Which statement best defines substrate channeling and provides an example pathway?

• A. Substrate channeling is the direct transfer of intermediates between enzymes, reducing diffusion losses; examples include the pyruvate dehydrogenase complex and purine biosynthesis enzyme clusters.
• B. Substrate channeling is the diffusion of products into the bloodstream.
• C. Substrate channeling requires impermeable membranes.
• D. Substrate channeling only occurs in prokaryotes.

Answer: (A)