Photosynthesis

Question 1

Features of the chloroplasts

Answer 1

• Stroma
• Granum
• Thylakoid
• Inner membrane + Outer membrane
• Intermembrane space
• Lamella

Question 2

Stroma

Answer 2

Fluid containg enzymes that catalyse light INdependent stage reactions

Question 3

Grana

Answer 3

Stacks of thylakoids

Question 4

What are photosyntheic pigments?

Answer 4

• Light harvesting systems
• They are found in thylakoid membranes
• Responsible for light- dependent reactions
• Chlorophyll a&b is one of the photosynthetic pigments -(arranged as photosystems) (blue/red light)

Question 5

Light harvesting systems

Answer 5

Arranged in a funnel shape called antennae complexes
-Which are arranged in photosystem I & II
Several pigments allow for light to be harvested across a spectrum ending at the reaction centre

Question 6

What is photosynthesis?

Answer 6

The reaction in which light energy is used to split strong bonds in water molecules to produce glucose.
There are two stages of photosynthesis:
1. The light-dependent stage
2. The light- independent stage

Question 7

Where does the light-dependent reaction take place?

Answer 7

Thylakoid membranes

Question 8

What occurs in the light dependent stage?

Answer 8

1. Light harvesting at the photosystems
2. Photolysis of water
3. Photophosphorylation
4. The formation of NADP (reduced NADP)

Question 9

1. Light harvesting at the photosystems

Answer 9

1. Photon of light strikes PSII, then energy passed onto reaction centre
2. Reaction centre gets rid of energy by passing it to a series of enzymes (ETC)
3. **energy lost **from e-s as it moves down the ETC, is used to pumped H+ into thylakoid to generate an electrochemical gradient

Question 10

2.Photolysis of water

Answer 10

1. The e-s lost from PSII are replaced when H2O molecules split into protons, e-s & O2 (2H20 -> 4H+ +4e- +O2)
2. e-s at the end of the ETC are absobed by chlorophyll molecules in PSI
3. Photons also hit the reaction centre in PSI- e-s are then emitted and go down a series of e- carriers (but this time the electrons combine w/ H+ (from water) to reduce NADP

Question 11

3.Photophosphorylation (production of ATP)

NON-CYCLIC PHOTOPHOSPHORYLATION

Answer 11

Chemiosmosis powers ATP synthesis:
1. ETCs arranged w/ the photosystems in the thylakoid membranes
2. As e-s are transferred from carrier to carrier, their energy is used to pump H+ through that membrane
3. The flow of H+ is used by ATP synthase to make ATP

Question 12

4.The formation of NADPH

NON-CYCLIC PHOTOPHOSPHORYLATION

Answer 12

In the stoma the H+ (from water) NADP combines w/ the H+ (from water) and electrons to form NADPH

Question 13

What are the products of the Light-dependent reaction?

Answer 13

ATP and NADPH

Question 14

What is NADPH?

Answer 14

The coenzyme for photosynthesis

Question 15

What is photophosphorylation?

Answer 15

The process of producing ATP during photosynthesis in the presence of light

Question 16

What is cyclic photophosphorylation?

Answer 16

Where ADP is used to make ATP
* Process only uses PSI. e-s asre then recylced back to the start of of the reaction centre via e- carriers
NADPH &O2 ARE NOT FORMED IN CYCLIC PHOTOPHOSPHORYLATION