Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule...

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Macromolecules Ch. 5

Transcript of Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule...

Page 1: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Macromolecules

Ch. 5

Page 2: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Macromolecules are polymers, built from monomers

• A polymer is a long molecule consisting of many similar building blocks

• These small building-block molecules are called monomers

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

Page 3: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Glucose is a monomer

• Make a ball and stick glucose model.• C6H12O6

Page 4: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

• Combine your glucose model with another glucose model at the #1 Carbon of one model and the #4 Carbon of the other model.

• What must occur?

Page 5: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

• A condensation reaction or dehydration reaction occurs when two monomers bond together through the loss of a water molecule

• Enzymes are macromolecules that speed up the dehydration process

The Synthesis of Polymers

Page 6: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-2a

Dehydration removes a watermolecule, forming a new bond

Short polymer Unlinked monomer

Longer polymer

Dehydration reaction in the synthesis of a polymer

HO

HO

HO

H2O

H

HH

4321

1 2 3

(a)

Page 7: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

The Breakdown of Polymers

• Polymers are disassembled to monomers by hydrolysis, a reaction that is essentially the reverse of the dehydration reaction

Page 8: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-2b

Hydrolysis adds a watermolecule, breaking a bond

Hydrolysis of a polymer

HO

HO HO

H2O

H

H

H321

1 2 3 4

(b)

Page 9: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

The Diversity of Polymers

• Each cell has thousands of different kinds of macromolecules

• Macromolecules vary among cells of an organism, vary more within a species, and vary even more between species

• An immense variety of polymers can be built from a small set of monomers

2 3 HOH

Page 10: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Carbohydrates

• Carbohydrates – sugars and the polymers of sugars

• Monosaccharides - single sugars

• Polysaccharides - polymers composed of many sugar building blocks

Page 11: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Monosaccharide Structure

• Monosaccharides have molecular formulas that are usually multiples of CH2O

• Glucose (C6H12O6) is the most common monosaccharide

• Monosaccharides are classified by – The location of the carbonyl group

• aldose • ketose

– The number of carbons in the carbon skeleton

Page 12: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-3

Dihydroxyacetone

Ribulose

Ket

ose

sA

ldo

ses

Fructose

Glyceraldehyde

Ribose

Glucose Galactose

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

Page 13: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

• What 2 functional groups are the trademarks of a sugar molecule?

• Functional groups of sugars:– Carbonyl groups– Hydroxyl groups

Page 14: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-4a

(a) Linear and ring forms

•In aqueous solutions many sugars form rings

Page 15: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Monosaccharide Function

• Monosaccharides serve as a major fuel for cells and as raw material for building molecules

Page 16: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Disaccharide Structure

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

• This covalent bond is called a glycosidic linkage

Page 17: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-5

Glucose Fructose Sucrose

MaltoseGlucoseGlucose

1–4glycosidic

linkage

1–2glycosidic

linkage

Page 18: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Polysaccharides

• Polysaccharides– polymers of sugars– Function: storage and structural

• The structure and function of a polysaccharide are determined by – its sugar monomers – the positions of glycosidic linkages

Page 19: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Storage Polysaccharides

• Starch– a storage polysaccharide of plants– consists entirely of glucose monomers

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

Page 20: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Storage Polysaccharides

• Glycogen – a storage polysaccharide in animals

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

Page 21: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-6

(b) Glycogen: an animal polysaccharide

Starch

GlycogenAmylose

Chloroplast

(a) Starch: a plant polysaccharide

Amylopectin

Mitochondria Glycogen granules

0.5 µm

1 µm

Page 22: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Structural Polysaccharides

• Cellulose– major component of the tough wall of plant cells

– a polymer of glucose • the glycosidic linkages differ from that of starch• difference is based on two ring forms for glucose:

alpha () and beta ()

Page 23: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-7

(a) and glucose ring structures

Glucose Glucose

(b) Starch: 1–4 linkage of glucose monomers (b) Cellulose: 1–4 linkage of glucose monomers

Page 24: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

• Polymers with glucose are helical

• Polymers with glucose are straight

• In straight structures, H atoms on one strand can bond with OH groups on other strands

• Parallel cellulose molecules held together this way are grouped into microfibrils, which form strong building materials for plants

Page 25: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-8

b Glucosemonomer

Cellulosemolecules

Microfibril

Cellulosemicrofibrilsin a plantcell wall

0.5 µm

10 µm

Cell walls

Page 26: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

• 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

Page 27: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

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

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

The structureof the chitinmonomer.

Chitin forms theexoskeleton ofarthropods.

