T5 Energy transfer in and between organisms Flashcards

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1
Q

1 mark

In photosynthesis, which chemicals are needed for the light-dependent reaction?

A

☑ NADP, ADP, Pi and water;

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2
Q

2 marks

Describe what happens during photoionisation in the light-dependent reaction.

A

1.   Chlorophyll absorbs light
OR
Light excites/moves electrons in chlorophyll;
Ignore photosystems.
2. Electron/s are lost
OR
(Chlorophyll) becomes positively charged;
Ignore site/molecule from where electrons are lost.
Accept electrons go to electron transport/carrier chain for ‘electrons lost’.

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3
Q

A student obtained a solution of pigments from the leaves of a plant. Then the student used paper chromatography to separate the pigments. Explain why the student marked the origin using a pencil rather than using ink. 1 mark

Describe the method the student used to separate the pigments after the solution of
pigments had been applied to the origin. 2 marks

A

Ink and (leaf) pigments would mix
OR
(With ink) origin/line in different position
OR
(With pencil) origin/line in same position
OR
(With pencil) origin/line still visible;

1.   Level of solvent below origin/line;
Reject water or any named aqueous solution.
Accept named organic solvent.
2. Remove/stop before (solvent) reaches top/end;

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4
Q

1 mark

The pigments in leaves are different colours. Suggest and explain the advantage of having
different coloured pigments in leaves.

A

(Absorb) different/more wavelengths (of light) for photosynthesis;
Accept wider/larger range of wavelengths.
Accept frequency for wavelength.
Accept light-dependent reaction /photophosphorylation /photoionisation
for photosynthesis.

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5
Q

2 marks

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 in photosynthesis.
Explain why this decreases the light-independent reaction. 2 marks

A
  1. (Less/no) ATP;
  2. (Less/no) reduced NADP;
    Accept NADPH, NADPH + H, NADPH2 NADPH + H+
    Reject reduced NAD, NADH etc,
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6
Q

2 marks

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.
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

A
  1. (Less/no) carbon dioxide (reacts) with RuBP;
  2. (Less/no) GP;
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7
Q

1 mark

Where precisely is rubisco found in a cell?

A
  1. Stroma (of/in chloroplast);
    Reject: stoma
    Reject stroma of cytoplasm/chlorophyll
    Reject stroma of mitochondrion
    Ignore references to Calvin cycle or the light-independent reaction
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8
Q

4 marks + 1 mark

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

When treated with Atrazine, weeds have been shown to give off small amounts of heat.
Suggest an explanation for this observation.

A
  1. Reduced transfer of protons across thylakoid membrane
    OR
    Reduced chemiosomotic gradient / proton gradient across thylakoid membrane;
  2. (So) less ATP produced;
  3. (So) less reduced NADP produced;
    Accept NADPH / NADPH2 / NADPH+
    Reject reduced NAD
  4. (So) light-independent reaction slows / stops;
    OR
    Less reduction of GP to triose phosphate.

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

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9
Q

Crops use light energy to produce photosynthetic products.
Describe how crop plants use light energy during the light-dependent reaction 5 marks

A
  1. Excites electrons / electrons removed (from chlorophyll);
    Accept: higher energy level as ‘excites’.
  2. Electrons move along carriers/electron transfer chain releasing
    energy;
    Accept: movement of H+
    /protons across membrane releases
    energy.
    Reject: ‘produces energy’ for either mark but not for both.
  3. Energy used to join ADP and Pi to form ATP;
    Reject: ‘produces energy’ for either mark but not for both.
    Accept: energy used for phosphorylation of ADP to ATP
    Do not accept P as Pi but accept phosphate.
  4. Photolysis of water produces protons, electrons and oxygen;
  5. NADP reduced by electrons / electrons and protons / hydrogen;
    Accept: NADP to NADPH (or equivalent) by addition of
    electrons/hydrogen.
    Do not accept NADP reduced by protons on its own
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10
Q

