Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A2 AQA Biology - Burnley College (2024-25) > Energy Transfers 3.5 > Flashcards

Energy Transfers 3.5 Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

Photosynthesis (AO1)

Which reaction comes first in photosynthesis?

A

Light-dependent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Photosynthesis (AO1)

During photosynthesis, plants produce ____________ compounds which contain carbon, such as carbohydrates, lipids and proteins.

A

organic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Photosynthesis (AO1)

Most of the sugars synthesised by plants during photosynthesis are used by the plant in ____________ .
The rest are used to make other groups of biological molecules.

A

respiration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Photosynthesis (AO1)

Chlorophyll location

A

Thylakoid membrane
(found in chloroplasts).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Photosynthesis (AO1)

What process do photoautotrophic organisms use to convert carbon dioxide into organic molecules?

A

Photosynthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Photosynthesis (AO1)

Examples of photoautotrophic organisms

A

plants

algae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Photosynthesis (AO1)

Light-dependent reaction location

A

Thylakoid membrane
(found in chloroplasts).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Photosynthesis (AO1)

What molecule’s electrons are excited / released during photoionisation?

A

Chlorophyll

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Photosynthesis (AO1)

TRUE or FALSE:
Chlorophyll absorbs all wavelengths of light

A

FALSE

The pigment ‘chlorophyll a’ does NOT absorb green light, so reflects it

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Photosynthesis (AO1)

What is the term for the splitting of water by light energy into protons, electrons and oxygen?

A

Photolysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Photosynthesis (AO1)

Which chemicals are needed for the light-dependent reaction

A

NADP, ADP, Pi and water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Photosynthesis (AO1)

Describe photoionisation
(2 marks).

A

1. Chlorophyll absorbs light energy

OR light energy excites / releases electrons from chlorophyll;

2. Electron/s go to the electron transport chain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Photosynthesis (AO1)

Molecules located in the thylakoid membranes

A

Chlorophyll

Electron transport chain proteins
(includes channel protein for protons)

ATP Synthase
(includes channel protein for protons)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Photosynthesis (AO1)

Products of the light-dependent reaction

A

NADPH and ATP

Reduced NADP is accepted.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Photosynthesis (AO1)

Describe what happens during the light-dependent reaction (5 marks).

A
  1. Chlorophyll absorbs light energy;
  2. Excites electrons / electrons removed (from chlorophyll);
  3. Electrons move along electron transport chain releasing energy;
  4. Energy used to join ADP and Pi to form ATP;
  5. Photolysis of water produces protons, electrons and oxygen;
  6. NADP reduced by electrons and protons
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Photosynthesis (AO1)

______________ enters most ecosystems through the light-dependent reaction of photosynthesis.

A

Energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Photosynthesis (AO1)

Describe the role of chlorophyll in photolysis (3 marks).

A

Absorbs light energy;

Loses electrons;

Accepts electrons from water;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Photosynthesis (AO1)

Describe how NADP is reduced in the light-dependent reaction of photosynthesis (2 marks).

A

by electrons and protons from photolysis;

by electrons from chlorophyll;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Photosynthesis (AO1)

What molecule is a nitrogen-containing biological molecule, a type of nucleotide, and has two phosphate groups?

A

NADP

This is useful knowledge for the essay!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Photosynthesis (AO1)

What process involves the movement of protons down an electrochemical gradient to produce ATP?

A

Chemiosmosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Photosynthesis (AO1)

The light independent reaction is also known as the __________ cycle

A

Calvin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Photosynthesis (AO1)

Light independent reaction location

A

Stroma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Photosynthesis (AO1)

Rubisco location

A

Stroma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Photosynthesis (AO1)

Describe the function of NADPH in the light-independent reaction.

A

Provides H / electrons for the reduction of GP to triose phosphate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Photosynthesis (AO1)

Describe the function of ATP in the light-independent reaction (1 mark).

A

Provides energy for the reduction of GP to triose phosphate;

Provides Pi / inroganic phosphate to convert triose phosphate to RuBP;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Photosynthesis (AO1)

Describe the light-independent reaction of photosynthesis (6 marks).

A
  1. Carbon dioxide combines/reacts with ribulose bisphosphate/RuBP;
  2. Produces two GP molecules using (enzyme) Rubisco;
  3. GP reduced to triose phosphate;
  4. Using reduced NADP / NADPH;
  5. Using energy from ATP hydrolysis;
  6. Triose phosphate converted to glucose / RuBP / named organic substance;
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Photosynthesis (AO1)

Describe how the products of the light-dependent reaction are used in the light-independent reaction to produce triose phosphate (3 marks).

