[Campbell Biology P.221] What is the direct ATP equivalent yield from one turn of the citric... | Practice Question

What is the direct ATP equivalent yield from one turn of the citric acid cycle, considering the stated differences in animal tissues versus plant/bacterial cells?

  • A: 1 ATP directly in all cells.
  • B: 1 GTP in animal cells, which is similar to ATP, and 1 ATP directly in plant/bacterial cells.
  • C: 1 ATP in animal cells, and 1 GTP in plant/bacterial cells.
  • D: No direct ATP or GTP is produced; all energy is in NADH and FADH2.

Explanation

The text states: 'In many animal tissue cells, the reaction in step 5 produces a guanosine triphosphate GTP molecule by substrate-level phosphorylation.' and 'In the cells of plants, bacteria, and some animal tissues, step 5 forms an ATP molecule directly by substrate-level phosphorylation.' GTP is noted to be similar to ATP in structure and function, acting as an ATP equivalent. Therefore, the direct yield is 1 GTP equivalent to ATP in animal cells or 1 ATP in plant/bacterial cells.