5) Energy Transfer Between Oragnisims

Question 1

Light Dependent Reaction –
Describe the process

Answer 1

1. Light (energy) excites / raises energy level of electrons in chlorophyll;
2. Electrons pass down electron transport chain;
3. (Electrons) reduce carriers / passage involves redox reactions;
4. Electron transport chain / role of chain associated with chloroplast membranes / in thylakoids / grana;
5. Energy released / carriers at decreasing energy levels;
6. ATP generated from ADP and phosphate / Pi / phosphorylation of ATP;

Question 2

Light Dependent Reaction –
Describe the electron transport
chain

Answer 2

1. Excites electrons (from chlorophyll);
2. Electrons move along carriers/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

Light Independent Reaction
– Describe the Calvin Cycle

Answer 3

1. Carbon dioxide 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 / hexose / RuBP / ribulose bisphosphate / named organic substance;

Question 4

Why weedkillers cause plants to
give off heat?

Answer 4

Energy is released from high energy/excited electron/s (that were lost from chlorophyll)

This energy which should be used to form ATP, cannot do this as the weedkiller blocks the ETC, (so the energy is lost as heat);

Question 5

Why does increased light
intensity stimulate plant growth?

Answer 5

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

Question 6

Respiration – How is ATP
produced?

Answer 6

• produced in glycolysis
• involved in oxidation of glucose/TP to pyruvate
• ATP is produced in Kreb cycle during substrate level phosphorylation
• Glycolysis/Krebs cycle produce reduced NAD/FAD;
• Reduced NAD/FAD transfer electrons to electron transport chain;
• Electrons transferred down a chain of carriers;
• (Carriers) at decreasing energy levels;
• Energy (lost by electrons) used to produce ATP;
• From ADP and (inorganic) phosphate;
• Protons move into intermembrane space;
• ATP synthase;

Question 7

Describe chemiosmosis

Answer 7

1. Electrons transferred down electron transfer chain;
2. Provide energy to transport protons into space between membranes;
3. Protons diffuse/pass back, through membrane/into matrix/through ATP synthase;
4. Energy (from H+ movement) used to combine ADP and phosphate to form ATP;

Question 8

Why is there less ATP produced in anaerobic respiartion

Answer 8

1. ATP formed as electrons pass along transport chain;
2. Oxygen is terminal electron acceptor
3. Forms H2O;
4. Electrons cannot be passed along electron transport chain if no O2 to accept them

Question 9

Describe anaerobic respiartion in animals

Answer 9

• pyruvate formed into lactate
• uses NADH
• NAD is regenerated
• NAD allows glycolysis to continue
• can still release energy from ATP when no oxygen

Question 10

Why is energy transfer along
food chain not 100% efficient?

Answer 10

1. Some light energy fails to strike/is reflected/not of appropriate wavelength;
2. Efficiency of photosynthesis in plants is low
3. Respiratory loss / excretion / faeces / not eaten;
4. Loss as heat;
5. In excreta / excretion / urine / carbon dioxide;
6. Inedible parts / indigestible parts / egestion / to decomposers
7. Efficiency of transfer to consumers greater than transfer to producers;
8. Efficiency lower in older animals/herbivores/ primary consumers/warm blooded animals/homoiotherms;
9. Carnivores use more of their food than herbivores;

Question 11

How do we improve
productivity during farming of
animals?

Answer 11

1. Slaughtered while young so more energy transferred to biomass;
2. Fed on controlled diet so higher proportion of food absorbed/lower proportion lost in faeces;
3. Movement restricted so less respiratory loss;
4. Heating/Kept inside so less heat/respiratory loss;
5. Genetically selected / selective breeding (for high productivity);

Question 12

Nitrogen cycle -
How nitrogen compounds in animals made
available for plants?

Answer 12

§

Question 13

Nitrogen cycle -
How nitrogen compounds in animals made
available for plants?

Answer 13

1. Proteins/amino acids broken down;
2. by saprophytes/decomposers;
3. deamination/ammonium compounds/ammonia formed;
4. Ammonia converted to nitrite
5. by nitrifying bacteria;
6. Nitrite converted to nitrate;
7. Nitrate can be absorbed by roots;
8. Nitrogen fixation forms ammonium compounds;

Question 14

Describe
the phosphorus cycle.

Answer 14

1. Phosphate ions in rocks released to soil by erosion/weathering;
2. Phosphate ions taken into plants by roots/root hair cells;
3. Phosphate ions assimilated into DNA/RNA/phospholipids/NADP/RuBP;
4. Rate of absorption increased by mycorrhizae;
5. Phosphate ions transferred through food chain;
6. Some phosphate ions lost by excretion/when plants and animals die;
7. Phosphorus containing compounds are decomposed by saprobionts/fungi;
8. Weathering of rocks releases phosphate ions into seas and taken up by aquatic producers/algae;
9. Phosphate ions passed along food chain to birds;
10. Guano returns phosphate ions to soils;

Question 15

Importance of phosphorylation

Answer 15

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

Question 16

Eutrophication – Describe
eutrophication

Answer 16

1. Growth of algae / algal bloom blocks light;
2. Reduced / no photosynthesis so (submerged) plants die;
3. Saprobiotic (microorganisms / bacteria);
4. Aerobically respire / use oxygen in respiration;
5. Less oxygen for fish / aerobic organisms to respire;
6. (So) they die;

Question 17

The functioning of saprobionts
releasing carbon dioxide

Answer 17

1. Microorganisms are saprobionts/saprophytes;
2. Secrete enzymes (onto dead tissue) / extracellular digestion;
3. Absorb products of digestion/smaller molecules/named relevant substance;
4. Synthesis of structural compounds/named compound;.
5. Respiration provides energy for growth
6. Respiration (by microorganisms) produces carbon dioxide;

Question 18

Evaluate use of fertilisers for
mycorrhizas

Answer 18

(Should not use fertilisers because)

• Fertilisers prevent development of mycorrhizae;
• Mycorrhizae help plants to defend themselves (causing an increase in crop yield);
• Mycorrhizae help plants to take up nitrates/phosphates (causing an increase in crop yield);

(Should use fertilisers because)

• Fertilisers containing phosphate and nitrate increase gross primary production so increase yield;
• Most soil is poor in phosphate so without fertiliser so plant might not get enough phosphate;