Krebs' cycle also called TCA (Tricarboxylic acid cycle) or citric acid cycle (organic acid cycle). It is also called metabolic sink as it is

Options

A. common pathway for carbohydrates . fats and proteins (amino acids)
B. common pathway for carbohydrates and fats only
C. common pathway for carbohydrates and organic acids only
D. none of the above

Answer

### Step-by-Step Solution:

1. **Understanding the Krebs Cycle**: The Krebs cycle, also known as the Tricarboxylic Acid (TCA) cycle or Citric Acid cycle, is a crucial metabolic pathway that plays a significant role in cellular respiration. It is referred to as a "metabolic sink" because it is involved in the breakdown of various macromolecules, including carbohydrates, fats, and proteins.

2. **Components of the Krebs Cycle**: The cycle begins with the conversion of glucose (C6H12O6) into pyruvic acid (C3H4O3) through glycolysis. Pyruvic acid is then converted into acetyl coenzyme A (acetyl CoA), which combines with oxaloacetic acid to form citric acid.

3. **Metabolic Processes Involved**: The Krebs cycle involves the breakdown of:
- **Carbohydrates**: Through glycolysis, glucose is broken down into pyruvic acid, which enters the Krebs cycle.
- **Fats**: Fatty acids are broken down into acetyl CoA, which can also enter the Krebs cycle.
- **Proteins**: Amino acids can undergo deamination to form intermediates that enter the Krebs cycle.

4. **Identifying the Correct Option**: The question asks which types of macromolecules are involved in the Krebs cycle. The options provided are:
- A) Carbohydrate, fat, and protein (like amino acids)
- B) Carbohydrate and fats only
- C) Carbohydrate and organic acid only
- D) Protein and fats only

Since the Krebs cycle involves the breakdown of carbohydrates, fats, and proteins, the correct answer is **Option A**: Carbohydrate, fat, and protein.

5. **Conclusion**: The Krebs cycle is a metabolic pathway that integrates the breakdown of carbohydrates, fats, and proteins, making it a metabolic sink.