or A)

Valine(Val or V)

Leucine(Leu or L)

Isoleucine (Ile or I)

Methionine(Met or M)

Phenylalanine(Phe or F)

Tryptophan(Trp or W)

Proline(Pro or P)

Polar side chains; hydrophilic

Serine(Ser or S)

Threonine(Thr or T)

Cysteine(Cys or C)

Tyrosine(Tyr or Y)

Asparagine(Asn or N)

Glutamine(Gln or Q)

Electrically charged side chains; hydrophilic

Acidic (negatively charged)

Basic (positively charged)

Aspartic acid(Asp or D)

Glutamic acid(Glu or E)

Lysine(Lys or K)

Arginine(Arg or R)

Histidine(His or H)

Polypeptides: a chain of amino acids

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

• A protein has one or more polypeptides

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Polypeptide: Amino Acid Polymers

• can be short or more than a thousand monomers

• Each polypeptide has a carboxyl end (C-terminus) and an amino end (N-terminus)

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Four Levels of Protein Structure

• The primary structure of a protein is its unique sequence of amino acids

• Secondary structure, found in most proteins, consists of coils and folds in the polypeptide chain

• Tertiary structure is determined by interactions among various side chains (R groups)

• Quaternary structure results when a protein consists of multiple polypeptide chains

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Animation: Protein Structure Introduction

• A protein’s structure determines its function

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

• Primary structure, the sequence of amino acids in a protein

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• 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

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Animation: Primary Protein Structure

• secondary structure: 3-D shape in local regions of peptide chain

• Caused by hydrogen bonds between parts of the polypeptide backbone

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

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Animation: Secondary Protein Structure

• Tertiary structure is determined by interactions between R groups– hydrogen bonds– ionic bonds– hydrophobic interactions– Van der Waals interactions

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Animation: Tertiary Protein Structure

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

Quaternary structure: if there is more than one polypeptide chains in protein

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Animation: Quaternary Protein Structure

•Collagen is a fibrous protein consisting of three polypeptides coiled like a rope

•Hemoglobin is a globular protein consisting of four polypeptides: two alpha and two beta chains

Sickle-Cell Disease: A Change in Primary Structure

• Changing the primary structure can change the shape and function of a protein

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

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Figure 5.21

PrimaryStructure

Secondaryand TertiaryStructures

QuaternaryStructure Function Red Blood

Cell Shape

subunit

subunit

Exposedhydrophobicregion

Molecules do notassociate with oneanother; each carriesoxygen.

Molecules crystallizeinto a fiber; capacityto carry oxygen isreduced.

Sickle-cellhemoglobin

Normalhemoglobin

10 m

10 m

Sic

kle-

cell

hem

og

lob

inN

orm

al h

emo

glo

bin

1

23

456

7

1

23

456

7

What Determines Protein Structure?

• The chemical environment affects a protein• Changing pH, salt concentration, temperature,

or other environmental factors can cause a protein to unravel

• Denature: changing a protein away from its natural shape

• A denatured protein is biologically inactive• Alzheimer’s • Parkinson’s• Mad cow disease

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Protein Folding in the Cell

• It is hard to predict a protein’s structure from its primary structure

• Most proteins probably go through several stages on their way to a stable structure

• Chaperonins are protein molecules that assist the proper folding of other proteins

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Concept 5.5: Nucleic acids store, transmit, and help express hereditary information

• a nucleic acid polymer is made of monomers called nucleotides

• Genes are instructions written in DNA (many genes on each chromosome)

• The DNA sequence of a gene has instructions to make a polypeptide

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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 on ribosomes

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Figure 5.25-3

Synthesis ofmRNA

mRNA

DNA

NUCLEUSCYTOPLASM

mRNA

Ribosome

AminoacidsPolypeptide

Movement ofmRNA intocytoplasm

Synthesisof protein

1

2

3

The Components of Nucleic Acids

• Nucleic acids are chains of nucleotides– pentose sugar– phosphate groups – a nitrogenous base

• Nucleoside: nucleotide without phosphate

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The Components of Nucleic Acids

• Nucleic acids are chains of nucleotides– a nitrogenous base– phosphate groups – pentose sugar

• Nucleoside: nucleotide without phosphate

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• Nucleoside = nitrogenous base + sugar

• There are two families of nitrogenous bases

– Pyrimidines (cytosine, thymine, and uracil) have a single six-membered ring

– Purines (adenine and guanine) have a six-membered ring fused to a five-membered ring

• In DNA, the sugar is deoxyribose; in RNA, the sugar is ribose

• Nucleotide = nucleoside + phosphate group

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Nucleotide Polymers

• Nucleotide polymers are linked together to build a polynucleotide

• Adjacent nucleotides are joined by covalent bonds that form between the —OH group on the 3 carbon of one nucleotide and the phosphate on the 5 carbon on the next abc…lmnop

• sugar-phosphate backbone (side of ladder) with nitrogenous bases as rungs of ladder

• The sequence of bases along a DNA or mRNA polymer is the genetic code, the instructions – unique for each gene

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The Structures of DNA and RNA Molecules

• RNA molecules usually exist as single polypeptide chains (exception: some viruses)

• DNA molecules have two chain, – forming a double helix (twisty ladder)

• Antiparallel: DNA strands in opposite directions

• One DNA molecule includes many genes

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DNA• adenine (A) thymine (T)• guanine (G) cytosine (C)

RNA• adenine (A) Uracil (U)• guanine (G) cytosine (C)

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complementary base pairing

Figure 5.27

Sugar-phosphatebackbones

Hydrogen bonds

Base pair joinedby hydrogen bonding

Base pair joinedby hydrogen

bonding

(b) Transfer RNA(a) DNA

5 3

53

DNA and Proteins as Tape Measures of Evolution

• DNA sequences: parents offspring• closely related species have more similar DNA

than distantly related species• Molecular biology is used to assess evolutionary

kinship

• Why people are fighting about protista right now

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The Theme of Emergent Properties in the Chemistry of Life: A Review

• Higher levels of organization result in the emergence of new properties

• Organization is the key to the chemistry of life

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Figure 5. UN12

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