Proteins

Question 1

What is primary structure?

Answer 1

Specific linear sequence of amino acids joined via peptide bonds

Question 2

What is secondary structure

Answer 2

Regular folding of polypeptide chain into alpha helices or beta pleated sheets due to hydrogen bonds between peptide bonds

Question 3

What is secondary structure

Answer 3

Regular folding of polypeptide chain into alpha helices or beta pleated sheets due to hydrogen bonds between chains

Question 4

What is tertiary structure

Answer 4

Further folding of polypeptide chains into specific 3D conformation

Question 5

What is quaternary structure?

Answer 5

2 or more polypeptide chains associating to form functional protein

Question 6

Describe the structure to function of amino acids

Answer 6

S1: contains basic amine group and acidic carboxyl group
F1: able to form zwitterions in water

S2: contains basic amine group and acidic carboxyl group
P2: can act as buffer by resisting pH changes
F2: making it amphoteric

S3: R group side chain
P3: unique to each amino acid
F3: give rise to specific physical and chemical properties

Question 7

Describe the structure to function of haemoglobin

Answer 7

S1: Each subunit contains a haem prosthetic group.
P1: each haem group binds to one oxygen molecule
F1: one Hb molecule can bind with up to 4 oxygen molecule

S2: Hydrophilic residue lies outside, hydrophobic residues buried in the interior
P2: Hb is soluble in aqueuous environment
F2: can be transported in blood while carrying O2 to lungs and vice versa

S3: 4 subunits are held together by weak intermolecular interactions formed between R groups
P3: Binding of one oxygen molecule to a subunit induces conformational change in the remaining 3 subunits
F3: increasing their affinity for oxygen molecule

Question 8

State the structure to function of collagen

Answer 8

S1: Every third amino acid is glycine, which is the smallest amino acid due to smallest R group
P1: allow tighter packing of three alpha chain
F1: making tropocollagen rigid and have high tensile strength

S2: Extensive hydrogen bonds form between amino group of glycine and carboxyl group of other residue in adjacent polypeptides
F2: High tensile strength and rigidity of tropocollagen molecules

S3: Covalent cross-links form between carboxyl ends and amino ends tropocollagen molecules
P3: to form collagen fibrils
F3: give rise to high strength and rigidity

S4: Staggered arrangement of tropocollagen maintained by hydrophobic interaction
F4: confer high strength to collagen fibril

S5: Many collagen fibril bundle
P5: form collagen fibres
F5: large size makes it insoluble