Photosynthesis Ch. 11

Question 1

Give some examples of how the structure of a leaf helps photosynthesis.

Answer 1

Large surface area to absorb light.
Transparent cuticle lets light pass through.
Lots of stomata allows for gas exchange.
Xylem brings water, phloem carries away glucose.
Mesophyll cells are packed long and narrow and contains lots of chlorophyll.

Question 2

`What is the general equation for photosynthesis?

Answer 2

6CO2 + 6H2O = C6H12O6 +6O2

Question 3

What’s the first reaction of photosynthesis?

Answer 3

Light- Dependen Reaction

Question 4

Where does the light-dependant reaction occur?

Answer 4

In the thylakoid in the chloroplast

Question 5

Whats in the thylakoid?

Answer 5

Chlorophyll

Question 6

What is the first stage of the light - dependant reaction?

Answer 6

Photoionisation

Question 7

What happens in photoionisation?

Answer 7

Chlorophyll molecule absorbs light and excites a pair of electrons so they leave the molecule.

Question 8

What happens to the electrons from the chlorophyll?

Answer 8

Electrons pass along the electron transfer chain

Question 9

Describe how in the light- dependent reaction of photosynthesis, light energy generates ATP?

Answer 9

- Light excites a pair of electrons in
 chlorophyll;
- Electrons pass down electron transfer chain
- In the thylakoid
- Electrons reduce carriers
- Energy released 
- ATP generated from ADP and Pi

Question 10

What coenzymes are used in photosynthesis?

Answer 10

NADPH

Question 11

How is ATP made in photosynthesis?

Answer 11

By oxidative phosphorylation.

Question 12

From where to where are H+ ions pumped to in chloroplast?

Answer 12

Across the thylakoid membrane, from stroma to the thylakoid.

Question 13

What is photolysis?

Answer 13

When water breaks down into H+ ions, electrong and oxygen using light energy.

Question 14

Why is photolysis important?

Answer 14

The electrons are used to replace those lost in Photoinoisation in the chlorophyll molecule. The H+ contributes to the gradient.

Question 15

What acts as the final electron acceptor?

Answer 15

NAD. NAD gets reduced to NADH.

Question 16

What is produced in the Light dependent reaction?

Answer 16

ATP, NADH and Oxygen

Question 17

Where does the light independent reaction occur?

Answer 17

In the stroma

Question 18

What is produced in the light independent reaction?

Answer 18

Glucose

Question 19

What happens in the light independent reaction?

Answer 19

1) CO2 combines with RuBP.
2) RuBP is catalysed by Rubisco enzyme and produces 2x GP.
3) Each GP is reduced to TP using ATP and NADPH
4) 2 TP are produces in each cycle. 2 TPs are required to form glucose and 10 are required to reform RuBP.

Question 20

What is TP ?

Answer 20

triose phosphate

Question 21

How many TP needed to form glucose?

Answer 21

2

Question 22

How many TPs needed to reform RuBP?

Answer 22

10

Question 23

What is the light independent reaction dependent on?

Answer 23

ATP and NADPH produced from the light dependent stage.

Question 24

What would happen to the concentration of RuBP and GP, if CO2 concentration suddenly decreased?

Answer 24

RuBP concentration increases and then decreases because RuBP is not being combined with CO2 and some TP is still regenerating RuBP. When all the TP runs out because there is not GP being produced the concentration decreases. GP decreases straight away as CO2 no longer combines with RuBP to produce GP.

Question 25

Where is RuBP found?

Answer 25

In the Stroma.

Question 26

Why does increasing oxygen concentration decrease CO2 absorption?

Answer 26

Oxygen acts as a competitive inhibitor for the active site of Rubisco enzyme.

Question 27

What happens to carriers in the electron transfer chain?

Answer 27

They get reduced.

Question 28

What happens if one electron carrier doesn’t work

Answer 28

The next carriers are not reduced

Question 29

Why does changing the CO2 concentration effect the rate of transpiration in plants that are watered than in dry?

Answer 29

In dry the stomata is partially closed due to the less turgid guard cells.

Question 30

Describe the part played by chlorophyll in photosynthesis?

Answer 30

light (energy) absorbed by chlorophyll;
electrons are excited
ATP formed;

Question 31

What’s GP?

Answer 31

glycerate 3-phosphate