A
  1. ATP and reduced NADP / NADPH;
  2. GP reduced to triose phosphate;
  3. ATP provides energy;
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Photosynthesis (AO3)

Environmental factors that should be controlled when measuring the rate of photosynthesis

A
  1. Light intensity
  2. Carbon dioxide concentration
  3. Temperature
  4. Water OR humidity
  5. Wavelength of light

Note: which factors are controlled depends on the IV of the experiment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Photosynthesis (AO1)

Limiting factors for photosynthesis

A

Temperature
Carbon dioxide concentration
Light intensity
Wavelength of light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Photosynthesis (AO3)

Explain why scientists measured the rate of production of oxygen when investigating the rate of photosynthesis (2 marks).

A

Oxygen is produced in the light dependent reaction;

The faster the oxygen produced, the faster the light dependent reaction;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Photosynthesis (AO2)

Heat stress is a condition that often occurs in plants exposed to high temperatures for a prolonged period of time. Heat stress is a major factor in limiting the rate of photosynthesis.

Heat stress decreases the light-dependent reaction of photosynthesis.

Explain why this leads to a decrease in the light-independent reaction (2 marks).

A
  1. Less ATP;
  2. Less reduced NADP / NADPH;
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Photosynthesis (AO2)

Atrazine is a herbicide used to reduce the growth of weeds.

Atrazine 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 (4 marks).

A
  1. Reduced transfer of protons across thylakoid membrane

OR

Reduced chemiosomotic gradient / proton gradient across thylakoid membrane;

  1. (So) less ATP produced;
  2. (So) less reduced NADP / NADPH produced;
  3. (So) less reduction of GP to triose phosphate.

OR

(So) light-independent reaction slows / stops;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Photosynthesis (AO2)

Iron deficiency reduces electron transport. Use this information and your knowledge of photosynthesis to explain the decrease in production of triose phosphate in the iron-deficient plants (4 marks).

A
  1. ATP and reduced NADP produced during light-dependent reaction;

(In the case of iron deficiency)

  1. Less ATP produced;
  2. Less reduced NADP produced;
  3. Less GP to triose phosphate;
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Photosynthesis (AO2)

Some bacteria use hydrogen sulfide, H2S, to produce organic compounds. The hydrogen sulfide has a similar role to that of water in photosynthesis.

A simple equation for this process in bacteria is shown below:

hydrogen sulfide + carbon dioxide → glucose + sulfur + water

Suggest what the hydrogen sulfide is used for in these bacteria (2 marks).

A
  1. (Provides) hydrogen/protons/H+ and electrons/e-;
  2. For reduction (of NADP);
  3. Source of electrons for chlorophyll / electron transfer chain;
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Photosynthesis (AO2)

Another effect of heat stress is a decrease in the activity of the enzyme rubisco. A decrease in the activity of an enzyme means that the rate of the reaction it catalyses becomes slower.

A decrease in the activity of the enzyme rubisco would limit the rate of photosynthesis.

Explain why (2 marks).

A
  1. Less carbon dioxide (reacts) with RuBP;
  2. Less GP;
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Photosynthesis (AO2)

An investigation was carried out into the effect of carbon dioxide concentration and light intensity on the rate of photosynthesis in a species of plant.

The temperature was kept constant during this investigation. Explain why (2 marks).

A

Temperature affects photosynthesis;

because it affects enzyme activity;

So that any change in photosynthesis rate is result of carbon dioxide / light intensity;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Photosynthesis (AO2)

Data from an investigation showed that mutant plants producing more chlorophyll b grow faster than normal plants in all light intensities.

Explain how (4 marks).

