(Biochemistry)

A biochemist working with Hb purified from blood performs a series of in vitro experiments. She is able to further purify Hb which results in two separate and distinct samples: Stripped Hb and Blood Hb. Blood Hb has a sigmoidal theta plot with a normal p50 value of ~40 mm Hg. Stipped Hb appears hyperbolic with a p50 value of ~2 mm Hg. Interestingly, when she adds very high concentrations of NaCl to the Blood Hb oxygen binding reactions, the result is a decrease in p50 for Blood Hb to ~2 mm Hb. Which of the following experimental factors are most likely responsible for the observed results?

A) The NaCl is likely preventing the Blood Hb from undergoing a T to R transition and therefore the result is a decrease in p50

B) The NaCl is probably disrupting the quaternary and tertiary structure of Blood Hb resulting in the decrease in p50 and leading to a hyperbolic theta plot

C) At high concentrations in solution, the Na+ ions are likely binding to Bohr positions resulting in the decrease in Blood Hb p50

D) At high concentrations in solution, the Na+ ions are likely forming ionic interactions with the proximal and distal histidine residues thus decreaseing the p50 value

E) At high concentrations in solution, the Cl- ions are probably out competing 2,3 BPG for the binding site in the central cavity of Blood Hb resulting in a decrease in p50

The enzyme alcohol dehydrogenase catalyzes the following redox reaction:

Acetaldehyde + NADH + H+ -> Ethanol + NAD+

Which of the following statements correctly describes this reaction:

A) Two electrons and a single proton are transferred in the form of a Hydride ion from NADH to Acetaldehyde yielding Ethanol. The second H+ reacts with OH- to yield H2O

B) Both protons and electrons from NADH + H+ are transferred to Acetaldehyde yielding the ethanol and the fully reduced NAD+.

C) The Hydride ion from NADH + H+ likely attacks the carbonyl of acetaldehyde while the H+ is picked up by the carbonyl O- during the reaction to yield the primary alcohol function.

D) Only answers B and C are correct statements.

E) Answers A, B and C are all correct statements.