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A-Level Biology > Energy Transfers In and Between Organisms > Flashcards

Energy Transfers In and Between Organisms Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

how many stages are there in respiration?

A

4

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2
Q

list the steps of respiration in order

A
  • glycolysis
  • link reaction
  • krebs cycle
  • oxidative phosphorylation
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3
Q

describe the process of glycolysis

A
  • glucose phosphorylated by 2 ATP to form glucose phosphate
  • glucose phosphate breaks down into 2 molecules of triose phosphate
  • triose phosphate oxidised to produce pyruvate
  • NAD coenzyme gains the hydrogen to form reduced NAD
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4
Q

what are the products of glycolysis?

A

2 x reduced NAD
2 x pyruvate molecules
2 x ATP (net gain)

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5
Q

where does glycolysis take place?

A

cytoplasm

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6
Q

where does the link reaction take place?

A

mitochondrial matrix

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7
Q

describe the process of the link reaction

A
  • pyruvate from glycolysis actively transported from cytoplasm into mitochondrial matrix + is decarboxylated in form of CO2 + oxidised to form acetate
  • NAD reduced to form NADH
  • acetate combines with coA to produce acetyl coA
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8
Q

how many times does the link reaction occur for every glucose molecule?

A

2

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9
Q

what are the products of the link reaction per glucose molecule?

A

2 x acetyl coenzyme A
2 x CO2
2 x reduced NAD

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10
Q

where does the krebs cycle take place?

A

mitochondrial matrix

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11
Q

describe the process of the krebs cycle

A
  1. acetyl CoA (2c) reacts with oxaloacetate (4c) to form citrate (6c). CoA returns to link reaction to be reused
  2. citrate decarboxylated so converted to a 5 carbon compound. dehydrogenation occurs - hydrogen used to produce NADH
  3. 5c molecule is converted to oxalacetate due to decarboxylation and dehydrogenation. this also caused 1 molecule of FADH and 2 molecules of NADH to be produced
  4. ATP produced by direct transfer of a phosphate group from an intermediate to ADP (substrate-level phosphorylation)
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12
Q

how many times does the krebs cycle occur for every glucose molecule?

A

2

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13
Q

what are the products of the krebs cycle per glucose molecule?

A

2 x CoA
2 x Oxaloacetate
4 x CO2
2 x ATP
6 x NADH
2 x FADH

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14
Q

where does oxidative phosphorylation take place?

A

mitochondrial inner membrane

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15
Q

describe the process of oxidative phosphorylation

A
  1. NADH + FADH oxidised - release H atoms. H atoms split into H+ + e-
  2. e move along etc, lose energy at each carrier
  3. e carriers pump H+ from matrix into intermembrane space
  4. conc of H+ now higher in intermebrane space than in matrix - forms echem gradient
  5. H+ move down echem gradient back across inner membrane + into matrix - happens via ATP synthase
  6. movement of H+ through ATP synthase drives synthesis of ATP from ADP + Pi
  7. in matrix, at end of etc, H+, e- + oxygen combine to form water
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16
Q

what is an electrochemical gradient?

A

a concentration gradient of ions

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17
Q

what is the final electron acceptor in respiration?

A

oxygen

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18
Q

where does anaerobic respiration occur?

A

cytoplasm only

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19
Q

describe the process of anaerobic respiration in animals

A
  1. pyruvate from glycolysis reduced using H from NADH to form lactate
  2. this reoxidises NAD so can be used in glycolysis + ensures even more ATP is continued to be produced
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20
Q

give an equation for anaerobic respiration in animals

A

pyruvate + NADH –> lactate + NAD

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21
Q

describe the process of anaerobic respiration in plants and microbes

A
  1. pyruvate produced in glycolysis is reduced to form ethanol and carbon dioxide by gaining the hydrogen from NADH
  2. this reoxidises NAD so that it can be used in glycolysis + ensures even more ATP is continued to be produced
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22
Q

why can anaerobic respiration only occur for a short period of time?

