Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A2 Biology > Topic 5: Energy Transfer In And Between Organisms > Flashcards

Topic 5: Energy Transfer In And Between Organisms Flashcards

1
Q

3.5.1 Photosynthesis

What is photosynthesis?

A
  • Photosynthesis is a reaction in which light energy is used to
    produce glucose in plants. The process requires water and carbon
    dioxide, with the products being glucose and oxygen.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the two key stages of photsynthesis?

A
  • the light dependent reaction
  • the light independent reaction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What factors affect the rate of photosynthesis?

A
  • carbon dioxide concentration
  • light intensity
  • temperature
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the four key stages in the light dependent reaction?

A
  1. Photolysis of water
  2. Photoionisation
  3. Chemiosmosis
  4. Production of ATP and reduced NADP
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How are chloroplasts adapted for photosynthesis?

A
  • contains stacks of thylakoid membrane called the grana, these are folded to provide a large surface area for the attachment of chlorophyll, electrons and enzymes
  • the granal membrane has ATP synthase channels embedded allowing ATP to be synthesised and its selectively permeable which creates a proton gradient
  • chloroplasts contain DNA and ribosomes allowing them to synthesise proteins needed in the light dependent reaction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What happens in photolysis?

A
  • light energy is absorbed by the chloropyll
  • this splits water into oxygen protons and electrons
  • the protons are used to create reduced NADP and is used in the LIR
  • the electrons are passed along a chain of electron carrier proteins
  • the oxygen is either used for respiration or diffuses out of the leaf through the stomata
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How many photons of light is required to split one molecule of water?

A
  • 4 photons of light are required to split one molecule of water
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How many molecules of oxygen protons and electrons does the photolysis of water produce?

A
  • 1 molecule of oxygen
  • 4 protons
  • 4 electrons
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What happens in photoionisation?

A
  • The light energy absorbed by the chloropyll results in the electrons becoming excited
  • the electrons raise up an energy level and leave the chloropyll
  • chloropyll becomes positively charged and has now been ionised
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is some of the energy released from the electrons in photoionisation used for?

A
  • is conserved in the production of ATP and
    reduced NADP
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What happens in chemiosmosis?

A
  1. the electrons move along a series of proteins embedded within the thylakoid membrane
  2. As the electrons move along the proteins they release energy and some of this energy is used to pump the protons across chloroplasts membranes
  3. An electrochemical gradient is created. The protons pass through the enzyme ATP synthase by facilitated diffusion which phosphorylates ATP from ADP + pi
  4. The protons combine with coenzyme NADP to become reduced NADPH
  5. Because the protons move from an area of high to low concentration gradient. This is known as chemiosmosis
  6. NADPH and ATP are now used in the LIR
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Where does the light independent reaction take place?

A
  • the stroma
  • also known as the calvin cycle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the enzyme involved in the LIR?

A
  • Rubisco which catalyses the reaction
  • the stage is temperature reactive due to the fact it contains enzymes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What does the calvin cycle use to form a hexose sugar?

A
  • CO2
  • reduced NADP
  • ATP
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the role of ATP and NADPH in the calvin cycle?

A
  • ATP is hydrolysed to provide energy for the reaction
  • reduced NADP donates the hydrogen to reduces the molecule GP in the cycle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the main stages in the calvin cycle?

A
  1. carbon dioxide fixation
  2. reduction phase
  3. regeneration of RuBp
  4. organic molecule production
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What happens in the first stage of the calvin cycle (carbon dioxide fixation)?

A
  • CO2 reacts with ribulose bisphosphate (RuBP) in a process known as carboxylation
  • to form 2 molecules of GP a three carbon compound
  • this reaction is catalysed by the enzyme rubisco
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What happens in the second stage of the calvin cycle (reduction phase)?

A
  • GP is reduced by reduced NADP to form 2 molecules of TP and also energy is used by ATP
  • All of the NADP from the LDR has been used
  • Only some of the ATP has been used
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What happens in the third stage of the calvin cycle (regeneration of RuBP)?

A
  • Some of the carbon from TP leaves the cycle each turn to be converted into useful organic substances
  • 5 molecules of triose phosphate are used in order to regenerate 3 molecules of RuBP
  • The remaining amount of ATP from the light
    stage is now used.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What happens in the last stage of the calvin cycle (organic molecule production)?

