Proteins

Question 1

Describe the primary structure of proteins

Answer 1

Straight chain sequence of amino acids joined by peptide bonds (CONH). Amino acids are arranged in specific order for a specific function.

Question 2

Describe the basic functions of proteins

Answer 2

Catalysis (enzymes), movement, cellular control (hormones/receptors), transport, structural support, immune system.

Question 3

What is an amino acid?

Describe/draw the structure/isomerism of amino acids.

Answer 3

A structural unit that makes up proteins. There are 20.

Central alpha-carbon, alpha-amino group, alpha-carboxylic group and R group. Natural isomer = CORN (L)

Question 4

Describe properties and ionisation states of amino acids

Answer 4

R groups can be titrated/ionised. Ratio of protonated:non-protonated can be calculated via HH equation.

Can also form Zwitterions (net charge = 0)

Isoelectric point = point at which the amino acid has net - charge. Calculated using pKa values.

Question 5

Explain the structure of a peptide bond, including steric constraints.

Favoured arrangement?

Answer 5

Peptide bonds are formed in condensation reaction (CONH - between C-N) Bond is planar and restricted by resonance. R groups favour trans position (as far apart as possible) TO AVOID STERIC CONSTRAINT