Question

question 11 (1 point)
what molecile reacts with acetyl-coa at the beginning of the citric acid cycle to produce citrate and is later re-formed in step 8 so the cycle can happen again?
isocitrate
citric acid
oxaloacetate
pyruvate

Explanation:

To solve this, we recall the citric acid cycle (Krebs cycle) steps. At the start, acetyl - CoA combines with oxaloacetate (a 4 - carbon molecule) to form citrate (a 6 - carbon molecule) via the enzyme citrate synthase. In step 8 of the cycle, oxaloacetate is regenerated, allowing the cycle to repeat. Isocitrate is a product after citrate is isomerized, citric acid is another name for citrate (the product of the first reaction), and pyruvate is involved in glycolysis and the link reaction (converted to acetyl - CoA), not the initial reaction of the citric acid cycle. So the molecule that reacts with acetyl - CoA and is re - formed is oxaloacetate.

Answer:

C. oxaloacetate