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2023-25 Biology > 5: Energy Transfers (Photo/Resp/E transfers & N. Cycles) > Flashcards

5: Energy Transfers (Photo/Resp/E transfers & N. Cycles) Flashcards

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1
Q

Describe what happens during photoionisation in the light dependent reaction. [2]

A
  • Chlorophyll absorbs light energy OR Light energy excites/moves electrons in chlorophyll;
  • Electron/s are lost **OR ** (Chlorophyll) becomes positively charged;
  • Accept electrons go to electron transport/carrier chain for ‘electrons lost’.
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2
Q

Describe the light dependent reaction [6]

A
  • Chlorophyll absorbs light energy and excites electrons
  • Electrons removed (Oxidation of chlorophyll) via photoionisation;
  • Electrons move along carriers/electron transport chain** releasing energy** (Series of REDOX reactions)
  • Energy released (by electrons) used to form proton (electrochemical) gradient;
  • H+ ions diffuse through ATP synthase;
  • providing energy to join ADP and Pi to form ATP; Photophosphorylation
  • Photolysis of water produces 2 protons, 2 electrons and ½ oxygen; electrons regenerate chlorophyll.
  • NADP reduced by electrons / electrons and protons / hydrogen;
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3
Q

Name the two products of the light-dependent reaction that are required for the light-independent reaction.

A
  • ATP;
  • Reduced NADP;

Accept: NADPH / NADPH2

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4
Q

Proton pumping to form a proton gradient is an example of active transport.

True or False

A

False:

  • Active transport requires ATP!
  • Energy for proton pumping is from high energy electrons.
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5
Q

Describe the light independent reaction [6]

A
  • Carbon dioxide combines/reacts with RuBP;
  • Produces two glycerate (3- )phosphate/GP using (enzyme) Rubisco;
  • GP reduced to triose phosphate;
  • Using reduced NADP;
  • Using energy from ATP;
  • Triose phosphate converted to glucose / hexose / RuBP (ribulose bisphosphate) / other correctly named organic substance;
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6
Q

Where precisely is rubisco found in a cell?

A

Stroma

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7
Q

Explain why scientists measure the rate of production of oxygen in this investigation. (Rate of photosynthesis) [2]

A
  • Oxygen produced in light-dependent reaction;
  • The faster (oxygen) is produced, the faster the light-dependent reaction.
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8
Q

Explain why plants that have more chlorophyll will grow faster than plants with less chlorophyll. [5]

A
  • Have faster production of ATP and reduced NADP;
  • (So) have faster / more light-independent reaction;
  • (So) produce more sugars that can be used in respiration;
  • (So) have more energy for growth;
  • Have faster / more synthesis of new organic materials.
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9
Q

ATP is produced in the light dependent reaction, suggest why this is not their (plants) only source of ATP. [4]

A
  • Plants don’t photosynthesis in the dark;
  • Not all the parts of the plants photosynthesise;
  • Plants require more ATP than is produced in the light dependant reaction;
  • ATP used in Active Transport (accept other named processes)
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10
Q

Describe the effect of introducing a herbicide/inhibitor on the electron transport chain (4)

A
  • Reduced transfer of protons across thylakoid membrane OR Reduced chemiosmotic gradient/proton gradient across thylakoid membrane;
  • (So) less ATP produced;
  • (So) less reduced NADP produced;
  • (So) light-independent reaction slows/stops OR Less reduction of GP to triose phosphate;
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11
Q

When producing a chromatogram explain why the origin is marked using a pencil rather than ink.

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;
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12
Q

While making a chromatogram, describe the method used to separate the pigments after the solution of pigment had been applied to the origin. [2]

A
  • Level of solvent below origin/line;
  • Remove/stop before (solvent) reaches top/end;
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13
Q

Suggest and explain the advantage to plants of having different colour pigments in leaves.

A
  • Absorb different/more wavelengths of light for photosynthesis;
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14
Q

Explain the relationship between stomatal opening and photosynthesis. [2]

A
  • Stomata allow uptake of carbon dioxide;
  • Carbon dioxide used in / required for photosynthesis;
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15
Q

What is the equation to calculate the Rf value?

A

Distance pigment moved from origin / Distance solvent front moved from origin

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16
Q

Describe the process of glycolysis.[5]

A
  • Phosphorylation of glucose using ATP;
  • Oxidation of triose phosphate to pyruvate;
  • Net gain of ATP;
  • NAD reduced;
  • Occurs within the cytoplasm
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17
Q

Describe the link reaction [4]

A
  • Occurs in the matrix (mitochondrion)
  • Pyruvate oxidised and decarboxylated into Acetate.
  • Produces reduced NAD and CO2
  • Acetate combines with coenzyme A to produce Acetyl co A

Reject ATP is formed.

