Question

The net requirement of assimilatory power for the formation of 6 hexose molecules in a maize plant is:
A. 72 ATP, 48 NADPH
B. 90 ATP. 60 NADPH
C. 108 ATP, 72 NADPH
D. 180 ATP, 72 NADPH

Answer 1

Hint: Maize belongs to the group of the C4 plants. These plants form a four-carbon compound in the Calvin- Benson cycle. That 4 carbon compound is oxaloacetate (OAA)

Complete answer: Maize is an example of a C4 plant.For every carbon dioxide molecule that is fixed, 3 ATPs are utilized in C4 plants (2 ATPs in C3 plants).
C4 plants undergo both C4 and C3 cycles for the formation of sugars (glucose).
Hence, for every glucose molecule that is produced, (3 x 6) + (2 x 6) = 18 + 12 = 30 ATPs are required.
12 NADPH (Nicotinamide adenine dinucleotide phosphate) is used/ reduced to form NADP for the formation of one glucose.
Each NADPH corresponds to 2.5 ATPs in the Electron Transport Chain/ System (ETC).
For six hexose/ glucose molecules formed, 6 times the amount of ATP and NADPH is required.
Hence, 12 x 6 = 72 NADPH and 30 x 6 = 180 ATPs are required.

So the correct answer is C.

Note: Hatch and Slack Pathway is the other name of the C4 pathway.
Here, the primary acceptor of carbon dioxide (for fixation) is phosphoenolpyruvate (PEP). This forms oxaloacetate (OAA)
The C4 pathway occurs in both the mesophyll cells and the bundle sheath cells
Bundle sheath cells are part of the Kranz anatomy unique to C4 plants.
Kranz means ‘wreath’, it is a reflection of the cell arrangement. The bundle sheath cells may form several layers around the vascular bundles.

They have the following characteristic features:
1. They have a large number of chloroplasts.
2. They have thick walls that are impervious to gaseous exchange with no intercellular spaces.