Practice free Botany NEET multiple-choice questions online with instant answers and detailed explanations. No login required.
In animal cells, the centriole duplicates during which phase of the cell cycle?
In animal cells, during the S phase, DNA replication begins in the nucleus, and the centriole duplicates in the cytoplasm. This is an important event for the formation of the spindle poles during mitosis.
Which of the following statements is true regarding mitotic cell division in plants?
In animals, mitotic cell division is only seen in diploid somatic cells, with a few exceptions like male honey bees. Against this, the plants can show mitotic divisions in both haploid and diploid cells. This is a key difference mentioned in the NCERT text.
If the chromosome number of a parent cell is 2n, what will be the chromosome number of its daughter cells after mitosis?
Mitosis is also called as equational division because the number of chromosomes in the parent and progeny cells is the same. Therefore, if the parent cell has 2n chromosomes, the daughter cells will also have 2n chromosomes.
How do daughter cells produced by mitosis compare to the parent cell in terms of genetic content and chromosome number?
Mitosis is an equational division in which the chromosome number of the parent is conserved in the daughter cell. The genome is duplicated during S phase, and then precisely distributed to the two daughter cells, ensuring they contain intact and identical genomes.
Which of the following processes is directly responsible for creating a proton gradient across the thylakoid membrane during the light reaction?
According to the NCERT text, 'Splitting of water molecules is associated with PS II resulting in the release of O2, protons and transfer of electrons to PS II.' The release of protons ($H^+$) into the thylakoid lumen directly contributes to the proton gradient.
What is the primary role of the F0 part of the ATPase enzyme in chemiosmosis?
The NCERT states, 'The breakdown of the protons gradient due to movement through the F0 part of the ATPase enzyme releases enough energy for synthesis of ATP.' The F0 part functions as the transmembrane channel allowing protons to flow down their electrochemical gradient.
The energy released from the proton gradient is primarily utilized for:
The NCERT explicitly mentions, 'The breakdown of the protons gradient due to movement through the F0 part of the ATPase enzyme releases enough energy for synthesis of ATP.' This highlights the direct link between the proton gradient and ATP production.
Where does the chemiosynthetic pathway (generation of ATP and NADPH) primarily occur within the chloroplast?
The NCERT states, 'Within the chloroplasts, the membranes are sites for the light reaction, while the chemosynthetic pathway occurs in the stroma.' However, in the summary, it clarifies that 'a proton gradient is created across the membrane of the thylakoid. The breakdown of the protons gradient due to movement through the F0 part of the ATPase enzyme releases enough energy for synthesis of ATP.' This implies that the chemiosmosis, leading to ATP synthesis, occurs across the thylakoid membrane. The question refers to the 'chemosynthetic pathway' which in the summary is referred to as the process involving ATP and NADPH synthesis following the light reaction across the thylakoid membrane. If it means 'carbon fixation' then it is stroma. Given the context of the question following proton gradient, it refers to ATP synthesis part of light reaction, which happens on thylakoid membrane.
Which of the following is NOT a consequence of the proton gradient across the thylakoid membrane?
The NCERT states that 'Splitting of water molecules is associated with PS II resulting in the release of O2, protons and transfer of electrons to PS II.' The release of oxygen occurs before and independently of the proton gradient breakdown for ATP synthesis. The proton gradient facilitates ATP synthesis via ATPase and its formation is related to electron transport which ultimately leads to NADPH formation.
A crucial event in chemiosmotic hypothesis is the accumulation of protons ($H^+$) in which specific compartment of the chloroplast?
The proton (hydrogen ion) gradient is created across the thylakoid membrane, meaning protons accumulate within the thylakoid lumen.
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