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18
Q

NAD is a coenzyme. What is a coenzyme?

A
  • NAD is a dinucleotide (derivative)
  • Organic NON-PROTEIN
    *Binds to with an enzyme to help catalyse a reaction
  • often refered to as a carrier molecule
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19
Q

Describe how oxidation takes place in glycolysis and in the Krebs cycle. [4]

A
  • removal of hydrogen/dehydrogenation;
  • by enzymes/dehydrogenases;
  • Hydrogen accepted by NAD/reduced NAD formed;
  • in Krebs cycle, FAD (used as well);
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20
Q

Water is a waste product of aerobic respiration.

Describe how water is formed at the end of aerobic respiration. [2]

A
  • oxygen is terminal/final electron acceptor;
  • combines with electrons and protons (to form water);
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21
Q

Explain how the amount of ATP is increased by reactions occurring inside a mitochondrion. [6]

A
  • oxidation of/removal of electrons and H+ from pyruvate
  • acetyl CoA / 6 carbon compound; (credit oxidative decarboxylation)
  • substrate level production of ATP / ATP produced in Krebs cycle;
  • production of reduced NAD / FAD (allow they take up hydrogen);
  • **in matrix **of mitochondria;
  • electrons fed into electron transport chain / used in oxidative
  • (Electrons) pass along carriers/through electron transport chain/through series of redox reactions;
  • Energy released as heat;
  • Protons pumped into intermembrane space;
  • ADP + Pi to ATP using ATP synthase
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22
Q

Describe the roles of the coenzymes and carrier proteins in the synthesis of ATP.

OR

Describe the events of oxidative phosphorylation

[5]

A
  • NAD/FAD reduced / hydrogen attached to NAD/FAD;
  • H+ ions/electrons transferred from coenzyme to coenzyme/carrier to carrier (ETC on cristae of inner membrane)
  • Energy released (from electrons) through series of redox reactions;
  • Energy released used to pump H+/ protons into intermembrane space forming an electro-chemical gradient (of protons);
  • H+/ protons flow back through ATP synthase to produce ATP from ADP and phosphate.

(some energy lost as heat)

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23
Q

In many mammals, ‘uncoupling proteins’ help to maintain a constant body temperature during hibernation.

Suggest and explain how.
[2]

A
  • Allow passage of protons/H+;
  • (Energy) released as heat;
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24
Q

The mitochondria in muscles contain many cristae. Explain the advantage of this. [2]

AO2 (More / Less)

A
  • larger surface area for electron carrier system / MORE oxidative phosphorylation;
  • provide MORE ATP / energy for contraction;
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25
Q

Give two reasons why the respirometer was left for 10 minutes when it was first placed in the water bath.

A
  • Equilibrium reached;
  • Allow for expansion (gases/liquids) /pressure change in apparatus;
  • Allow respiration rate of seeds to stabilise;
26
Q

In a respirometer why does the coloured liquid move to the left (towards the organism). [3]

A
  • Oxygen taken up by organism
  • Carbon dioxide absorbed by KOH
  • Pressure/volume decreases inside
27
Q

Apart from time, give two measurements a student would have to make to determine the rate of aerobic respiration of seeds in a respirometer in cm3 per hour.

A
  • Distance liquid moves (cm)
  • Diameter/radius of the tube (cm)
28
Q

Explain why a log scale is used to record the number of cells/bacteria. [1]

A
  • Large range/difference/increase in numbers;
  • Accept reference to exponential (increase)
29
Q

Explain why converting pyruvate to lactate allows the continued production of ATP by anaerobic respiration. [2]

A
  • Regenerates NAD / Oxidises reduced NAD;
  • (So) glycolysis continues;
30
Q

Malonate inhibits a reaction in the Krebs cycle.

Explain why malonate would decrease the uptake of oxygen in a respiring cell.
[2]

A
  • Less/no reduced NAD/coenzymes OR Fewer/no hydrogens/electrons removed (and passed to electron transfer chain);
  • Oxygen is the final/terminal (electron) acceptor;
31
Q

Explain why converting pyruvate to ethanol is important in allowing the continued production of ATP in anaerobic respiration. [2]

A
  • allows NAD to be recycled / re-formed;
  • so that glycolysis continues / so that (more) glucose can be converted to pyruvate
32
Q

Give two ways in which anaerobic respiration of glucose in yeast is similar to anaerobic respiration of glucose in a muscle cell. [2]

A
  • ATP formed / used;
  • pyruvate formed / reduced;
  • NAD / reduced NAD;
  • glycolysis involved
33
Q

Give two ways in which anaerobic respiration of glucose in yeast is different from anaerobic respiration of glucose in a muscle cell. [2]

A
  • ethanol / alcohol formed by yeast whereas lactate by muscle cell;
  • CO2 released by yeast but not by muscle cell;
34
Q

Name the two substances produced by anaerobic respiration in humans.

