Question

Metabolism comprises:
A. Digestion of food
B. Elimination of wastes
C. Exchange of gases
D. Various energy exchanges in a cell

Answer 1

Hint: Metabolism is an integral part of all living systems and is one of the distinguishing features between the living and the non-living. It is some total of all the reactions taking place inside the living systems. It comprises anabolism and catabolism. All the life processes are actually the result of either the catabolic i.e., breakdown reactions or the anabolic i.e., synthesis reactions.

complete solution:
If we carefully look at the options, we can clearly see one or the life processes in all the options except one which is our answer. To understand this point let us see each of the options one after the other.
Option A: Digestion of food is a catabolic reaction and should be a part of metabolism. But this is not our answer because metabolism is the sum total of catabolism as well as anabolism.
Thus, option A is not correct.
Option B: Elimination of wastes is again a life process and consists of various metabolic reactions however, just elimination of wastes cannot define metabolism in its wholesome part. So, this option is not correct.
Thus, option B is incorrect.
Option C: Exchange of gases is a part of respiration which is a catabolic process. But again, it cannot define metabolism completely.
Thus, option C is also incorrect.
Option D: “Various energy exchanges in a cell” – this is a statement which defines metabolism in terms of thermodynamics and bioenergetics. In other words, metabolism consists of energy releasing (catabolism) and energy consuming reactions (Anabolism) and both of the types of reactions involve various energy exchanging reactions utilizing ATP –the energy currency of the cell. Thus, this option is correct in view of Bioenergetics.
Thus, option D is correct.

Hence, Option D. Various energy exchanges in the cell is the correct answer.

Note:
Bioenergetics is a discipline of biology that studies how cells convert energy, most often through the production, storage, or consumption of adenosine triphosphate (ATP). Most components of cellular metabolism, and hence life itself, rely on bioenergetic activities such as cellular respiration and photosynthesis. All energy exchange in a cell is studied in bioenergetics.