A
  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 (e.g. amino acids).
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Respiration (AO1)

Respiration produces ………………………

A

ATP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Respiration (AO1)

Aerobic respiration stages

A

1. Glycolysis
2. Link reaction
3. Krebs cycle
4. Oxidative phosphorylation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Respiration (AO1)

TRUE OR FALSE:

Glycolysis is the first stage of anaerobic AND aerobic respiration

A

TRUE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Respiration (AO1)

Glycolysis location

A

Cytoplasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Respiration (AO1)

Describe glycolysis (4 marks)

A

1. Phosphorylation of glucose using ATP;

2. Oxidation of triose phosphate to pyruvate;

3. Net gain of (2) ATP (molecules);

4. NAD reduced/ NADH produced;

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Respiration (AO1)

Dehyrogenase action during glycolysis

A

Removes hydrogen from triose phosphate so oxidised to pyruvate

Adds hydrogen to NAD so reduced to NADH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

Respiration (AO1)

During glycolysis, ATP is produced via ____________-____________ phosphorylation

A

substrate-level

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

Respiration (AO1)

Net yield of 2 ATP during glycolysis

A

2 ATP used to phosophorylate glucose

4 ATP produced during substrate level phosphorylation (triose phosphate to pyruvate)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

Respiration (AO1)

TRUE or FALSE:
Anaerobic respiration produces more ATP than aerobic respiration

A

False

Lots of ATP is produced during oxidative phosphorylation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

Respiration (AO1)

If respiration is aerobic, pyruvate from glycolysis enters the mitochondrial matrix by…………………….

A

active transport

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

Respiration (AO1)

TRUE or FALSE:
Glucose crosses the double membrane of mitochondria via active transport

A

FALSE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

Respiration (AO1)

Link reaction location

A

(Mitochondrial) matrix

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

Respiration (AO1)

Fill in the blanks:

During the first step of the link reaction pyruvate is oxidised to [1] and the removed hydrogen is used to reduce [2]. During this step, carbon [3] is also released/removed by the enzyme [4].

A
  1. acetate
  2. NAD
  3. dioxide
  4. decarboxylase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

Respiration (AO1)

Carbons in pyruvate

A

3 carbons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

Respiration (AO1)

Carbons in acetate

A

2 carbons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

Respiration (AO1)

A

A - pyruvate

B - reduced NAD / NADH

C - coenzyme A

D - AcetylcoenzymeA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

Respiration (AO1)

Decarboxylase action during link reaction

A

removes carbon during oxidation of pyruvate, releasing carbon dioxide and resulting in the formation of acetate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

Respiration (AO1)

Describe how acetylcoenzyme A is formed in the link reaction (2 marks)

A

1. Oxidation of / hydrogen removed from pyruvate AND carbon dioxide released;

2. Addition of coenzyme A (to 2C acetate).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

Respiration (AO1)

Link reaction reactants

A

Pyruvate
NAD
CoenzymeA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

Respiration (AO1)

Acetylcoenzyme A reacts with a four-carbon molecule, releasing coenzyme A and producing a six-carbon molecule that enters the ……………………..

A

Krebs cycle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

Respiration (AO1)

Krebs cycle location

A

(Mitochondrial) matrix

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

Respiration (AO1)

The Krebs cycle is a series of oxidation-reduction reaction that produces………

A

Products through oxidation-reduction:

Reduced NAD / NADH
Reduced FAD / FADH

other products:

ATP by substrate-level phosphorylation
Carbon dioxide
A 4C molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

Respiration (AO1)

Importance of the 4C product from the Krebs cycle

A

Allows the Krebs cycle to continue;

So more NADH and FADH produced;

So more ATP can be produced during oxidative phosphorylation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

Respiration (AO1)

Enzyme that produces NADH and FADH

A

Dehydrogenase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

Respiration (AO1)

Enzyme that produces carbon dioxide during the link reaction and Krebs cycle

A

Decarboxylase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

Respiration (AO1)

TRUE OR FALSE:

FADH is produced during the link reaction and Krebs cycle

A

FALSE

FADH is only produced during the Krebs cycle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
64
Q

Respiration (AO1)

Draw out the Krebs cycle

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
65
Q

Respiration (AO1)

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
66
Q

Respiration (AO2)

Malonate inhibits a reaction in the Krebs cycle.

Explain why malonate would decrease the uptake of oxygen in a respiring cell (2 marks).

A

1. Less/no reduced NAD/ reduced FAD

2. Oxygen is the final/terminal (electron) acceptor;

Less NADH/FADH = less electron transfer, so less oxygen required.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
67
Q

Respiration (AO1)

What do NADH and FADH bring to the electron transport chain?

A

(High energy) electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
68
Q

Respiration (AO1)

Oxidative phosphorylation / electon transport chain location

A

In the cristae (the folds of the inner mitochondrial membrane)

69
Q

Respiration (AO1)

Advantage of the cristae during oxidative phoshorylation

A

Large surface area, so more inner membrane to embed more electron transport chain (e.g. proton pumps) and ATP synthase.

