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Biology A-Level > Topic 5 - Energy transfers > Flashcards

Topic 5 - Energy transfers Flashcards

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1
Q

state the two stages of photosynthesis

A

LDR (light dependent reaction)

LIDR (light independent reaction) - also known as the dark reaction

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2
Q

where does LDR occur

A

thylakoid membrane of chloroplast

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3
Q

where does LIDR occur

A

stroma of chloroplast

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4
Q

describe the structure of chloroplasts

A

did you mention:
double membrane (envelope), stoma containing thylakoid membrane, 70s ribosomes, circular DNA, starch granules, lamella, grana

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5
Q

describe photoionisation in the LDR

A
  • chlorophyll absorbs light energy which exites its electrons (higher energy levels)
  • so electrons are released from chlorophyll (chlorophyll becomes positively charged)
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6
Q

describes what happens after photoionisation in the LDR

A

some energy from electrons released in photoionisation is conserved in the production of ATP./reduced NADP:

  • electrons move along electron transfer chain (electron carriers), releasing energy
  • energy is used to actively pump pprotons from stroma into thylakoid
  • protons move by facilitated diffusion down electrochemical gradient into stroma via ATP synthase
  • energy used to join ADP and Pi to form ATP (photophosphorylation
  • NADP accepts a proton and an electron to become reduced NADP
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7
Q

state 3 products of LDR

A

ATP, reduced NADP, half an O2 molecule

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8
Q

describe photolysis of water in the LDR

A

water splits to produce protons, electrons and oxygen (H2O –. 0.5 O2 + 2e- + 2H+)

electrons replace those lost from chlorophyll

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9
Q

what is the light independent reaction known as (2 names)

A

the dark reaction or the calvin cycle

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10
Q

where does the LIDR occur

A

stroma of the chloroplast

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11
Q

what 2 products of the LDR is used in the LIDR

A

reduced NADP and ATP

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12
Q

why are reduced NADP and ATP used in the LIDR

A

to reduce CO2

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13
Q

describe the LIDR

A
  • CO2 reacts with ribulose bisphosphate (RuBP) and is catalysed by the enzyme rubisco
  • this forms 2 glycerate 3-phosphate (GP) molecules [3C]
  • GP is then reduced to triose phosphate (TP) [3C]. this uses reduced NADP oxidised into NADP and ATP reduced into ADP + Pi
  • some TP is converted into useful organic substances e.g. glucose (6C)
  • some TP is used to regenerate RuBP (5C) in the calvin cycle using energy from ATP (ATP is reduced into ADP + Pi)
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14
Q

does LIDR require light?

A

not directly

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15
Q

describe how temperature affects rate of photosynthesis

A

temperature increases = rate increases
above optimun temperature, rate decreases = fewer sucessful collisions and fewer ES complexes form

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16
Q

explain how temperature affects rate of photosynthesis

A

temp increases because enzymes like rubisco gain kinetic energy

enzymes will denature above optimun temperature. H bonds in tertiary structure break = fewer ES complexes form

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17
Q

describe how light intensity affects rate of photosynthesis

A

light intensity increases as rate increases but above a certain light intensity, rate stops increasing

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18
Q

explain how light intensity affects rate of photosynthesis

A

light increases as rate increases
LDR increases so more ATP and reduced NADP -produced so LIDR increases as more GP reduced to TP and more TP regenerates RuBP

above certain light intensity, rate stops increasing
another factor is limiting when light intensity rate stops increasing e.g. tmeperature or Co2 concentration

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19
Q

describe how CO2 conc affects rate of photosynthesis

A

as CO2 conc increases, rate increases

above certain CO2 conc, rate stops increasing

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20
Q

explain why CO2 conc affects rate of photosynthesis

A

rate increases as CO2 increases
LIDR increases as more CO2 combines w RuBP to form GP so more GP reduced to TP so more TP converted to organic substances and more RuBP regenerated

rate stopping after certain CO2 conc
another factor is limiting e.g. temp or light intensity

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21
Q

what is the law of limiting factors

A

when a process depends on two or more factors, the rate of that process if limited by the factor which is in shortest supply

