Rubisco catalyzes competing carboxylase and oxygenase reactions. The oxygenase r

ID: 856797 • Letter: R

Question

Rubisco catalyzes competing carboxylase and oxygenase reactions. The oxygenase reaction converts ribulose-1,5-bisphosphate to 3-phosphoglycerate and 2-phosphoglycolate. Many tropical plants have developed a mechanism to minimize this wasteful side reaction by concentrating CO2 in the cell containing rubisco, where it successfully competes with oxygen for the enzyme. This mechanism, shown below, is called the C4 pathway, and it involves reactions in two neighboring cell types: mesophyll and bundle-sheath cells. Identify the missing enzymes and pathway intermediates of the C4 pathway by dragging the names to the appropriate positions. (Not all names will be used, and some may be used more than once).

Explanation / Answer

C4 Cycle in Chloroplast

Mesophyll cells

Bundle sheath cell

Carbondioxide fixed from atmosphere is coverted to bicarbonate,

Enzymes : PEP Carboxylase,

phosphoenol pyruvate (PEP) is converted to Oxalo acetate, OAA is converted to malate.

The pyruvate from bundle sheath cells enter into mesophyll cells, pyruvate is converted to PEP,where ATP is hydrolysed to AMP.

Enzyme: Malic enzyme,

Malate from mesophyll cells

Malate is converted to pyruvate, and NADP+ is converted to NADPH.

Carbon dioxide is released .

The pyruvate enters into mesophyll cell

Cytosol