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aqa bio > 3.5 energy transfers in and between organisms > Flashcards

3.5 energy transfers in and between organisms Flashcards

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Biology 101 flashcards
1
Q

fixation

A
  • process by which gaseous CO2 is converted into sugars (e.g photosynthesis)
  • endothermic process
  • helps to regulate the conc of CO2 in atmospheres and oceans
  • the carbon needed to synthesise all types of organic molecule are provided by this process
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2
Q

what are organic molecules

A
  • all biological molecules that contain ‘C’
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3
Q

glucose uses in plants

A

F ats
O ils
S tarch
R esipiration
A mino acids
C ellulose

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4
Q

what are organisms that photosynthesise called

A

photoautotrophs/ producers

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5
Q

properties of ATP

A
  • stores and releases only a small amount of energy at a time so no energy is wasted as heat
  • small soluble molecule = can be transported about easily
  • easily broken down so energy can be released instantaneously
  • can make other molecules more reactive by transferring one of its phosphate groups to them
  • can’t pass out of the cell so cell always has an immediate supply of energy
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6
Q

what is the compensation point

A

when rate of photosynthesis = rate of respiration ; there is no net gain or loss of carbohydrate

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7
Q

which plants reach the compensation point sooner

A

shade plants:
- they photosynthesise at lower light intensities which means they can photosynthesise even when it is becoming dark alongside respiration, which allows it to reach it’s compensation point sooner

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8
Q

what is the time a plant takes to reach the compensation point called

A

compensation period

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9
Q

components of chloroplasts

A
  • thylakoids
  • granum
  • stroma
  • double membrane
  • photosynthetic pigments
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10
Q

thylakoids

A
  • pigment containing flattened sacs
  • site of light dependent reaction
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11
Q

granum

A
  • stack of thylakoids
  • grana stacks provide chloroplast with an increased SA (allows photosynthesis to occur in a limited space)
  • all grana held together by inter-granal thylakoids (site of light dependent reaction)
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12
Q

stroma

A
  • gel material containing enzymes
  • second part of photosynthesis occurs here (light independent reaction)
  • thylakoids embedded within stroma
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13
Q

double membrane in chloroplasts

A
  • controls molecular traffic in and out of chloroplast
  • inner membrane folded extensively to form thylakoids
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14
Q

photosynthetic pigments

A
  • coloured biological compound
  • present in chloroplasts and photosynthetic bacteria
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15
Q

2 types of pigments found in plants

A
  • chlorophyll
  • carotenoids
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16
Q

what light does chlorophyll reflect

A

green

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17
Q

what light do carotenoids reflect

A

orange, red or yellow light

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18
Q

location of photosynthetic pigments

A
  • found in photosystems (I AND II) which are found in thylakoid membranes
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19
Q

photophosphorylation

A

addition of a phosphate group using energy from sunlight

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20
Q

photolysis

A

splitting of a molecule using energy from sunlight

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21
Q

photoionisation

A

loss of an electron due to absorption of light energy

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22
Q

chemiosmosis

A

movement of ions down a gradient across a semi-permeable membrane

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23
Q

3 main processes that take place in the light dependent reaction

A
  • cyclic photophosphorylation
  • non cyclic photophosphorylation
  • photolysis of water
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24
Q

what does cyclic photophosphorylation include

A

photosystem 1
electron acceptor
electron transport chain

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25
Q

electron transport chain

A

cluster of proteins that transfer electrons through a membrane, allowing the energy they have to be gradually released and ultimately captured within ATP molecules