70
Q

Respiration (AO1)

Describe how ATP is made in mitochondria (6 marks).

A

Substrate level phosphorylation

  1. ATP produced in Krebs cycle;

Oxidative phosphorylation

  1. Krebs cycle and link reaction produces NADH;

OR Krebs cycle produces FADH;

  1. Electrons released from NADH / FADH;
  2. (Electrons) pass along carriers / through electron transport chain / through series of redox reactions;
  3. Energy released;
  4. Protons move into intermembrane space (electrochemical / proton gradient forms);

(Protons move down electrochemical gradient and release energy used to combine)

  1. ADP + Pi;
  2. ATP synthase
71
Q

Respiration (AO1)

Explain why oxygen is needed for the production of ATP on the cristae of mitochondria (3 marks)

A

1. ATP formed as electrons pass along transport chain (ETC);

2. Oxygen is final electron acceptor / accepts electrons from electron transport chain;

3. Forms H2O;

4.. Electrons cannot be passed along electron transport chain if there is no O2 to accept them;

72
Q

Respiration (AO1)

Describe how oxidation takes place in glycolysis and in the Krebs cycle (4 marks).

A

1. Removal of hydrogen;

2. By enzymes/dehydrogenases;

3. H accepted by NAD / reduced NAD formed;

(Triose phosphate is oxidised)

4. In Krebs cycle, FAD (used as well);

73
Q

Respiration (AO1)

List alternative respiratory substrates

A

Fatty acids

Glycerol

Amino acids

74
Q

Respiration (AO1)

TRUE OR FALSE:

Fatty acids, glycerol and amino acids can also enter the Krebs cycle to contribute to the generation of ATP

A

TRUE

75
Q

Respiration (AO2)

A
  1. Less / no malonyl-CoA produced;
  2. More fatty acids transported / moved into mitochondria;
  3. Respiration / oxidation of fatty acids provides ATP;
76
Q

Respiration (AO1)

Which organisms produce carbon dioxide AND ethanol during anaerobic respiration?

A

Yeast
Bacteria
Some plants

77
Q

Respiration (AO1)

Which animal cell(s) does anaerobic respiration mainly take place?

A

Muscle cells

Specifically fast-twich muscle fibres e.g. for sprinting

78
Q

Respiration (AO1)

Products of anaerobic respiration in animal cells

A

Lactate / lactic acid

ATP (net yield of 2 ATP)

NAD

79
Q

Respiration (AO1)

2 main phases of anaerobic respiration

A
  1. Glycolysis
  2. Regeneration of NAD
80
Q

Respiration (AO1)

Anaerobic respiration location

A

Cytoplasm

81
Q

Respiration (AO1)

Pyruvate is ____________ to ethanol and carbon dioxide in some plants and yeast during anerobic respiration.

A

reduced

82
Q

Respiration (AO1)

Pyruvate is ________________ to lactate in animal cells

A

reduced

83
Q

Respiration (AO1)

A

Reduction of pyruvate

84
Q

Respiration (AO1)

Explain why converting pyruvate to lactate allows the continued production of ATP during anaerobic respiration (2 marks).

A
  1. Regenerates NAD
    (accept oxidises reduced NAD);
  2. NAD used in glycolysis.
85
Q

Respiration (AO2)

In muscles, some of the lactate is converted back to pyruvate when they are well supplied with oxygen.

Suggest one advantage of this (1 mark).

A

Pyruvate used in aerobic respiration / can enter the link reaction

OR

Less lactate so less cramp / muscle fatigue.

86
Q

Respiration (AO1)

Humans synthesise more than their body mass of ATP each day.

Explain why it is necessary for them to synthesise such a large amount of ATP.

A
  1. ATP cannot be stored / is an immediate source of energy;
  2. ATP only releases a small amounts / packets of energy at a time;
87
Q

Respiration (AO1)

Aerobic respiration produces more ATP per molecule of glucose than anaerobic respiration.

Explain why (2 marks).

A
  1. Oxygen is final/terminal (electron) acceptor /
  2. (This allows aerobic respiration) oxidative phosphorylation / electron transfer chain;
  3. Anaerobic (respiration) only glycolysis occurs
    (so some ATP produced via substrate level phosphorylation)
88
Q

Respiration (AO2)

A
  1. Fewer cristae/smaller surface area (of cristae);
  2. So less electron transport/oxidative phosphorylation;
  3. (So) not enough ATP produced

OR Not enough energy to keep neurones alive;

89
Q

Respiration (AO1)

During anaerobic respiration, a build up of ethanol in yeast cells is ____________ .

