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IB Biology HL C1.3 Photosynthesis Questions

Practise IB Biology HL C1.3 by linking pigments and limiting factors to photosystems, photophosphorylation and carbon fixation evidence.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • explain conversion of light energy into chemical energy and use of carbon dioxide to make carbon compounds
  • separate and identify pigments using chromatography and calculate Rf values from measured distances
  • interpret absorption, action or rate graphs to identify useful wavelengths and limiting factors
  • trace light-dependent reactions through photosystems, photolysis, electron transport and photophosphorylation
  • trace carbon fixation through Rubisco, GP, triose phosphate and RuBP regeneration in the Calvin cycle

Covered syllabus points

C1.3.1—Light energy → chemical energyC1.3.2—CO₂ → glucoseC1.3.3—Oxygen as by-productC1.3.4—Photosynthetic pigment separationC1.3.5—Absorption of specific wavelengthsC1.3.6—Absorption vs. action spectraC1.3.7—Limiting factors investigationC1.3.8—CO₂ enrichment experimentsC1.3.9 (HL)—PhotosystemsC1.3.10 (HL)—Advantages of pigment arraysC1.3.11 (HL)—Photolysis of waterC1.3.12 (HL)—ATP production in thylakoidsC1.3.13 (HL)—NADP reductionC1.3.14 (HL)—Thylakoids as light-dependent systemsC1.3.15 (HL)—Carbon fixation by RubiscoC1.3.16 (HL)—Triose phosphate synthesisC1.3.17 (HL)—RuBP regenerationC1.3.18 (HL)—Synthesis of other compoundsC1.3.19 (HL)—Interdependence of light and light-independent reactions

Learn this topic

Study C1.3 Photosynthesis conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

Question 1

[Maximum number: 8]

In ecosystems, energy is used to convert inorganic compounds into organic matter. Energy enters ecosystems through producers.

Explain the processes by which light energy is converted into chemical energy.

Question 2

[Maximum number: 9]

In water, shorter wavelengths of light such as blue and green penetrate deepest, and longer wavelengths of light penetrate less far. Red light does not reach depths of more than 50 m . Marine algae live at various water depths. Certain species of algae contain the pigments that enable them to adapt to life at different depths.

The graphs show the absorption and action spectra for two species of algae: Ulva taeniata, which is green, and Porphyra nereocystis, which is red.

Figure for Question 2 — IB Biology HL

Absorption / \%

Figure for Question 2 — IB Biology HL
Figure for Question 2 — IB Biology HL

Question (a)

(a)

In each species, identify the colour of light that is used mainly for photosynthesis.

Ulva taeniata:
Porphyra nereocystis:

[ 2 ]

Question (b)

(b)

Deduce, with a reason, which algae lives at a greater depth.

[ 1 ]

Question (c)

(c)

Describe how the rate of photosynthesis could be measured in a marine alga, to produce an action spectrum.

[ 3 ]

Question (d)

(d)

Outline the structure and location of photosystems.

[ 2 ]

Question (e)

(e)

State the method used to separate photosynthetic pigments in a leaf extract.

[ 1 ]

Question 3

[Maximum number: 10]

Question (a)

(a)

Distinguish between the absorption of red light, blue light and green light by plants.

[ 4 ]

Question (b)

(b)

Outline how light intensity and concentration of carbon dioxide affect photosynthesis.

[ 6 ]
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