Question

which of the following statements is/are true?? can make more than ONE answer

a The oxidation of glyceraldehyde-3-phosphate requires NAD+ as an electron acceptor. b Under aerobic conditions NADH passes electrons to 02. c Under anaerobic conditions NADH reduces pyruvate to lactate and is thereby recycled to NAD+. You are given three tubes containing three unidentified bacteria. One bacterium lives by fermentation. d One bacterium lives by aerobic oxidation of glucose via the citric acid cycle. One bacterium lives by photosynthesis. The culture that grows aerobically in the dark is the fermenter. e Glycogen phosphorylase in muscle catalyzes hydrolytic cleavage of the terminal residue at the nonreducing end producing glucose-1-phosphate. Muscle glycogen consists of linear polymers of alpha 1+4 -Linked glucose with alpha 1 +4-linked branches When phosphorylase approaches a branch point a second enzyme (debrancher) removes the four & glucose residues nearest the branch point and reattaches them in alpha 1-4 linkage at a nonreducing end. In glycogen degradation epinephrine binds to a specific receptor on the cell surface. Occupation of the h receptor activates the adenyl cyclase which catalyzes production of CAMP which phosphorylates the glycogen phosphorylaseb to glycogen phosphorylase a. Lavad Submit

Answer 1

Ans: In Muscle glycogen glucose units are linked together linearly by α(1→4) glycosidic bonds from one glucose to the next. Branches are linked to the chains from which they are branching off by α(1→6) glycosidic bonds between the first glucose of the new branch and a glucose on the stem chain.

Hence statement F is false.

Phosphorylase b is converted into phosphorylase a when it is phosphorylated at a single serine residue (serine 14) in each subunit. The regulatory enzyme phosphorylase kinase catalyzes this covalent modification. So phosphorylase a is the active form which catalyzes the glycogen breakdown when epinephrine binds to the GPCRs.

Hence statement J is also false.

The bacteria that lives by fermentation cannot grow im the presence of oxygen or in aerobic condition. So this means that the bacterial culture that grow aerobically in the dark is not of fermenter bacteria.

Hence option D is also false.

Glycogen phosphorylase catalyzes the sequential phosphorolysis of glycogen to release glucose-1-phosphate; it is thus the key enzyme in the utilization of muscle and liver reserves of glycogen. So this means that the reaction is not hydrolytic but phosphorolytic cleavage.

Hence option E is also false.