9477 / 2027

Photosynthesis and energy capture

Try it without your notes

Choose an answer or explain your thinking. Then check what you understand.

Quick checks

0 answered / 0 correct. Your first try counts; you can try again any time.

Check your understanding

Which y-axis belongs to an action spectrum?

  1. Rate of photosynthesis
  2. Absorbance of isolated pigment only
  3. Wavelength of the light supplied
Show the answer

Rate of photosynthesis

This reports biological effectiveness at each wavelength.

Check your understanding

Which statement about absorption and action spectra is NOT correct?

  1. Chlorophylls absorb mostly blue and red light
  2. Accessory pigments widen the range of light used
  3. An action spectrum measures light absorbed by one pigment
  4. The two spectra have similar shapes
Show the answer

An action spectrum measures light absorbed by one pigment

An action spectrum measures the rate of photosynthesis at each wavelength, not absorption by a pigment.

Check your understanding

What is the main role of reduced NADP in the Calvin cycle?

  1. It supplies carbon atoms as CO2.
  2. It directly supplies ATP for RuBP regeneration.
  3. It provides reducing power for carbon reduction.
Show the answer

It provides reducing power for carbon reduction.

Its electrons support reduction of carbon intermediates.

Check your understanding

Which is produced by cyclic photophosphorylation without net NADP reduction?

  1. Oxygen from a required new water-splitting step in that cycle
  2. Reduced NADP as a net product
  3. ATP
Show the answer

ATP

Cyclic electron flow supports proton-gradient-driven ATP synthesis.

Check your understanding

What is the direct role of rubisco?

  1. Making ATP from a proton gradient
  2. Splitting water to release oxygen
  3. Catalysing CO2 fixation to RuBP
Show the answer

Catalysing CO2 fixation to RuBP

This begins the Calvin-cycle carbon-fixation phase.

Check your understanding

A plant in light is suddenly put in the dark. What happens to the amounts of RuBP and GP in its chloroplasts over the next minute?

  1. RuBP falls and GP rises.
  2. Neither changes, as the Calvin cycle needs no light.
  3. Both RuBP and GP rise.
  4. RuBP rises and GP falls.
Show the answer

RuBP falls and GP rises.

Without ATP and reduced NADP, GP cannot be reduced and RuBP cannot be regenerated, but RuBP is still fixed into GP for a while.

Check your understanding

Which design best isolates a light-intensity effect?

  1. Vary light while controlling temperature, CO2 and sample amount.
  2. Move a hot lamp closer while allowing temperature to rise freely.
  3. Use a different plant species at every light intensity.
Show the answer

Vary light while controlling temperature, CO2 and sample amount.

This helps attribute rate differences to light.

Explain your thinking

Write a short answer, then compare it with a sample and check for missing ideas.

Question 1 of 7

Plan: find the compensation point (10 marks)

8 marks

Design your own investigation that uses hydrogencarbonate indicator to determine the light intensity at which spinach leaf discs balance their carbon dioxide uptake and release (their compensation point). Your plan should allow another student to carry it out, and should include: the independent and dependent variables and how each is set or measured; at least three controlled variables and how each is controlled; control set-ups; repeats; how you would analyse the results; the theory behind the method; and a risk assessment. (10 marks) [8]

Structure: theory, variables, method, controls, repeats, analysis, risk. At the compensation point the indicator stays red.

Loading saved work...

0 / 6000
Ctrl / Cmd + Enter

Use the checklist to compare your answer. This is a self-check, not an exam mark.

Keep one idea for tomorrow

Try a question again without looking at the answer. If you get stuck, revisit its lesson.

Open the chapter summary