Question

Chemicals that store energy for the majority of work within cells are called

• A. Lipid
• B. Protein
• C. Carbohydrate
• D. Enzyme

Hint:

Although lipids contain more energy per unit mass (\(9 \text{ kcal/g}\) vs \(4 \text{ kcal/g}\) for carbohydrates), the solubility and rapid metabolic mobilization of carbohydrates make them the preferred choice for immediate cellular work.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Cells perform active transport, mechanical contractions, and chemical synthesis using stored chemical energy.
While Adenosine Triphosphate (ATP) is the immediate energy currency, the energy is stored long-term in organic macromolecules.

Step 3: Detailed Explanation:
Carbohydrates are the main organic molecules that store easily accessible energy for cellular work.
During cellular respiration, carbohydrates like glucose, glycogen, and starch are broken down to synthesize ATP.
Carbohydrates can be metabolized through glycolysis in the cytoplasm and oxidative phosphorylation in the mitochondria.
This makes them the most rapidly mobilized and preferred energy source for most cell types.
Let us analyze the other options:
Lipids store more than twice the energy per gram compared to carbohydrates.
However, they serve as highly concentrated, long-term energy reserves that are slower to mobilize.
Proteins serve structural and catalytic roles and are only used as an energy source under starvation conditions.
Enzymes are biological catalysts that lower activation energy; they do not store or provide energy.
Therefore, carbohydrates are the primary class of chemicals utilized to store energy for daily cellular work.

Step 4: Final Answer:
The chemicals storing energy for the majority of cellular work are carbohydrates, matching Option (C).