Maximum energy is liberated on respiratory breakdown of

Options

A. Protein
B. Fat
C. Carbohydrate
D. Nucleic acid

Answer

To solve the question regarding which macromolecule liberates the maximum energy upon respiratory breakdown, we can follow these steps:

### Step 1: Identify the macromolecules
The options provided are:
- Protein
- Fat
- Carbohydrate
- Nucleic acid

### Step 2: Understand the energy yield of each macromolecule
- **Carbohydrates**: When carbohydrates are broken down, they yield approximately 4 calories of energy per gram.
- **Proteins**: Similarly, proteins also yield about 4 calories of energy per gram upon breakdown.
- **Fats**: Fats are more energy-dense and yield about 9 calories of energy per gram when they are metabolized.
- **Nucleic acids**: Nucleic acids do not primarily serve as energy sources and are not typically broken down for energy in the same way as the other macromolecules.

### Step 3: Compare the energy yields
From the above information:
- Carbohydrates: 4 calories/gram
- Proteins: 4 calories/gram
- Fats: 9 calories/gram
- Nucleic acids: Not a significant energy source

### Step 4: Determine which macromolecule liberates the maximum energy
Since fats yield the highest amount of energy at 9 calories per gram, we can conclude that the macromolecule that liberates the maximum energy upon respiratory breakdown is **fat**.

### Final Answer:
The maximum energy is liberated on the respiratory breakdown of **fat**.

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