Chlorophyll Degradation in Darkness — NEET Biology
📚 Practice ConceptWhy is the colour of a leaf kept in the dark frequently becomes yellow, or pale green? Which pigment do you think is more stable?
Which of the following statements are correct regarding photosynthesis? S1: The formation of starch in green leaves is directly dependent on the light energy captured during the photochemical phase of photosynthesis. S2: The products of light reaction, ATP and NADPH, are exclusively used in the stroma to drive the biosynthetic phase (carbon fixation). S3: Oxygen, a byproduct of photosynthesis, is released from the water splitting complex associated with PS II, into the lumen of the thylakoid. S4: The biosynthetic phase of photosynthesis, often called the 'dark reaction,' can continue for an extended period without the presence of light, provided ATP and NADPH are initially available. S5: RuBisCO has a much greater affinity for O2 when the CO2:O2 ratio is nearly equal, leading to photorespiration in C3 plants.
View solution & NCERT explanation
Correct answer: D — S1, S2 and S3 are correct
Let's evaluate each statement: S1: The formation of starch in green leaves is directly dependent on the light energy captured during the photochemical phase of photosynthesis. This statement is correct. Light energy is essential for the light reactions, which produce ATP and NADPH. These products are then used in the biosynthetic phase to fix carbon dioxide into sugars, which are stored as starch. The NCERT states, "photosynthesis occurred only in the green parts of the leaves in the presence of light." S2: The products of light reaction, ATP and NADPH, are exclusively used in the stroma to drive the biosynthetic phase (carbon fixation). This statement is correct. The NCERT mentions, "ATP and NADPH are used to drive the processes leading to the synthesis of food, more accurately, sugars. This is the biosynthetic phase of photosynthesis... taking place in the stroma, responsible for fixing CO2, and synthesis of sugars." S3: Oxygen, a byproduct of photosynthesis, is released from the water splitting complex associated with PS II, into the lumen of the thylakoid. This statement is correct. The water-splitting complex is located on the inner side of the thylakoid membrane, and the protons (and oxygen) produced accumulate within the lumen of the thylakoids. The NCERT states, "Since splitting of the water molecule takes place on the inner side of the membrane, the protons or hydrogen ions that are produced by the splitting of water accumulate within the lumen of the thylakoids." S4: The biosynthetic phase of photosynthesis, often called the 'dark reaction,' can continue for an extended period without the presence of light, provided ATP and NADPH are initially available. This statement is incorrect. The NCERT specifies, "immediately after light becomes unavailable, the biosynthetic process continues for some time, and then stops." It does not continue for an 'extended period'. S5: RuBisCO has a much greater affinity for O2 when the CO2:O2 ratio is nearly equal, leading to photorespiration in C3 plants. This statement is incorrect. The NCERT explicitly states, "RuBisCO has a much greater affinity for CO2 when the CO2 : O2 is nearly equal." The statement reverses the affinity. Therefore, statements S1, S2, and S3 are correct. The final answer is D
What does NCERT say about Why colour leaf kept?
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Through deep analysis of NEET and NTA, 176 of the 180 ReNEET 2026 (June 21) questions were already in the MedicNEET question bank before the exam.
176/180MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.