A
  • 2 molecules of triose phosphate can combine to form
    the intermediate hexose sugar
  • whilst glucose is the product this monosaccharide can join to form disaccharides such as sucrose and polysaccharides such as cellulose and starch
  • glucose can also be converted to glycerol and therefore combine with fatty acids to make lipids for the plant
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How many turns of the calvin cycle are needed to produce 1 molecule of glucose per molecule of CO2?

A
  • 6 turns of the Calvin Cycle are required in order to produce 1 molecule of glucose per
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Describe the structure of a chloroplast

A
  • usually disc shaped
  • Double membrane
  • Thylakoids-flattended discs stack to form grana
  • Intergranal lamellae
  • stroma-fluid filled matrix
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How does the structure of the chloroplast maximise the rate of the LDR?

A
  • ATP synthase channels within granal membrane
  • Large surface area of thylakoid membrane for ETC
  • photosystems position chlorophyll to enable maximum absorption of light
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How does the structure of the chloroplast maximise the rate of the LIR?

A
  • own DNA and ribosomes for synthesis of enzymes e.g. rubisco
  • concentration of enzymes and substrates in stroma is high
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What are the limiting factors of photosynthesis ?

A
  • Light intensity (LDR)
  • CO2 levels (LIR)
  • Temperature (enzyme controlled steps)
  • Mineral/magnesium levels (maintain normal functioning of chloropyll
  • Chlorophyll concentration
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Wnat are some techniques agricultural producers incorporate to remove limiting factors?

A
  • growing plants with artificial lighting to maximise light intensity
  • heating a greenhouse to increase temperature
  • burning fuel to release more co2
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Why do farmers try to overcome the effect of limiting factors?

A
  • to increase yield
  • additional cost must be balanced with yield to ensure maximum profit
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

3.5.2 Respiration

What are the two types of respiration?

A
  • Aerobic and Anaerobic respiration
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is aerobic respiration?

A
  • Aerobic respiration is the splitting of a respiratory
    substrate, to release carbon dioxide as a waste product.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What is anaerobic respiration?

A
  • Anaerobic
    respiration occurs in the absence of oxygen.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What are the main stages of aerobic respiration?

A
  1. glycolysis (cytoplasm)
  2. the link reaction (mitochondrial matrix)
  3. the krebs cycle (mitochondrial matrix)
  4. oxidative phosphorylation (inner membrane cristae of mitochrondria)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What happens in glycolysis?

A
  • this is the first process of both aerobic
    and anaerobic respiration.
  • glucose is phosphorylated to glucose phosphate using ATP
  • This produces 2 molecules of triose phosphate
  • TP is oxidised to produce 2 molecules of pyruvate, with a net gain of 2× ATP and 2×NADH
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What happens in the link reaction?

A
  • the pyruvate from glycolysis is actively transported into the mitochondrial matrix
  • pyruvate is oxidised to acetate producing reduced NAD in the process
  • acetate combines with co-enzyme A in the link reacrion to produce acetylcoenzyme A
  • Per glucose molecule 2 molecules of
    acetyl coenzyme A are formed and 0 ATP
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What happens in the krebs cycle?

A
  • acetylcoenzyme A reacts with a four-carbon molecule,
    releasing coenzyme A and producing a six-carbon molecule
    that enters the Krebs cycle
  • in a series of oxidation-reduction reactions, the Krebs cycle
    generates reduced coenzymes     and ATP by substrate-level
    phosphorylation    , and carbon dioxide is lost
  • The Krebs cycle turns
    2 times     per molecule of glucose
  • per molecule of glucose 2 ATP molecules, 6
    NADH     molecules, 2 FADH molecules and 4 CO2 molecules are produced.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What happens in oxidative phosphorylation?