A

ethanol is toxic and lactic acid is an acid so both would denature enzymes if anaerobic repiration occured for a long period of time

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23
Q

how many ATP molecules can be produced from one NADH? how does this compare to the ATP produced from one FADH?

A
  • one NADH can result in a yield of 3 ATP molecules
  • one FADH can result in a yield of 2 ATP molecules
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24
Q

what is the total yield of ATP molecules from aerobic respiration?

A

38

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25
Q

why is aerobic respiration only approximately 32% efficient?

A
  • some protons leak across the mitochondrial membrane during oxidative phosphorylation
  • some ATP used to actively transport pyruvate and NADH into the matrix
  • some energy is lost as heat
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26
Q

what is the total yield of ATP molecules for anaerobic respiration?

A

2

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27
Q

what happens when oxygen is used up quicker that it is supplied?

A

an oxygen debt occurs

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28
Q

what is the effect of lactate on muscle tissue? how is this reversed?

A
  • causes cramp and fatigue
  • can be oxidised back to pyruvate or taken to liver and converted to glycogen
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29
Q

why is oxygen important?

A

so H atoms produced in glycolysis + krebs cycle can be converted to water + drive production of ATP

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30
Q

what happens in the absence of oxygen?

A
  • link reaction, krebs cycle and oxidative phosphorylation can’t take place so glycolysis is the only source of ATP molecules
  • pyruvate builds up in the cell
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31
Q

list 8 key structures of a chloroplast

A
  • outer and inner membranes
  • intermembrane space
  • stroma
  • thylakoids
  • lumen (inside of thylakoid)
  • lamella (links grana)
  • granum ( a stack of thylakoids)
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32
Q

describe the structure and adaptations of the thylakoid membranes

A
  • folded membranes (large sa = more proteins) that contain photosynthetic proteins (chlorophyll)
  • electron carrier proteins are embedded on the membranes
  • both proteins involved in LDR
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33
Q

describe the structure of the stroma

A

fluid centre which contains enzymes involved in the LIR

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34
Q

describe the function of the inner and outer membranes of the chloroplast

A

control what can enter and leave the cytoplasm

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35
Q

how many key pigments make up chlorophyll?

A

5

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36
Q

what is the most abundant pigment in chlorophyll?

A

chloropyhyll a

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37
Q

list the 5 key pigments that make up chlorophyll in all plants

A
  • chlorophyll a
  • chlorophyll b
  • carotene
  • xanthophyll
  • phaeophytin
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38
Q

what colour is chlorphyll a?

A

blue/green

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39
Q

what colour is chlorophyll b?

A

yellow/green

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40
Q

what colour is carotene?

A

orange

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41
Q

what colour is xanthophyll?

A

yellow

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42
Q

what colour is phaeophytin?

A

grey

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43
Q

at what wavelength is light poorly absorbed by all pigments?

A

500-550nm

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44
Q

what is the advantage of chlorophyll being made up of multiple different pigments?

A
  • wider range of wavelengths of light is absorbed
  • therefore more light energy is absorbed for the LDR (more photoionisation of chlorophyll)
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45
Q

what are the 2 stages of photosynthesis?

A
  • light dependent reaction (LDR)
  • light independent reaction (LIR)
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46
Q

where does the LDR occur?

A

thylakoid membranes

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47
Q

where does the LIR occur?

A

stroma

48
Q

what are the 4 key stages of LDR?

A
  • photolysis of water
  • photoionisation of chlorophyll
  • chemiosmosis
  • production of ATP and NADPH
49
Q

describe the photolysis of water in the LDR

A
  • light absorbed by chlorophyll + splits water into oxygen, H+ and e-
  • H+ are picked up by NADP to form NADPH
  • e- are passed along a chain of electron carrier proteins
  • oxygen is either used for respiration or diffuses out of the leaf through the stomata
50
Q

give an equation for the photolysis of water

A

H2O –> 1/2O2 + 2H+ + 2e-

51
Q

describe the photoionisation of chlorophyll in the LDR

A
  • light energy absorbed by chlorophyll
  • energy results in the e- becoming excited + raising up an energy level to leave the chlorophyll
  • chlorophyll has been ionised
  • some of energy released from e- is used to make ATP and NADPH in chemiosmosis
52
Q

describe the process of chemiosmosis in the LDR

A
  • the e- that gained energy + left the chlorophyll move along a series of proteins embedded within the thylakoid membranes
  • as they move along, they release energy + some of the energy from e- is used to actively transport the protons across the chloroplast membranes
  • an electochemical gradient is created
  • H+ pass through ATP synthase, resulting in ATP being produced
  • H+ combine with NADP to produce NADPH
53
Q

what is the LIR also known as?