A
  • Lactate;
  • ATP;
35
Q
A

A: Pyruvate
B: Reduced NAD / NADH/ NADH2
C: Coenzyme A
D: Acetylcoenzyme A / Acetyl co A

36
Q

Name 3 respiratory substrates

A
  1. Glucose
  2. Amino acids
  3. Glycerol
  4. Fatty acids
37
Q

Define Biomass

A
  • Mass of carbon (organic compounds)
    OR
  • Dry mass of tissue per given area
38
Q

Suggest what you should do to ensure all water is removed from a tissue / sample. [2]

A
  • Regularly weigh and re heat (less than 100 °C to prevent combustion)
  • Until mass is constant
39
Q

Define: Gross Primary Productivity (GPP)

A
  • Chemical energy store in plant biomass, in a given area or volume. (Rate of photosynthesis)
40
Q

Define: Net Primary Production (NPP)

A
  • Chemical energy store in plant biomass after respiratory losses to the environment have been taken into account. NPP= GPP - R
    • NPP is available for new plant growth and reproduction OR available for other trophic levels in the ecosystem, such as herbivores and saprobionts.
  • kJ ha–1 year–1 OR kJ km–2 year–1 OR kJ km–3 year–1
41
Q

Define: Net production of consumers

A

N = I – ( F + R)

where:
I represents the chemical energy store in ingested food;
F represents the chemical energy lost to the environment in faeces and urine;
R represents the respiratory losses to the
environment.

42
Q

State the units for BIOMASS (in terms of productivity)

A

kJ ha–1 year–1
.

43
Q

The percentage of the light energy trapped by the producers is very low. Give THREE reasons why.

A
  • Reflected / absorbed by water vapour;
  • Reflected from producers / wrong wavelength;
  • Transmitted / passes between chloroplasts / does not strike chlorophyll / passes between plants / too few chloroplasts;
44
Q

In natural ecosystems, most of the light falling on producers is not used in photosynthesis.

Suggest two reasons why.

A
  • (Light is) reflected / Light energy is not absorbed
  • (Light is) wrong wavelength / frequency.
  • Accept reference to absorbing specified wavelengths/frequencies.
  • (Light) misses chlorophyll / chloroplasts/ photosynthetic tissue;
  • CO2 concentration or temperature is a limiting factor.
45
Q

The biomass of primary consumers is less than the biomass of producers. Explain why. [4]

A
  • Loss of energy / heat / use of energy for…. / less energy to be passed on;
  • In respiration;
  • In excreta / excretion / urine / carbon dioxide;
  • Inedible parts / indigestible parts / egest/ egestion / to decomposers;
46
Q

Describe how and explain why the efficiency of energy transfer is different at different stages in the transfer. [5]

A
  • Some light energy fails to strike/is reflected/not of appropriate wavelength;
  • Efficiency of photosynthesis in plants is low/approximately 1-3% efficient;
  • Respiratory loss / excretion / faeces / not eaten;
  • Loss as heat;
  • Efficiency of transfer to consumers greater than transfer to producers/approximately 10%;
  • Efficiency lower in older animals/herbivores/ primary consumers/warm blooded animals;
  • Carnivores consume, digest & assimilate more of their food than herbivores;
47
Q

Explain how the intensive rearing of domestic livestock increases net productivity. [5]

A
  • Slaughtered when still growing/before maturity/while young so more energy transferred to biomass/tissue/production;
  • Fed on concentrate /controlled diet /controlled conditions/so higher proportion of (digested) food absorbed/lower proportion lost in faeces / valid reason for addition;
  • Movement restricted** so** less respiratory loss / less energy used;
  • Kept inside/heating/shelter / confined so less heat loss / no predators;
  • Genetically selected for high productivity;
48
Q

Describe the need for plants to both photosynthesise AND respire [5]

A
  • In the dark no ATP production in Light dependent reactions / photosynthesis;
  • Some tissues unable to photosynthesise/produce ATP;
  • ATP cannot be moved from cell to cell/stored;
  • Plant uses more ATP than produced in photosynthesis;
  • ATP for active transport of ions / sucrose;
  • ATP for synthesis (of named substance);
49
Q

Explain what is meant by the term carbon sink.
Not on spec (GCSE)

A
  • Takes up / locks up / stores carbon / carbon dioxide (for a long time) / eq ;
  • Named example e.g. peat / coal / limestone / trees / fossil fuel / chalk / shells / seagrass;
50
Q

Explain what is meant by the term global warming.