A

toxic

This may lead to some yeast cells dying

90
Q

Respiration (AO2)

A
91
Q

Respiration (AO1)

Equipment used to measure the
rate of respiration

A

respirometer

92
Q

Respiration (AO1)

Respirometer can investigate the rate of respiration in which organisms…

A

Insects
Seeds
Yeast
Other mircoorganisms e.g., bacteria

Respirometer is suited for small organisms only

93
Q

Respiration (AO1)

TRUE or FALSE:
Respirometers can only be used to measure the rate of aerobic respiration

A

FALSE

Can be adapted to measure anaerobic respiration

94
Q

Respiration (AO1)

A

1. Oxygen used by seeds (aerobic respiration);

2. Carbon dioxide produced is absorbed by potassium hydroxide;

3. Decrease in pressure/volume (of air inside);

95
Q

Respiration (AO1)

In an experiment using a respirometer, apart from time, give two measurements the student would have to make to determine the rate of aerobic respiration of these seeds in cm^3 hour^–1.

A

1. Distance liquid moves;

2. Diameter/radius of the tubing/lumen

96
Q

Respiration (Maths)

A
97
Q

Respiration (AO1)

A

1. Equilibrium reached / allow to equilibrate

2. Allow for pressure change in apparatus;

3. Allow respiration rate of seeds to stabilise.

98
Q

Respiration (AO2)

A

Prevents oxygen being taken up / entering / being absorbed

99
Q

Respiration (AO2)

A
  1. Affects enzymes;
  2. Affects respiration;

OR

  1. Affects volume / pressure of gases;
  2. Affects readings;
100
Q

Respiration (AO2)

In laboratory conditions, yeast will initially grow rapidly. The population then plateaus and then decreases. Explain why (2 marks).

A

1. Decrease/no glucose/substrate;

(Switch from aerobic to anerobic respiration)

2. Increase in ethanol/carbon dioxide/acidity;

101
Q

Energy transfers (AO1)

In any ecosystem, plants synthesise ________________ compounds from atmospheric, or aquatic, carbon dioxide.

A

organic

Organic means the molecule contains c-c or c-h bonds

102
Q

Energy transfers (AO1)

Most of the sugars synthesised by plants are used as respiratory substrates. The rest are used to make other groups of biological molecules. These biological molecules form the ______________ of the plants.

A

biomass

103
Q

Energy transfers (AO1)

Producers are _______________ organisms that manufacture their own organic compounds using light energy, water and carbon dioxide.

A

photosynthetic

104
Q

Energy transfers (AO1)

Primary consumers obtain their energy by feeding on ___________.

A

producers

105
Q

Energy transfers (AO1)

____________________ are a group of microorganisms that break down the organic materials in dead organic matter and faeces into simple ones.

A

Saprobionts / decomposers

106
Q

Energy transfers (AO1)

In natural ecosystems, most of the light energy falling onto producers is NOT used in photosynthesis. Explain why (2 marks).

A

1. Light being reflected

2. Pigments may not absorb the wavelength of light received

3. Light may miss the chlorophyll

4. There is another limiting factor that means that the light cannot be used e.g. carbon dioxide concentration

107
Q

Energy transfers (AO1)

Farming cattle for humans to eat is less efficient than farming crops because of energy transfer. Explain why (2 marks).

A

1. Energy lost during transfer between trophic levels;

(Humans eating cattled adds a trophic level)

2. Energy lost via respiration / heat loss / maintaining temperature / muscle contraction / movement

Also accept: excretion / faeces / parts of food not eaten e.g. roots/bones;

108
Q

Energy transfers (AO1)

Give three reasons for the low efficiency of energy transfer from secondary consumers to tertiary consumers in an ecosystem.

A

1. Heat loss from respiration;

2. Food not digested / not all eaten OR faeces;

3. Excretion OR urine;

109
Q

Energy transfers (AO1)

Energy efficiency equation

A
110
Q

Energy transfers (Maths)

A

0.155%

111
Q

Energy transfers (AO1)

Biomass definition

A

Total mass of carbon per given area per given time

OR

Total dry mass of tissue per given area per given time

112
Q

Energy transfers (AO1)

The chemical energy stored in dry biomass can be estimated using _____________.

