Energy Transfers In and Between Organisms Flashcards
(116 cards)
1
Q
how many stages are there in respiration?
A
4
2
Q
list the steps of respiration in order
A
- glycolysis
- link reaction
- krebs cycle
- oxidative phosphorylation
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
4
Q
what are the products of glycolysis?
A
2 x reduced NAD
2 x pyruvate molecules
2 x ATP (net gain)
5
Q
where does glycolysis take place?
A
cytoplasm
6
Q
where does the link reaction take place?
A
mitochondrial matrix
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
8
Q
how many times does the link reaction occur for every glucose molecule?
A
2
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
10
Q
where does the krebs cycle take place?
A
mitochondrial matrix
11
Q
describe the process of the krebs cycle
A
- acetyl CoA (2c) reacts with oxaloacetate (4c) to form citrate (6c). CoA returns to link reaction to be reused
- citrate decarboxylated so converted to a 5 carbon compound. dehydrogenation occurs - hydrogen used to produce NADH
- 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
- ATP produced by direct transfer of a phosphate group from an intermediate to ADP (substrate-level phosphorylation)
12
Q
how many times does the krebs cycle occur for every glucose molecule?
A
2
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
14
Q
where does oxidative phosphorylation take place?
A
mitochondrial inner membrane
15
Q
describe the process of oxidative phosphorylation
A
- NADH + FADH oxidised - release H atoms. H atoms split into H+ + e-
- e move along etc, lose energy at each carrier
- e carriers pump H+ from matrix into intermembrane space
- conc of H+ now higher in intermebrane space than in matrix - forms echem gradient
- H+ move down echem gradient back across inner membrane + into matrix - happens via ATP synthase
- movement of H+ through ATP synthase drives synthesis of ATP from ADP + Pi
- in matrix, at end of etc, H+, e- + oxygen combine to form water
16
Q
what is an electrochemical gradient?
A
a concentration gradient of ions
17
Q
what is the final electron acceptor in respiration?
A
oxygen
18
Q
where does anaerobic respiration occur?
A
cytoplasm only
19
Q
describe the process of anaerobic respiration in animals
A
- pyruvate from glycolysis reduced using H from NADH to form lactate
- this reoxidises NAD so can be used in glycolysis + ensures even more ATP is continued to be produced
20
Q
give an equation for anaerobic respiration in animals
A
pyruvate + NADH –> lactate + NAD
21
Q
describe the process of anaerobic respiration in plants and microbes
A
- pyruvate produced in glycolysis is reduced to form ethanol and carbon dioxide by gaining the hydrogen from NADH
- this reoxidises NAD so that it can be used in glycolysis + ensures even more ATP is continued to be produced
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
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
24
Q
what is the total yield of ATP molecules from aerobic respiration?
A
38
25
why is aerobic respiration only approximately 32% efficient?
- 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
26
what is the total yield of ATP molecules for anaerobic respiration?
2
27
what happens when oxygen is used up quicker that it is supplied?
an oxygen debt occurs
28
what is the effect of lactate on muscle tissue? how is this reversed?
- causes cramp and fatigue
- can be oxidised back to pyruvate or taken to liver and converted to glycogen
29
why is oxygen important?
so H atoms produced in glycolysis + krebs cycle can be converted to water + drive production of ATP
30
what happens in the absence of oxygen?
- 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
31
list 8 key structures of a chloroplast
- outer and inner membranes
- intermembrane space
- stroma
- thylakoids
- lumen (inside of thylakoid)
- lamella (links grana)
- granum ( a stack of thylakoids)
32
describe the structure and adaptations of the thylakoid membranes
- folded membranes (large sa = more proteins) that contain photosynthetic proteins (chlorophyll)
- electron carrier proteins are embedded on the membranes
- both proteins involved in LDR
33
describe the structure of the stroma
fluid centre which contains enzymes involved in the LIR
34
describe the function of the inner and outer membranes of the chloroplast
control what can enter and leave the cytoplasm
35
how many key pigments make up chlorophyll?
5
36
what is the most abundant pigment in chlorophyll?
chloropyhyll a
37
list the 5 key pigments that make up chlorophyll in all plants
- chlorophyll a
- chlorophyll b
- carotene
- xanthophyll
- phaeophytin
38
what colour is chlorphyll a?
blue/green
39
what colour is chlorophyll b?
yellow/green
40
what colour is carotene?
orange
41
what colour is xanthophyll?
yellow
42
what colour is phaeophytin?
grey
43
at what wavelength is light poorly absorbed by all pigments?
500-550nm
44
what is the advantage of chlorophyll being made up of multiple different pigments?
- wider range of wavelengths of light is absorbed
- therefore more light energy is absorbed for the LDR (more photoionisation of chlorophyll)
45
what are the 2 stages of photosynthesis?
- light dependent reaction (LDR)
- light independent reaction (LIR)
46
where does the LDR occur?
thylakoid membranes
47
where does the LIR occur?
stroma
48
what are the 4 key stages of LDR?
- photolysis of water
- photoionisation of chlorophyll
- chemiosmosis
- production of ATP and NADPH
49
describe the photolysis of water in the LDR
- 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
give an equation for the photolysis of water
H2O --> 1/2O2 + 2H+ + 2e-
51
describe the photoionisation of chlorophyll in the LDR
- 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
describe the process of chemiosmosis in the LDR
- 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
what is the LIR also known as?
calvin cycle
54
what enzyme is contained within the stroma?
rubisco
55
describe the process of the calvin cycle
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
what are the other products from the calvin cycle (as a result of 1 carbon from TP)?