A
  • the current model for this process is the chemiosmotic theory
  • synthesis of ATP by oxidative phosphorylation is associated
    with the transfer of electrons down the electron transfer chain
    and passage of protons across inner mitochondrial
    membranes     and is catalysed by ATP synthase embedded in
    these membranes
  • Hydrogen atoms are donated by reduced NAD (NADH) and reduced FAD (FADH2) from the Krebs Cycle
  • Hydrogen atoms split into protons (H+ ions) and electrons
  • The high energy electrons enter the electron transport chain and release energy as they move through the electron transport chain
  • The released energy is used to transport protons across the inner mitochondrial membrane from thematrix into the intermembrane space
  • A concentration gradient of protons is established between the intermembrane space and the matrix
  • The protons return to the matrix via facilitated diffusion through the channel protein ATP synthase
  • The movement of protons down their concentration gradient provides energy for ATP synthesis
  • Oxygen acts as the ‘final electron acceptor’ and combines with protons and electrons at the end of the electron transport chain to form water
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

What is the role of oxygen in aerobic respiration?

A
  • acts as the final electron acceptor
37
Q

What is the benefit of an electron transfer chain rather than a single electron?

A
  • energy is released gradually
  • less energy is released as heat
38
Q

What happens to the pyruvate produced in glycolysis if respiration is only anaerobic?

A
  • pyruvate can be converted to
    ethanol or lactate using reduced NAD.
  • The oxidised NAD produced
    in this way can be used in further glycolysis.
39
Q

Name 2 types of molecule that can be used as alternative respiratory substrates

A
  • amino acids from proteins
  • glycerol and fatty acids from lipids
40
Q

How can lipids act as an alternative respiratory substrate?

A
  • Lipid—>glycerol+fatty acids
  1. Phosphorylation of glycerol–> TP for glycolysis
  2. Fatty acid–> acetate
    a) acetate enters lin reaction
    b) H atoms produced for oxidative phosphorylation
41
Q

How can amino acids act as an alternative respiratory substrates?

A
  • Deamination produces:
  1. 3Ccompounds–>pyruvate for link reaction
  2. 4C/5C compounds–> intermediates in krebs cycle
42
Q

Name the stages in respiration that produce ATP by substrate-level phosphorylation

A
  • Glycolysis (anaerobic)
  • Krebs Cycle (aerobic)
43
Q

3.5.3 Energy and ecosystems

What is an ecosystem?

A
  • includes all the organisms living in a particular area known as the community as
    well as all the non-living elements of that particular environment.
44
Q

What is the distribution and abunance of organisms in a habitat controlled by?

A
  • both biotic factor (living) e.g. predators,
    disease and abiotic factors (non-living) such as light levels and temperature.
  • Each species has a
    particular role in its habitat called its niche which consists of its biotic and abiotic interactions
    with the environment.
45
Q

What are the sugars synthesised by plants used for?

A
  • Most of the sugars synthesised by plants are used by the plant as
    respiratory substrates.
  • The rest are used to make other groups of
    biological molecules.
  • These biological molecules form the biomass
    of the plants.
46
Q

What is biomass and how can it be measured?

A
  • Total dry mass of tissue or mass of carbon measured over a given time in a specific area
  • The chemical energy store in dry biomass can be estimated using calorimetry
47
Q

What is the importance of the sun?

A
  • The sun is the source of all energy in ecosystems with photosynthetic organisms using this to produce their own food
48
Q

Why is most of the suns energy not converted to organic matter?

A
  • Most solar energy is absorbed by atmosphere or reflected by clouds
  • photosynthetic pigments cannot reabsorb some wavelengths of light
  • not all light falls directly on a chloropyll molecule
  • energy is lost as heat during respiration/photosynthesis
49
Q

What are autotrophs?

A
  • they are producers and make their own foods
50
Q

What are heterotrophs?

A
  • Those organisms
    that cannot synthesise their own food
  • all animals being these
51
Q

What is gross primary production?

A
  • ( GPP) is the chemical energy store in
    plant biomass, in a given area or volume
52
Q

What is net primary production?

A
  • ( NPP) is the chemical energy store in
    plant biomass after respiratory losses to the environment have
    been taken into account,
  • This net primary production is available for plant growth and
    reproduction.
  • It is also available to other trophic levels in the
    ecosystem, such as herbivores and decomposers.
53
Q

What is the equation that links GPP, NPP and R together?

