Photosynthesis

Question 1

What is photosynthesis?

Answer 1

Process where energy from light is used to make glucose and oxygen from carbon dioxide and water

Question 2

Where does photosynthesis take place in the cell?

Answer 2

Chloroplasts

Question 3

What are photosynthetic pigments? Can you name the known ones

Where are they found and what are they attached to?

Answer 3

Coloured substances that absorb light energy need for photosynthesis.

Examples: chlorophyll a and b, carotene

Thylakoid membrane, there attached to a protein forming a photosystem

Question 4

What is a scientific name you can use to called NADP in photosynthesis and it’s job.

Answer 4

Co enzyme

Transfers hydrogen ions from one molecule to another

Question 5

Four key stages of light dependent reaction?

Answer 5

1. Photoionisation of chlorophyll
2. Production of ATP and reduced NADP
3. Chemiomosis
4. Photolysis

Question 6

What happens in the photo ionisation of chlorophyll?

Answer 6

Light energy is absorbed by chlorophyll (and the other photosynthetic pigments) in the Photosystem. This excites the electrons in chlorophyll, giving them more energy, which eventually causes them to be released from the chlorophyll molecule. The high energy electrons released move down the electron transport chain to PS1

Question 7

What happens during the photolysis of water?

Equation

Answer 7

As the excited electrons leave PSII to move down the electron transport chain, the must be replaced so light energy splits water into H+ ions, electrons and oxygen.

H2O ➡️ 2H+ ➕ 1/2 O2

Question 8

After the photo lysis of water what happens next?

Answer 8

Excited electrons lose energy as they move down the electron transport chain. This energy is used to actively transport H+ ions into the thylakoid from the stroma across the thylakoid membrane. So that the thylakoid membrane has a higher concentration of hydrogen ions than in the stroma. This forms a proton gradient across the membrane.

Protons then move down their concentration via ATP synthase (embedded in thylakoid membrane). The energy from the movement is used to make ATP from ADP and Pi

Question 9

Last step of the light dependent reaction?

Answer 9

Light energy is absorbed by PSl, which excites the electrons again to an even higher energy level. The electrons are then transferred to NADP along with H+ ions from the stroma, to form reduced NADP

Question 10

What is the chemiosmotic theory?

Answer 10

Process of electrons flowing down the electron transport chain and creating a proton gradient across the membrane to drive ATP synthesis