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
  1. Protein/amino acids/DNA into ammonium compounds /
    ammonia;
    Accept: any named nitrogen containing compound e.g. urea.
  2. By saprobionts;
    Accept: saprophytes.
  3. Ammonium/ammonia into nitrite;
  4. Nitrite into nitrate;
  5. By nitrifying bacteria/microorganisms;
    Reject: nitrifying bacteria in root nodules.
    1, 3 and 4. Accept: marks for conversion even if incorrect type of
    bacteria named as being involved.
    2 and 5. Reject: marks for type of bacteria if linked to incorrect
    process e.g. nitrite converted to nitrate by saprobionts.
    3 and 4. Accept: for one mark ammonia/ammonium into nitrate if
    neither mark point 3 or 4 awarded.
    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.
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11
Q

Explain the relationship between stomatal opening and photosynthesis. 2 marks

A
  1. Stomata allow uptake of carbon dioxide;
  2. Carbon dioxide used in / required for photosynthesis;
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12
Q

Describe the process of glycolysis. 4 marks

A
  1. Phosphorylation of glucose using ATP;
  2. Oxidation of triose phosphate to pyruvate;
    Accept removal of hydrogen from triose phosphate for oxidation.
  3. Net gain of ATP;
    Accept any description that indicates a net gain e.g., 4 produced, 2
    used.
  4. NAD reduced;
    Accept NADH/NADH2/NADH + H+
    produced.
    Accept all mark points in diagrams.
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13
Q

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/coenzymes
    OR
    Fewer/no hydrogens/electrons removed (and passed to electron transfer
    chain);
    Accept less/no FAD reduced.
  2. Oxygen is the final/terminal (electron) acceptor;
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14
Q

Where in a cell does glucose turn into pyruvate occur?

A

Cytoplasm/cytosol;

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15
Q

The Respiratory Quotient (RQ) can provide information on the type of respiration taking
place in an organism. The following equation is used to calculate the RQ.
RQ=Vol of CO2 produced during respiration/Vol of O2 used during respiration

What would be the RQ for aerobic respiration of glucose? 1 mark

A student calculated that the RQ of germinating seeds was 1.8.
Use the information provided to explain this result. 2 marks

A

1/one/1.0;

1. Aerobic and anaerobic respiration occurring;
Accept: some/mainly anaerobic respiration occurring.
2. More carbon dioxide produced than oxygen uptake;

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16
Q

Aerobic respiration produces more ATP per molecule of glucose than anaerobic respiration. Explain why. 2 marks

A
  1. Oxygen is final/terminal (electron) acceptor / oxygen combines
    with electrons and protons;
  2. (Aerobic respiration) oxidative phosphorylation / electron transfer
    chain;
  3. Anaerobic (respiration) only glycolysis occurs / no Krebs / no link
    reaction;
    Ignore: number of ATP produced.
  4. Accept: without oxygen.
  5. Ignore: converse.
17
Q

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.
    Accept: NAD reduced for oxidationDescribe how acetylcoenzyme A is formed in the link reaction 2 marks
18
Q

In the Krebs cycle, acetylcoenzyme A combines with four-carbon oxaloacetate to form
six-carbon citrate. This reaction is catalysed by the enzyme citrate synthase.
(i) Oxaloacetate is the first substrate to bind with the enzyme citrate synthase. This
induces a change in the enzyme, which enables the acetylcoenzyme A to bind.
Explain how oxaloacetate enables the acetylcoenzyme A to then bind to the enzyme. 2 marks

A
  1. Change (in shape) of active site / active site moulds around the substrate;
    Reject: reference to inhibitor
    Accept: change in tertiary structure affecting active site
  2. (Substrate / active site) now complementary.
    Neutral: references to two active sites
19
Q

