Question

which is true regarding the tca cycle (krebs cycle)?
pyruvate is an end product of the cycle
energy capture in the cycle is solely from the formation of atp in one of the steps
entry of carbon dioxide starts the cycle
some components of the cycle are used as building blocks for certain anabolic pathways
two of the above are true

Explanation:

Pyruvate is converted to acetyl - CoA before entering the TCA cycle, so it's not an end - product of the cycle. Energy capture in the cycle occurs through multiple steps and not just one step for ATP formation. The cycle starts with the entry of acetyl - CoA, not carbon dioxide. Some intermediates of the TCA cycle are used as building blocks for anabolic pathways, like α - ketoglutarate and oxaloacetate for amino - acid synthesis.

Answer:

some components of the cycle are used as building blocks for certain anabolic pathways