Question

atp serves as a common energy source for organisms because
a it is the smallest energy molecule
b it stores the least energy of any energy source
c its energy can be easily transferred to do cellular work
d it is extremely stable and can be stored in the cell for long periods of time
e traces of it have been found in fossils of ancient organisms dating back to the beginning of life on earth

Explanation:

ATP (adenosine triphosphate) is the energy currency of the cell. Its energy is easily transferable. When the high - energy phosphate bonds in ATP are broken (especially the last one), energy is released. This released energy can be directly used for various cellular processes such as muscle contraction, active transport, and biosynthesis.

• Option A: There are smaller energy - related molecules (e.g., some simple organic compounds involved in minor energy - transfer steps in some pathways), so this is incorrect.
• Option B: ATP stores a significant amount of energy in its phosphate bonds. Molecules like ADP (adenosine diphosphate) store less energy than ATP. So this option is wrong.
• Option C: As explained above, the energy in ATP can be easily transferred (by hydrolysis of phosphate bonds) to do cellular work. This is correct.
• Option D: ATP is not extremely stable. It is designed to be a readily available energy source, and its phosphate bonds are relatively easy to break (and form again during ATP synthesis). So this is incorrect.
• Option E: The presence of traces in fossils is not the reason for it being a common energy source. The functional aspect (energy transfer) is what matters. So this is incorrect.

Answer:

C. Its energy can be easily transferred to do cellular work