Photosynthesis

Question 1

What are the two main stages of photosynthesis?

Answer 1

• Light-dependent stage

- Light independent stage

Question 2

Where does the light-dependent stage occur in the chloroplast?

Answer 2

• Within and across the thylakoid membranes

Question 3

Where does the light-independent stage occur in the chloroplast?

Answer 3

-Occurs in the Stroma

Question 4

Describe 2 ways in which the thylakoids are adapted to their function

Answer 4

• Contains Electron carries (ATP synthase)
• Large SA to volume ratio for light absorption
• Contains Photosystems

Question 5

Why is there CO2 present in the gas collected?

Answer 5

-CO2 is present in the atmosphere
-CO2 produced during respiration
-

Question 6

Suggest how deep aquatic plants are adapted

Answer 6

• In deeper waters, there is low light intensity

- The light-absorbing pigment absorbs the wavelength that penetrates deeper into the water

Question 7

What 2 products are used up in the Calvin cycle?

Answer 7

• ATP

- NADPH (reduced NADP)

Question 8

What is photorespiration?

Answer 8

• Wasteful pathway where the Rubisco enzyme acts on oxygen instead of CO2
• High concentrations of O2

Question 9

Compensation point

Answer 9

-Point in which the rate of photosynthesis is equal to the rate of respiration

Question 10

One way of working out the compensation point

Answer 10

-measuring the rate of oxygen production for an increase I light intensity

Question 11

Granum

Answer 11

Thylakoid stack

Question 12

Chloroplast info

Answer 12

-Contain photosynthetic pigments that absorb light energy which is needed for photosynthesis

Question 13

Primary pigments

Answer 13

-Reaction centres where electrons are excited during LDS

Question 14

Accessory pigments

Answer 14

• make up light harvesting systems

- Transfer light energy to allow for electron excitement

Question 15

Photosystem

Answer 15

-Protein and pigment is called a photosystem

Question 16

PSI

Answer 16

• p700
• absorbs light best at the 700 nm wavelength
• Used in CYCLIC and NON-CYCLIC phosphorolysation

Question 17

PSII

Answer 17

• p680
• absorbs light best at 680 nm wavelength
• For Non-Cyclic phosphorolysation

Question 18

Photolysis

Answer 18

-H2O is split into 1/2 (O2) + (H+) + (e-) in the presence of light

Question 19

What happens in the LDS?

Answer 19

1. Making ATP from ADP
2. NADP -> NADPH (reduced NADP)
3. Photolysis

Question 20

Explain Non-cyclic photo phosphorylation

Answer 20

1. Photolysis of water produces H+ ions, electrons and a biproduct O2
2. Light energy excites electrons in chlorophyll and they get passed along an electron transport chain to PSII
3. The energy from the excited electrons is used to make ATP, H+ move down a conc gradient into the stroma via ATP synthase (energy from this movement is used to make ATP from ADP)
4. PSI excites the electron to an even higher energy level and this is then used to make NADPH in the stroma

Question 21

Cyclic Photophosphrolysation

Answer 21

• Uses only PSI
• Only produces ATP
• Electrons are recycled
• Produces small amounts of ATP

Question 22

Limiting factors

Answer 22

• Light intensity
• CO2 conc
• Water stress
• Temperature
• Wavelength

Question 23

Effect of Temperature on Phoyosynthesis

Answer 23

Low: less reactions catalysed by Rubisco (becomes inactive)

High: Rubisco becomes denatured

• Thylakoid & Chloroplast membranes may be damaged
• Stomata close
• Chlorophyll could be damaged