13
QuizMultiple Choice

Catalysts — Unit test

Question 13 • PA Human Anatomy & Physiology A 2026-2027 SMITH IC

Which statement best describes the process of chemiosmosis and the direct result of its occurrence?

Answer
A
Hydrogen ions flow from the thylakoid down a concentration gradient through ATP synthase channels into the stroma. ADP is converted to ATP.
B
Hydrogen ions flow from the thylakoid down a concentration gradient through ATP synthase channels into the stroma. ATP is converted to ADP.
C
Hydrogen ions flow from the stroma down a concentration gradient through ATP synthase channels into the thylakoid. ADP is converted to ATP.
D
Hydrogen ions flow from the thylakoid against a concentration gradient through ATP synthase channels into the stroma. ADP is converted to ATP.

Explanation

During photosynthesis, hydrogen ions build up inside the thylakoid, creating a higher concentration there than in the stroma. They flow down this concentration gradient through ATP synthase into the stroma, and that movement provides energy to convert ADP into ATP. Choice A describes both the direction of ion flow and the direct result.

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