Chitin is used to makea strong and flexiblesurgical thread.

Page 28: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

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Page 29: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Lipids

• Lipids – the one class of large biological molecules that do not form

polymers

• Unifying feature – having little or no affinity for water

• Hydrophobic because– consist mostly of hydrocarbons– these form nonpolar covalent bonds

• Most biologically important lipids – Fats– Phospholipids– steroids

Page 30: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fats

• Fats are constructed from glycerol and fatty acids– Glycerol

• A three-carbon alcohol with a hydroxyl group attached to each carbon

– Fatty acid• a carboxyl group attached to a long carbon skeleton

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

Page 31: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-11

Fatty acid(palmitic acid)

Glycerol

(a) Dehydration reaction in the synthesis of a fat

Ester linkage

(b) Fat molecule (triacylglycerol)

Page 32: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

What is the Difference?

Page 33: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

• Fatty acids vary in length (number of carbons) and in the number and locations of double bonds

• Saturated fatty acids have the maximum number of hydrogen atoms possible and no double bonds – they are solid at room temp.

• Unsaturated fatty acids have one or more double bonds - they are liquid at room temp.

Page 34: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-12a

(a) Saturated fat

Structuralformula of asaturated fatmolecule

Stearic acid, asaturated fattyacid

Page 35: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-12b

(b) Unsaturated fat

Structural formulaof an unsaturatedfat molecule

Oleic acid, anunsaturatedfatty acid

cis doublebond causesbending

Page 36: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

• 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

Page 37: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fat Function

• The major function of fats is energy storage

• Humans and other mammals store their fat in adipose cells

• Adipose tissue also cushions vital organs and insulates the body

Page 38: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Phospholipids

• Phospholipid– two fatty acids and a phosphate group are

attached to glycerol • the two fatty acid tails are hydrophobic• the phosphate group and its attachments form a

hydrophilic head

Page 39: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-13

(b) Space-filling model(a) (c)Structural formula Phospholipid symbol

Fatty acids

Hydrophilichead

Hydrophobictails

Choline

Phosphate

Glycerol

Hyd

rop

ho

bic

tai

lsH

ydro

ph

ilic

hea

d

Page 40: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Function of Phospholipids

• Phospholipids are the major component of all cell membranes

• When phospholipids are added to water, they self-assemble into a bilayer, with the hydrophobic tails pointing toward the interior

Page 41: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Steroids• Steroids are lipids characterized by a carbon

skeleton consisting of four fused 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

Page 42: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

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Page 43: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Proteins

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

• Protein functions – Enzymatic proteins– Structural proteins– Storage proteins– Transport proteins– Hormonal proteins– Receptor proteins– Contractile and motor proteins– Defense proteins

Page 44: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

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

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

Page 45: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-16

Enzyme(sucrase)

Substrate(sucrose)

Fructose

Glucose

OH

HO

H2O

Page 46: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Structure of Proteins

• A protein consists of one or more polypeptides

• Polypeptides – polymers built from the same set of 20 amino

acids linked by peptide bonds

• Amino acids are organic molecules with carboxyl and amino groups

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

Page 47: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-UN1

Aminogroup

Carboxylgroup

carbon

Page 48: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

• Amino acids can be classified according to the properties of their side chains:

– nonpolar– Polar– Electrically charged (acidic or basic)

Page 49: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-17a

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)

Tryptophan (Trp or W)

Proline (Pro or P)

Page 50: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-17b

Polar

Asparagine (Asn or N)

Glutamine (Gln or Q)

Serine (Ser or S)

Threonine (Thr or T)

Cysteine (Cys or C) Tyrosine

(Tyr or Y)

Page 51: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

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

Page 52: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Amino Acid Polymers

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

• Each polypeptide has a unique linear sequence of amino acids

• The backbone is the chain of C, H, O, and N

• The side chains are formed by the R groups

Page 53: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Peptidebond

Fig. 5-18

Amino end(N-terminus)

Peptidebond

Side chains

Backbone

Carboxyl end(C-terminus)

(a)

(b)

What type of reaction is this?

