Question

"DNP inhibits respiration by preventing a proton gradient being maintained across membranes. When DNP was added to isolated mitochondria, the following changes were observed:

less ATP was produced
more heat was produced
the uptake of oxygen remained constant.
Explain how DNP caused these changes. (3)"
a) DNP increases the production of ATP.
b) DNP has no effect on ATP production.
c) DNP uncouples the proton gradient, leading to less ATP production and increased heat generation.
d) DNP enhances oxygen uptake, resulting in more ATP production.

Answer 1

DNP uncouples the proton gradient in mitochondria, resulting in less ATP production and increased heat generation. Oxygen uptake, however, remains constant.

Step-by-step explanation:

DNP uncouples the proton gradient, leading to less ATP production and increased heat generation. When DNP is added to isolated mitochondria, it makes the inner mitochondrial membrane leaky to protons, preventing the maintenance of a proton gradient. This hampers the flow of protons through ATP synthase, resulting in decreased ATP production. The stored energy that would have been used to produce ATP is then dissipated as heat, causing an increase in heat production. However, the uptake of oxygen remains constant.