- Photosynthesis (Light Dependent Reactions) Flashcards Preview

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Describe how NADP+ is reduced in the LDR of photosynthesis.

2e- from electron carrier protein (originally from chlorophyll) are gained.

H+ is gained from stroma.


What are the products of the light dependent reactions of photosynthesis?


NADPH (Reduced NADP)



Identify the labels.


Identify the labels.


Why is ATP sometimes referred ot as an immediate energy source of energy?

Because only one bond needs ot be broken to release energy.

ATP is rapidly resynthesised.


In biology what is meant by OXIDATION?

The loss of electrons

The loss of hydrogen

The gain of oxygen


Identify the labels.


For what are the products of the light dependent reactions used for?

NADPH and ATP are required in the light independent reacitons of photosynthesis (Calvin cycle)

Oxygen is used in respiraiton or exits the plant via the stomata.



Why does the plant need to carry out the Calvin cycle and respiration if the light dependent reactions produce ATP?

Not enough ATP is produced.

ATP is difficult to transport around the plant.

ATP can not be produced in the dark.

Not all plant cells contain chlorophyll

ATP is not a stable store of energy.



Identify the labels.


In biology, what is meant by REDUCTION?

The gain of electrons.

The gain of hydrogen.

The loss of oxygen.


Describe the Light Dependent Reactions of photosynthesis.

  1. Light enters chloroplast and excites 2 electrons in chlorophyll transmembrane protein (photosystem II) spanning thylakoid membrane.
  2. 2e- leave PSII (oxidation) and move to Proton pump (reduction).
  3. Proton pump actively transports H+ from stroma into thylakoid space creating an electrochemical gradient.
  4. 2e- leave Proton pump (oxidation) and move to electron carrier (PSI - reduction).
  5. H+ ions in thylakoid space diffuse through ATP Synthase, providing the energy to catalyse the formation of ADP + Pi -> ATP
  6. 2e- and H+ move onto NADP+ to make NADPH (reduced NADP).
  7. Chlorophyll's 2e- are replaced via the photolysis of water in the thylakoid space to give 2e- + 2H+ + 1/2O2 




Identify the labels.


Identify the labels.


What does the diagram show?

The thylakoid membrane of a chloroplast.

Where the light dependent reactions of photosynthesis take place.


What is NADP+?

A coenzyme that works alongside an enzyme, in this case it is a hydrogen carrier and electron acceptor.

It works alongside the enzyme: dehydrogenase


How can we measure the rate of the light dependent reactions of photosynthesis?

Measure the volume of oxygen produced.

Over time.


 In the light-dependent reaction of photosynthesis, light energy generates ATP. Describe how. (5 marks)

1.      Light (energy) excites / raises energy level of electrons in chlorophyll;

2.      Electrons pass down electron transfer chain;

3.      (Electrons) reduce carriers / passage involves redox reactions;

4.      Electron transfer chain / role of chain associated with chloroplast
membranes / in thylakoids / grana;

5.      Energy released / carriers at decreasing energy levels;

6.      ATP generated from ADP and phosphate / Pi / phosphorylation of ATP;


When investigating how light intensity affects plant growth what variables should you control?


concentration carbon dioxide

volume of water

concentation of ions in soil

pH of soil