Unit 5

Question 1

Describe the process of the Light Independent Reaction (6)

Answer 1

1. Excites electrons, so removed from chlorophyll
2. Electrons move along electron transfer chain, releasing energy
3. Energy used to join ADP and Pi to form ATP
4. Photolysis of water produces protons
5. NADP reduced by electrons

Question 2

Describe the electron transport chain (5)

Answer 2

1. Excites electrons
2. Electrons move along electron transfer chain releasing energy
3. Energy used to join ADP and Pi to form ATP
4. Photolysis of water produces protons, electrons and oxygen
5. NADP reduced by electrons

Question 3

Describe the Calvin Cycle (6)

Answer 3

1. CO2 combines with RuBP
2. Produces two GP
3. GP reduced to TP
4. Using reduced NADP
5. Using energy from ATP
6. TP converted to glucose

Question 4

Why weedkillers cause plants to give off heat? (2)

Answer 4

1. Energy is released from excited electrons
2. This energy which is used to form ATP, cannot do as the weedkiller blocks

Question 5

Why does increased light intensity stimulate plant growth? (5)

Answer 5

1. Have faster production of ATP and reduced NADP
2. Have faster light-independent reaction
3. So produce more sugars that can be used in respiration
4. So have more energy for growth
5. Have faster synthesis of new organic material

Question 6

How is ATP produced? (11)

Answer 6

1. ATP produced in glycolysis
2. Involving the oxidation of glucose
3. ATP production directly from Krebs Cycle
4. Glycolysis produce reduced NAD
5. Reduced NAD transfer electrons to electron transport chain
6. Electrons transferred down a chain of carriers
7. Carries at decreasing energy levels
8. Energy is used to produce ATP
9. From ADP and Pi
10. Protons move into intermembrane space
11. ATP Synthase

Question 7

Describe Chemiosmosis (4)

Answer 7

1. Electrons transferred down electron transfer chain
2. Provide energy to transport protons into space between membranes
3. Protons diffuse through the membrane into ATP Synthase
4. Energy is then used to combine ADP and Pi

Question 8

Why is there less ATP produced in anaerobic respiration? (4)

Answer 8

1. ATP is formed as electrons pass along the transport chain
2. Oxygen is the terminal electron acceptor
3. Forms H20
4. Electrons cannot be passed along electron transport chain in of 02 is there to accept them

Question 9

Describe anaerobic respiration in animals (5)

Answer 9

1. Forms lactate
2. Uses NADH
3. Regenerates NAD
4. NAD allows glycolysis to continue
5. Can still release energy from ATP when no oxygen

Question 10

Why is the energy transfer along the food chain not 100% efficient? (9)

Answer 10

1. Some light energy isn’t the right wavelength
2. Efficiency of photosynthesis in plants is low
3. Respiratory loss
4. Loss of heat
5. Loss in excretion such as urine
6. Inedible parts
7. Efficient of transfer to consumers is greater than transfer to produces
8. Efficiency lower in older animals
9. Carnivores use more of their food than herbivores

Question 11

How do we improve productivity during farming of animals? (5)

Answer 11

1. Slaughtered while young so more energy transferred to biomass
2. Fed on controlled diet so higher proportion of food absorbed
3. Movement restricted so less respiratory loss
4. Kept inside so less heat loss
5. Genetically selected for high productivity

Question 12

How are nitrogen compounds in animals made available for plants? (8)

Answer 12

1. Proteins are broken down
2. By saprobionts
3. Ammonia is formed
4. Ammonia is converted into nitrate
5. by nitrifying bacteria
6. Nitrite converted to nitrate
7. Nitrate can be absorbed by roots
8. Nitrogen fixation forms ammonium compounds

Question 13

Describe how the action of microorganisms in the soil produces a source of nitrates for crop plants (5)

Answer 13

1. Protein into ammonium compounds
2. By Saprobionts
3. Ammonium is turned into nitrites
4. Nitrite into nitrate
5. By nitrifying bacteria
6. Nitrogen to ammonia
7. By nitrogen-fixing bacteria

Question 14

Describe the phosphorus cycle (10)

Answer 14

1. Phosphate ions in rocks released to soil by erosion
2. Phosphate ions taken into plants by roots
3. Phosphate ions assimilated into DNA
4. Rate of absorption increased by mycorrhizae
5. Phosphate ions transferred through food chain
6. Some phosphate ions lost by excretion
7. Phosphorus containing compounds are decomposed by saprobionts
8. Weathering of rocks releases phosphate ions into seas and taken up by aquatic producers
9. Phosphate ions passed along food chain to birds
   10, Guano returns phosphate ions to soils

Question 15

Describe the importance of phosphorylation (2)

Answer 15

1. Makes the substrates more reactive
2. Lowers activation energy for the reaction

Question 16

Describe eutrophication (6)

Answer 16

1. Growth of algae blocks the light
2. Reduced photosynthesis so plants die
3. Saprobiotic
4. Aerobically respire
5. Less oxygen for the fish
6. So they die

Question 17

Describe the function of saprobionts releasing Carbon Dioxide (6)

Answer 17

1. Microorganisms are saprobionts
2. Secrete enzymes onto dead tissue
3. Absorb products of digestion
4. Synthesis of structural compounds
5. Respiration provides energy for growth
6. Respiration produces Carbon Dioxide

Question 18

Evaluate use of fertilisers for mycorrhizas (4)

Answer 18

Should not use fertilisers because:
1. Fertilisers prevent development of mycorrhizae
2. Mycorrhizae help plants to take up nitrates
Should use fertilisers because:
1. Fertilisers containing phosphate and nitrate increase gross primary production so increase yield
2. Most soil is poor in phosphate so without fertiliser so plant might not get enough phosphate.

Question 19

Where precisely is rubisco found in a cell?

Answer 19

Thylakoid

Question 20

After harvesting the remains of crop plants are often ploughed into the soil.
Explain how microorganisms in the soil produce a source of nitrates from these remains? (5)

Answer 20

1. Protein/DNA turned into ammonium compounds
2. By Saprobionts
3. Ammonium into nitrite
4. Nitrite into Nitrate
5. By nitrifying bacteria

Question 21

Plants absorb a number o other nutrients from the soil including phosphates.
Describe why phosphates are needed by a growing plant? (4)

Answer 21

1. Phosphates are required for phospholipid production
2. Which make up the cell membrane
3. Required for the production of DNA and RNA
4. Required for ATP synthesis

Question 22

Describe the process of Glycolysis (4)

Answer 22

1. Phosphorylation if glucose using ATP
2. Oxidation of triose phosphate to pyruvate
3. Net gain of ATP
4. NAD reduced

Question 23

What are Mycorrhizae and why are they beneficial for plant growth? (4)

Answer 23

1. Mycorrhizae are fungal associations between plant roots and beneficial fungi
2. It increase the surface area for water and mineral absorption
3. Mycorrhizae acts like a sponge so holds water and minerals around the roots
4. Makes the plants more drought resistant and able to take up more inorganic ions.