photosynthesis

Question 1

Explain the role of chlorophyll in photolysis

Answer 1

1. Chlorophyll accepts electrons from photolysis of water
2. Light energy is absorbed
3. Chlorophyll is oxidised as it loses electrons

Question 2

Explain how light energy is converted into chemical energy in LDR

Answer 2

1. Electrons raised to higher energy levels
2. Use of electron acceptors
3. For the production of ATP

Question 3

Describe role of chlorophyll in photosynthesis

Answer 3

1. Absorbs light energy
2. Excites electrons
3. ATP formed

Question 4

Suggest advantage of having multiple pigments in photosystems

Answer 4

1. Absorb more wavelengths of light
2. More photosynthesis can occur

Question 5

During the LIR of photosynthesis, carbon dioxide is converted into organic substances, explain how

Answer 5

1. Co2 reacts with RuBP to form 2x glycerate -3 - phosphate
2. This reaction is catalysed by the RUBISCO enzyme
3. Each glycerate is reduced by NADPH to from 2 molecules of triose phospahte, 2 molecules of NADP
4. ATP provides the energy for this reaction (2 ATP molecules)
5. 5/6th of triose phosphate is used to regenerate RuBP
6. 1/6th is used to produce organic substances such as glucose, cellulose and lipids

Question 6

Describe what happens during photoionisation in the LDR

Answer 6

1. Chlorophyll absorbs light
2. Electrons are lost

Question 7

Explain why the origin line uses a pencil rather than using ink in chromatography

Answer 7

1. Ink and pigments would mix

Question 8

Describe the method used to separate the pigments after a solution of pigments had been applied to the origin of chromatography paper

Answer 8

1. level of solvent below origin
2. remove before solvent reaches top

Question 9

Explain why scientists measured the rate of production in oxygen when investigating rate of photosynthesis

Answer 9

1. oxygen produced in LDR
2. the faster oxygen is produced, the faster the LDR

Question 10

Explain how two features of a calorimeter enable a valid measurement of total energy released after combusting biomass

Answer 10

1. stirrer distributes heat
2. insulation/space/air reduces loss of heat
3. water has high specific heat capacity

Question 11

In photosynthesis most of the light falling on producers is not used in photosynthesis. Suggest 2 reasons why

Answer 11

1. light is reflected – because light is wrong wavelength
2. light misses chlorophyll – CO2 conc is a limiting factor

Question 12

A herbicide binds to proteins in the electron transfer chain in chloroplasts of weeds, reducing the transfer of electrons down the chain. Explain how this reduces the rate of photosynthesis in weeds

Answer 12

1. reduced transfer of protons across thylakoid membrane
2. less ATP is synthesised
3. amount of NADP is reduced
4. LIR slows