A

calorimetry

113
Q

Energy transfers (AO2)

Suggest how you could determine the dry mass of a sample of plant material (2 marks).

A

1. Heat at 100°C to evaporate water;

2. Weigh and heat until no further change in mass

114
Q

Energy transfers (AO2)

What is the advantage of using dry mass and not fresh mass to compare the yield of plants (2 marks).

A

1. Water content present will vary in fresh mass;

2. This issue will not affect dry mass;

115
Q

Energy transfers (AO1)

Gross primary production (GPP) is the ____________ energy store in plant biomass, in a given area or volume.

A

chemical

116
Q

Energy transfers (AO1)

The higher GPP, the higher the rate of ______________

A

photosynthesis

117
Q

Energy transfers (AO1)

Net Primary Production (NPP) equation

A

NPP = GPP-R
Where:
GPP = Gross primary production
R = respiratory losses

118
Q

Energy transfers (AO1)

This NPP is available for _____________

A

plant growth and reproduction;

contains energy that can passed onto the next trophic level;

119
Q

Energy transfers (AO1)

Net production of consumers (N) equation

A

N = I - (F+R)

120
Q

Energy transfers (AO1)

What does I represent?

N = I - (F+R)

A

I = Chemical energy/store of ingested/consumed food

121
Q

Energy transfers (AO1)

What does F represent?

N = I - (F+R)

A

(energy loses due to)

F = faeces AND urine

122
Q

Energy transfers (AO1)

What does R represent?

N = I - (F+R)

A

R = Respiratory losses

(due to heat loss / maintaining temperature / movement)

123
Q

Energy transfers (AO1)

What does N represent?

N = I - (F+R)

A

N = net production of consumers

124
Q

Energy transfers (Maths)

A
125
Q

Energy transfers (Maths)

Units for the energy stored in biomass

A
Units for biomass must have energy, area & time
126
Q

Energy transfers (Maths)

Units for NPP or GPP

A
Units for productivity must have energy, area & time
127
Q

Energy transfers (AO1)

Describe how calorimetry can estimate the energy stored in biomass.

A

Sample of (dry) biomass is combusted;

This releases heat energy;

This warms the surrounding water;

The larger the temperature increases of water, the more energy stored in the biomass;

Water is used because it has a high specific heat capacity
(we know much energy is required to heat 1cm3 of water by 1oC).

128
Q

Energy transfers (AO2)

A
  1. Stirrer distributes heat energy;
  2. Insulation by air spaces reduces heat loss
  3. Water has a high specific heat capacity
129
Q

Energy transfers (Maths)

A
130
Q

Energy transfers (AO1)

To increase the net productivity (N) of domestic livestock, farmers aim to decrease energy losses due to ________.

A

Respiration / heat loss / maintaining body temperature / movement;

131
Q

Energy transfers (AO1)

A
  1. Organic
  2. Respiration
  3. Carbon

Accept tissue(s)/plant(s)/animal(s)/organism(s)

  1. Calorimetry;
132
Q

Energy transfers (AO2)

A

1. Low respiration;

Accept less energy lost in respiration

2. More growth/biomass

133
Q

Energy transfers (AO1)

Explain why farmers try to reduce respiratory losses (e.g. by keeping animals indoors during the winter).

A

More energy is available for growth/biomass

134
Q

Energy transfers (AO1)

Explain why simplifying food webs reduces energy losses to non-human food chains (2 marks).

A

1. Insecticides/pesticides/fungicides are used to exclude competitors who may feed on crops;

2. This means a higher N (net production of consumers) / more energy available for growth/biomass of crops

135
Q

Nutrient Cycles (AO1)

Nitrogen cycle stages

A

Nitrogen fixation
Nitrification
Ammonification
Denitrification

136
Q

Nutrient Cycles (AO1)

Microorganism for
nitrogen fixation

A

Nitrogen fixing bacteria

137
Q

Nutrient Cycles (AO1)

Nitrogen fixing
bacteria location

A

Root nodules

OR

Free in the soil

138
Q

Nutrient Cycles (AO1)

Nitrogen fixing bacteria reaction

A

Convert atmospheric nitrogen
into ammonia

139
Q

Nutrient Cycles (AO1)

Describe nitrification

A

Ammonia into nitrites;
Nitrites into nitrates;
By nitrifying bacteria

140
Q

Nutrient Cycles (AO1)

