Which statement BEST describes the function of an enzyme in the body?
A All of the above describe the function.
B An enzyme catalyzes chemical reactions.
C An enzyme transports waste out of the blood.
D An enzyme signals cellular events.
E An enzyme acts as a buffer.
The correct answer and explanation is :
Correct Answer: B. An enzyme catalyzes chemical reactions.
Explanation:
Enzymes are specialized biological catalysts that speed up the rate of virtually all of the chemical reactions that take place within cells. Without enzymes, many of these reactions would occur too slowly to sustain life. The key function of enzymes is to lower the activation energy required for a reaction to proceed, thus facilitating and accelerating biological processes.
Each enzyme is highly specific for the substrate (reactant) it acts upon. This specificity is often described using the “lock-and-key” model, where the enzyme (the lock) fits precisely with the substrate (the key). Once the substrate binds to the enzyme’s active site, the enzyme promotes the chemical transformation of the substrate into the product(s), after which the enzyme is released unchanged and can be reused in another reaction.
Enzymes are involved in digestion, where they help break down large macromolecules like proteins, fats, and carbohydrates into smaller components that the body can absorb and utilize. They also play vital roles in metabolism, DNA replication, cell signaling, and energy production (e.g., cellular respiration). Examples include amylase (breaks down starch), lipase (breaks down fats), and DNA polymerase (synthesizes DNA).
Let’s examine why the other choices are incorrect:
- C. An enzyme transports waste out of the blood: This is a function of the excretory system, not enzymes. Transport proteins or organs like the kidneys perform this role.
- D. An enzyme signals cellular events: While enzymes may be part of signal transduction pathways, they do not directly signal events. That’s typically done by hormones or receptor proteins.
- E. An enzyme acts as a buffer: Buffers maintain pH levels. This is not an enzymatic function.
- A. All of the above describe the function: Since only option B is correct, this is not the best answer.
Thus, B best captures the primary and defining function of enzymes in the body.