A
  • NPP = GPP – R

where GPP represents gross production
R represents
respiratory losses to the environment.

54
Q

How can the net production of consumers be calculated?

A
  • N = I – ( F + R)

I=chemical energy store in ingested
F=chemical energy store lost to the environment in faeces and urine
R= respiratory losses to the environment

55
Q

Why does biomass decrease along a food chain?

A
  • energy lost in nitrogenous waste (urine) and faeces
  • some of the organism is not consumed
  • energy lost to surroundings as heat
56
Q

What is primary and secondary productivity?

A
  • Primary and secondary productivity is the rate of primary or
    secondary production, respectively.
  • It is measured as biomass in a
    given area in a given time eg kJ ha–1 year–1
57
Q

Outline some common farming practices used to increase the efficiency of energy transfer

A
  • Exclusion of predators- no energy lost to other organisms in a food web
  • Artificial heating-reduce energy lost to maintain it
  • Restriction of movement
  • Feeding is controlled at the optimum
  • reducing respiratory losses within a human food chain.
58
Q

Give a general equation for % efficiency

A

energy converted to useful form (j) x 100 / total energy supplied (j)

59
Q

Explain why the length of food chains is limited

A
  • Energy is lost at each trophic level
  • So there is insufficient energy to support a higher trophic level
60
Q

What is a pyramid of biomass?

A
  • Diagram that shows the biomass at each trophic level
61
Q

Why is a pyramid of biomass preferable to a pyramid of numbers?

A
  • shape of pyramid of numbers may be skewed since a small number of producers can support many consumers
62
Q

3.5.4 Nutrient cycles

What happens to nutrients?

A
  • Nutrients are recycled within natural ecosystems, exemplified by
    the nitrogen cycle and the phosphorus cycle.
63
Q

What is nitrogen?

A
  • Nitrogen is an element used in many biological molecules of which there is a finite amount on
    earth.
  • Due to this it must be recycled from dead organisms and waste products.
  • Most of this is
    carried out by bacteria in the soil.
64
Q

What are the 4 stages of the nitrogen cycle?

A
  1. Ammonification
  2. Nitrification
  3. Dentrification
  4. Nitrogen fixation
65
Q

Why cant organisms use nitrogen directly from the atmosphere?

A
  • N2 is very stable due to strong covalent triple bond
66
Q

1.

What happens in ammonification?

A
  • microbes known as saprobionts break down organic matter to
    ammonia in a two stage process.
  • Firstly, proteins are broken down into amino acids
    with the use of extracellular protease enzymes.
  • These are then subsequently broken
    down further     to remove amino groups with the use of deaminase enzymes
  • Saprobionts use the products of decomposition for respiration.
67
Q

What happens in nitrification?

A
  • nitrifying bacteria convert ammonia to nitrite ions, NO2- in an
    oxidation reaction, with a nitrate ion, NO3-, intermediate.
  • Most plants can take in
    nitrate ions     through their roots
68
Q

What happens in dentrification?

A
  • nitrate ions, NO3-, are converted to nitrogen gas, N2, by the
    anaerobic denitryfing bacteria.
  • This process is wasteful and can be prevented from occurring by
    soil     being well drained and aerated.
69
Q

What happens in nitrogen fixation?

A
  • nitrogen gas is fixed into other compounds by bacteria with
    nitrogen fixing ability.
  • They do so by reducing nitrogen gas to ammonia which
    subsequently dissolves to form ammonium ions.
  • Nitrogen fixing bacteria live in root
    nodules of leguminous plants    .
  • The relationship between nitrogen fixing bacteria and
    the plant is known as mutualistic, as it is beneficial to both organisms.
70
Q

Outline the role of bacteria in nitrogen fixation

A
  • Mutualistic nitrogen-fixing bacteria in nodules of legumes and free-living bacteria in soil
  • use the enzymes nitrogenase to reduce gaseous nitrogen into ammonia
71
Q

Explain the significance of nitrogen to living organisms

A
  • Plant roots uptake nitrates via active transport and use them to make biological molecules e.g Amino acids, NAD/NADP, nucleic acids
72
Q