Microorganism that returns nitrogen to the atmoshphere

A

Denitrifying bacteria

141
Q

Nutrient Cycles (AO1)

Denitrifying bacteria reaction

A

Convert nitrates in the soil into atmospheric nitrogen

142
Q

Nutrient Cycles (AO1)

Denitrifying bacteria conditions

A

Anerobic / waterlogged soil

143
Q

Nutrient Cycles (AO1)

Chemical form nitrogen is
absorbed into plant roots

A

Nitrates

144
Q

Nutrient Cycles (AO1)

After nitrates have been absorbed from the soil via the plant roots. This nitrogen is _________ into the plant’s tissues.

A

assimilated

145
Q

Nutrient Cycles (AO1)

Ammonification microorganism

A

Saprobionts

146
Q

Nutrient Cycles (AO1)

Describe the role of saprobionts in the nitrogen cycle (Ammonification stage) (2 marks).

A

1. (use enzymes to decompose) proteins / DNA / RNA / urea;

2. Producing ammonia / ammonium ions;

147
Q

Nutrient Cycles (AO1)

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

A

(Nitrogen fixation)
1. Nitrogen into ammonia;
2. By nitrogen-fixing bacteria;

(Nitrification)
3. (oxidation of) ammonia into nitrite;
4. Nitrite into nitrate;
5. By nitrifying bacteria;

(Ammonification)
6. protein / amino acids / DNA into ammonia
7. (use enzymes to decompose) by saprobionts;

148
Q

Nutrient Cycles (AO1)

Give two examples of biological molecules containing nitrogen that would be removed when a crop is harvested.

A

Any two from:
1. amino acid / protein / polypeptide / peptide;

  1. nucleic acid / nucleotide / base;
  2. DNA;
  3. RNA;
  4. ATP / ADP;
  5. NAD / NADP (reduced or not);
  6. Cyclic AMP / cAMP;
  7. Chlorophyll;
149
Q

Nutrient Cycles (AO1)

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 marks).

A

(Ammonification)
1. Protein/amino acids/DNA/urea into ammonia;
2. By saprobionts

(Nitrification)
3. Ammonia into nitrite;
4. Nitrite into nitrate ;
5. By nitrifying bacteria;

Note: there are no marks for the role of nitrogen-fixing bacteria as the question refers to producing a source of nitrates from the remains of crops.

150
Q

Nutrient Cycles (AO2)

Denitrification requires anaerobic conditions.

Ploughing aerates the soil.

Explain how ploughing would affect the fertility of the soil (2 marks).

A

1. (Fertility increased as) less nitrate removed;

Accept: Nitrate remains

2. Less denitrification / fewer denitrifying bacteria.

Accept: more nitrification / more nitrifying bacteria / process R is increased

151
Q

Nutrient Cycles (AO1)

How can a farmer replace the nitrates and phosphates lost from the soil following the harvest of crops?

A

Add natural (e.g. manure / compost) AND/OR
artificial (e.g. liquid ammonia) fertilisers

152
Q

Nutrient Cycles (AO2)

Freshwater marsh soils are normally waterlogged. This creates anaerobic conditions.

Use your knowledge of the nitrogen cycle to suggest why these soils contain relatively high concentrations of ammonium compounds and low concentrations of nitrite ions and nitrate ions (2 marks).

A

1. Less nitrification

OR Fewer/less active nitrifying bacteria;

OR Nitrifying bacteria require oxygen/aerobic conditions;

2. (Less) oxidation/conversion of ammonia to nitrite (ions) and to nitrate (ions);

3. More denitrification

OR More/more active denitrifying bacteria

OR denitrifying bacteria require anaerobic conditions;

  1. (So more) nitrate (ions) reduced/converted to nitrogen (gas);
153
Q

Nutrient Cycles (AO2)

Name of symbiotic relationship between plant roots and fungus

A

Mycorrhizae

154
Q

Nutrient Cycles (AO1)

Role of mycorrhizae

A

Increase uptake of water and inorganic / mineral ions (e.g. phosphate and nitrate) by plants

155
Q

Nutrient Cycles (AO1)

TRUE OR FALSE

Mycorrhizal networks can connect the roots of plants growing next to each other so the plants can exchange biological molecules.

