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