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22
Q

what three factorrs can the rate of photosynthesis in a plant can be limited by

A

light intensity, conc of CO2, temperature

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23
Q

what happens to rate of photosynthesis when temeprature is too low

A

lower kinetic energy so fewer sucessful collision and fewer ES complexes form and a slower rate of reaction = lower rate of electron transport chain/lower rate of carboxylation by rubisco

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24
Q

what happen to rate of photosynthesis when temperature is high

A

high kinetic energy breaks the hydrogen bonds in the tertiary structure of enzymes and proteins involved in the LDR and calvin cycle. enzymes + proteins lose their tertiary structure and change shape [denature] so cannot perform role in LDR or calvin cycle
lower rate of electron transport chain/lower rate of carboxylation by rubisco

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25
Q

what happens to rate of photosynthesis when CO2 is low

A

less CO2 so less RuBP to combine with and less GP produced. So less GP for the NADPH2 and ATP to convert into and less TP = less glucose

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26
Q

what happens to rate of photosynthesis when light intensity is lower

A

less light
less photoionisation which means less electrons are excited
so reduced electron transport chain = less NADPH2 and ATP produced
CO2 will combine with RuBP to produce GP but cannot change into TP as no NADPH2 or ATP so less TP converted into glucose

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27
Q

when there is a line with a gradient what does this mean regarding limiting factors

A

independent variable is limiting the rate of photosynthesis - xaxis

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28
Q

when there is a flat line what does this mean in limiting factor graphs

A

a factor other than the independent variable is limiting rate of photosynthesis = yaxis

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29
Q

what happens to rate of photosynthesis when there is a lack of chlorophyll

A

this is mainly due to being deficient iin Mg2+ so less light absorbed, less photoionisation, reduced electron transport chain = less NADPH2 and ATP so reduced production of TP and so less glucose

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30
Q

how does a lack of water affect rate of photosynthesis

A

less water split into two to replace the electrons lost in the Photosystem II and so reduced photolysis of water so cannot replace electrons so stays ionised and reduced electron transport chain. less NADPH2 and ATP produced so less GP turned into TP which means less glucose

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31
Q

why are fertilisers are used

A
  • to replace nitrates/phosphates lost when plants are harvested and livestock are removed
  • those removed from soil and incorporated into biomass can’t be released back into the soil through decomposition by saprobionts
  • so improve efficiency of energy transfer = increase productivity/yield

faster growth, increased biomass, higher productivity (rate at which biomass is produced), higher yield and cheaper food

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32
Q

what are natural fertilisers made of

A

organic substances and ions are released during decompositioni by saprobionts e.g. manure, compost and sewage

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33
Q

what are artificial fertilisers made of

A

inorganic compounds of nitrogen, phosphorus and potassium

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34
Q

how do fertilisers increase productivity

A

nitrogen is an essential compound of amino acids, ATP and nucleotides in DNA all needed for plant growth. increased conc = plants develop quicker - greater leaf area, grow taller = more photosynthesis can occur and improved crop productivity

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35
Q

state 3 effects of using fertilisers

A

redeuced species diversity, leaching, eutrophication

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36
Q

state what happens in eutrophication

A
  • rapid growth of algae in pond/river so light blocked
  • submerged plants die as they cannot photosynthesise
  • saprobionts decompose dead plant matter using oxygen in aerobic respiration
  • so less oxygen for fish to aerobically respire, leading to their death
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37
Q

state how leaching affects it

A

phosphates/nitrates disssolve in water, leading to leaching of nutrients into lakes/river/oceans + eutrophication

pollutes watercourses

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38
Q

explain key advantages of using natural fertiliser over artificial fertiliser

A
  • less water soluble so less leaching = eutrophication is less likely
  • organic molecules require breaking down by saprobionts = slow release of nitrate/phosphate etc.
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39
Q

what is leaching

A

soluble mineral ions (nitrate ions) dissolve in rainwater and carry the ions deep into the ground beyond the reach of plant roots = mineral ions travel into watercourses (rivers and streams) via groundwater flow