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26
Q

what happens in photoionisation in the light dependent reaction

A
  • chlorophyll absorbs light
  • electrons are lost/ chlorophyll becomes positively charged
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27
Q

process of cyclic photophosphorylation

A
  1. light hits photosystem 1 and excited 2 electrons
  2. electrons accepted by electron acceptor (leaves photosystem 1 electron deficient)
  3. electrons pass along electron transport chain (losing energy each time they’re carried on)
  4. the energy released is used to pump H+ ions from stroma into lumen creating an electrochemical gradient
  5. H+ ions now diffuse via chemiosmosis from the lumen through ATP synthase converting ADP + Pi into ATP
  6. electrons then pass back to photosystem I (cyclic) and process repeats
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28
Q

product of cyclic photophosphorylation

A

ATP - used in light independent reaction

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29
Q

difference between cyclic and non-cyclic photophosphorylation

A

cyclic = involves only photosystem I
non-cyclic = involves photosystem I and II

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30
Q

process of non cyclic photophosphorylation

A
  1. light hits photosystem II and excited 2 electrons
  2. electrons accepted by electron acceptor (leaves photosystem II electron deficient)
  3. electrons pass along electron transport chain (losing energy each time they’re carried on)
  4. energy released is used to make ATP from ADP + Pi
  5. light also hits photosystem I (exciting 2 electrons that pass on to an electron acceptor)
  6. to replace those electrons, photosystem I absorbs the 2 electrons originally from photosystem II
  7. electrons pass along electron transport chain
  8. this time, the energy released and electrons are used to reduce NADP to NADPH
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31
Q

products of non cyclic photophosphorylation

A

ATP and reduced NADPH

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32
Q

what happens in photolysis

A

water molecules are split by light energy

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33
Q

where does photolysis occur

A

thylakoid lumen

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34
Q

process of photolysis

A
  • light energy hits a water molecule
  • with aid of enzymes, the water is split into oxygen, H+ ions and electrons
  • H+ ions reduce NADP which passes to the light-independent reaction
  • electrons replace those lost from photosystem II in non cyclic photophosphorylation
  • oxygen released as a waste gas
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35
Q

where does the light dependent reaction occur

A

thylakoids of chloroplasts

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36
Q

where does the light independent reaction occur

A

stroma of chloroplasts

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37
Q

process of light independent reaction

A
  1. carbon dioxide reacts with RuBP to form 2 molecules of GP (reaction catalysed by enzyme rubisco)
  2. GP is reduced by ATP and NADPH (from the light dependent reaction) into 2 molecules of TP
  3. some of the TP is used to build other carbohydrates and complex molecules
  4. most of the TP is recycled to regenerate RuBP
  5. for every molecule of glucose made, 5 molecule of RuBP is produced
38
Q

products of the Calvin Cycle

A

NADP
ADP
Pi

39
Q

what is the light independent reaction also known as

A

calvin cycle

40
Q

what provides additional energy for the light independent reaction

A

hydrolysis of ATP

41
Q

factors affecting rate of photosynthesis

A

light intensity
temperature
CO2
water

42
Q

how does light intensity affect rate of photosynthesis

A
  • only certain wavelengths of light are used for photosynthesis
  • the higher the light intensity, the more energy it provides
43
Q

what colour light does chlorophyll A absorb

A

red

44
Q

what colour light does chlorophyll B absorb

A

blue/violet

45
Q

what colour light does carotene absorb

A

orange

46
Q

how does temperature affect rate of photosynthesis

A
  • ideal temp = 25
  • at high temps, stomata closes to avoid losing water = photosynthesis slows because less CO2 enters leaf
  • because photosynthesis involves enzymes e.g rubisco, if the temperature is below 10, the enzymes become inactive. if temp is above 45, the enzymes start to denature
47
Q

how does CO2 affect rate of photosynthesis

A
  • CO2 makes up 0.04% of the gases in the atmosphere
  • increasing this % up to 0.4%, gives a higher rate of photosynthesis, but any higher and the stomata start to close
48
Q

how does water affect rate of photosynthesis

A
  • too little water = photosynthesis stops
  • too much water = soil becomes waterlogged
  • reduces intake/uptake of minerals e.g magnesium
49
Q

farming and plant growth

A
  • farmers know factors that limit photosynthesis and therefore limit plant growth
  • this means that they try to create an environment where plants are in optimum conditions which increases growth and yield
50
Q

how do farmers manage conditions

A
  • co2 conc: added to atmosphere e.g burning a small amount of propane
  • light: glass allows light in
  • temp: glasshouse trap heat energy
51
Q

community

A

all the populations that live in a particular place at the same time

52
Q

ecosystem

A

a community of living organisms and the abiotic factors that affect them

53
Q

niche

A

the role an organisms has in an ecosystem, including where it lives and what it eats (biotic and abiotic factors)

