Botany MCQs for NEET — Practice Questions with Answers

The Calvin cycle, which is the set of chemical reactions that take place in chloroplasts during photosynthesis, utilizes 9 ATP and 6 NADPH₂ molecules for the fixation and reduction of 3 molecules of CO₂. This energy and reducing power are used to convert CO₂ into G3P, which can then be used to form glucose and other carbohydrates.

RuBP carboxylase, also known as RuBisCO, is the enzyme that catalyzes the first major step of carbon fixation in the Calvin cycle. It is present in the chloroplast stroma and is the most abundant protein in the chloroplast, and indeed, on Earth. This enzyme facilitates the attachment of carbon dioxide to ribulose bisphosphate (RuBP) to start the Calvin cycle.

Thylakoids are involved in the light-dependent reactions of photosynthesis, where they help in the formation of ATP and NADPH. However, the Calvin cycle, which assimilates CO₂ to form hexose sugars, requires specific enzymes such as Rubisco. If thylakoids are removed and kept in a culture medium, the CO₂ assimilating enzymes are absent, and hence, hexose sugars cannot be formed. This makes option o3 the correct answer.

Sugarcane is one of the most efficient plants in converting solar energy into biomass. It has a high net productivity of 2-4 kg/m²/yr or even higher, making it the correct answer. Sugarcane's efficiency is due to its C4 pathway of photosynthesis, which is more efficient under high light intensity and temperature conditions.

The quantum requirement in photosynthesis refers to the number of photons needed to release one mole of O₂. It is a measure of the efficiency of photosynthesis in converting light energy into chemical energy. Thus, option o2 is the correct answer.

The Calvin cycle, also known as the C3 cycle, is a series of biochemical redox reactions that take place in the stroma of chloroplasts in photosynthetic organisms. It is referred to as reductive carboxylation because it involves the reduction of carbon dioxide into glucose. This process uses ATP and NADPH produced during the light-dependent reactions of photosynthesis.

Maximum photosynthesis typically occurs under red light. Red light (around 680 nm) is most effectively absorbed by chlorophyll a, the main pigment involved in photosynthesis. Thus, red light drives the highest rate of photosynthesis compared to other wavelengths.

In C₄ plants, the Kranz anatomy is characterized by bundle sheath cells that lack grana and mesophyll cells that contain grana. This specialization allows for the efficient functioning of the C₄ photosynthetic pathway, which minimizes photorespiration and maximizes photosynthetic efficiency.

Chlorophyll a is absent in bacteria. Bacteria use different pigments such as bacteriochlorophylls for photosynthesis, which are distinct from the chlorophylls found in plants, algae, and cyanobacteria.