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40
Q

state how fertilisers reduce species diversity

A

nitrogen rich soil favours the growth of grasses, nettles and other rapidly growing species which outcompete other species, leading to a reduced biodiveristy of plants = fewer plant speicies = reduced food sources and habitat options

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41
Q

what is eutrophication caused by

A

leaching of fertiliser into watercourses

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42
Q

what is eutrophication

A

soluble nitrates are washed into watercourse, algae absorb the nitrates and the opulation grows rapidly = alglal bloom which blocks aquatic plants so as they cannot photosynthesise, they die

lots of dead, organic material for bacteria to feed on = population grows rapidly = water is anoxic (lacking oxygen) due to anaerobic respiration.

lack of oxygen = reduced biodiversity as all organisms die

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43
Q

what can farmers do to increase growth

A

use greenhouses, propane burners, night lights, irrigation systems and pesticides

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44
Q

how does use of greenhouses increase growth in farming

A

increases radiation = increased LDR and increases temperature = increased KE

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45
Q

how does use of propane burners increase growth in farming

A

increase temperature = increased KE and increase CO2 = increased CAlvin cycle

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46
Q

how does the use of night lights increase growth in farming

A

more constant radiation = increased LDR

47
Q

how does use of irrigation systems increase growth in farming

A

increased volume of water = increased LDR

48
Q

how do pesticides increase growth in farming

A

kill pests which …..

leaves eaten = less photoionisation = reduced LDR

broken phloem tissue = reduced carbohydrates for respiration, storage and synthesis of molecules = reduced growth because reduced DNA reeplication, protein synthesis, cell division

damage root cells = reduced water and mineral ion absorption = reduced LDR and turgidity = reduced SA exposed so reduced LDR

mineral ion deficiency = reduced chlorophyll (less LDR), enzyme action, protein synthesis and ATP production

49
Q

explain how crop farming practices increases efficiency of energy transfer

A

simplifying food webs to reduce energy/biomass losses to non-human food chains e.g.
- herbicides kill weeds = less competition for light so more energy to create biomass
- pesticides kill insects = reduce loss of biomass from crops
- fungicides reduce fungal infections = more energy to create biomass

fertilisers e.g. nitrates to prevent poor growth due to lack of nutrients

50
Q

why are magnesium ions needed in fertilisers

A

required to synthesise chlorophyll molecules

51
Q

why are nitrate ions needed in fertilisers

A

synthesises amino acids and mononucleotides = proteins, ATP, polynucleotides

52
Q

why are potasssium ions needed in fertilisers

A

required for co-transport (NaK pump) = absorption of mineral ions by roots = generates osmotic pressure = movement of sucrose into the phloem

52
Q

why are phosphate ions needed in fertilisers

A

to phosphorylate ADP into ATP, for phospholipids and nucleotides (mono and poly)

53
Q

explain how livestock farming practices increase efficiency of energy transfer

A

reduce respiratory losses within a human food chain = more energy to create biomass:
- reduce movement and keep warm = less energy lost as heat from respiration
- slaughter animal while still growing/young when most energy is used for growth
- treated with antibiotics = prevent loss of energy due to pathogens
- selective breeding to produce breeds with higher growth rates

54
Q

state 3 advantages of inorganic fertiliser

A
  • can tailor the fertiliser to the specific needs of the soil/crop
  • concentrated = large amount in small area
  • soluble = easily spread in fields
55
Q

state 2 disadvantages of inorganic fertilisers

A

favours the growth of fast growing plants (weeds) which results in reduced species diversity and doesn’t replace soil structure, leaving it vulnerable to wind and soil erosion. solubleeading to leeching and eutrophication