A

calvin cycle

54
Q

what enzyme is contained within the stroma?

A

rubisco

55
Q

describe the process of the calvin cycle

A
  1. CO2 reacts with RuBP (5C) (fixation of CO2) to form 2 x GP molecules (3C) - catalysed by rubisco
  2. GP reduced to TP using energy from ATP + by accepting a H from NADPH
  3. some of the carbon from TP leaves cycle + is used for synthesis of useful organic substances
  4. RuBP is regenerated using energy from ATP
56
Q

what are the other products from the calvin cycle (as a result of 1 carbon from TP)?

A
  • glucose (main product)
  • glycerol, fatty acids, amino acids + proteins, disaccharides + polysaccharides
57
Q

list 3 limiting factors of photosynthesis

A
  • light intensity
  • temperature
  • CO2 concentration
58
Q

explain how light intensity is a limiting factor of photosynthesis

A
  • affects LDR -> light needed for photolysis and photoionisation
  • before graph plateau: light intensity = limiting factor
  • when graph plateau: saturation point reached
59
Q

explain how CO2 is a limiting factor of photosynthesis

A
  • affects LIR -> CO2 is one of the reactants entering the calvin cycle
  • before graph plateau: CO2 = limiting factor
  • when graph plateau: saturation point reached
60
Q

explain how temperature is a limiting factor of photosynthesis

A
  • affects LIR -> enzyme controlled reaction
  • too hot: enzymes denature
  • too cold: not enough KE
61
Q

explain how agricultural practices are used to maximise yield

A
  • techniques implemented to remove limiting factors to maximise photosynthesis
  • extend of each technique used depends on profit and must be cost effective
62
Q

in any given ecosystem, what are the producers?

A

plants

63
Q

why are plants considered producers?

A

they are able to produce their own carbohydrates using CO2 in the atmosphere or water

64
Q

why is energy lost between trophic levels?

A

respiration and excretion

65
Q

what is biomass in an organism measured in terms of?

A

mass of carbon or mass of dry mass of tissue per given area

66
Q

how can productivity of an ecosystem be quantified?

A
  • GPP (gross primary product)
  • NPP (net primary product)
67
Q

what is GPP?

A
  • chemical energy store in plant biomass in a given area or volume
  • total energy resulting from photosynthesis
68
Q

what is NPP?

A
  • chemical energy store in plant biomass taking into account the energy lost due to respiration
  • NPP = GPP - R
  • energy leftover that is available to the plant to create new biomass and therefore available to the next trophic level in a food web
69
Q

what factors (biotic and abiotic) may impact productivity of an ecosystem?

A
  • plenty of warmth, water, light and green plants maximise the rate of photosynthesis and therefore increase the amount of carbphydrates produced in plants
  • more carbs produced = more available to next trophic level
70
Q

give an equation to calculate the net production of a consumer

A

N = I - (F + R)
- I = the chemical energy store in ingested food
- F = the chemical energy lost to the environment in faeces and urine
- R = respiratory losses

71
Q

what are the units of rates of productivity?

A

kJ ha-1 year-1

72
Q

justify each component of the units of rates of productivity

A
  • kJ: unit for energy
  • ha (hectacres): per unit of area to standardise the results in order for environments to be compared, takes into account diffrerent environments will vary in size
  • per year: takes into account the impact seasons will have on rain, light and heat, provides an annual average to allow fair comparison between environments
73
Q

what is phosphorus used for?

A
  • DNA/RNA
  • ATP
  • phospholipid bilayer
74
Q

how does the phosphorus cycle differ from the nitrogen cycle?

