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13.1.413 · Photosynthesis

Chloroplast Pigments — Cambridge AS & A Level Biology 9700 Revision Notes & Topical Questions

5 min read 7 parts Lesson 5 of 13 1 quiz

📚 Cambridge AS & A Level Biology 9700 Hub / Topical Revision
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Lesson summary

13.1.4 Chloroplast Pigments — CAMBRIDGE AS & A LEVEL BIOLOGY 9700 — REVISION NOTES notes: Name the chloroplast pigments, their colours and the light they absorb.Location — several photosynthetic pigments lie within the thylakoids.Function — each pigment absorbs different waveleng…

  • Chlorophylls
  • Green light
  • Carotenoids
  • Accessory pigments
  • Pigment colour
  • Absorbed colour

Part 1 of 5Pigments in the thylakoids

Pigments in the thylakoids
Location
  • Location several photosynthetic pigments lie within the thylakoids.
Function
  • Function each pigment absorbs different wavelengths of light.

Part 2 of 5The pigment groups

GroupPigmentColour
ChlorophyllsChlorophyll aLight green
ChlorophyllsChlorophyll bDark green
CarotenoidsCaroteneOrange
CarotenoidsXanthophyllYellow

Part 3 of 5Wavelengths absorbed

Chlorophylls
  • Chlorophylls absorb blue-violet and red light.
Green light
  • Green light chlorophylls reflect green light, so plants look green.
Carotenoids
  • Carotenoids absorb mainly blue-violet light.
Accessory pigments
  • Accessory pigments broaden the range of wavelengths absorbed and pass energy to chlorophyll a.

Part 4 of 5Pigment colour compared with light absorbed

Pigment colour
  • Pigment colour the colour of light that the pigment reflects into the eye.
Absorbed colour
  • Absorbed colour the wavelengths taken in, which differ from the pigment colour.

Part 5 of 5More from the specification

1
Light-Dependent Stage Reactions
  • The light-dependent stage of photosynthesis takes place across the thylakoid membrane within chloroplasts, capturing photon energy to drive light-dependent reactions.
2
Photosystem Excitation and Electron Transport
  • When light strikes photosystem II and photosystem I, chlorophyll reaction centres emit high-energy electrons, initiating a process where electrons pass along an electron transport chain embedded in the thylakoid membrane.
3
Non-Cyclic and Cyclic Photophosphorylation
  • Photophosphorylation generates ATP via chemiosmosis as protons re-enter the stroma through ATP synthase,
  • while reduced NADP is synthesised in the stroma to fuel the light-independent Calvin cycle.
4
Cyclic photophosphorylation
  • ATP formation using only PSI with electrons returning to it.
5
Electron carrier
  • A molecule such as NAD or FAD that accepts and donates electrons.
6
Non-cyclic photophosphorylation
  • ATP formation using PSII and PSI with electrons ending in NADP.
7
Triose phosphate
  • Three-carbon sugar phosphate made from GP.
8
Photosystem
  • A cluster of pigments and proteins that harvest light.
9
Photophosphorylation
  • Making ATP using light energy, an electron transport chain and chemiosmosis.
10
Stroma
  • The fluid of the chloroplast where the Calvin cycle occurs.
11
Reduced
  • Having gained electrons
12
Photolysis
  • Splitting of water by light at PSII.
13
Calvin cycle
  • Light-independent reactions that fix CO2 in the stroma.
14
Light-dependent stage
  • Stage in thylakoids making ATP, reduced NADP and oxygen.
15
Light-independent stage
  • Stage in the stroma where CO2 is converted to organic molecules.

Key terms

TermMeaning
Chlorophyll aLight green primary pigment.
Chlorophyll bDark green accessory pigment.
CaroteneOrange carotenoid.
XanthophyllYellow carotenoid.
CarotenoidPigment absorbing mainly blue-violet light.
Accessory pigmentPigment that passes absorbed energy to chlorophyll a.

Avoid these mistakes

1
Saying chlorophyll absorbs green light — it reflects green light.
2
Saying the pigment colour is the colour it absorbs — it is the colour reflected.
3
Thinking carotenoids absorb red light — they absorb mainly blue-violet.
4
Listing xanthophyll as a chlorophyll — it is a carotenoid.

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