Question: how many carbon atoms are there in one molecule of phosphoglycolate?
Answer: Two molecules are produced: a three-carbon compound, 3-PGA, and a two-carbon compound, phosphoglycolate. 3-PGA is a normal intermediate of the Calvin cycle, but phosphoglycolate cannot enter the cycle, so its two carbons are removed, or "stolen," from the cycle 5start superscript, 5, end superscript.