Photosynthesis

Question 1

What are the two stages in photosynthesis?

Answer 1

The light independent reaction and the light dependent reaction

Question 2

Where does the Light dependent reaction occur?

Answer 2

On the thylakoid membranes or grana

Question 3

Where does the Light independent reaction occur?

Answer 3

In the stroma

Question 4

What happens in the light dependent reaction?

Answer 4

Light energy and water are used to create ATP and reduced NADP which are needed for the light independent stage

Question 5

What are the four stages of the light dependent reaction?

Answer 5

1. Photoionisation of chlorophyll
2. Production of ATP and reduced NADP
3. Chemiosmosis
4. Photolysis

Question 6

What happens during the photolysis of water?

Answer 6

1. Light energy is absorbed by the chlorophyll and splits water into oxygen protons (H+) and electrons (e-)
   2.The H+ is picked up by NADP to form NADPH and is used in the light independent reaction
2. The electrons are passed along a chain of electron carrier proteins
3. The oxygen is either used for respiration or diffuses out of the leaf through the stomata

Question 7

What is the symbol equation for the photolysis of water?

Answer 7

H2O> 1/2 O2 + 2e- + 2H+

Question 8

What happens during photoionisation of chlorophyll?

Answer 8

Light energy is absorbed by the chlorophyll and the energy results in electrons becoming excited and raising up an energy level to leave chlorophyll.
Some of the energy from the released electrons is used to make ATP and reduced NADP in chemiosmosis.

Question 9

What happens during chemiosmosis?

Answer 9

1. The electrons from photoionisation move along a series of proteins embedded within the thylakoid membrane
2. As they move along they release energy and some of the energy from electrons is used to pump the protons across chloroplast membranes
3. An electrochemical gradient is created, the protons pass through the enzyme ATP synthase which results in the production of ATP
4. The protons combine with the co enzyme NADP to become reduced NADP. Because the protons move from a high to low concentration gradient this is known as chemiosmosis.

Question 10

What is another name for the light independent reaction?

Answer 10

The calvin cycle

Question 11

What does the stroma contain for the light independent reaction?

Answer 11

The fluid contains the enzyme Rubisco which catalyses this reaction.
This stage is temperature sensitive due to the fact that it involves enzymes.

Question 12

What does the light independent reaction use to form a hexose sugar?

Answer 12

Carbon dioxide, reduced NADP and ATP

Question 13

What provides the energy for this reaction?

Answer 13

The ATP is hydrolysed to provide energy and the reduced NADP donates the hydrogen to reduce molecules GP in the cycle

Question 14

What happens in the calvin cycle?

Answer 14

1. Carbon dioxide reacts with RuBP to form two molecules of GP a 3 carbon compound. This reaction is catalysed by the enzyme Rubisco
2. GP is reduced to triose phosphate using energy from ATP and by accepting a H from reduced NADP
3. Some of the carbon from TP leaves the cycle each in turn to be converted into useful organic substances
4. The rest of the molecule is used to regenerate RuBP with the energy from ATP
5. Whilst glucose is the product, this monosaccharide can join to form disaccharides such as sucrose and polysaccharides such as cellulose and starch. It can also be converted into glycerol and therefore combine with fatty acids to make lipids for the plant.