Page 54: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Protein Structure and Function

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

A ribbon model of lysozyme A space-filling model of lysozyme

Page 55: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

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

• A protein’s structure determines its function

Antibody protein Protein from flu virus

Page 56: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Four Levels of Protein Structure

1. 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

Page 57: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

2. Secondary structure

• coils and folds resulting from hydrogen bonds between repeating constituents of the polypeptide backbone

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

Page 58: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-21c

Secondary Structure

pleated sheet

Examples ofamino acidsubunits

helix

Page 59: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

3. Tertiary structure – determined by interactions between R groups,

rather than interactions between backbone constituents• hydrogen bonds• ionic bonds• hydrophobic interactions• van der Waals interactions

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

Page 60: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-21f

Polypeptidebackbone

Hydrophobicinteractions andvan der Waalsinteractions

Disulfide bridge

Ionic bond

Hydrogenbond

Page 61: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-21e

Tertiary Structure Quaternary Structure

Page 62: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

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

• 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

Page 63: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-21g

Polypeptidechain

Chains

Chains

CollagenHemoglobin

Page 64: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-22

Primarystructure

Secondaryand tertiarystructures

Quaternarystructure

Normalhemoglobin(top view)

Primarystructure

Secondaryand tertiarystructures

Quaternarystructure

Function Function

B subunit

Molecules donot associatewith oneanother; eachcarries oxygen.

Red bloodcell shape

Normal red bloodcells are full ofindividualhemoglobinmolecules, eachcarrying oxygen.

10 µm

Normal hemoglobin

B

B

a

a

1 2 3 4 5 6 7

Val His Leu Thr Pro Glu Glu

Red bloodcell shape

B subunit

Exposedhydrophobicregion

Sickle-cellhemoglobin

B

a

Moleculesinteract withone another andcrystallize intoa fiber; capacityto carry oxygenis greatly reduced.

B

a

Fibers of abnormalhemoglobin deformred blood cell intosickle shape.

10 µm

Sickle-cell hemoglobin

GluProThrLeuHisVal Val

1 2 3 4 5 6 7

Page 65: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

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 native structure is called denaturation

• A denatured protein is biologically inactive

Page 66: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-23

Normal protein Denatured protein

Denaturation

Renaturation

If the denatured protein remains dissolved it may be able to renature once the environment is returned to normal.

Page 67: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Animation of Denaturation

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Page 68: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-24

Hollowcylinder

Cap

Chaperonin(fully assembled)

Polypeptide

Steps of ChaperoninAction:

An unfolded poly-peptide enters thecylinder from one end.

1

2 3The cap attaches, causing thecylinder to change shape insuch a way that it creates ahydrophilic environment forthe folding of the polypeptide.

The cap comesoff, and the properlyfolded protein isreleased.

Correctlyfoldedprotein

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

Page 69: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

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Page 70: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Nucleic Acids

• The amino acid sequence of a polypeptide is programmed by a unit of inheritance called a gene

• Genes are made of DNA, a nucleic acid

Page 71: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

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

Page 72: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

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

Page 73: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

The Structure of Nucleic Acids

• Nucleic acids are polymers called polynucleotides

• Each polynucleotide is made of monomers called nucleotides

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

• The portion of a nucleotide without the phosphate group is called a nucleoside

Page 74: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-27

5 end

Nucleoside

Nitrogenousbase

Phosphategroup Sugar

(pentose)

(b) Nucleotide

(a) Polynucleotide, or nucleic acid

3 end

3C

3C

5C

5C

Nitrogenous bases

Pyrimidines

Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA)

Purines

Adenine (A) Guanine (G)

Sugars

Deoxyribose (in DNA) Ribose (in RNA)

(c) Nucleoside components: sugars

Page 75: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Nucleotide Monomers

• 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

Page 76: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Nucleotide Polymers

• Nucleotide polymers are linked together to build a polynucleotide– 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

– These links create a backbone of sugar-phosphate units with nitrogenous bases as appendages

• The sequence of bases along a DNA or mRNA polymer is unique for each gene

Page 77: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

The DNA Double Helix

• Two polynucleotides spiraling around an imaginary axis, forming a double helix

• The two backbones run in opposite 5 → 3 directions from each other, an arrangement referred to as antiparallel

• One DNA molecule includes many genes

• The nitrogenous bases pair up and form hydrogen bonds: – adenine (A) always with thymine (T)

– guanine (G) always with cytosine (C)

• Van der Waals forces hold the stacked bases

Page 78: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Fig. 5-28

Sugar-phosphatebackbones

3' end

3' end

3' end

3' end

5' end

5' end

5' end

5' end

Base pair (joined byhydrogen bonding)

Old strands

Newstrands

Nucleotideabout to beadded to anew strand

Page 79: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

Can DNA sequences be used to support the Theory of Evolution?

• The linear sequences of nucleotides in DNA molecules are passed from parents to offspring

• Two closely related species are more similar in DNA than are more distantly related species

• Molecular biology can be used to assess evolutionary kinship

Page 80: Macromolecules Ch. 5. Macromolecules are polymers, built from monomers A polymer is a long molecule consisting of many similar building blocks These small.

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