A
  • phosphorus is not found as a gas in the atmosphere
  • phosphorus mainly found as a phosphate ion in mineral form in sedimentary rocks
75
Q

what is mycorrhizae

A

fungal associations between plant roots and beneficial fungi

76
Q

what is the role of mycorrhizae in the nutrient cycle?

A
  • the fungi increase the surface area for water + mineral absorption
  • the mycorrhizae acts as a sponge so holds water + minerals around the roots, making plants more drought resistant + able to take up more inorganic ions
77
Q

why is mycorrhizae beneficial for plant growth?

A

improves uptake of relatively scarce ions, e.g. phosphate ions

78
Q

outline the phosphorus cycle

A
  • phosphate ions are dissolved in water e.g. oceans + soil
  • plants absorb phosphate ions by active transport
  • plants containing phosphate ions are eaten by animals
  • animals will excrete some of the phosphate ions
  • waste + remains, e.g. guano (bird faeces), bones + shells erode over time + will release the phosphate back into oceans/soil
  • some used to create phosphate ions in rocks, whuch also erode over time
  • when animal dies, some released during decomposition
  • sediment from rivers build up which contains phosphate ions
79
Q

why is the nitrogen cycle important?

A

plants and animals cant obtain nitrogen through gas exchange

80
Q

why cant plants and animals obtain nitrogen through gas exchange?

A
  • nitrogen contains a triple bond (hard to break)
  • microorganisms are needed to convert nitrogen gas into nitrogen containing substances that plants and animals can absorb
81
Q

which biological molecules contain nitrogen?

A
  • proteins
  • ATP
  • nucleic acids (DNA/RNA)
82
Q

what are the 4 key processes of the nitrogen cycle?

A
  1. nitrogen fixation
  2. ammonification
  3. nitrification
  4. denitrification
83
Q

what is nitrogen fixing?

A

converting N2 gas into nitrogen containing compounds

84
Q

how is nitrogen fixation able to occur in a leguminous plant?

A

bacteria in root nodules of the plant can convert nitrogen gas into ammonium or nitrates

85
Q

what is a symbiotic relationship?

A

both parties gain benefit from coexisting

86
Q

how is nitrogen fixation able to occur in a plant that is not leguminous?

A
  • ammonification
  • naturally occuring nitrogen fixing bacteria in soil react with nitrogen to produce ammonium
87
Q

what happens in nitrification?

A

ammonium is converted into nitrites (NO2-) which are then converted to nitrates (NO3-)

88
Q

what happens in assimilation?

A

nitrates are absorbed into plants by active transport + will be assimilated into the cell to be used to create amino acids, ATP, DNA, etc.)

89
Q

how do animals gain nitrogen?

A

by eating plants

90
Q

how is nitrogen transferred from animals and plants to soil?

A
  • animals produce urea containing ammonia in urine
  • when animals + plants die, they decompose
  • saprobionts will digest + breakdown proteins in dead plant matter into other nitrogen containing compounds
91
Q

what is the role of saprobionts in the nitrogen cycle?

A

digest + breakdown proteins in dead plant matter into other nitrogen containing compounds

92
Q

what happens in denitrification?

A

denitrifying bacteria within the soil willl convert the nitrates back into nitrogen gas in the atmosphere

93
Q

why is denitrification a problem in agriculture?

A

nitrogen lost from soil

94
Q

why do farmers plough/aerate soil?

A
  • nitrifying bacteria are anaeroic, so denitrification can only occur if not enough O2, e.g. if soil waterlogged/flooded (O2 displaced by water)
  • ploughing/aerating soil makes sure there is enough O2 to prevent denitrification
95
Q

what are fertilisers used for?

A

added to soil to replace the nitrate and phosphate ions lost when plants are harvested an removed from nutrient cycles as crops

96
Q

what are the 2 types of fertilisers? give an example of each

A
  • natural (manure)
  • artificial (inorganic chemicals)
97
Q

give one advantage and one disadvantage of natural fertilisers

A
  • cheaper/free if farmer owns animals
  • exact minerals + proportions cannot be controlled
98
Q

what are the advantages and disadvantages of artificial fertilisers?

