All questions of June for NEET Exam

The by-product of photorespiration in C3 plants is oxygen. Photorespiration is a process that occurs when there is an abundance of oxygen, and it produces carbon dioxide as a by-product. This CO2 is essential for photosynthesis, while the oxygen produced can interfere with the photosynthetic process. Understanding the role of oxygen in photorespiration is crucial for comprehending the complexities of photosynthesis in different plant types.

The hydrogen molecule (H2) is described as diamagnetic because it lacks unpaired electrons.

The bond order of the carbon molecule (C2) is 2. It is a stable, diamagnetic molecule with a bond order of 2.

Understanding the C4 Pathway
The C4 pathway is a photosynthetic process that enhances the efficiency of carbon fixation in certain plants, particularly in hot and dry environments. Let’s analyze the statements to identify the false one.
Option A: The mesophyll cells lack RuBisCO enzyme.
- This statement is true. In C4 plants, RuBisCO is predominantly found in bundle sheath cells rather than mesophyll cells.
Option B: The C4 acid OAA is formed in the mesophyll cells.
- This statement is true. In mesophyll cells, carbon dioxide is initially fixed to phosphoenolpyruvate (PEP) to form oxaloacetic acid (OAA).
Option C: The bundle sheath cells contain the enzyme PEPCase.
- This statement is false. The enzyme PEPCase (phosphoenolpyruvate carboxylase) is located in the mesophyll cells, not in the bundle sheath cells. The bundle sheath cells primarily contain RuBisCO to carry out the Calvin cycle.
Option D: The primary CO2 acceptor is phosphoenol pyruvate.
- This statement is true. In the C4 pathway, PEP acts as the primary CO2 acceptor, forming OAA.
Option E: The enzyme responsible for CO2 fixation is PEPCase.
- This statement is true. PEPCase catalyzes the initial carbon fixation step in the C4 pathway.
Conclusion
- The false statement regarding the C4 pathway is option C, as PEPCase is not found in the bundle sheath cells but rather in the mesophyll cells. Understanding these distinctions is crucial for grasping the efficiency of the C4 photosynthetic pathway.

Location of the Electron Transport Chain
The electron transport chain (ETC) is a crucial component of cellular respiration, primarily occurring in the mitochondria of eukaryotic cells.
Correct Answer: D) In the mitochondrial cristae
Understanding the Mitochondrial Structure
- The mitochondria have a double-membrane structure:
- Outer Membrane: Smooth and permeable to small molecules.
- Inner Membrane: Highly folded into structures called cristae.
Function of Cristae
- Increased Surface Area: The folds of the cristae increase the surface area available for the electron transport chain and ATP synthesis.
- Location of ETC Components:
- The proteins and complexes involved in the electron transport chain, such as NADH dehydrogenase, cytochrome b-c1 complex, and cytochrome oxidase, are embedded in the inner membrane.
Process of the Electron Transport Chain
- Electron Transfer: Electrons from NADH and FADH2 are passed through a series of protein complexes in the cristae.
- Proton Gradient Creation: As electrons move through these complexes, protons (H+) are pumped from the mitochondrial matrix into the intermembrane space, creating a proton gradient.
- ATP Production: This gradient drives ATP synthase, which synthesizes ATP as protons flow back into the matrix.
Conclusion
The electron transport chain's location in the cristae is vital for its function, maximizing energy production through aerobic respiration. Understanding this process is essential for topics related to cellular metabolism, particularly in NEET and other biological examinations.

The enthalpy change that occurs when one mole of a substance is dissolved in a specific amount of solvent at a specific temperature is called the enthalpy of hydration.

NADH and FADH2 are significant because they transfer electrons to the electron transport chain and revert to NAD+ and FAD, which are essential for the proper functioning of glycolysis and the citric acid cycle.