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Biology > 3.5 Energy transfers in and between organisms > Flashcards

3.5 Energy transfers in and between organisms Flashcards

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1
Q

Give 3 ways a plant is adpated for photosynthesis.

A
  1. Large flat leaves for a large SA for light absorption, spread out so that they can access as much ligth as possible
  2. Transparent cuticle layer on leaves, allowing sunlight to pass through and photoionisation/photlysis to occur
  3. Xylem and phloem for transport of water to leaves and tranport of dissolved sugars to sinks
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2
Q

Where is chlorophyll found in a plant?

A

Photosystems in the thylakoid membrane
- accessory pigments = chlorophyll b, carotenoids
- primary pigment = chlorophyll a

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3
Q

What energy stores are found in a chloroplast?

A

Lipid droplet, starch grains

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4
Q

What are the main structures of chloroplasts?

A

Stroma, double membrane, grana, thylakoids and thylakoid membrane, lamella, lipid droplet, starch grain

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5
Q

What are the different photosynthetic pigments and what colours do they absorb/reflect?

A

Chlorophyll- absorb blue and red, reflect green

Carotenoids - absorb blue, reflect orange/red

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6
Q

Why is it important that a plant has several pigmenets present?

A
  • Different pigments absorb different wavelengths of light
  • More light is able to absorbed during different conditions
  • More photosynthesis and more growth from the production of more organic substances
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7
Q

What happens during the LDR?

A
  • Photoionisation: light energy absorbed by chlorophyll, electrons excited and chlorophyll is oxidised
  • Electrons transferred down ETC, releasing energy which is used to pump protons into the thylakoid lumen
  • Final electron acceptor is NADP, which is reduced using electrons and protons to produce NADPH
  • Chemiosmosis: proton gradient created, protons move down electrochemical gradient back into stroma through ATP synthase, catalysing the production of ATP
  • Photolysis: water molecules split into oxygen, hydrogen and elctrons (used in chlorophyll)
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8
Q

Describe what happens in the LIR?

A

Calvin cycle
- Carbon fixation: RuBP + carbon dioxide (substrate to RuBisCo) producing GP
- GP reduced using energy from ATP and NADPH to form triose phosphate
- Some molecules of TP are converted into organic substances, the majority however are used to regenerate RuBP using energy from ATP
1/6 = glucose, 5/6 = RuBP regeneration

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9
Q

Why is the LIR not techincally the ‘dark’ reaction or light independent reaction?

A

Relies on products ATP and NADPH from the LDR

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10
Q

What are the 3 factors affecting photosynthesis?

A
  1. Temperature
  2. Light intensity
  3. Carbon dioxide concentration
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11
Q

How would a gardener control temperature and carbon dioxide concentration in his greenhouse?

A

Burn a fuel, releases heat and carbon dioxide

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12
Q

What do the following terms mean:
a) light compensation point
b) saturation point

A

a) Rate of respiration = rate of photsynthesis, so there is no net production of carbon dioxide
b) New limiting factor

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13
Q

How does increased light intensity affect the rate of photosynthesis?

A
  • More light energy absorbed by chlorophyll, more elctrons excited and chlorophyll oxidised
  • More elctrons transferred down ETC, more protons pumped into thylakoid lumen, steeper conc. gradient
  • More NADP reduced at final elcetron acceptor
  • More ATP synthesised as protons pass through ATP synthase back into the stroma
  • Increased rate of LDR, more ATP and NADPH for LIR
  • Increased reduction of GP and increased rate of Calvin cycle
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14
Q

How does increased carbon dioxide concentration affect the rate of photosynthesis?

A
  • More carbon dioxide so more substrate for RuBisCo
  • More GP produced from RUBP so more available to be reduced to triose phosphate using energy from ATP and NADPH
  • Increased rate of Calvin cycle
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15
Q

How does increased temperature affect the rate of photosynthesis?

A
  • Increase in kinetic energy, more successful collisions over time
  • More E-S complexes form (RuBisCo)
  • If temperature is too high proteins/enzymes denature
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16
Q

Explain 3 ways you can measure the rate of photosynthesis.

A
  1. Photosynthometer- measures volume of oxygen produced
  2. Density of leaves- remove air, air spaces fill up with gas as plants photosynthesise, less dense, float to the top
  3. Hydrogencarbonate indicator- monitors carbon dioxide uptake, use colorimetry to quantify
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17
Q

What are the 2 limitations of measuring the volume of oxygen produced overtime whilst measuring the rate of photosynthesis?

A
  • Other gases (nitrogen, carbon dioxide) could be present in the sample
  • Some oxygen that is produced is used up in respiration
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18
Q

Describe and explain the Hill Reaction as a technique to measure the rate of photosynthesis?

A
  • Measuring the activity of dehydrogenase enzymes in the reduction of DCPIP, acts as final electron accpetor (instead of NADPH)
  • DCPIP is reduced and there is a colour change from blue to colourless (with chloroplasts, this is a colour change from blue-green to green)
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19
Q

In the Hill reaction, describe and explain the results for the green filter and the blue/purple/orange filter.

