Question

Question 6 (1 point) in the A pH versus rate curve with an inflection point at pH-4 suggests the involvement of an catalytic step Question 8 (1 point) Cellulose and glycogen are both structural polysaccharides proton donation that is mediated by a coenzyme True False free proton surrounded by a hydrophobic environment proton transfer with a pK close to 4 Question 9 (1 point) proton abstraction that requires a metal ion in close proximity The activity of lysozyme is greater than 50% of maximum between pH 3.8 and 6.1 with peak activity occurring around pH 5. Below 3.8 and above 6.1, the activity drops rapidly. Which of the following provides the best explanation for this? Question 7 (1 point) In the mechanism of RNase A... the active site contains a histidine that must be protonated and a glutamic acid that must be deprotonated the active site contains an aspartic acid that must be deprotonated and a glutamic acid that must be protonated O a cyclic 3' 5 phosphate is an intermediate in the reaction. the active site contains a serine that must be deprotonated and an aspartic acid that must be deprotonated O 2 aspartic acids residues with very different pKa values participate in catalysis. 2 histidine residues with somewhat different pKa values act as acids and bases during catalysis the active site contains an aspartic acid and glutamic acid, both of which must be deprotonated two histidine residues in the active site one must be protonated for enzyme activity and the other deprotonated an activated serine forms a covalent intermediate with the ribose.

Answer 1

6. "Proton transfer with pK close to 4 "is correct option

Inflection point is point with highest slope and also an equivalence point. Hence,inflection at pH=4 means pka is 4 as all acid and base are neutralized and a proton transfer has been carried out.

7.Two histidine residue with somewhat different pka value act as acids and bases during catalysis.

In first step histidine-119 act as acid while histidine-12 act as base and form a 2'​​​​3'-cyclic intermediate which further reacts with water.

8. Cellulose and glycogen both are polysaccharides. Both have α-D Glucose as a subunit . Cellulose form plant cell wall, while glycogen helps in storage of glucose in animals

Hence, Above statement is true.

​​​9. The active site contains an aspartic acid that must be Deprotanated and glutamic acid that must be protonated.

At pH less than 5 , glutamic acid ionises and cannot supply hydrogen ion

At pH above 5,aspartic acid gets protonated hence will not be able to stabilise the carbonium ion

Hence, Activitiy is highest at pH=5