In the reaction that converts citrate to isocitrate, the enzyme that catalyzes t
ID: 92453 • Letter: I
Question
In the reaction that converts citrate to isocitrate, the enzyme that catalyzes this step in the citric acid cycle, aconitase, accomplishes the rearrangement of the hydroxyl on C-3 of citrate to the C-2 position in isocitrate. This rearrangement takes place because of: an oxidative decarboxylation of one of the carboxyl groups of citrate. a removal and addition of water. an oxidation and transfer of electrons to FAD. an oxidation and transfer of electrons to NAD+. In the sequence of reactions that convert pyruvate to glucose in cells capable of gluconeogenesis, three reactions are used to by-pass enzymes used in glycolysis. Which one of the following enzymes does NOT function in both pathways? Glyceraldehyde-3-phosphate dehydrogenase Phosphoglycerate kinase Pyruvate kinase Enolase AldolaseExplanation / Answer
Answers: -
18.option "b"-a removal and addition of water.
Explanation: -
The tertiary hydroxyl group is not properly located in the citrate molecule for the oxidative decarboxylations that follow.
**Thus, citrate is isomerized into isocitrate to enable the six-carbon unit to undergo oxidative decarboxylation. The isomerization of citrate is accomplished by a dehydration step followed by a hydration step.
**The result is an interchange of a hydrogen atom and a hydroxyl group.
**The enzyme catalyzing both steps is called aconitase because cis-aconitate is an intermediate.
19.option- "d"-enolase.
Explanation: -aldolase enzyme (EC 4.1.2.13), and plays a key role in bothglycolysis and gluconeogenesis.
**But enolase enzyme do not have any role in gluconeogenesis.