🌿 Bioenergetics | Photosynthesis MCQs and Short Questions with Answers

Preparing for MDCAT Biology or FSc Part-II exams? Then this post is perfect for you! Here you’ll find solved MCQs and short questions from the chapter Bioenergetics with a focus on Mechanism of Photosynthesis. These questions are exam-relevant and will help you practice concepts like light reaction, dark reaction, glycolysis, electron transport chain, and ATP formation.

Practice solved MCQs and short questions from Bioenergetics | Photosynthesis. Perfect for FSc Biology & MDCAT prep. Learn glycolysis, ATP, Calvin cycle & more.

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✅ Section 1: Multiple Choice Questions (MCQs)

1- What main process occurs during the dark reaction of photosynthesis?
👉 (c) Adding of hydrogen to CO2

2- What is TRUE about glycolysis?
👉 (d) It reduces 2 molecules of NAD+ for every glucose molecule processed

3- Which of the following are produced by the reactions that occur in the thylakoid and consumed by the reactions that occur in the stroma?
👉 (d) ATP and NADPH

4- When deprived of oxygen, yeast cells obtain energy by fermentation, producing CO2, ATP and;
👉 (b) Ethyl alcohol

5- Conversion of Glucose 6-phosphate into Fructose 6-phosphate is;
👉 (a) Isomerization

6- In which of the following conversions, ATP is produced?
👉 (b) Succinyl CoA into succinic acid

7- In electron transport chain, FADH2 produces how many ATPs?
👉 (b) Two

8- Which of these is CO2 acceptor during photosynthesis?
👉 (b) Ribulose biphosphate (RuBP)

9- Which of the following takes the electrons lost by Photosystem I on absorption of light energy?
👉 (a) Ferredoxin

10- Photosystem-II makes up the electrons lost due to light excitation by taking up the electrons released from,
👉 (d) Photolysis of water

✅ Section 2: Short Questions with Answers

1- Differentiate between action spectrum and absorption spectrum.
👉 Action spectrum shows the effectiveness of different wavelengths of light in photosynthesis, while absorption spectrum shows which wavelengths of light pigments absorb.

2- How is photosynthesis a redox reaction?
👉 CO2 is reduced to form glucose, while H2O is oxidized to release oxygen — making it a redox process.

3- Which molecule contributes Oxygen in glucose? Water or carbon dioxide?
👉 Oxygen in glucose comes from CO2, while oxygen released as a byproduct comes from water.

4- State the role of CO2 in photosynthesis.
👉 CO2 provides the carbon skeleton for glucose during the Calvin cycle.

5- Define electron transport chain.
👉 A series of protein complexes in the mitochondrial or thylakoid membrane that transfer electrons and pump protons to generate ATP.

6- What do you mean by glycolysis?
👉 Breakdown of one molecule of glucose (6C) into two molecules of pyruvic acid (3C) in the cytoplasm, releasing ATP and NADH.

7- What is the main structural difference between chlorophyll-a and chlorophyll-b?
👉 Chlorophyll-a has a methyl group (-CH3), while chlorophyll-b has an aldehyde group (-CHO).

8- How can a cell synthesize ATP through substrate-level phosphorylation?
👉 By direct transfer of a phosphate group from a high-energy substrate to ADP (e.g., in glycolysis and Krebs cycle).

9- Can pyruvic acid enter Krebs cycle as such? If not, what changes are made to it before Krebs cycle?
👉 No, pyruvic acid is converted into Acetyl CoA before entering Krebs cycle.

10- Differentiate between C-3 and C-4 photosynthesis.
👉 C-3 plants fix CO2 directly into a 3-carbon compound (PGA).
👉 C-4 plants first fix CO2 into a 4-carbon compound (oxaloacetate) to minimize photorespiration.

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