Question

1. If Cys donates its sulfur to iron to make Fe-S proteins most likely becomes
   1. Ser                   b. Ala             c. Gly             d. Thr

2. The most important aa in the production of AcCoA from pyruvate is
   1. His                  b. Lys             c. Tyr             d. Ser

3. Lactase, trehalase and sucrase can all be grouped as
   1. hydroxylases               c. transferases
   2. lyases                          d. oxidoreductases

4. The nucleophile involved in the conversion of acetaldehyde to ethanol is
   1. Zn²⁺                 b. H⁺                c. H^-                d. H^.

Answer 1

1- b. Alanine

cysteine donates its silfide to form iron sulfide cluster, after which it is converted into alanine

2- d. Serine

serine enters TCA via its conversion into pyruvate.

3- a. Hydroxylases (I think it's hydrolases)

Hydrolases includes all digestive enzymes. Since lactase, trehalase and sucrase are all digestive enzymes so they come under this category. They use H₂O to break carbohydrate molecules.

4- b. H⁺

acetaldehyde is converted into ethanol in presence of alcohol dehydrogenase, NADH and H⁺