Learner Resource 2 – Sorting activity
Sort the sentences into the correct order to produce an overview of the light-dependent and
light-independent reactions.
The light-dependent reaction – the production of ATP and NADPH
The protons flow back through an ATP synthase channel, producing ATP from ADP and Pi.
This causes 2 electrons from chlorophyll a to become excited and rise to a higher energy
level.
These electrons pass down a series of electron carriers and is energy released. The final
electron acceptor is NADP+. NADP+ joins with H+ to produce NADPH using energy from the
electron carriers.
The energy released is used to pump protons from the stroma across the thylakoid
membranes into the thylakoid space producing a proton gradient.
Photons of light are absorbed by chlorophyll a molecule in photosystem II.
Light energy also causes water to split – photolysis.
Light hits chlorophyll in photosystem I causing electrons to become excited and rise to a
higher energy level.
The electrons produced by photolysis replace the electrons lost by the chlorophyll a molecule
in photosystem II.
2e-, 2H+and O2 are produced. The O2 is released as a by-product.
The excited electrons are picked up by electron acceptors and passed through a series of
electron carriers releasing energy and then passed to photosystem I.
The light-dependent reaction
Most of the TP is used to regenerate RUBP so the cycle can continue.
Some TP is converted into molecules such as glucose.
ATP provides the energy and NADPH provides the H to reduce GP to triose phosphate (TP)
Some TP is modified to produce lipids and proteins.
The 6C molecule produced is unstable and breaks down to produce 2 molecules of GP (3C)
– glycerate phosphate.
CO2 combines with RUBP (5C). The reaction is catalysed by Rubisco.
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Photosynthesis, food production and populations
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