A

Green filter: Infinite time for colour change
- Only green light allowed through filter
- DCPIP was not reduced as no light was absorbed so no photoionisation and no electrons transferred down ETC and therefore no colour change

Blue/purple/orange: Shorter time for colour change
- DCPIP was reduced quicker
- There is more photoionisation and more elctrons transferred down ETC and increased rate of photosynthesis
- This is because blue/purple/orange light is more strongly absorbed by chlorophyll

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20
Q

Describe glycolysis.

think: location, products, reactions

A
  • Occurs in cytoplasm
  • Glucose phosphorylated using 2 molecules of ATP
  • Forms hexose bisphospahte (6C) which is highly unstable and splits into 2 molecules of triose phosphate (3C)
  • Triose phosphate oxidised using 2 NAD molecules (NAD is reduced)
  • Produces 2 x pyruvate and 4 x ATP
  • Net production of 2 pyruvate, 2 ATP and 2 NADH
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21
Q

Describe the link reaction.

think: location, products, reactions

A
  • Occurs in matrix of mitochondria
  • Decarboxylation and oxidation of pyruvate (3C) using NAD to produce acetate (2C)
  • Acetate reacts with conenzyme A to produce acetylcoenzyme A
  • Reaction occurs twice, producing 2 NADH, 2 carbon dioxide and 2 acetycoenzyme A
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22
Q

Describe the Krebs cycle.

think: location, products, reactions

A
  • Occurs in the matrix
  • Acetycoenzyme A reacts with a 4C molecule to produce a 6C molecule
  • Series of oxidation (NAD reduced) and decarboxylation (carbon dioxide produced) reactions produce a 5C then a 4C molecule
  • The 4C molecule is rearranged, releasing energy for ATP synthesis, and then oxidised using FAD and NAD to regenerate the original 4C molecule
  • Cycle happens twice, once for each molecule of acetylcoenzyme A
  • Overall 6 NADH, 2 FADH2, 2 ATP and 4 carbon dioxide are produced
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23
Q

Describe oxidative phosphorylation.

think: location, products, reactions

A
  • Occurs in the inner membrane of mitochondria
  • Oxidation of NADH and FADH2 releases protons and electrons
  • Electrons transferred down ETC, releasing energy to pump protons into the intermembrane space through the inner mitochondrial membrane
  • Protein gradient forms, protons move back into matrix through ATP synthase (chemiosmosis), synthesesising ATP
  • Oxygen is the final electron acceptor and produces water molecules from oxyegen, protons and electrons
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24
Q

What happens to the aerobic pathway when no oxygen is present?

A
  • No final electron acceptor on ETC
  • Electrons not transferred down so coenzymes are not oxidised
  • Less NAD and FAD avalable for oxidation in glycolysis, Kreb’s cycle and link reaction
  • Can’t get reduced coenzymes from Kreb’s cycle, can’t synthesise ATP
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25
Q

What happens to oxidative phosphorylation when no oxygen is present?

A
  • Oxygen is final electron acceptor, so when not present electrons aren’t transferred down ETC
  • No energy released to pump protons into intermembrane space, no proton gradient builds, so no protons pass through ATP synthase, ATP not synthesised
26
Q

Why does aerobic respiration produce more ATP per molecule of glucose than anaerobic respiration.

A
  • Oxygen avaliable in aerobic respirationn, oxygen acts as final electron acceptor in oxidative phosphorylation ETC
  • In anaerobic respiration there is only glycolysis
27
Q

Describe the process of lactate fermentation.

think: reactions, products

A
  • Pyruvate reduced by NADH to form lactate
  • NAD regenerated for use in glycolysis
28
Q

How does lactate build up cause fatigue?
How does the body breakdown lactate to prevent muscle fatigue?

A
  • Lactic acid lowers pH and causes enzymes to denature
  • Lactate oxidised (oxygen debt) in liver back into pyruvate
29
Q

Describe the process of ethanol fermentation.

think: reactions, products

A
  • Pyruvate undergoes decarboxylation reaction (producing carbon dioxide) to form ethanal
  • Ethanal reduced using NADH to produce ethanol and NAD
30
Q

How can lipids be used in respiration?

think: fatty acids, glycerol, oxidation of lipids

A
  • Fatty acids can be converted to acetylcoenzyme A (no need for glycolysis/link)
  • Glycerol can be phosphorylated to triose phosphate (no need for glucose)
  • Lipids can be oxidised and produce hydrogen (used in oxidative phosphorylation)
31
Q

How can different proteins be used in respiration?

A
  • Broken down into amino acids which are deaminated
  • Remaining keto acid can join respiration in different stages depending on the number of C in amino acid:
  • 3C = glycolysis
  • 4C/5C = Kreb’s cycle
32
Q

How are monosaccharides converted into glucose?

A

Isomerase enzymes

33
Q

How could you set up an experiment for measuring the rate of respiration by measuring the volume of oxygen taken up?

