Chapter 3 Chapter 3

Proteins, Carbohydrates,Proteins, Carbohydrates,and Lipidsand Lipids

MacromoleculesMacromolecules

PolymersPolymers with molecular weights >1,000 with molecular weights >1,000

Made up of smaller molecules calledMade up of smaller molecules called

monomersmonomers

Four Main Groups:Four Main Groups:

Proteins Proteins (Amino Acids)(Amino Acids)

Carbohydrates Carbohydrates (Simple Sugars)(Simple Sugars)

Lipids Lipids (Fatty Acids)(Fatty Acids)

Nucleic Acids Nucleic Acids (Nucleotides - Chapter 4)(Nucleotides - Chapter 4)

Functional Functional GroupsGroups

Groups of atoms with Groups of atoms with specific chemicalspecific chemical

properties and consistent properties and consistent behaviorbehavior

IsomersIsomers

Molecules with the same chemical formula, but Molecules with the same chemical formula, but atoms are arranged differentlyatoms are arranged differently

Structural Isomers:Structural Isomers: differ in how their atoms differ in how their atoms are joined togetherare joined together

Optical IsomersOptical Isomers

Occur when a carbon Occur when a carbon atom has four atom has four different atoms or different atoms or groups of atoms groups of atoms attached to it.attached to it.

Optical isomers result Optical isomers result from from asymmetrical asymmetrical carbonscarbons..

Macromolecules Found in Macromolecules Found in Living TissuesLiving Tissues

Functions of MacromoleculesFunctions of Macromolecules

• Energy StorageEnergy Storage• Structural SupportStructural Support• CatalystsCatalysts• TransportTransport• Protection and Protection and

DefenseDefense• Regulation of Regulation of

Metabolic ActivitiesMetabolic Activities

• Maintenance and Maintenance and HomeostasisHomeostasis

• Movement Movement • GrowthGrowth• DevelopmentDevelopment• HeredityHeredity• Information StorageInformation Storage

Condensation ReactionsCondensation Reactions

Polymers are formed in Polymers are formed in condensation reactionscondensation reactions..

Monomers are joined by Monomers are joined by covalent bonds.covalent bonds.

A water is removed; so A water is removed; so they are also called they are also called dehydration dehydration reactions.reactions.

Hydrolysis ReactionsHydrolysis Reactions

Polymers are broken Polymers are broken down into monomers down into monomers in hydrolysis in hydrolysis reactions.reactions.

Protein StructureProtein Structure

Proteins are polymers of Proteins are polymers of 20 different amino acids20 different amino acids..

Polypeptide chain:Polypeptide chain: single, unbranched chain of amino single, unbranched chain of amino acids.acids.

The chains are folded into specific The chains are folded into specific three dimensional three dimensional shapesshapes defined by the sequence of the amino acids. defined by the sequence of the amino acids.

Proteins can consist of Proteins can consist of more than one type of more than one type of polypeptide chainpolypeptide chain..

Functions of ProteinsFunctions of Proteins

enzymesenzymes—catalytic proteins —catalytic proteins

defensive proteins (e.g., antibodies) defensive proteins (e.g., antibodies)

hormonal and regulatory proteinshormonal and regulatory proteins—control physiological —control physiological processesprocesses

receptor proteinsreceptor proteins—receive and respond to molecular signals —receive and respond to molecular signals

Storage proteinsStorage proteins store amino acids. store amino acids.

Structural proteinsStructural proteins provide physical stability and movement. provide physical stability and movement.

Transport proteins Transport proteins carry substances within the organism (e.g.,carry substances within the organism (e.g., hemoglobin). hemoglobin).

Genetic regulatory proteinsGenetic regulatory proteins regulate when, how, and to what regulate when, how, and to what extent a gene is expressed.extent a gene is expressed.

Building Blocks of Proteins: Building Blocks of Proteins: Amino AcidsAmino Acids

αα-carbon is “asymmetric”-carbon is “asymmetric”

4 Main Groups4 Main Groups• Amino GroupAmino Group• Carboxyl GroupCarboxyl Group• HydrogenHydrogen• Side Chain (R)Side Chain (R)

–Specific to each type of Specific to each type of amino acidamino acid

•Optical Isomers Optical Isomers

D-amino acids (dextro, “right”)

L-amino acids (levo, “left”)

(this form is found in organisms)

Types of Amino Acid Side Chains (R)Types of Amino Acid Side Chains (R)

These hydrophylic amino acids attract ions of These hydrophylic amino acids attract ions of opposite charges.opposite charges.

