Topic 5A: Photosynthesis Reactions

Question 1

Where does the light dependent reaction takes place?

Answer 1

In the thylakoids membrane

Question 2

In the light dependent reaction what are the three things light energy is used for?

Answer 2

– Making ATP from 80p and inorganic phosphate

– Making reduced NADP from NADP

– photolysis

Question 3

What is the difference between cyclic photophosphorylation and non cyclic photophosphorylation?

Answer 3

• In cyclic Photosynth. only ps1 used and electrons are passed onto NADP

– Only produce a small amounts of ATP

Question 4

How many electrons are excited to higher energy levels in PS2 chlorophyll?

Answer 4

2

Question 5

What is another a name for the Light independent reaction?

Answer 5

Calvin Cycle / Carbon fixation

Question 6

Where does the Calvin cycle take place?

Answer 6

In the Stroma

Question 7

What is Carbon fixation?

Answer 7

When Carbon from CO2 is fixed into an organic molecule

Question 8

In the Calvin Cycle, how many molecules of ATP are used and where?(3)

Answer 8

• 3
• 2 when turning GP into GALP
• 1 when turning GALP into RuBP

Question 9

Suggest how GALP could be used to synthesise cellulose(5)

Answer 9

1. GALP is a 3C molecule / eq
2. reference to formation of {glucose / hexose/ 6C sugar} (from GALP)
3. idea of enzymes involved in the synthesis of {glucose / cellulose}
4. idea that cellulose consists of {ß-glucose / beta glucose }
5. joined by glycosidic bonds / eq
6. reference to 1-4 (bonds)
7. reference to condensation reactions (between glucoses)
8. idea that cellulose is a long chain molecule e.g. polysaccharide, polymer
9. {unbranched / eq} molecule

Question 10

Explain the effect of temperature on the rate of photosynthesis in a plant (4)

Answer 10

• increasing temperature increases {movement of both enzyme and substrate molecules / kinetic energy of molecules} (1)
• therefore molecules collide {more often / with more force} causing the rate to increase (1)
• resulting in {enzyme denaturation / change in bonding in the enzyme} above 30 °C (1)
• which causes active site shape to change and causing the rate to decrease (1)