Give 3 benefits of planting a different crop on the same field each year

A
  • Plants with nitrogen-fixing bacteria grow crops e.g. legumes make soil more fertile by increasing soil nitrate content
  • Different crops have different pathogens
  • Different crops use different proportions of certain ions
73
Q

Name two categories of fertiliser and state the purpose of using fertiliser

A
  • Organic/Natrual-decaying organic matter and animal waste
    -reduced risk of leaching/eutrophication but slower release of minerals
  • Inorganic/Artificial-minerals from rocks usually containing nitrogen, phosphorus and potassium
  • faster release of minerals and higher concentration but risk of leaching/eutrophication and lowers water potential of soil(so plant absorbs less water by osmosis)
  • Purpose of fertiliser is to increase gross productivity for higher yield
74
Q

```

At a certain point, using more fertiliser no longer increases crop yield. Why?

A
  • A factor unrelated to the concentration of mineral ions limits the rate of photosynthesis, so rate of growth cannot increase any further
75
Q

Outline 2 main environmental issues caused by the use of fertiliser

A
  • Leaching-nitrates dissolve in rainwater and “runoff” into water sources
  • Eutrophication-water sources becomes putrid as a result of algal bloom
76
Q

What is phosphorus?

A
  • Phosphorus is another element found in many biological molecules that needs to be
    recycled.
  • Plants can take in phosphate ions, PO43-,
    from soil.
77
Q

Name the general stages in the phosphorus cycle

A
  • Weathering
  • Runoff
  • Assimilation
  • Decomposition
  • Uplift
78
Q

Why is the phosphorus cycle a slow process?

A
  • Phosphorus has no gas phase so there is no atmospheric cycle
79
Q

What happens during weathering and runoff?

A
  • Phosphate compounds from sedimentary rocks leach into surface water and soil
80
Q

What is phosphate released from?

A
  • Phosphate is released from
    sedimentary rocks     as a result of weathering, as well as through the decay of bones, shells
    and the excreta of some birds.
81
Q

What happens during uplift?

A
  • Sedimentary layers from oceans (formed by the bodies of aquatic organisms) are brought up to land over many years
82
Q

Explain the significance of phosphorus to living organisms

A
  • Plants convert inorganic phosphate intio biological molecules e.g. DNA ATP NADP
  • Phosphorus is passed to consumers via feeding
83
Q

How does mining affect the phosphorus cycle?

A
  • Speeds up uplift
84
Q

What is the role and importance of mycorrhizae in the phosphorus cycle?

A
  • Mycorrhizae are important in facilitating the uptake of water and inorganic ions by plants.
  • These are associations between certain types of fungi and the roots of the vast majority of
    plants    .
  • They increase the surface area and act as a sponge holding water and minerals.
  • As a
    result a plant can better resist drought and take up inorganic ions more easily.
85
Q

What are natural and artificial fertilisers used for during cycles?

A
  • to replace the nitrates and phosphates lost by
    harvesting plants and removing livestock.
86
Q

What are nitrogen fertilisers used for?

A
  • greatly increase crop yields and therefore can help to deal with the
    demands of a growing human population    .
  • However they have negative effects on the
    environment     which include reducing biodiversity, leaching and eutrophication
87
Q

What is leaching?

A
  • process by which mineral ions, such as nitrate, dissolve in rainwater and are
    carried from the soil to end up in rivers and lakes.
  • As a result of this eutrophication occurs
88
Q

What is eutrophication?

A
  • if large amounts of chemical fertilisers are sprayed onto fields and heavy rainfall occurs, the fertiliser may leach into local water sources
  • the fertiliser will travel and build up in ponds or lakes
  • Nitrates will be absorbed and used by Algae
    which will lead to an increase growth of algae = algal bloom
  • the algae grows on the upper surface of the water, this prevents light reaching the plants at the bottom of the water
  • these plants cannot photosynthesise, so die
  • these provide more nutrients to saprobiotic decomposers, so these increase in number
  • the decomposers will aerobically respire, using up the oxygen in the water
  • therefore fish die as less oxygen is available
89
Q

How can the risk of eutrophication be reduced?

A
  • Sewage treatment marshes on farms
  • pumping nutrient-enriched sediment out of water
  • using phosphate-free detergent

A2 Biology (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions