Question

Which of the following is correct in regards to photorespiration?

• A. In mitochondria, serine in converted into hydroxypyruvate
• B. In mitochondria, two glycine molecules unite to form serine
• C. In mitochondria, glycolate is oxidised to form glyoxylate
• D. In peroxisomes, three molecules of glycine unite to form serine

Answer 1

The correct option is B In mitochondria, two glycine molecules unite to form serine

In photorespiration, the glycine is transported out of peroxisomes into mitochondria, where two molecules of glycine interact to form one molecule each of serine, CO${}_2$, NH${}_3$.

2 Glycine + H${}_2$O + NAD${}^{+}\to$ Serine + CO${}_2$+ NH${}_3$ + NADH

The CO${}_2$ is then released in photorespiration from mitochondria. The NH${}_3$ released during glycine decarboxylation is transported to cytoplasm or chloroplast, where it is incorporated into the synthesis of glutamic acid.

Hence, the correct answer is 'In mitochondria, two glycine molecules unit to form serine'.