NUMS — Medical & Dental Entry Test
Take the NUMS Biology — Bioenergetics (Set 2): 30 multiple-choice questions (40 minutes) with instant scoring and a full answer review. Covers 30 NUMS…
What this test covers
The first 5 questions of this test, with the correct answer and explanation.
Q1. Engelmann placed a filamentous alga under light split into a spectrum and added aerobic bacteria. The bacteria clustered mostly around regions lit by red and blue light. This showed that:
Answer: A. Photosynthesis (O₂ release) is fastest at wavelengths absorbed by chlorophyll
Explanation: Aerobic bacteria gathered where most O₂ was produced; this matched the absorption peaks of chlorophyll, giving an early action spectrum.
Q2. A plant is given water containing ordinary oxygen and CO₂ labelled with ¹⁸O. Where will most of the ¹⁸O be found after photosynthesis?
Answer: C. In the carbohydrate and water produced, not in the released O₂
Explanation: O₂ released comes from water (photolysis); oxygen atoms from CO₂ end up in the sugar and in the water formed in the overall reaction.
Q3. The overall balanced equation of photosynthesis producing one molecule of glucose uses how many molecules of CO₂?
Answer: D. 6
Explanation: 6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O: six carbon atoms in glucose come from six CO₂.
Q4. In paper chromatography of leaf pigments, carotene travels furthest with the solvent front. This is because carotene:
Answer: D. Is the most soluble in the non-polar solvent and least attracted to the paper
Explanation: Carotene is a hydrocarbon, very non-polar, so it moves with the solvent and has the highest Rf value.
Q5. The chlorophyll molecule has a porphyrin head with a central atom of:
Answer: B. Magnesium
Explanation: Chlorophyll's porphyrin ring holds Mg²⁺; haem has Fe²⁺. Mg deficiency therefore causes chlorosis.
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Q6. The reaction-centre chlorophyll of photosystem I absorbs maximally at 700 nm. If a plant is lit only with light of wavelength above 690 nm, which effect is expected?
Q7. The enzyme complex that splits water during the light reactions is associated with photosystem II and requires ions of:
Q8. A herbicide blocks electron flow from photosystem II to plastoquinone. Which immediate effect would be observed in illuminated chloroplasts?
Q9. The final electron acceptor in non-cyclic photophosphorylation is:
Q10. How many turns of the Calvin cycle are required to make one molecule of glucose?
Q11. To produce one molecule of glucose, the Calvin cycle uses how many molecules of ATP and NADPH?
Q12. RuBisCO, the enzyme that fixes CO₂ in the Calvin cycle, combines CO₂ with:
Q13. In C₄ plants, the first stable product of CO₂ fixation in mesophyll cells is:
Q14. On a hot, bright day with partly closed stomata, sugarcane continues to photosynthesise rapidly whereas wheat slows down. The main reason is that sugarcane:
Q15. Pineapple and cacti open their stomata at night and store CO₂ as organic acids. The main advantage of this is:
Q16. In a greenhouse on a bright winter day, the factor most likely to limit photosynthesis is:
Q17. In glycolysis, the step that uses ATP and commits glucose to the pathway is catalysed by phosphofructokinase. The product formed is:
Q18. During glycolysis, a total of how many ATP molecules are produced (gross) and used per glucose?
Q19. Why must yeast in an anaerobic fermenter convert pyruvate to ethanol rather than simply accumulating pyruvate?
Q20. Aerobic respiration of one glucose yields about 38 ATP (textbook value), whereas lactic acid fermentation yields 2 ATP. How many times more ATP does aerobic respiration release per glucose?
Q21. The enzyme complex that converts pyruvate to acetyl CoA requires several coenzymes. A deficiency of which vitamin impairs this step and causes beriberi?
Q22. The Krebs cycle takes place in the:
Q23. Per molecule of glucose, the Krebs cycle (two turns) directly produces:
Q24. Electrons from FADH₂ enter the electron transport chain at a lower energy level than electrons from NADH. As a result, FADH₂ yields:
Q25. Which component carries electrons between complex III and complex IV in the mitochondrial chain?
Q26. The enzyme that makes ATP as protons flow back through the inner mitochondrial membrane is:
Q27. Carbohydrate has a respiratory quotient (RQ) of 1.0 and fat about 0.7. If an organism's measured RQ is 0.9, the most likely substrate mixture is:
Q28. Germinating seeds are placed in a respirometer with KOH to absorb CO₂. The coloured liquid in the capillary moves towards the seeds. This movement measures:
Q29. Hydrolysis of ATP to ADP and inorganic phosphate releases energy mainly because:
Q30. Stacks of thylakoids in a chloroplast are called grana. Their arrangement benefits photosynthesis mainly by: