Catching light in the thylakoid

Science · Organisms & Life Processes · ages 16-17

Name ______________________ Date ____________

Which gas is ultimately released when water molecules are split in the light-dependent reactions?
- Carbon dioxide
- Nitrogen
- Oxygen
Where do the light-dependent reactions run?
- In the stroma
- In the thylakoid membrane
- In the cytoplasm
The light-dependent reactions make ATP and reduced NADP.
Circle one: True False
How is the proton gradient cashed in?
- Through ATP synthase
- It fixes carbon dioxide
- It splits more water
Why must this stage sit in a membrane?
- Pigments need light, which membranes store
- To build a proton gradient
- To keep oxygen away from chlorophyll
Which pair supplies energy and reducing power to carbon-fixing reactions?
- Glucose and oxygen
- Water and oxygen
- ATP and NADPH
A student says the electrons from split water are released as a gas, like the oxygen. What actually happens to them?
- They collect in the thylakoid space to form the proton gradient
- They move through an electron transport chain
- They join carbon dioxide in the thylakoid membrane to make sugar
Sugar production can slow soon after lights-out. What best explains this?
- ATP and NADPH supplies run down
- Chlorophyll is used up in the dark
- Water runs out in the leaf at night

Answer key

For grown-ups. Fold this page away before handing over the rest.

Oxygen · Splitting water supplies oxygen atoms, which combine to form oxygen gas that is released.
In the thylakoid membrane · They sit where the pigments are: the thylakoid membrane.
True · The light-dependent reactions make ATP and reduce NADP+ to NADPH, which is also called reduced NADP.
Through ATP synthase · Protons flowing back through ATP synthase build ATP.
To build a proton gradient · The thylakoid membrane separates the thylakoid space from the stroma, allowing protons to build up on one side and form a gradient.
ATP and NADPH · ATP supplies usable energy, and NADPH supplies high-energy electrons to the next stage.
They move through an electron transport chain · Splitting water gives oxygen, protons and electrons. Only the oxygen is released as a gas. The protons collect in the thylakoid space, and the electrons move through an electron transport chain.
ATP and NADPH supplies run down · Carbon-fixing reactions can use stored ATP and NADPH for a while. Without light, the supplies are not replenished and eventually run down.