Question

which process occurs only in autotrophic organisms?
a. calvin cycle
b. chemiosmosis
c. krebs cycle
d. proton pump mechanism

Explanation:

• Option A: The Calvin cycle is part of photosynthesis, which is a process that autotrophs (like plants, algae) use to convert carbon dioxide and water into glucose using energy from light (or in some cases, chemical energy for chemoautotrophs). Only autotrophs perform photosynthesis (including the Calvin cycle) to make their own food.
• Option B: Chemiosmosis occurs in both autotrophs (during photosynthesis and cellular respiration) and heterotrophs (during cellular respiration). It's the process of using a proton gradient to make ATP, so it's not unique to autotrophs.
• Option C: The Krebs cycle (citric acid cycle) is part of cellular respiration, which both autotrophs and heterotrophs perform to break down organic molecules and generate ATP. So heterotrophs (which consume food) also do the Krebs cycle.
• Option D: Proton pump mechanisms are used in various processes like cellular respiration (both in autotrophs and heterotrophs) and can also be involved in other transport processes. They aren't unique to autotrophs.

Answer:

A. Calvin cycle