In muscles, pyruvate is converted to lactate during anaerobic respiration.
(i) Explain why converting pyruvate to lactate allows the continued production of ATP
during anaerobic respiration. 2 marks

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
  1. Regenerates / produces NAD / oxidises reduced NAD;
  2. (NAD used) in glycolysis.
    Accept: description of glycolysis
    Accept: glycolysis can continue / begin

(Pyruvate used) in aerobic respiration / (lactate / lactic acid) is toxic / harmful /
causes cramp / (muscle) fatigue.
Accept: (pyruvate) can enter link reaction
Accept: reduces cramp / (muscle) fatigue
Neutral: ‘reduces muscle aches’

20
Q

Freshwater marshes have one of the highest rates of gross primary production (GPP) and net
primary production (NPP) of all ecosystems.
Carbon use efficiency (CUE) is the ratio of NPP:GPP. Freshwater marshes have a high CUE.
1.
(a)  Use your knowledge of NPP to explain why freshwater marshes have a high CUE and the
advantage of this.
Do not refer to abiotic factors in your answer.
Explanation:
Advantage: 2 marks

A
  1. Low respiration;
    Accept less energy lost in respiration
  2. More growth/biomass/colonisation;
    Allow examples of more carbon-containing molecules eg glucose
21
Q

  Succession occurs in natural ecosystems. Describe and explain how succession occurs. 4 marls

A

1.   (Colonisation by) pioneer species;
2.   Pioneers/species/organisms change the environment/habitat/conditions/factors;
Accept example of change e.g. forms soil/humus/organic matter/nutrients.
Must convey idea of change being caused by pioneers/species
/organisms
3.   (Environment becomes) less hostile for other/new species
OR
(Environment becomes) more suitable for other/new species
OR
(Environment becomes) less suitable for previous species;
Accept previous species out-competed.
4.   Change/increase in diversity/biodiversity;
Ignore increase in genetic diversity.
5.   (To) climax community;

22
Q

Biofuels are fuels which can be produced from plants. Scientists have developed a standard
method called net life-cycle carbon dioxide production (NLP) to find the overall effect of
producing and using particular biofuels on carbon dioxide production.
(a) Petroleum is used as a comparison when evaluating NLPs of biofuels. Suggest two reasons why. 2 marks

Biofuels are produced by a variety of different companies. The scientists who developed
the method of calculating NLPs are funded by the government’s environmental agency.
Suggest two advantages of this method being developed by these scientists. 2 marks

A
  1. Is widely / commonly used;
  2. Provides a standard / benchmark / reference;
    Allow a variety of descriptors for marking point 2 e.g. ‘provides a
    base line’,
    ‘produces known amount of carbon dioxide’
    Mark point 2, do not accept ‘for comparison’ on its own as
    ‘comparison’ is in stem of question
  3. Produces large amount of carbon dioxide;
  4. Is a decreasing resource / could be replaced by biofuel;
    Ignore reference to a control

Independent / no bias / trustworthy;
2. Non-profit making;
3. (Focused on) effect on environment / climate;

23
Q

Producing and using biofuels from corn ethanol results in a negative percentage change in
carbon dioxide production. Explain why.
2 marks

A
  1. CO2 taken up in photosynthesis;
  2. More taken up than produced (when it is used) with less CO2 produced than
    petrol;
24
Q

Ethanol can be produced from cellulose. It is produced by anaerobic respiration of
cellulose-based biomass by microorganisms. The cellulose is pre-treated by adding
cellulose-digesting enzymes before it is used in anaerobic respiration. Suggest why
pre-treatment is necessary. 3 marks

