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Biological Macromolecules

•Much larger than other particles found in cells•Made up of smaller subunits•Found in all cells•Great diversity of functions

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Four Classes of Biological Macromolecules•Lipids•Polysaccharides•Proteins•Nucleic Acids

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Lipids

•Hydrophobic or amphipathic•Important for:•energy storage•membrane structure•signaling•cushioning•insulation

•Include:•fats•phospholipids•cholesterol and phytosterol•some hormones•others

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Fatty acid(palmitic acid)

Glycerol(a) Dehydration reaction in the synthesis of a fat

Ester linkage

(b) Fat molecule (triacylglycerol)

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Structuralformula of asaturated fatmolecule

Stearic acid, asaturated fattyacid(a) Saturated fat

Structural formulaof an unsaturatedfat molecule

Oleic acid, anunsaturatedfatty acid

(b) Unsaturated fat

cis doublebond causesbending

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

Fatty acids

Hydrophilichead

Hydrophobictails

Choline

Phosphate

Glycerol

Hyd

roph

obic

tails

Hyd

roph

ilic

head

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Hydrophilichead

Hydrophobictail WATER

WATER

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Polysaccharides

•Complex sugars•Polymers of monosaccharides (simple sugars)•Polysaccharides and monosaccharides are carbohydrates•Important for:•structure•storage of energy•cell identity marking

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Dihydroxyacetone

Ribulose

Ket

ose s

Ald

o se s

Fructose

Glyceraldehyde

RiboseGlucose Galactose

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

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(b) Dehydration reaction in the synthesis of sucroseGlucose Fructose Sucrose

MaltoseGlucoseGlucose(a) Dehydration reaction in the synthesis of maltose

1–4glycosidic

linkage

1–2glycosidic

linkage

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(b) Glycogen: an animal polysaccharide

Starch

GlycogenAmylose

Chloroplast

(a) Starch: a plant polysaccharide

Amylopectin

Mitochondria Glycogen granules

0.5 µm

1 µm

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(a) and glucose ring structures

Glucose Glucose

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

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Glucosemonomer

Cellulosemolecules

Microfibril

Cellulosemicrofibrilsin a plantcell wall

0.5 µm

10 µm

Cell walls

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The structureof the chitinmonomer.

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

Chitin is used to makea strong and flexiblesurgical thread.

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Proteins

•Polymers of amino acids•Highly complex shape•Function is based on shape•Huge variety of functions

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Enzyme(sucrase)

Substrate(sucrose)

Fructose

Glucose

OH

H O

H2O

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Aminogroup

Carboxylgroup

carbon

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Nonpolar

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)

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)

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Peptidebond

Amino end(N-terminus)

Peptidebond

Side chains

Backbone

Carboxyl end(C-terminus)

(a)

(b)

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Polypeptidechain

Chains

HemeIron

Chains

CollagenHemoglobin

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Antibody protein Protein from flu virus

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Primarystructure

Secondaryand tertiarystructures

Quaternarystructure

Normalhemoglobin(top view)

Primarystructure

Secondaryand tertiarystructures

Quaternarystructure

Function Function

subunit

Molecules donot associatewith oneanother; eachcarries oxygen.

Red bloodcell shape

Normal red bloodcells are full ofindividualhemoglobinmoledules, eachcarrying oxygen.

10 µm

Normal hemoglobin

1 2 3 4 5 6 7Val His Leu Thr Pro Glu Glu

Red bloodcell shape

subunit

Exposedhydrophobicregion

Sickle-cellhemoglobin

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

Fibers of abnormalhemoglobin deformred blood cell intosickle shape.

10 µm

Sickle-cell hemoglobinGluProThrLeuHisVal Val

1 2 3 4 5 6 7

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Normal protein Denatured protein

Denaturation

Renaturation

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Nucleic Acids

•Polymers of nucleotides•also called polynucleotides

•Store and convey information•Instruction manual of the cell

•Include:•DNA (deoxyribonucleic acid)•RNA (ribonucleic acid)

•Important for:•reproduction of cells•production of proteins

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5 end

Nucleoside

Nitrogenousbase

Phosphategroup Sugar

(pentose)

(b) Nucleotide

(a) Polynucleotide, or nucleic acid

3 end

3C

3C

5C

5C

Nitrogenous basesPyrimidines

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

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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

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mRNA

Synthesis ofmRNA in thenucleus

DNA

NUCLEUS

mRNA

CYTOPLASM

Movement ofmRNA into cytoplasmvia nuclear pore

Ribosome

AminoacidsPolypeptide

Synthesisof protein

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2

3

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