Question

The importance of Krebs cycle is in the production of-
a. Acetyl-CoA
b. Water
c. ADP
d. ATP

Answer 1

Hint: An energy-carrying molecule found in the cells of all living organisms, absorbing and releasing chemical energy from the breakdown of food molecules to fuel other cellular processes.

Complete answer:
> Option A is incorrect. Acetyl coenzyme A or acetyl-CoA, used in many biochemical reactions, is an important molecule in metabolism. Its main purpose is to transfer the carbon atoms within the acetyl group into the cycle of citric acid (Krebs cycle) to be oxidised for the production of energy.

> Option B is incorrect. The enzyme citrate synthase catalysed the first reaction of the cycle of citric acid. In this step oxaloacetate is joined to form citric acid with acetyl-CoA. If the two molecules are joined together, a water molecule attacks the acetyl which results in the release of coenzyme A from the complex.

> Option C is incorrect. Since citrate synthase is inhibited as ATP by the final product of the cycle of citric acids, ADP (adenosine diphosphate) acts as the enzyme's allosteric activator as ATP is produced from ADP. It controls the rate at which the isocitrate citrate isomer loses a carbon to form the α-ketoglutarate, a five-carbon molecule.

> Option D is correct. The Krebs cycle is the second of three cellular respiration stages in which glucose, fatty acids and some amino acids, the so-called fuel molecules, are oxidised (see Figure). These molecules' oxidation is mainly used to turn the energy found in those molecules into ATP.

Hence, The correct answer is option (D).

Note: In the process, a total of 34 ATP is extracted via kreb's cycle. It is at the heart of cellular metabolism and plays a leading role in both the energy production and biosynthesis processes. It completes the sugar-breaking task started in glycolysis and eventually fueling ATP production.