56
Q

how is the mitrochondrion structure adapted to its function

A
  • long and thin = large SA:V for movement of particles in and out of mitochondrion = short diffusion distance
  • envelope = controls what enters and exits = H+ conc gradient to be set up
  • cristae = high SA for attachment of respiratory proteins
  • has its own DNA and ribosomes = make its own respiratory proteins
57
Q

state the structures found in mitochondria

A
  • inner and outer membrane (envelope)
  • cristae
  • matrix
  • 70S ribosomes
  • mitochondrial DNA
  • intermembranal space
58
Q

overall reaction for respiration

A

glucose + oxygen -> carbon dioxide + water + (38 ATP)

heat energy is also released = exothermic

chemical energy released initiates condensation reaction of ADP to ATP

59
Q

define respiration

A

a chemical reaction that releases the chemical potential energy from molecules

60
Q

what is the difference btwn respiration and breathing

A

respiration occurs ‘everywhere’ but breathing occurs in the lungs

61
Q

what does ATP stand for

A

adenosine triphosphate

62
Q

why ATP

A
  • muscle contraction
  • metabolic processes such as protein synthesis
  • phosphorylation of molecules to make them more reaction
  • active transport
  • good energy carrier = invovles one step reaction = immediate source of energy which is released in small manageable amounts
  • easily reformed in a condensation reaction
63
Q

why is ATP a bad source of energy

A
  • easily hydrolysed
  • cannot travel through the phospholipid bilayer as it is soluble = difficult to keep in one place. if kept in one place, affects water potential
64
Q

what are the 4 main processes in aerobic respiration

A

substrate-level phosphorylation:
- glycolysis
- link reaction
- krebs cycle

  • oxidative phosphorylation
65
Q

what is the purpose of substrate-level phosphorylation

A

break down substrates to produce reduced co-enzymes to be used in oxidative phosphorylation

66
Q

what does oxidative phosphorylation allow

A

create a H+ conc. gradient which allows phosphorylation of ADP to ATP

67
Q

what is a co-enzyme

A

a non-protein compound necessary for the function on an enzyme

68
Q

what co-enzymes are used in respiration

A

NAD, CoA, FAD

69
Q

where does glycolysis occur

A

in the cytoplasm

70
Q

where in the stage of respiration are co-enzymes used

A

reduced are used in the final stage of respiration (oxidative phosphorylation which produces a lot of ATP)

71
Q

does glycolysis require oxygen

A

no

72
Q

what happens in glycolysis

A

glucose is split into 2 molecules of pyruvate (a 3 carbon sugar) via phosphorylation

73
Q

what two phases are there in glycolysis

A

energy pay off phase and energy investment (glucose -> triose phosphate -> pyruvate)

74
Q

what are the resulting products of glycolysis

A

2 pyruvate molecules, net gain of 2 ATP molecules (4 overall gross gain of ATP molecules but 2 used in the reaction for phosphorylation to triose phosphate), 2 reduced NADP

75
Q

where does the link reaction occur

A

matrix in the mitochondria

76
Q

what happens in the link reaction

A
  • pyruvate is produced in glycolysis is passed through the inner and outer membrane of the mitochondrion by active transport
  • decarboxylatioin (CO2 removed from pyruvate) which requires enzyme decarboxylas
  • CO2 diffuses out of the mitochondrion and cell
  • dehydrogenation = hydrogen atom produced which is used by NAD to become reduced NADH
  • coenzyme A picks up acetyl which results in acetyl coenxyme A (2C) which is then used in the Krebs cycle)
77
Q

what occurs in the krebs cycle

A
  • acetylee coenzyme A from the link reaction combines its acetyl group with oxalacetates (4C) to produce citrate (6C)
  • citrate is decarboxylated and dehydrogenated to an intermediate 5C molecule
  • futher decarboxylation and dehydrogenation produces an oxalacetate , 2 NADP molecules are reduced, FAD is reduced, ATP is produced and CO2 is produced.
  • oxalacetate is now recycled with another acetyl coenzyme A to begin the cycle again
78
Q

how many krebs cycles occur per glucose molecule

A

2

glucose > 2 triose phosphates > 2 pyruvates > 2 acetyl coenzyme As

79
Q

what is produced in two link reactions which come from one glucose molecule

A

acetyl coenzyme A, 2 CO2, 2 NADH

80
Q

what is produced in two krebs cycle from the one glucose molecule

A

4 CO2, 6 NADH, 2 FADH, 2 ATP

81
Q

what is oxidative phosphorylation

A

it is the final stage of respiration where the majority of ATP is produced

82
Q

where does oxidative phosphorylation occur

A

on the inner membrane of the mitochondria (cristae)