Types of Amino Acid Side Chains (R)Types of Amino Acid Side Chains (R)

Hydrophylic amino acids with polar but uncharged Hydrophylic amino acids with polar but uncharged side chains form hydrogen bonds.side chains form hydrogen bonds.

Types of Amino Acid Side Chains (R)Types of Amino Acid Side Chains (R)

Hydrophobic amino acidsHydrophobic amino acids

Types of Amino Acid Side Chains (R)Types of Amino Acid Side Chains (R)

Cysteine: Can form disulfide bridgesCysteine: Can form disulfide bridges

Glycine: Smallest a.a. (Unique why?)Glycine: Smallest a.a. (Unique why?)

Proline: Causes “kinks” in protein structureProline: Causes “kinks” in protein structure

Peptide BondsPeptide Bonds

N-terminus: start of a polypeptide chain N-terminus: start of a polypeptide chain

C-terminus: end of a polypeptide chain C-terminus: end of a polypeptide chain

Levels of Protein Structure:Levels of Protein Structure:Primary StructurePrimary Structure

Made up of a single chain of amino acids Made up of a single chain of amino acids bound together (polypeptide)bound together (polypeptide)

The number of different proteins that can The number of different proteins that can be made from 20 amino acids is enormous!be made from 20 amino acids is enormous!

Levels of Protein Structure: Levels of Protein Structure: Secondary StructureSecondary Structure

αα helix: helix: right-handed coil right-handed coil resulting from resulting from hydrogen bonding hydrogen bonding between N—H groups between N—H groups on one amino acid and on one amino acid and C=O groups on C=O groups on another.another.

ββ pleated sheet: pleated sheet: two or two or more polypeptide more polypeptide chains are aligned; chains are aligned; hydrogen bonds from hydrogen bonds from between the chains.between the chains.

Bonds do NOT form between side chains!Bonds do NOT form between side chains!

Levels of Protein Structure:Levels of Protein Structure:Tertiary StructureTertiary Structure

• Bending and Bending and folding results in a folding results in a macromolecule macromolecule with specific three-with specific three-dimensional dimensional shape.shape.

• Bonds form Bonds form between side between side chainschains

Levels of Protein Structure:Levels of Protein Structure:Quaternary StructureQuaternary Structure

Results from the Results from the interaction of interaction of subunitssubunits by hydrophobic by hydrophobic interactions, van der interactions, van der Waals forces, ionic Waals forces, ionic bonds, and hydrogen bonds, and hydrogen bonds.bonds.

Each subunit has its own Each subunit has its own unique tertiary structure.unique tertiary structure.

Environmental Conditions Environmental Conditions affect Protein Foldingaffect Protein Folding

Conditions that affect secondary and Conditions that affect secondary and tertiary structure:tertiary structure:

• High temperatureHigh temperature

• pH changespH changes

• High concentrations of polar moleculesHigh concentrations of polar molecules

• Nonpolar substancesNonpolar substances

DenaturationDenaturation

ChaperonesChaperones

Help some proteins fold correctlyHelp some proteins fold correctly

CarbohydratesCarbohydrates

Carbohydrates have the general formula Carbohydrates have the general formula CCnn(H(H22O)O)nn

Source of stored energy Source of stored energy

Transport stored energyTransport stored energy

Types of CarbohydratesTypes of Carbohydrates

Monosaccharides: simple sugarsMonosaccharides: simple sugars

Disaccharides: two simple sugars linked Disaccharides: two simple sugars linked by covalent bondsby covalent bonds

Oligosaccharides: three to 20 Oligosaccharides: three to 20 monosaccharidesmonosaccharides

Polysaccharides: hundreds or thousands Polysaccharides: hundreds or thousands of monosaccharides—starch, glycogen, of monosaccharides—starch, glycogen, cellulosecellulose

MonosaccharidesMonosaccharides

Simple SugarsSimple Sugars

Hexoses: sixHexoses: six

Pentoses: five carbonsPentoses: five carbons

Glyceraldehyde: three Glyceraldehyde: three carbonscarbons

Monosaccharides: GlucoseMonosaccharides: Glucose

All cells use glucose (monosaccharide) as an All cells use glucose (monosaccharide) as an energy source.energy source.

