Question

$C_4$-cycle was discovered by

• A. Hatch and Slack
• B. Calvin
• C. Hill
• D. Arnon

Answer 1

The correct option is A Hatch and Slack

$C_4$ cycle which is also known as the Hatch-Slack pathway is a cyclic process. It occurs in chloroplasts. It was discovered by two Australian scientists Hatch and Slack. It is found in $C_4$ plants. Carbon dioxide fixation is done in this pathway. The primary $C{O}_2$ acceptor is a three-carbon molecule phosphoenolpyruvate (PEP) and it is present in mesophyll cells. The enzyme that catalyzes this $C{O}_2$ fixation is PEP carboxylase or PEPcase. The mesophyll cells of $C_4$ plants lack the enzyme RuBisCO. The 4-carbon oxaloacetic acid (OAA) is formed in the mesophyll cells which is further converted into the malic acid or aspartic acid and then transported into bundle sheath cells. In the bundle sheath cells, these $C_4$ acids are broken down to release $C{O}_2$ and a three-carbon molecule.