Question

In $C_3$ plants, the first stable product of photosynthesis during the dark reaction is

• A. malic acid
• B. oxaloacetic acid
• C. 3-phosphoglyceric acid
• D. phosphoglyceraldehyde

Answer 1

Answer: (C)

In $C_3$ plants, the first stable product formed during dark reaction is $3$-phosphoglyceric acid. Since, it is a $3$-carbon compound hence, the pathway is referred as $C_3$ pathway. Oxaloacetic acid $(OAA)$ is the first stable compound in $C_4$ plants. It is a $4C$ compound. This acid is converted to another $4C$ acid malic acid which enters into the chloroplast of bundle sheath cells.
In $C_3$ cycle, $3PGA$ is phosphorylated into $1,3$-diphosphoglyceric acid, which is reduced into 3-phosphoglyceraldehyde.