Photosynthesis

Question 1

What are the two stages of photosynthesis?

Answer 1

1) Light dependent reaction

2) Light independent reaction

Question 2

1) Light dependent reaction:

Answer 2

• takes place in the thylakoid membrane
• Light energy is absorbed by photosynthetic pigments and converted into chemical energy
• The light energy is used to add a phosphate group to ADP and to reduce NADP to reduced NADP
• ATP transfers energy and reduced NADP transfers hydrogen to the second stage of photosynthesis.
• In this process water is oxidised to oxygen

Question 3

2) Light- independent reaction:

Answer 3

• This is also called the Calvin cycle
• takes place in the stroma
• In this stage the ATP and reduced NADP, provide energy and hydrogen to make glucose from CO2

Question 4

What 3 different things is the light absorbed by photosystems used for?

Answer 4

1) using light to make ATP from ADP and inorganic phosphate molecule, (photophosphorylation)
2) Making reduced NADP from NADP
3) Using light to split water into : protons, electrons and oxygen, (photolysis)

Question 5

What does non-cyclic phosphorylation produce?

Answer 5

Produces ATP, reduced NADP and Oxygen

Question 6

4 stages of non cyclic phosphorylation:

Answer 6

1) Light energy excites electrons in chlorophyll
2) Photolysis of water produces: protons, electrons, oxygen.
3) Energy from excited electrons make ATP
4) Reduced NADP is produced

Question 7

1) Light excites electrons in the chlorophyll:

Answer 7

• light energy is absorbed by PSII and the light energy excites electrons in chlorophyll
• Electrons move to a higher energy level and move along the ETC to the PSI

Question 8

Why do plants emit chlorophyll fluoresecense

Answer 8

When plants absorb to much light they emit fluorescent light, which is called chlorophyll fluorescence.

Question 9

2) Photolysis of water:

Answer 9

• Electrons that leave the PSII need to be “replaced”

- Photolysis occurs (light energy splits water into protons, electrons and oxygen)

Question 10

equation for photolysis of water

Answer 10

H2O -> 2H+ + 1/2 O2

Question 11

3) Energy from excited electrons makes ATP

Answer 11

• The excited electrons lose energy as they move along the ETC
• This energy is used to transport protons into the thy1lakoid via proton pumps. This causes the thylakoid to have a higher concentration of protons than the stroma, which causes a proton gradient to form across the membrane.

-Protons move down the proton gradient into the stroma via ATP synthase.
And the energy from this movement causes ADP and pi to bind to form ATP.

Question 12

4) Reduced NADP is produced:

Answer 12

• Light energy is absorbed by PSI, which excites the electrons again to an EVEN HIGHER energy level
• Electrons and protons are transferred to NADP to form “reduced NADP”.

Question 13

What does cyclic phosphorylation produce

Answer 13

ONLY ATP

Question 14

Cyclic phosphorylation:

Answer 14

• Only uses PSI
  “cyclic” because electrons from chlorophyll are not passed onto NADP BUT are passed back to PSI via electron carriers.
• This means electrons are “recycled” and can keep flowing through the PSI

Question 15

Where does the calvin cycle take place?

Answer 15

Takes place in the stroma of the chloroplast

Question 16

Why is calvin cycle known as “carbon dioxide fixation”

Answer 16

This is because carbon from CO2 is fixed into an organic molecule.

Question 17

How is Ribulose phosphate (RuBP) regenerated in the Calvin cycle?

Answer 17

5 out of every 6 triose phosphate molecules are used to regenerate RuBP

Question 18

How can carbohydrates be made from TP

Answer 18

• By joining 2 TP together to form a hexose molecule (e.g. glucose)
• Then to make bigger carbohydrates (e.g. starch, cellulose, sucrose), these are made by joining hexose molecules together in different ways.

Question 19

when making lipids, where does the glycerol come from?

Answer 19

From the triose phosphate

Question 20

When making lipids where do the fatty acids come from?

Answer 20

From the Glycerate 3-phosphate

Question 21

How are amino acids made

Answer 21

Made using glycerate 3-phosphate

Question 22

Is calvin cycle light dependent or light independent

Answer 22

Light independent

Question 23

How much ATP and reduced NADP is needed for 6 turns of the calvin cycle?

Answer 23

18ATP

12 reduced NADP