Exists as a straight chain or ring form. Ring is Exists as a straight chain or ring form. Ring is more common—it is more stable.more common—it is more stable.

Glycosidic LinkagesGlycosidic Linkages

Monosaccharides bind together in Monosaccharides bind together in condensation reactionscondensation reactions to form glycosidic to form glycosidic linkages.linkages.

Glycosidic linkages can be Glycosidic linkages can be αα or or ββ..

OligosaccharidesOligosaccharides

Often covalently bonded to proteins and Often covalently bonded to proteins and lipids on cell surfaces and act as lipids on cell surfaces and act as recognition signals.recognition signals.

Human blood groups get specificity from Human blood groups get specificity from oligosaccharide chains.oligosaccharide chains.

PolysaccharidesPolysaccharides

Giant polymers of monosaccharides.Giant polymers of monosaccharides.

Starch:Starch: storage of glucose in plants storage of glucose in plants

Glycogen:Glycogen: storage of glucose in animals storage of glucose in animals

Cellulose:Cellulose: very stable, good for structural very stable, good for structural componentscomponents

Carbohydrates can be modified by the addition Carbohydrates can be modified by the addition of functional groupsof functional groups

LipidsLipidsNonpolar hydrocarbonsNonpolar hydrocarbons

Not polymers in the strict sense, because they are not covalently Not polymers in the strict sense, because they are not covalently bonded.bonded.

FUNCTION:FUNCTION:

1) Fats and oils store energy1) Fats and oils store energy

2) Phospholipids—structural role in cell membranes2) Phospholipids—structural role in cell membranes

3) Carotenoids and chlorophylls—capture light energy in plants3) Carotenoids and chlorophylls—capture light energy in plants

4) Steroids and modified fatty acids—hormones and vitamins4) Steroids and modified fatty acids—hormones and vitamins

5) Animal fat—thermal insulation5) Animal fat—thermal insulation

6) Lipid coating around nerves provides electrical insulation6) Lipid coating around nerves provides electrical insulation

7) Oil and wax on skin, fur, and feathers repels water7) Oil and wax on skin, fur, and feathers repels water

TriglyceridesTriglycerides

Simple fats and oilsSimple fats and oils

Glycerol:Glycerol: 3 —OH groups (an alcohol) 3 —OH groups (an alcohol)

Fatty acid: Fatty acid: nonpolar hydrocarbon with a polar nonpolar hydrocarbon with a polar carboxyl groupcarboxyl group

Carboxyls bond with hydroxyls of glycerol in an Carboxyls bond with hydroxyls of glycerol in an ester linkageester linkage. (condensation reaction). (condensation reaction)

Ester LinkageEster Linkage

Types of Fatty AcidsTypes of Fatty Acids

Saturated fatty acids: no double bonds Saturated fatty acids: no double bonds between carbons—it is saturated with H between carbons—it is saturated with H atoms.atoms.

Unsaturated fatty acids: some double Unsaturated fatty acids: some double bonds in carbon chain.bonds in carbon chain.

monounsaturatedmonounsaturated: one double : one double bondbond

polyunsaturatedpolyunsaturated: more than one: more than one

Types of Fatty AcidsTypes of Fatty Acids

Saturated Saturated Unsaturated Unsaturated

PhospholipidsPhospholipids

Fatty acids bound to Fatty acids bound to glycerol; a phosphate glycerol; a phosphate group replaces one fatty group replaces one fatty acid.acid.

HHydrophilicydrophilic “head” “head”

HydrophobicHydrophobic “Tails” “Tails”

AmphipathicAmphipathic::

Have opposing chemical Have opposing chemical propertiesproperties

Phospholipid BilayerPhospholipid Bilayer

• In water, phospholipids line up with the In water, phospholipids line up with the hydrophobic “tails” together and the hydrophobic “tails” together and the phosphate “heads” facing outward, to form a phosphate “heads” facing outward, to form a bilayer.bilayer.

Other FatsOther Fats