Which of the following is NOT a product of the light reaction?
carbon dioxide
NADPH
ATP
oxygen
The Correct Answer is A
Choice A rationale: Carbon dioxide is not a product of the light reaction, but a reactant of the dark reaction. The light reaction does not use carbon dioxide, but water and light energy to produce ATP, NADPH, and oxygen¹.
Choice B rationale: NADPH is a product of the light reaction. It is an electron carrier that is reduced by the electrons from water in photosystem I. NADPH provides electrons and hydrogen for the dark reaction².
Choice C rationale: ATP is a product of the light reaction. It is an energy molecule that is synthesized by the enzyme ATP synthase using the proton gradient created by the electron transport chain. ATP provides energy for the dark reaction³.
Choice D rationale: Oxygen is a product of the light reaction. It is released as a by-product of the splitting of water in photosystem II. Oxygen is either used for cellular respiration or released into the atmosphere⁴.
Choice E rationale: Energy intermediates are not a specific product of the light reaction, but a general term for molecules that store energy or electrons, such as ATP and NADPH. Therefore, this choice is not incorrect, but less specific than choice A⁵.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
Choice A rationale: Sudan IV is a stain used to stain lipids. It is a red powder that dissolves in lipids and stains them red, but does not react with sugars. ¹
Choice B rationale: Benedict's is a reagent used to test for reducing sugars. It is a blue solution of copper (II) sulfate, sodium carbonate, and sodium citrate that reduces the copper (II) ions to copper (I) ions when heated with a reducing sugar, forming a red, orange, or green precipitate of copper (I) oxide. ⁴
Choice C rationale: Biuret is a reagent used to test for proteins and polypeptides. It is a blue solution of copper (II) sulfate and sodium hydroxide that forms a violet or pink complex with the peptide bonds in proteins or peptides. ⁸
Choice D rationale: Phenol red is a pH indicator. It is a red solution that changes color from yellow to red over the pH range 6.8 to 8.2, and from pink to fuchsia over 8.2 to 10.0. It does not react with sugars. ¹¹
Choice E rationale: Iodine is a reagent used to test for starch. It is a brown solution of iodine and potassium iodide that forms a blue-black complex with the starch molecules. It does not react with simple sugars. ¹⁴
Correct Answer is A
Explanation
Photosynthesis is the process by which plants, algae, and some bacteria use light energy to convert water and carbon dioxide into organic molecules, such as glucose, that can be used as food or building blocks for other molecules. Photosynthesis also releases oxygen as a by-product, which is essential for aerobic respiration in animals and other organisms.
Photosynthesis is the primary source of energy and organic matter for most living organisms on Earth, either directly or indirectly. Directly, photosynthesis provides food for the primary producers, such as plants and algae, that make their own food. Indirectly, photosynthesis provides food for the consumers, such as animals and fungi, that eat the primary producers or other consumers.
Photosynthesis also affects the global climate and the carbon cycle by removing carbon dioxide from the atmosphere and storing it in organic matter. Therefore, photosynthesis is the most important metabolic pathway of living organisms because its products have a significant impact on the biosphere.
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