Question

The term, "floating respiration" is used when the respiratory substrate is
A. Carbohydrates
B. Fats
C. Both A and B
D. Protein

Answer 1

Hint: Sugars are the preferred substrates for respiration. The use of simple sugars as a substrate for respiration does not produce the toxic end products.

 Complete answer:
We will first learn the basics of respiration.
All living beings require energy to support vital life processes. This energy is provided by the food we eat. However, to obtain the energy stored in the food, the nutrients present in it should be broken down into simpler substances.
The process of digestion of food inside the gastrointestinal tract splits the complex macromolecules of nutrients into the simpler monomers. For example, complex carbohydrates and proteins are digested into simpler sugars (such as glucose) and amino acids respectively. Fats are digested into fatty acids and glycerol.
The simple sugars, amino acids, and fatty acids are absorbed by cells where they serve different roles. One such role is their use as fuel during the process of respiration.
Respiration includes the breakdown of nutrients, mainly glucose, to retrieve the energy stored in its chemical bonds. This energy is then stored in the form of ATP.
Now, as mentioned, the digestion products of carbohydrates, proteins, and fats can serve as a substrate for the process of respiration. Based on the substrate used, respiration is categorized as protoplasmic and floating respiration.
When carbohydrates or fats serve as substrates, it is called floating respiration. On the other hand, if the substrate is protein, it is protoplasmic respiration.
Let’s talk about the floating respiration in detail. As we know, glucose (a simple sugar) directly enters the glycolysis, the first phase of the respiration. Likewise, other simple sugars can also enter at any stage of respiration. Fatty acids mostly enter the citric acid cycle (the second phase of the respiration). In either case, the end products are carbon dioxide and water. It is the most common type of respiration that occurs in the living cells.

So, the answer is option C: Both A and B.

Note:
Respiration includes breathing and cellular respiration. The aerobic cellular respiration occurs in three stages: glycolysis, citric acid cycle, and the electron transport chain. Various nutrients can enter respiration as a substrate for the chemical reactions of glycolysis or the citric acid cycle.