A
  1. (These microorganisms) don’t have (cellulose-digesting) enzymes;
    Accept ‘don’t make enough of these enzymes’ for mark point 1
  2. (Cellulose) is a polysaccharide / polymer / long (molecule / chain);
    Accept ‘large’ for mark point 2
  3. (Cellulose) is insoluble / glucose / product of digestion is soluble;
  4. Broken down into glucose / monomers / monosaccharides;
    Ignore (alpha) glucose for mark point 4.
    Do not accept sugars for mark point 4
  5. Sugars / glucose used in glycolysis / glucose can be converted to pyruvate;
  6. Produces more ethanol / fuel produces ethanol / fuel quicker;
    Accept ‘speeds up process’ for mark point 6
25
Q

Large areas of land have to be used to grow the plants to make biofuels. Ecologists have
suggested that changes in land use could lead to a decrease in biodiversity.
Suggest how changes in land use could lead to a decrease in biodiversity.2 marks

A
  1. Removes species / fewer species / growth of single crop / single plant species /
    monoculture;
    Deforestation or removal of hedges on its own should not be
    credited
  2. Removes habitats / fewer habitats / niches / only one habitat;
  3. Removes variety of food sources / fewer food sources / only one food source;
26
Q

Describe the role of saprobionts in the nitrogen cycle 2 marks

A

1.   (They use enzymes to) decompose proteins/DNA/RNA/urea;
Accept any named molecule containing nitrogen eg enzymes, NAD, ATP,
amino acids
Accept digest/breakdown/hydrolyse for decompose
Ignore ‘nitrogen -containing compounds’ unqualified
2.   Producing/releasing ammonia/ammonium compounds/ammonium ions;
Accept (they) perform ammonification
Accept named ammonium compound

27
Q

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

Principle is
1. Named apparatus
2. What is measured
3. Standardisation of method
Accept any valid method, for example
1.   Use of colorimeter;
Reject calorimeter
2.   Measure the absorbance/transmission (of light);
Reject if samples are filtered unless filtering to remove debris
Accept descriptions
3.   Example of how method can be standardised eg same volume of water,
zeroing colorimeter, same wavelength of light, shaking the sample;
Ignore references to calibration curves

28
Q

Describe the role of microorganisms in producing nitrates from the remains of dead organisms. 3 marks

A
  1. Saprobiotic (microorganisms / bacteria) break down remains / dead
    material / protein / DNA into ammonia / ammonium;
    Accept: saprobionts / saprophytes / saprotrophs
    Neutral: decomposer
  2. Ammonia / ammonium ions into nitrite and then into nitrate;
    Allow correct chemical symbols.
    Accept: correct answers which use incorrect bacteria e.g. nitrogenfixing but then reject m.p. 3.
  3. (By) Nitrifying bacteria / nitrification;
29
Q

Upwelling often results in high primary productivity in coastal waters.
Explain why some of the most productive fishing areas are found in coastal waters. 2 marks

A
  1. Nitrate / phosphate / named ion / nutrients for growth of / absorbed / used by
    plants / algae / producers;
  2. More producers / consumers / food so more fish / fish reproduce more / fish
    grow more / fish move to area;
    Must have idea of more plants related to some increase in fish.
30
Q

Leguminous crop plants have nitrogen-fixing bacteria in nodules on their roots.
On soils with a low concentration of nitrate ions, leguminous crops often grow better than
other types of crop. Explain why.
2 marks

A
  1. (Nitrogen) to ammonia / NH3 / ammonium;
  2. Do not disqualify mark for any references to ammonia being
    converted to nitrite, nitrate etc
  3. Produce protein / amino acids / named protein / DNA / RNA;
  4. Do not disqualify mark for any references to protein being formed
    from nitrogen, nitrite or nitrate
31
Q

Applying very high concentrations of fertiliser to the soil can reduce plant growth. Use your knowledge of water potential to explain why. 2 marks

A

Soil has lower water potential so water moves out of the plants by osmosis

32
Q

Net production of consumers Formula

A

N = I - F+ R
I = Chemical energy stored in ingested food
F = Energy lost to the environment in faeces or urine
R = Respiratory losses

33
Q

Units for Rates of Productivity

A

KJha^-1year^-1