Carbohydrates, proteins, fats, and nucleic acids all

Options

A. Are digested and absorbed in the human stomach
B. Cannot be digested by an animal unless it has a gizzard
C. Are chemically digested by enzymes produced in the oesophagus
D. Must be broken down into simple compounds before being absorbed

Answer

To solve the question regarding carbohydrates, proteins, fats, and nucleic acids, we will analyze the options provided and determine the correct statement.

### Step-by-Step Solution:

1. **Understanding the Components**:
- Carbohydrates, proteins, fats, and nucleic acids are all essential macromolecules required by the body for various functions.

2. **Evaluating the Options**:
- **Option 1**: "Digested and absorbed in human stomach."
- This statement is incorrect. While some digestion begins in the stomach, the complete digestion and absorption of these macromolecules primarily occur in the small intestine.

- **Option 2**: "Cannot be digested by animals unless it has a gizzard."
- This statement is also incorrect. While some animals, like birds, have gizzards to help mechanically break down food, many animals (including humans) digest these macromolecules without a gizzard.

- **Option 3**: "Chemically digested by enzymes produced in the esophagus."
- This statement is incorrect. The esophagus primarily serves as a passageway for food and does not produce enzymes for chemical digestion. Chemical digestion of these macromolecules occurs in the stomach and small intestine.

- **Option 4**: "Must be broken down into simple compounds before being absorbed."
- This statement is correct. For the body to absorb carbohydrates, proteins, fats, and nucleic acids, they must be broken down into their simpler forms (monosaccharides, amino acids, fatty acids, and nucleotides, respectively).

3. **Conclusion**:
- The correct answer is that carbohydrates, proteins, fats, and nucleic acids all must be broken down into simple compounds before being absorbed.

### Final Answer:
**Must be broken down into simple compounds before being absorbed.**