A
  • Test tube filled with KOH to absorb carbon dioxide produced
  • Add some metal wire/net to seperate respiring organism (maggots)
  • Add gas syringe and measure the change in volume over set time
  • Create a control as well to see the change in gas volume when no respiring organism is present, take away this value from your result
34
Q

How would you set up a control test tube for measuring respiration by volume of oxygen taken in?

A
  • Replace respiring organisms with glass beads
  • Keep other variables the same
35
Q

How would you set a test tube up when investigating respiration in plants using volume of oxygen taken up?

A
  • Use same apparatus as before but cover test tube in foil
  • No light available so plant can’t photosynthesise and produce/take in gases
36
Q

When measuring rate of respiration using volume of oxygen taken up, suggest 3 reasons why the apparatus should be left 10 minutes before you start recording data?

A
  1. Equilibrium reached
  2. Stabilise rate
  3. Allow for pressure changes in apparatus
37
Q

Why is the chosen temeprature 20 degrees when investigating plant respiration?

A
  • Optimum temperature for enzymes so they do not denature
  • Optimum temperature for growth of plant seeds
38
Q

What is NPP?

A

Net primary production
- The amount of energy available to herbivores in the plant’s biomass after plant respiratory losses

NPP = GPP - R

39
Q

What are the units for GPP?

A

kj per m^2 per year

40
Q

What is GPP?

A

Gross primary production
- The amount of chemical energy stored in the carbohydrates within plants (during photosynthesis)

41
Q

How do you calculate the net production of consumers?

A

N = I - (R + F)

I = chemical energy store
R = respiratory losses
F = chemical energy lost (faeces)

42
Q

What is biomass and how can you estimate the chemical energy stored in dry biomass?
Why do you use dry biomass?

A

Biomass = the chemical energy stored within the organism or tissue

  • Produce dry biomass by heating to constant mass
  • Calorimetry ( q = mcΔT )
  • Water levels fluctuate so use dry biomass
43
Q

What produces biomass and how?

A

Producers (photoautotrophs)
by photosynthesis

44
Q

What increases the production of biomass in plants?

A
  • Water
  • Light intensity
  • Warmth
45
Q

Give 4 ways chemical energy is lost between organisms of the food chain.

A
  • Not all of the dead organism can be consumed (bones)
  • Respiratory losses
  • Active processes
  • Excretory materials (urine, faeces)
46
Q

What increases the production of biomass in plants?

A
  • Water
  • Light intensity
  • Warmth
47
Q

What are the differences between detritivores and decomposers?

A
  • Decomposers are saprotrophs (fungi, bacteria) and release enzymes to break down their food
  • Detritivores are heterotrophs (maggots, woodlice) and consume their food
48
Q

What is the role of detritivores in decomposition?

A
  • Shred dead organisms
  • Increase the surface area for decomposers and their enzymes
49
Q

How can you increase plant productivity in farming?

A

Fertilisers (NPK)

50
Q

How can you improve consumer productivity in farming?

A

Intensive farming:
- Limit active processes and movement
- Control diet (protein)
- Exclude predators

51
Q

Give two ways crop rotation may lead to a higher crop yield?

A
  • Some crops may have nitrogen fixing bacteria in roots
  • Different crops require different amounts of nitrates and ions from the soil
52
Q

How is nitrogen gas in the atmosphere converted into nitrates for plants?

A
  1. Nitrogen fixing bacteria in roots of plants- take up nitrogen and when they die and decompose they release ammonia and amino acids into soil
  2. Lightning converts nitrogen to nitrates
53
Q

How is nitrogen returned to the atmosphere after organisms die?

A
  • Dead organism broken down by decomposers, saprobiots release ammonia and amino acids
  • Nitrification by nitrifying bacteria produces nitrides then nitrates
  • Nitrates can be converted to nitrogen gas by denitrfying bacteria in anaerobic conditions
54
Q

How do farmers limit the action of denitrifying bacteria?

A

Plough fields and keep them non-wateer logged

55
Q

What is the role of mycorrhizae?

A
  • Fungi forms a symbiotic relationship with plant roots
  • Increases the SA for absorption of ions
56
Q

How are phosphate ions returned to the soil in the phosphorus cycle?

A
  • Erosion of sedimentary rock, bones and guano
  • Excretion by consumers in the food web
57
Q

In what 2 ways is phosphate in soil lost/used in the cycle?

A
  • Forms sedimentary rock
  • Absorbed by producers from soil
58
Q

What are the top 3 ions for fertilisers?

A

NPK
nitrate, phosphate and potassium ions

59
Q

What are some examples of organic fertiliser?
How are these better than artificial?

A
  • Manure
  • Compost
    Are cheaper than artificial.
60
Q

What can happen when there is an excess of nitrate ions entering rivers/lakes?

A

Eutrophication:
- Algael bloom on surface of water, blocks sunlight from entering
- Plants below can’t photosynthesise and die
- Saprobiotic bacteria decompose the plants, they also aerobically respire
- Less oxygen in water available for fish, fish die

61
Q

How are some plants adapted to survive in low nitrate soils?

A
  • Carniverous plants (venus fly trap)
  • Amino acids/ammonia from decomposition of dead insects

Biology (10 decks)

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