FSc Part 1 Biology chapter 11: Bioenergetics MCQs with answers

By Team Megalecture · Updated 4 Nov 2026

29 exam-style questions on Bioenergetics, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.

29 questions · 3 topics · 10 per test

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What chapter 11 covers

Ten Bioenergetics questions with answers

Try each one, then open the answer. These ten stay the same; the test draws new ones every time.

1. Photolysis of water, which replaces the electrons lost by the reaction centre, is associated with

  1. A
    glycolysis
  2. B
    photosystem II
  3. C
    the Calvin cycle
  4. D
    photosystem I
Show answer

Answer: B. The water-splitting complex supplies electrons to P680 of PS II, releasing O2 and H+.

2. Why is photorespiration regarded as wasteful for the plant?

  1. A
    it destroys the chlorophyll in the leaf over time
  2. B
    it releases fixed CO2 but makes neither ATP nor sugar in return
  3. C
    it uses oxygen to make glucose more slowly
  4. D
    it stops the light reactions by using up the water
Show answer

Answer: B. Photorespiration uses energy and releases CO2 that had been fixed, lowering the net rate of photosynthesis, and yields no ATP.

3. The respiratory chain (electron transport chain) is located in the

  1. A
    mitochondrial matrix, where the Krebs cycle enzymes lie
  2. B
    cytosol, next to the glycolysis enzymes
  3. C
    thylakoid membrane of the chloroplast
  4. D
    inner mitochondrial membrane (cristae)
Show answer

Answer: D. Cytochromes and ATP synthase are in the inner membrane, whose folds (cristae) increase its surface area.

4. Taking each NADH as 3 ATP and each FADH2 as 2 ATP, how many ATP are produced by the complete oxidation of one pyruvic acid in the mitochondrion?

  1. A
    12
  2. B
    15
  3. C
    18
  4. D
    38
Show answer

Answer: B. Pyruvate oxidation gives 1 NADH (3). The Krebs cycle gives 3 NADH (9), 1 FADH2 (2) and 1 ATP. 3 + 9 + 2 + 1 = 15.

5. Glucose and yeast are sealed in a flask. Bubbles form that turn limewater cloudy, and the liquid later smells of alcohol. During this process pyruvic acid is being converted into

  1. A
    acetyl CoA and NADH inside the mitochondrion
  2. B
    lactic acid, with no carbon dioxide released
  3. C
    ethyl alcohol and carbon dioxide
  4. D
    citric acid and carbon dioxide
Show answer

Answer: C. The gas that turns limewater cloudy is carbon dioxide, and the smell of alcohol shows that ethanol has formed: alcoholic fermentation of pyruvic acid. Lactic acid fermentation releases no CO2.

6. What is the net gain from glycolysis of one glucose molecule?

  1. A
    4 ATP and 2 NADH
  2. B
    2 ATP and 2 NADH
  3. C
    2 ATP and 4 NADH
  4. D
    38 ATP
Show answer

Answer: B. 4 ATP are made but 2 are used in the first steps, so the net gain is 2 ATP, plus 2 NADH and 2 pyruvic acid.

7. On a very hot, dry day a C3 plant closes its stomata. What happens to its rate of photorespiration?

  1. A
    It decreases, because closed stomata stop oxygen entering the leaf
  2. B
    It decreases, because there is less water for photolysis
  3. C
    It stays the same, because RuBisCO cannot bind oxygen when hot
  4. D
    It increases, because CO2 cannot enter and O2 builds up in the leaf
Show answer

Answer: D. With stomata closed, CO2 cannot enter but photolysis continues to release O2, so the O2 to CO2 ratio rises. RuBisCO then binds O2 more often, and heat favours this too.

8. In the balanced equation 6CO2 + 12H2O → C6H12O6 + 6O2 + 6H2O, why are 12 molecules of water shown on the left?

  1. A
    each glucose is built from twelve water molecules
  2. B
    each O2 released is made from two water molecules
  3. C
    six of the water molecules end up in the glucose and six in the oxygen
  4. D
    water is needed as the solvent in which the reaction takes place
Show answer

Answer: B. The oxygen released in photosynthesis comes from water, and each O2 molecule needs two oxygen atoms, so 6 O2 need 12 water molecules. Six water molecules are formed again on the right-hand side, so the net equation uses 6 water molecules.

9. In the first step of the Krebs cycle, acetyl CoA (2 carbon atoms) combines with oxaloacetic acid (4 carbon atoms). How many carbon atoms are in the citric acid formed?

  1. A
    2
  2. B
    4
  3. C
    6
  4. D
    8
Show answer

Answer: C. The 2 carbons of acetyl CoA add to the 4 carbons of oxaloacetic acid: 2 + 4 = 6 carbons, so citric acid is a 6-carbon compound. The cycle then loses two carbons as CO2 and regenerates the 4-carbon acid.

10. Carotenoids help photosynthesis mainly by

  1. A
    acting as the reaction centre that passes excited electrons on
  2. B
    fixing carbon dioxide into 3-carbon compounds in the stroma
  3. C
    absorbing extra wavelengths of light and shielding chlorophyll from damage
  4. D
    splitting water to replace electrons at the reaction centre
Show answer

Answer: C. Carotenoids are accessory pigments: they broaden the range of light absorbed and protect chlorophyll from photo-oxidation.

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Ways to practise this chapter

Bioenergetics: questions students ask

How many Bioenergetics MCQs are there?

29, each with the answer and a short explanation, across 3 topics: Photosynthesis: pigments and light-dependent reactions, Photosynthesis: light-independent reactions and photorespiration, Respiration. Every chapter test draws ten of them, so you can take it many times.

Is the FSc Part 1 Biology chapter 11 test free?

Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.

How is the chapter test marked?

The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.

Can I read the explanations in Urdu?

Yes. In practice mode and on your results you can switch the explanations to Urdu.

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