A
  • can control exact proportion of minerals
  • inorganic substances are more water soluble + therefore more of the ions dissolve in the water surrounding the soil so plant absorbs more nitrates/phosphates
  • high solubility = larger quantities washed away with rainfall (leaching) = greater impact on environment
99
Q

what is leaching?

A

when water soluble compounds are washed away, often into rivers or ponds

100
Q

what happens if nitrogen fertilisers leach into waterways?

A

eutrophication

101
Q

what is eutrophication?

A

when nitrates leached from fertilised fields stimulate growth of algae in a pond

102
Q

what are the problems with eutrophication?

A
  • excessive growth of algae creates a blanket on the surface of the water which blocks out light
  • as a result, plants below cannot photosynthesise + so they die
  • bacteria in the water feed + respire on the dead plant matter, resulting in an increase in bacteria
  • bacteria respire + use up the oxygen within the water
  • eventually fish + other aquatic organisms die due to the lack of dissolved oxygen in the water
103
Q

what was the aim of Calvin’s experiment?

A
  • incorporation of carbon 14 isotope into carbohydrate molecules measured
  • movement of carbon traced through the calvin cycle
  • visualise the distribution of radioactivity in the plant material
104
Q

what equipment was used to carry out Calvin’s experiment?

A
  • lollipop flask
  • syringe
  • rapid action tap
  • hot methanol
  • carbon isotope
  • algae
  • funnel
105
Q

justify the use of a funnel during Calvin’s experiment

A

needed to add algae

106
Q

justify the use of a syringe during Calvin’s experiment

A

to inject radioactive carbon isotope C14 in the form of CO2

107
Q

justify the use of hot methanol during Calvin’s experiment

A

to denature enzymes + stop reaction

108
Q

justify the use of a rapid action tap during Calvin’s experiment

A

for taking samples at precise times + rapidly in quick succession

109
Q

justify the use of a flat lollipop flask during Calvin’s experiment

A
  • to have a greater surface area for light
  • to continuously supply CO2 to the plant material while simultaneously removing the carbohydrate molecules that were produced
110
Q

during the Calvin experiment, what method was used for the isolation of chloroplasts?

A

ultracentrifugation

111
Q

during the Calvin experiment, what was done to ensure the carbon 14 was fully incorporated into the plant?

A
  • left for set amount of time under exact conditions to allow CO2 to be fully incorporated into all carbon-containing compounds in the calvin cycle
112
Q

during the Calvin experiment, what happened after the C14 was fully incorporated into the plant?

A
  • continue to inject C14 isotope in CO2 form, whilst also taking samples at a precise period
  • measure the exact quantity of the C14 isotope in all the different carbon containing compounds
113
Q

Calvin’s experiment was carried out in light and in the dark. why would there be a high amount of radioactive substance in GP in the light compared to RuBP?

A
  • GP is a 3c compound, and there are 2 in the calvin cycle
  • RuBP is a 5c compound and there is only one in the calvin cycle
  • GP therefore will always have a higher amount of radioactivity compared to RuBP as GP has more carbons
114
Q

Calvin’s experiment was carried out in light and in the dark. why would the amount of radioactively labelled C14 to decrease in the dark?

A

light dependent reactions stop, so no NADH or ATP produced, both of which are required in the calvin cycle to reduce GP into TP

115
Q

Calvin’s experiment was carried out in light and in the dark. why would GP levels rise in the dark?

A
  • light dependent reactions stop, so no NADH or ATP produced
  • GP cannot be reduced into TP so GP levels rise
116
Q

Calvin’s experiment was carried out in light and in the dark. why would RuBP levels decrease in the dark?

A
  • RuBP still able to bind with CO2 using rubisco enzyme to form GP
  • GP not converted to TP so no TP available to regenerate RuBP
  • also no ATP which is needed to regenerate the RuBP
  • RuBP still used but not regenerate so levels decrease

A-Level Biology (6 decks)

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