Question

Maize, sugarcane and some other tropical plants have high efficiency of $CO_2$ fixation because they operate :
a. Calvin cycle
b. Hatch-Slack cycle
c. TCA cycle
d. PP pathway

Answer 1

These plants are called $C_4$ plants because the first stable photosynthetic product is a 4-carbon compound .

Complete answer:
Let’s discuss given options and find the correct answer:

a. The Calvin cycle consists of four main steps namely, carbon fixation, reduction phase, carbohydrate formation, and regeneration phase. Chemical compounds which contain the energy plants have captured from sunlight, energy to fuel chemical reactions during this sugar-generating process is provided by ATP and NADPH.

b. Most of the plants that are adapted to dry tropical regions have the $C_4$ pathway. These plants are called C4 plants.
Sugarcane, Maize, Sorghum, Corn, etc., are the examples of these plants. These plants have high efficiency $CO_2$ fixation because they operate Hatch-Slack pathways. It is also known as the $C_4$ pathway. It is a cyclic process. It occurs in chloroplasts.

c. The TCA cycle (tricarboxylic acid cycle) also known as the citric acid cycle or the Krebs cycle. It is a list of chemical reactions used from all aerobic organisms to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.

d. The pentose phosphate pathway is a metabolic pathway parallel to glycolysis. It generates NADPH and pentoses as well as ribose 5-phosphate, a precursor for the synthesis of nucleotides. While the pentose phosphate pathway does involve oxidation of glucose, its primary role is anabolic rather than catabolic.

Hence option ‘b’ Hatch - Slack Cycle is the correct answer.

Note: It is the primary step in extracting carbon from $CO_2$ to be ready to use it in sugar and other biomolecules.Hatch - Slack Cycle is a photosynthetic reaction in some plants.