83
Q

what does oxidative phosphorylation use and require to occur

A

it uses NADH, FADH and requires oxygen (known as the terminal electron acceptor)

84
Q

what is oxidative phosphorylation also known as

A

the electron transport chain

85
Q

give a brief description of what happens in oxidative phosphorylation

A
  • hydrogen atoms are picked up and transported by NADH and FADH are split into H+ and e-
  • electrons are passed down a series of electron transport carrier molecules (involves redox reactions) which releases energy that is then used to pump H+ into intermembranal space
  • H+ diffuses down an electrochemical gradient (chemiosmosis) through ATP synthase which catalyses the condensation reaction of ADP and Pi
  • once electrons have transferred their energy they combine with H+ in the mitochondrial matrix and oxygen to form water = oxygen is the terminal electron acceptor

4e- + O2 + 4H+ -> 2H2O

86
Q

how many ATP molecules does NADH create

A

3

87
Q

how many ATP molecules does FAD create

A

2

88
Q

where is some energy lost in oxidative phosphorylation

A

heat

89
Q

where in oxidative phosphorylation is energy released

A

electrons being passed from a higher energy carrier to a lower energy carrier = phosphorylate ADP to ATP

90
Q

aerobic respiration requires oxygen, why is oxygen needed in oxidative phosphorylation

A

it is the terminal electron acceptor

91
Q

what happens in oxidative phosphorylation if oxygen isn’t available

A

oxidative phosphorylation cannot occur and the reduced NAD and FAD cannot be oxidised so the link reaction and krebs cycle stops, leaving only glycolysis

92
Q

word equation for anaerobic respiration in animals

A

glucose -> lactate + (2 ATP)

93
Q

word equation for anaerobic respiration in yeast (and plants)

A

glucose -> ethanol + carbon dioxide

94
Q

how is pyruvate reduced in glycolysis in anaerobic respiration

A

reduced by the 2 NADs that come from glycolysis, recycling NAD, allowing further glycolysis to take place, converting it to lactate

95
Q

what is pyruvate converted into in anaerobic respiration

A

lactate

96
Q

what can happen to lactate when pyruvate is converted into it

A
  • oxidised back to pyruvate, can be oxidised to release energy
  • convert to glycogen as a store of carbohydrate
97
Q

what occurs in anaerobic respiration as well as aerobic respiration

A

glycolysis

98
Q

how is glycolysis able to occur when there is a lack of oxygen

A

oxygen isn’t needed and the NAD is recycled to form reduced NAD to convert pyruvate into lactate

99
Q

where does the Krebs cycle occur

A

in the mitochondrial matrix

100
Q

where does oxidative phosphorylation occur

A

inner mitochondiral membrane

101
Q

where does NAD regernation of anaerobic respiration occur

A

cytoplasm

102
Q

suggest why anaerobic respiration produces less ATP per molecule of glucose than aerobic respiration

A

only glycolysis is involved, produces little ATP. no oxidative phosphorylation which forms a majority of ATP

103
Q

how does pyruvate travel from glycolysis to the next reaction step if respiration is aerobic

A

active transporte

104
Q

how does the oxygen debt occur

A

extra oxygen is needed to oxidise lactate to turn back into pyruvate (on top of oxygen already needed in respiation)

105
Q

what happens to pyruvate in anaerobic respiration of yeast n plants

A

it is decarobyxlated and reduced by reduced NAD to form ethanol

106
Q

how can you measure the rate of a reaction

A

measure the rate at which reactants/products are used up/made

107
Q

which would be the easiest reactant/product to measure aerobic respiration

A

oxygen uptake or carbon dioxide production

108
Q

why are respirometers left for a time period to stabilise

A

to let temperature, pressure and the respiration to stabalise and reach equilibrium

109
Q

why would the fluid move in a manometer

A

there is a pressure gradient

110
Q

how would you calculate the respiratory quotient

A

volume of CO2 produced/ volume of O2 absorbed

111
Q

what can lipids be metabolised into

A

glycerol -> triose phosphate -> energy pay off phase in glycolysis

fatty acids -> acetyl coenzyme A -> combines with oxalacetate in the krebs cycle

112
Q
A

Biology A-Level (11 decks)

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