A

TRUE

156
Q

Nutrient Cycles (AO1)

Explain how mycorrhizae networks can increase plant growth

A

Increase surface area;

For absorption of water and inorganic / mineral ions;

Which are used for growth / protein synthesis / respiration / photosynthesis

157
Q

Nutrient Cycles (AO1)

Suggest one way in which arbuscular mycorrhiza fungi may benefit from their association with plants.

A

Receive a carbon-containing biological molecule e.g. glucose / carbohydrate / amino acid;

158
Q

Nutrient Cycles (AO1)

Arbuscular mycorrhiza fungi (AMF) are fungi which grow on, and into, the roots of plants. AMF can increase the uptake of inorganic ions such as phosphate.

Suggest one way in which an increase in the uptake of phosphate could increase plant growth.

A

Used to produce named phosphate compound in cells;

e.g. ATP / ADP / phospholipids / DNA / RNA / RuBP / Triose Phosphate /GP.

159
Q

Nutrient Cycles (AO2)

Nitrogenase catalyses the reduction of nitrogen during nitrogen fixation. The reaction requires 16 molecules of ATP for each molecule of nitrogen that is reduced.

When ammonia inhibits nitrogenase activity, nitrogen-fixing bacteria may benefit.

Explain how (2 marks).

A

1. Less/no ATP/energy required/used

OR More ATP/energy available;

2. ATP/energy can be used for growth/synthesis/replication

OR Lower (rate of) respiration required

OR ATP for phosphorylation;

160
Q

Nutrient Cycles (AO1)

A

R

161
Q

Nutrient Cycles (AO2)

One farming practice used to maintain high crop yields is crop rotation. This involves growing a different crop each year in the same field.

Suggest two ways in which crop rotation may lead to high crop yields.

A

1. Grow crops / plants with nitrogen-fixing (bacteria);

Accept: grow legumes / named example e.g. peas, beans, clover

Accept: fallow year

2. (Different crops use) different minerals / salts / nutrients / ions (from the soil);

3. (Different crops have) different pests / pathogens / diseases.

162
Q

Nutrient Cycles (AO1)

Describe the phosphorus cycle
(5 marks).

A
  1. Phosphate ions in rocks are eroded by water/weather
  2. Dissolve into water systems and soil
  3. Absorbed by plants and assimilated into compounds such as nucleic acids and phospholipids
  4. These can be passed on during feeding to higher trophic levels
  5. Excretion of phosphate ions in waste and decomposition of remains by saprobionts
  6. Deposition of these phosphate ions leads to phosphate held in rocks

OR

Sedimentation of phosphate ions in water leads to phosphates in rocks

163
Q

Nutrient Cycles (AO1)

A

P = Nitrification

Q = Denitrification

164
Q

Nutrient Cycles (AO1)

Name the process by which some bacteria oxidise ammonia to nitrate.

A

Nitrification

165
Q

Nutrient Cycles (AO1)

As fertiliser use increases and soil quality decreases, excess Nitrogen, Phosphorus (and potassium) used on farmlands can be picked up by rainfall in a process known as ________________.

A

leaching

166
Q

Nutrient Cycles (AO1)

What happens after leaching?

A

Increase concentration of nitrate and phosphate in freshwater;

Leds to algal growth / algal bloom which block light

167
Q

Nutrient Cycles (AO1)

Why do fish die during eutrophication?

A

Saprobionts decompose dead plant material;

Aerobically respire / use oxygen in respiration;

Less oxygen for fish to aerobically respire so they die;

168
Q

Nutrient Cycles (AO1)

Nitrate from fertiliser applied to crops may enter ponds and lakes. Explain how nitrate may cause the death of fish in fresh water (5 marks).

A

(Eutrophication)
1. Growth of algae / surface plants / algal bloom blocks light;

  1. Reduced / no photosynthesis so submerged plants die;
  2. Saprobiont;
  3. Aerobically respire / use oxygen in respiration;
  4. Less oxygen for fish to respire / aerobic organisms die;
169
Q

Nutrient Cycles (AO3)

One environmental issue arising from the use of fertilisers is eutrophication.

Eutrophication can cause water to become cloudy.

You are given samples of water from three different rivers.

Describe how you would obtain a quantitative measurement of their cloudiness (3 marks).

A

1. Use of colorimeter;

2. Measure the absorbance/transmission (of light);

3. Example of how method can be standardised eg same volume of water, zeroing colorimeter, same wavelength of light, shaking the sample;

A2 AQA Biology - Burnley College (2024-25) (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions