Question

TCA cycle is named after
A. Embden
B. Calvin
C. Krebs
D. Emerson

Answer 1

Hint: TCA cycle refers to Tricarboxylic cycle. We will first explain the TCA cycle- what is it, who named it.

Complete Answer:
TCA cycle: TCA cycle is also called the Citric acid cycle or Krebs cycle.
- This cycle was named after the name of its discoverer who was Hans Adolf Krebs.
- TCA cycle is a part of aerobic respiration (a process which occurs in the presence of Oxygen to convert food into carbon dioxide, water and energy).
- TCA cycle is a series of chemical reactions in all aerobic organisms to release energy.
- In the TCA cycle Acetyl coenzyme A gets oxidized.
- Acetyl coenzyme A is derived from the fats, proteins and carbohydrates.
- This cycle takes place in the matrix of Mitochondria of a cell.

Oxidative decarboxylation of pyruvate to Acetyl coenzyme A.
- This is the linkage step between the glycolysis and Kreb’s cycle.
- In this step, the end product of glycolysis i.e the pyruvate is oxidatively decarboxylated to acetyl coenzyme A and carbon dioxide with the help of enzyme pyruvate dehydrogenase.

There are a total 8 steps occurred in the TCA cycle. These all eight steps are enzyme catalysed.

Sl.No.	Steps involved in Krebs cycle	Enzyme used
1	Condensation of acetyl coenzyme A with Oxaloacetate	Citrate synthase
2	Isomerisation of citrate into isocitrate	Aconitase
3	Oxidative decarboxylation of isocitrate	Isocitrate dehydrogenase
4	Oxidative decarboxylation of alpha-ketoglutarate	Alpha-ketoglutarate dehydrogenase
5	Conversion of succinyl-coA into succinate	Succinyl-coA synthase
6	Dehydration of succinate to fumarate	Succinate dehydrogenase
7	Hydration of fumarate to malate	Fumarate hydratase
8	Dehydration of malate to oxaloacetate	Malate dehydrogenase

So, option C is the right answer to this question.

Note: TCA cycle takes place in the matrix of mitochondria. Its purpose is the complete oxidation of glucose and producing energy rich molecules that later produce ATP in the Electron transport chain.