Question

The term, “protoplasmic respiration” is used when the respiratory substrate is
A. Carbohydrate
B. Protein
C. Organic acid
D. Lipid

Answer 1

Only in certain seeds, the substrate is a storage material. It forms part of the protoplasm in others. It produces ammonia as a toxic product.

Complete Answer:
- Respiration is a biochemical mechanism in which various food compounds such as sugars, proteins and fats are oxidised and energy is produced where $O_2$ is drawn in and $CO_2$ is released as a result of this. 6-carbon glucose is the respiratory substrate that cells use. As a respiratory substrate, fats, proteins and various organic acids may also be used.
Now, let us find the solution from the options-
- Respiration that uses carbohydrate as a substrate is termed as floating respiration. Therefore, the option A is incorrect.
- Respiration that uses proteins as a substrate is termed protoplasmic respiration. It is difficult to maintain protoplasmic respiration as soon as it depletes structural and functional protein protoplasm as well as releases poisonous ammonia.
- Organic acids and lipids are not used as substrates in protoplasm reactions. Therefore, the options C and D are incorrect.

Thus, the correct answer is option (B) Protein.

Note: Protoplasmic respiration is a rare mode of respiration. The fuel of choice for cellular respiration is carbohydrates. If adequate carbohydrates are not usable, other biomolecules such as fats and proteins may be used to provide the requirements for cellular energy. When enough carbohydrates are not available, fats are burned first. Only where all carbohydrates and fats are not available, proteins are used.