NEET Practice Questions (MCQs) with Answers & Solutions

In angiosperms, the translocation of sugar primarily occurs in the form of sucrose. Sucrose is efficiently transported through the phloem to various parts of the plant where it can be utilized or stored.

Quinones are mobile electron carriers. They play a crucial role in the electron transport chain, a series of reactions that occur in the mitochondria during cellular respiration, helping in the transfer of electrons between different complexes.

During the dark reaction (Calvin cycle), carbon fixation occurs when carbon dioxide (CO₂) is attached to a five-carbon sugar named ribulose bisphosphate (RuBP). This reaction is catalyzed by the enzyme RuBP carboxylase/oxygenase (RuBisCO). The product of this reaction is an unstable six-carbon intermediate, which immediately splits into two molecules of 3-phosphoglyceric acid (PGA). Therefore, the three carbon atoms of each molecule of 3-phosphoglyceric acid (PGA) are derived from both RuBP and CO₂.

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.