Old Consolidation

Question 1

S & F of Haemoglobin

Answer 1

1. haem group contains an iron (II) ion that can bind reversibly with oxygen, allows oxygen binding (in oxygenrich lungs) and release (in metabolically active tissues);;
2. four polypeptide chains / subunits allows for cooperative binding to maximize both oxygen loading and release;;
3. hydrophilic amino acid residues present on exterior of each subunit, results in haemoglobin being soluble in red blood cell;;

Question 2

S & F of Collagen

Answer 2

1. every third amino acid of each polypeptide chain is glycine, has H atom as r group, small r group able to fit into centre of triple helix, allows forming of tight compact coil in tropocollagen;;
2. within tropocollagen, extensive hydrogen bonding between chains to form triple helix,
3. between tropocollagens, covalent bonds between ends of staggered arrangement (carboxyl and amino ends), results in high tensile strength;;
4. tropocollagen bundled to form fibrils and further assembled to form long collagen fibres;;

Question 3

Explain what is meant by an enzyme.

Answer 3

1. (Compulsory) Enzyme is a biological catalyst that;
2. increases the rate of metabolic / biological/ cell(ular) reaction ;
3. remains unchanged (at end of reaction) / not used up (in reaction) ;
4. lowers the activation energy (of a reaction)

Question 4

Explain the mode of action of elastase.

Answer 4

1. (shape of) elastin complementary to (shape of) active site ; 2. Upon successful collisions between elastase and elastin, enzyme substrate complexes are formed ;
2. Hydrogen/ temporary bonds form between enzyme/ active site and substrate ;
3. eventually leading to the formation of products which then leave the active site as the products no longer fit into the active site ;
4. (detail of how Ea lowered) Enzymes reduce the activation energy by straining the chemical bonds within the substrates until they break ;

Question 5

Distinguish between competitive and non-competitive inhibition of enzymes.

Answer 5

read RV Notes

Question 6

Define facilitated diffusion

Answer 6

Net movement of substances;

1. from a region of higher to lower concentration;
2. across a selectively permeable membrane;
3. with the help of transport proteins / carrier and channel proteins;;
4. without the additional investment of ATP by the cell;
5. reference to specificity of channel in transporting specific ions or molecules;
6. until a dynamic equilibrium is reached

Question 7

State the function of DNA and describe how its properties allow it to perform this function.

Answer 7

1. DNA stores genetic information;;
2. DNA must be chemically stable to encode information without being easily changed by age/nutrition/ environment;;
3. DNA must be able to replicate accurately so that the information can be pass down to the next generation;;

Question 8

Explain how the end replication problem arises.

Answer 8

1. DNA polymerase only extends in a 5’ → 3’ direction
2. unable to fill gap after the last RNA primer is removed at 5’ end of newly synthesised strand
3. as no upstream 3’ OH
4. resulting in shorter daughter strand compared to the template strand