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Photosynthesis and Chloroplasts Revision

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Photosynthesis and Chloroplasts Revision

A horticulture team is investigating how light and carbon dioxide affect photosynthesis in leafy plants. Use the text-based chloroplast structure cues and the investigation data to revise key structures, reactions and limiting factors. Answer in precise biological language. Unless stated otherwise, assume other conditions are controlled.

Chloroplast structure and the overall reaction

1.Use these text-based cues to identify the chloroplast structures: A is the double boundary; B is the fluid-filled interior; C is a stack of flattened membrane sacs; D is one flattened membrane sac; E is a membrane connecting stacks. Name structures A–E, then state where the light-dependent reactions and the Calvin cycle occur.

2.Complete the word equation for photosynthesis: carbon dioxide + + light energy → glucose + oxygen.

3.Complete the word equation for photosynthesis: carbon dioxide + water + light energy → glucose + .

4.Complete the balanced symbol equation for photosynthesis: 6CO₂ + 6H₂O → + 6O₂.

5.Match each term to its description. Terms: stroma; granum; chlorophyll; RuBP. Descriptions: A, pigment that absorbs light; B, stack of thylakoids; C, five-carbon carbon dioxide acceptor; D, fluid region containing enzymes for the Calvin cycle.

Stroma
Granum
Chlorophyll
RuBP

The two stages of photosynthesis

6.Which statement best describes the location and products of the light-dependent reactions?

They occur in the stroma and produce glucose directly.
They occur in the thylakoid membranes and produce ATP, NADPH and oxygen.
They occur in the chloroplast envelope and produce carbon dioxide.
They occur in the cytoplasm and produce RuBP.

7.Trace the fate of light energy during the light-dependent reactions. Include photosystems, water splitting, electron transport, the proton gradient, ATP synthase and NADP⁺.

8.Describe the Calvin cycle in the stroma, using the terms carbon fixation, RuBisCO, RuBP, GP, TP, ATP and NADPH. Explain how the cycle can continue.

9.True or false: The Calvin cycle uses light directly, so it stops immediately whenever the chloroplast is in darkness. Correct the statement if it is false.

TrueFalse

Interpreting greenhouse data

A technician measured oxygen production by leaf discs at different light intensities. Carbon dioxide concentration and temperature were held constant.

Light intensity (arbitrary units)

Oxygen production (arbitrary units)

10.5

100

10.5

10.Use the greenhouse data table. Describe the trend in oxygen production as light intensity rises, including the range where production levels off. Give a biological explanation for the plateau.

11.The technician repeats the test at a higher carbon dioxide concentration while keeping light intensity at 100 units. Predict the likely effect on oxygen production and explain your reasoning.

Apply your understanding

12.A greenhouse warms from a cool temperature towards the photosynthesis optimum, then becomes hotter than the optimum. Explain why the rate may first rise and then fall.

13.Explain how the arrangement of thylakoids, grana, lamellae and stroma supports photosynthesis. Link at least three structures to the reactions that occur there.