Not on spec (GCSE)

A
  • Increase in {temperature of earth’s surface / mean global temperature};
  • Carbon dioxide is a greenhouse gas / due to an increase in greenhouse gases
  • (Which) {trap / reflect back} {heat / long wave / infra red} (in the atmosphere) ;
  • Reference to an {increased / enhanced} greenhouse effect ;
  • Reference to valid {effect / consequence} e.g. melting ice caps, flooding, climate change ;
51
Q

Describe the role of saprobionts in the nitrogen cycle. [2]

A
  • (secrete enzymes to) decompose proteins / DNA / RNA / urea;
  • Producing / releasing ammonia / ammonium ions;
52
Q

Explain how carbon-containing compounds present in the pine leaves that fall from the trees are absorbed and used for growth by saprobionts/fungi that live in the soil. [5]

A
  • extracellular digestion;
  • by secretion of hydrolystic/digestive enzymes;
  • absorption of digested/soluble products;
  • synthesis of structural compounds/named compound;.
  • respiration provides energy for growth (of saprobiont)
53
Q

What are saprobionts?

A
  • Fungi / Bacteria that
  • Secrete extracelluar enzymes to digest large insoluble organic matter
  • absorb monomers for assimilation / respiration
54
Q

Nitrogen compounds in the plants are made available for the main crop after ploughing in spring.

Describe the role of microorganisms in this process.
[5]

A
  • proteins/amino acids broken down;
  • deamination/ammonification/ release of ammonium compounds;
  • By saprophytes/saprobionts;
  • conversion to nitrates via nitrites;
  • by nitrifying bacteria/named bacterium (Nitrosomonas then Nitrobacter);
  • Nitrates absorbed into roots via active transport
55
Q

The scientists used units of μg g−1 for the concentration of ammonia in soil.

Suggest why, in this investigation, the scientists used these units.

A
  • (μg because) very little ammonia (in soil);
  • (μg because) avoids use of (lots of) decimal places (in their results) / avoids the use of powers of 10 / avoids the use of standard form /makes numbers more manageable / Accept makes easier to plot graph
  • (g-1) to allow comparisons (between samples);
56
Q

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

A
  • amino acid/protein/ polypeptide/peptide;
  • nucleic acid/nucleotide/base;
  • DNA;
  • RNA / pre-mRNA / mRNA / rRNA / tRNA
  • ATP/ADP;
  • NAD/NADP (reduced or not);
  • Cyclic AMP/cAMP;
  • Chlorophyll;
57
Q

Plants absorb a number of other nutrients from the soil including phosphates.

Describe why phosphates are needed by a growing plant. [3]

A
  • production of DNA;
  • production of RNA;
  • production of NADP
  • production of phospholipids;
  • in cell membranes;
  • synthesis of ATP;
58
Q

Describe how a lack of phosphates in the soil surrounding a plant can affect its growth [4]

Potential essay link

A
  • (Required to) make ATP/glucose phosphate, so less respiration/less energy for growth;
  • (Required to) make nucleotides, so less DNA/mRNA/tRNA for cell division/production of protein (for growth);
  • (Required to) make RuBP/NADP, so less CO2 fixed/reduced into sugar;
  • (Required to) make phospholipids for membranes;
59
Q

Outline the advantages of having Mycorrhizae
growth near plants
[2]

Essay link

A
  • 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);
60
Q

You are given samples of water from three different rivers.

Describe how you would obtain a quantitative measurement of their cloudiness. [3]

A
  • Use of colorimeter;
  • Measure the absorbance/transmission (of light);
  • Example of how method can be standardised eg same volume of water, zeroing colorimeter, same wavelength of light/filter, shaking the sample;
61
Q

Describe the process of eutrophication. [5]

A
  • Nitrates / Phosphates / Ammonium ions flushed into waterway (leaching)
  • Increased algal bloom
  • Light blocked out
  • Submerged aquatic plant unable to photosynthesise and die
  • Increase in saprobionts so increases rate of aerobic respiration
  • Saprobionts / aero.resp organismsn die as lack of oxygen (anoxic conditions)
  • Increase in anaerobic microorganisms that production of toxins.

2023-25 Biology (9 decks)

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