3.5 Energy transfers in and between organisms

Question 1

Light Dependent Reaction

Answer 1

1. Light energy excites electrons in the chlorophyll
2. Electrons move along Electron Transport Chain
3. As electrons move along Electron Transport Chain they release energy
4. This energy is used to pump protons from stroma across thylakoid membrane
5. This creates a proton gradient
6. Which allows the reaction between ADP and Pi to form ATP catalysed by ATP synthase
7. NADP is reduced to reduced NADP
   Photolysis of water regenerates electrons

Question 2

Photolysis equation

Answer 2

H2O –> 2H+ + 2e- + 1/2 O2

Question 3

What is the final electron acceptor in photosynthesis

Answer 3

NADP, which is reduced to reduced NADP

Question 4

Light Independent Reaction

Answer 4

1. RuBP combines with CO2 molecule
2. Forming 2x GP catalysed by RuBisCO
3. GP is reduced to Triose Phosphate
4. Using ATP
5. Using reduced NADP
6. Triose phosphate is used to synthesise glucose/RuBP/other organic molecules

Question 5

What molecules is TP used to form

Answer 5

RuBP
Glucose
Cellulose
Starch
Lipids
Sucrose

Question 6

Glycolysis

Answer 6

1. Phosphorylation of glucose using ATP
2. Splitting of phosphorylated glucose into 2x Triose Phosphate
3. Triose Phosphate is oxidised to pyruvate
4. NAD is reduced to reduced NAD
5. Net gain of ATP

Question 7

Link reaction

Answer 7

1. Pyruvate is oxidised to acetate
2. NAD is reduced to reduced NAD
3. Acetate combines with Coenzyme A to form Acetyl Coenzyme A

Question 8

Krebs cycle

Answer 8

1. Acetylcoenzyme A reacts with a four-carbon molecule
2. Releasing coenzyme A
3. Producing a six-carbon molecule
4. Series of oxidation-reduction reactions
5. NAD is reduced to reduced NAD
6. Reduced coenzymes and ATP generated by substrate-level phosphorylation
7. CO2 is lost

Question 9

Oxidative phosphorylation

Answer 9

1. Electrons released form reduced coenzymes
2. Pass along Electron Transport Chain
3. Energy released form electrons
4. Energy is used to actively transport protons into intermembrane space
5. Proton gradient allows synthesis of ATP from ADP and Pi, catalysed by ATP synthase

Question 10

What is the final electron acceptor in respiration

Answer 10

Oxygen (reduced to water)

Question 11

Anaerobic respiration to produce lactate

Answer 11

1. Pyruvate is reduced to lactate
2. Reduced NAD is oxidised to NAD
3. Allowing glycolysis to occur

Question 12

Anaerobic respiration to produce ethanol

Answer 12

1. Pyruvate is decarboxylated, removing one CO2 molecule
2. 2C molecule is reduced to ethanol
3. Reduced NAD is oxidised to NAD
4. Allowing glycolysis to occur

Question 13

In aerobic respiration where does pyruvate enter after glycolysis

Answer 13

The mitochondrial matrix

Question 14

Where does each part of aerobic respiration take place

Answer 14

Glycolysis - Cytoplasm
Link reaction - Matrix
Krebs cycle - Matrix
Oxidative phosphorylation - Inter membrane space / Cristae

Question 15

Biomass

Answer 15

Can be measured in terms of mass of carbon or dry mass of tissue per given area.

Question 16

Net Primary Production equation

Answer 16

NPP = GPP - R

GPP - Gross primary production - chemical energy store in plant biomass in a given area
R - Respiratory losses to the environment

Question 17

What do NPP and N stand for

Answer 17

NPP - producer biomass
N - consumer biomass

Question 18

Net product of consumers equation

Answer 18

N = I - (F + R)

I - chemical energy store in ingested food
F - chemical energy lost to environment in faeces/urine
R - Respiratory losses to the environment

Question 19

How is chemical food energy lost

Answer 19

• Uneaten parts e.g. bones
• Decay of dead material
• Excretion
• Respiratory losses
• Exothermic reactions

Question 20

Why do plants only convert 1-3% of the suns available energy

Answer 20

• Most reflected by clouds and dust
• Not all wavelengths of light can be absorbed
• Light may not hit a chlorophyll molecule
• Other factors may limit rate of photosynthesis e.g. CO2 conc

Question 21

Saprobionts

Answer 21

Organisms that break down complex materials in dead organisms into simple ones, in doing so releasing valuable minerals

Question 22

Percentage efficiency equation (Energy)

Answer 22

percentage efficiency = energy available after transfer/energy available before transfer

Question 23

Steps of the nitrogen cycle

Answer 23

1. Nitrogen fixation
2. Ammonification
3. Nitrification
4. Denitrification

Question 24

1. Nitrogen fixation

Answer 24

Nitrogen fixing bacteria convert atmospheric N2 into ammonia.

Question 25

2. Ammonification

Answer 25

Saprobionts decompose organism biomass, releasing ammonium ions. Amino acids converted into ammonium ions.

Question 26

4. Denitrification

Answer 26

Denitrifying bacteria convert nitrates back into atmospheric N2 under anaerobic conditions

Question 27

3. Nitrification

Answer 27

Nitrifying bacteria convert ammonium ions into nitrite ions then into nitrate ions

Question 28

What relationship do saprobionts/other bacteria in nitrogen cycle have with the plant

Answer 28

Mutualistic. Plant provides sugar, bacteria provide ammonium ions.

Question 29

Saprobiotic nutrition

Answer 29

1. Saprobionts secrete enzymes onto the dead organic matter. This is called extracellular digestion. 2. The enzymes break down large, insoluble molecules into smaller, soluble molecules. 3. These smaller molecules can then be absorbed by the saprobiont. 4; The saprobiont will then either store the molecules or use them in respiration.

Question 30

Mycorrhizae

Answer 30

Fungi that form symbiotic relationships with the roots of plants

Question 31

What is a symbiotic relationship

Answer 31

A close or intimate relationship between members of two different species

Question 32

How do mycorrhizae help facilitate the uptake of ions/water in plants

Answer 32

They associate themselves with plant roots using hyphae Hyphae increase surface area of root Allowing more water/ions to be absorbed

Question 33

Eutrophication / Leaching

Answer 33

1. Eutrophication causes algal bloom 2. Organisms die and are decomposed by saprobionts 3. Saprobionts aerobically respire taking in oxygen from the water 4. less oxygen in water 5. Fish cannot aerobically respire so die too

Question 34

What intensive farming practices are used to conserve energy?

Answer 34

Movement restricted to reduce energy used for muscle contraction Environment kept warm to reduce energy used for heat Feeding controlled so that maximum growth and little wastage occurs Predators excluded

Question 35

Phosphate cycle

Answer 35

1. As phosphate ions are transferred through the food chain, they are lost as waste products or when an organism dies. 2. Saprobionts decompose waste and dead organisms through extracellular digestion. 3. Phosphate ions are released into the soil and can be recycled for reuse in the cycle.

Question 36

Effects of fertilisers (negatives)

Answer 36

Loss of biodiversity Leaching Eutrophication

Question 37

Two types of fertilizers

Answer 37

Natural e.g. Guano Artificial e.g. NPK

Question 38

Importance of fertilisers

Answer 38

Increase crop yields by replacing nutrients

Question 39

Malonate inhibits a reaction in the Krebs cycle. Explain why malonate would decrease the uptake of oxygen in a respiring cell [2]

Answer 39

1. Less/no reduced NAD/coenzymes 2. Oxygen is the final/terminal (electron) acceptor;