BIOCHEMISTRY

PROTEINS

Natural polymersC,H,O,N,(S)Monomer is Amino

AcidsGrowthRepairHormonesEnzymesAntibodiesEnergy Source

PROTEINS

15% of our bodiesComposed of 20

amino acids10 we cannot

synthesise and store (essential amino acids)

We get them from food

A Complete Protein contains all 10 (eg Casein)

2-amino acids

Contain carboxyl group and amine (amino) group

ColourlessCrystalline solidsExist as ZwitterionsTherfore high m.p.Soluble in waterAmphoteric

Zwitterions

Lysine

Basic amino acid

Aspartic Acid

Acidic amino acid

Amino Acids

Amphoteric nature makes it possible to act as buffers

Condensation Reaction

PRIMARY STRUCTURE

The sequence of amino acids

3 letter codes usedA tripeptide would

have 3 amino acids in sequence

Secondary Structure

Manner in which protein folds

Intramoleculer hydrogen bonding important

Between O on carbonyl group and H on amine

Alpha-helixBeta-pleated sheets

Tertiary Structure

Overall 3D shapeCovalent bonding (eg

disulphide bridges)H-bondingSalt bridges

(electrostatic attraction)

Affect of R group (eg polarity, hydrophobic interactions)

Quarternary Structure

How subunits join together

Haemoglobin

Denaturing

HeatIonising radiationStrong acids, basesConcentrated salt

solutionsOrganic solventsDetergents

To Do

Read pages 324 to 328Try questions on proteins on page 359

Analysis of Proteins

ChromatographyHydrolysis (strong

acid at 110 °C for several hours)

Amino acids seperated

Rf Values

Electrophoresis

Seperation based on electric charge

HydrolysisEach amino acid has

different isoelectronic point (pH at which positive and negative ions are balanced)

Therefore can be seperated using electrophoresis

Major Functions in the Body

StructuralBiological CatalystsHormonesAntibodiesTransportEnergy