- glucose (main product)
- glycerol, fatty acids, amino acids + proteins, disaccharides + polysaccharides
57
list 3 limiting factors of photosynthesis
- light intensity
- temperature
- CO2 concentration
58
explain how light intensity is a limiting factor of photosynthesis
- affects LDR -> light needed for photolysis and photoionisation
- before graph plateau: light intensity = limiting factor
- when graph plateau: saturation point reached
59
explain how CO2 is a limiting factor of photosynthesis
- 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
explain how temperature is a limiting factor of photosynthesis
- affects LIR -> enzyme controlled reaction
- too hot: enzymes denature
- too cold: not enough KE
61
explain how agricultural practices are used to maximise yield
- techniques implemented to remove limiting factors to maximise photosynthesis
- extend of each technique used depends on profit and must be cost effective
62
in any given ecosystem, what are the producers?
plants
63
why are plants considered producers?
they are able to produce their own carbohydrates using CO2 in the atmosphere or water
64
why is energy lost between trophic levels?
respiration and excretion
65
what is biomass in an organism measured in terms of?
mass of carbon or mass of dry mass of tissue per given area
66
how can productivity of an ecosystem be quantified?
- GPP (gross primary product)
- NPP (net primary product)
67
what is GPP?
- chemical energy store in plant biomass in a given area or volume
- **total** energy resulting from photosynthesis
68
what is NPP?
- 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
what factors (biotic and abiotic) may impact productivity of an ecosystem?
- 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
give an equation to calculate the net production of a consumer
**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
what are the units of rates of productivity?
kJ ha-1 year-1
72
justify each component of the units of rates of productivity
- 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
what is phosphorus used for?
- DNA/RNA
- ATP
- phospholipid bilayer
74
how does the phosphorus cycle differ from the nitrogen cycle?
- phosphorus is not found as a gas in the atmosphere
- phosphorus mainly found as a phosphate ion in mineral form in sedimentary rocks
75
what is mycorrhizae
fungal associations between plant roots and beneficial fungi
76
what is the role of mycorrhizae in the nutrient cycle?
- 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
why is mycorrhizae beneficial for plant growth?
improves uptake of relatively scarce ions, e.g. phosphate ions
78
outline the phosphorus cycle
- 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
why is the nitrogen cycle important?
plants and animals cant obtain nitrogen through gas exchange
80
why cant plants and animals obtain nitrogen through gas exchange?
- 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
which biological molecules contain nitrogen?
- proteins
- ATP
- nucleic acids (DNA/RNA)
82
what are the 4 key processes of the nitrogen cycle?
1. nitrogen fixation
2. ammonification
3. nitrification
4. denitrification
83
what is nitrogen fixing?
converting N2 gas into nitrogen containing compounds
84
how is nitrogen fixation able to occur in a leguminous plant?
bacteria in root nodules of the plant can convert nitrogen gas into ammonium or nitrates
85
what is a symbiotic relationship?
both parties gain benefit from coexisting
86
how is nitrogen fixation able to occur in a plant that is not leguminous?
- ammonification
- naturally occuring nitrogen fixing bacteria in soil react with nitrogen to produce ammonium
87
what happens in nitrification?
ammonium is converted into nitrites (NO2-) which are then converted to nitrates (NO3-)
88
what happens in assimilation?
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
how do animals gain nitrogen?
by eating plants
90
how is nitrogen transferred from animals and plants to soil?
- 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
what is the role of saprobionts in the nitrogen cycle?
digest + breakdown **proteins** in dead plant matter into other nitrogen containing compounds
92
what happens in denitrification?
denitrifying bacteria within the soil willl convert the nitrates back into nitrogen gas in the atmosphere
93
why is denitrification a problem in agriculture?
nitrogen lost from soil
94
why do farmers plough/aerate soil?
- 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
what are fertilisers used for?
added to soil to replace the nitrate and phosphate ions lost when plants are harvested an removed from nutrient cycles as crops
96
what are the 2 types of fertilisers? give an example of each
- natural (manure)
- artificial (inorganic chemicals)
97
give one advantage and one disadvantage of natural fertilisers
- cheaper/free if farmer owns animals
- exact minerals + proportions cannot be controlled
98
what are the advantages and disadvantages of artificial fertilisers?
- 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
what is leaching?
when water soluble compounds are washed away, often into rivers or ponds
100
what happens if nitrogen fertilisers leach into waterways?
eutrophication
101
what is eutrophication?
when nitrates leached from fertilised fields stimulate growth of algae in a pond
102
what are the problems with eutrophication?
- 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
what was the aim of Calvin's experiment?
- 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
what equipment was used to carry out Calvin's experiment?
- lollipop flask
- syringe
- rapid action tap
- hot methanol
- carbon isotope
- algae
- funnel
105
justify the use of a funnel during Calvin's experiment
needed to add algae
106
justify the use of a syringe during Calvin's experiment
to inject radioactive carbon isotope C14 in the form of CO2
107
justify the use of hot methanol during Calvin's experiment
to denature enzymes + stop reaction
108
justify the use of a rapid action tap during Calvin's experiment
for taking samples at precise times + rapidly in quick succession
109
justify the use of a flat lollipop flask during Calvin's experiment
- 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
during the Calvin experiment, what method was used for the isolation of chloroplasts?
ultracentrifugation
111
during the Calvin experiment, what was done to ensure the carbon 14 was fully incorporated into the plant?
- 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
during the Calvin experiment, what happened after the C14 was fully incorporated into the plant?
- 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
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?
- 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
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?
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
Calvin's experiment was carried out in light and in the dark. why would GP levels rise in the dark?
- light dependent reactions stop, so no NADH or ATP produced
- GP cannot be reduced into TP so GP levels rise
116
Calvin's experiment was carried out in light and in the dark. why would RuBP levels decrease in the dark?
- 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
