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AP Biology Unit 3B: Photosynthesis, Respiration & Cellular Energy — practice questions — page 2

Explore 87 free Unit 3B: Photosynthesis, Respiration & Cellular Energy questions in AP Biology Biology. Open each question or exercise to read its content, reference answers and available explanation.

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Unit 3B: Photosynthesis, Respiration & Cellular Energy questions and exercises with answers

Showing questions 31–60 of 87.

Light reactions of photosynthesis occur in the:Read the answer and worked solution →In photosynthesis, the source of O2 released into the atmosphere is:Read the answer and worked solution →In the Z-scheme of photosynthesis, electrons flow:Read the answer and worked solution →In the Calvin cycle, CO2 is fixed by the enzyme:Read the answer and worked solution →The C4 pathway (Hatch-Slack) uses which enzyme for the initial CO2 fixation?Read the answer and worked solution →CAM plants (like cactus and pineapple) open their stomata mainly:Read the answer and worked solution →The colour of light LEAST absorbed by chlorophyll (and most reflected by leaves) is:Read the answer and worked solution →Chlorophyll-a primarily absorbs:Read the answer and worked solution →Carotenoids serve in photosynthesis as:Read the answer and worked solution →Photolysis of water occurs at:Read the answer and worked solution →ATP in light reactions is made by:Read the answer and worked solution →RuBisCO catalyses the addition of CO₂ to:Read the answer and worked solution →CAM plants open stomata at night to:Read the answer and worked solution →Pop only structures found in a chloroplast.Read the answer and worked solution →Balance photosynthesis (overall equation).Read the answer and worked solution →Photosynthesis overall reaction.Read the answer and worked solution →NEET · Bio · Photosynthesis · Light vs Dark ReactionRead the answer and worked solution →NEET · Bio · Photosynthesis · Photosystem ComponentRead the answer and worked solution →NEET · Bio · Photosynthesis · Pigment to WavelengthRead the answer and worked solution →NEET · Bio · Photosynthesis · C3 or C4 PlantRead the answer and worked solution →NEET · Bio · Photosynthesis · Calvin Cycle Step OrderRead the answer and worked solution →NEET · Bio · Photosynthesis · Tap C4 CropsRead the answer and worked solution →NEET · Bio · Photosynthesis · Photolysis — Gap FillRead the answer and worked solution →NEET · Bio · Photosynthesis · Chloroplast Component to ReactionRead the answer and worked solution →NEET · Bio · Photosynthesis · C4 Anatomy — MemoryRead the answer and worked solution →NEET · Bio · Photosynthesis · Limiting FactorRead the answer and worked solution →NEET · Bio · Photosynthesis · RuBisCO ReactionRead the answer and worked solution →NEET · Bio · Photosynthesis · Tap Light Reaction ProductsRead the answer and worked solution →NEET · Bio · Photosynthesis · Hill's Reaction — Gap FillRead the answer and worked solution →NEET · Bio · Photosynthesis · Q-cycle OrderRead the answer and worked solution →

Worked practice questions

Light reactions of photosynthesis occur in the:

  1. Stroma of chloroplast (matrix fluid only)
  2. Thylakoid membrane (with chlorophyll)
  3. Cytoplasm of plant cell
  4. Nucleus of plant cell
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Correct answer: B. Thylakoid membrane (with chlorophyll)

Light reactions occur in the THYLAKOID MEMBRANE of the chloroplast (PSI, PSII, ATP synthase embedded there). Dark reactions (Calvin cycle) occur in the STROMA (fluid matrix).

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In photosynthesis, the source of O2 released into the atmosphere is:

  1. CO2 (the carbon dioxide molecule)
  2. Glucose (from carbon fixation)
  3. H2O (via photolysis in PS II)
  4. Ozone (O3) in the upper atmosphere
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Correct answer: C. H2O (via photolysis in PS II)

**WATER is split (photolysis) by PSII:** 2H2O → 4H+ + O2 + 4e⁻. This is the source of atmospheric O2 (proved by Ruben + Kamen using ¹⁸O isotope). NOT from CO2.

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In the Z-scheme of photosynthesis, electrons flow:

  1. From PSI to water (downhill)
  2. From NADPH to PSII
  3. Just within PSI only
  4. From water → PSII → PSI → NADPH
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Correct answer: D. From water → PSII → PSI → NADPH

NON-CYCLIC e⁻ flow (Z-scheme): water → PSII (P680) → ETC → PSI (P700) → NADPH. Generates ATP + NADPH + O2. CYCLIC flow uses only PSI, generates ATP only.

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