54
Q

carrying capacity

A

when an ecosystem supports a certain size of population of a species
- maximum stable population number

55
Q

population size can vary as a result of

A
  • the effect of abiotic factors
  • interactions between organisms ; intraspecific and interspecific competition and predation
56
Q

2 types of competition

A
  • intraspecific
  • interspecific
57
Q

competitive exclusion principle

A
  • when 2 species are competing for limited resources, one will typically have a competitive advantage and outcompete the other
  • this may be avoided if one or both species have adapted to utilise other resources or a different area of the habitat
58
Q

size of a population can be estimated by using:

A
  • randomly placed quadrats, or quadrats along a belt transect,
    for slow-moving or non-motile organisms
  • the mark-release-recapture method for motile organisms. The
    assumptions made when using the mark-release-recapture
    method.
59
Q

define exponential growth of a population and state why this is not possible in real life

A

exponential growth of a population is the continuous growth in population size.
- exponential growth is only possible where there is an infinite supply of resources.
- in real ecosystems, this is not the case, hence exponential growth is not possible

60
Q

how might temperature affect population size

A
  • extreme temperatures can affect enzyme action
  • can directly affect the survival & distribution of a species. Species adapted to thrive in specific temperature ranges will form larger populations in these areas
  • ff the temperature of a habitat is significantly lower/higher than the organism’s optimum temperature, the organisms in that habitat cannot grow as efficiently.
  • more energy will be spent maintaining body temperature which means less energy will be available for growth and reproduction, limiting the population size (and the opposite for idea temperature conditions)
61
Q

how might light affect population size

A
  • low light levels = less photosynthesis = smaller, slower growing, fewer plants = reduced food for primary consumers = knock on effect for all trophic levels
  • opposite in high light levels: more food for primary consumers, carrying capacity increases
62
Q

how might pH affect population size

A
  • extreme pHs affects enzyme action
  • All enzymes have an optimum pH. The population is larger when the optimum exists and smaller when the pH is different.
  • The pH of water can also affect the aquatic organisms that are found there. Different species have evolved to survive at different pH levels found within water
63
Q

how might water and humidity affect population size

A
  • where water is scarce, populations are small and consist of a few well-adapted species.
  • Humidity can affect transpiration and evaporation rates.
  • Many plants cannot survive in waterlogged soils. Their roots are unable to respire, they rot and the plant dies.
  • Other plants, such as pitcher plants, grow best in bogs where the moisture levels are high.
64
Q

how might intraspecific competition affect population size

A
  • when resources are abundant, the population size increases. This increases intraspecific competition since resources will need to be shared between more organisms, which causes population size to decrease.
  • this pattern causes population numbers to fluctuate around the carrying capacity (the maximum number of organisms that an ecosystem can support).
  • species that have adaptations that allow them to gain resources better than other species are more likely to survive and reproduce
65
Q

how might interspecific competition affect population size

A
  • interspecific competition means that resources have to be shared between the different species so there will be less available to both.
  • this means both species will have less energy for growth and reproduction, so population numbers of both species will decrease.
  • for example, leopards and lions show interspecific competition since they both feed on the same prey.
66
Q

define succession

A

the gradual change in a community/ecosystem (all the organisms of different species) over time. There are 2 types: primary and secondary

67
Q

why does succession occur?

A

succession occurs because the conditions (abiotic and biotic) in a habitat are gradually changed by the existing species living in it.
- the new conditions are less hostile and so more suitable for a different combination of species and less suitable for the previous species, causing the previous species to be outcompeted.

68
Q

define primary succession

A
  • primary succession is when an ecological community develops in the absence of organisms and soil (i.e. from bare rock).
  • this may happen after a volcanic eruption which results in the formation of new rock or if the sea level lowers and exposes new land, glaciers retreating and depositing rock
69
Q

define secondary succession

A
  • when an ecological community develops from a barren landscape in which soil is present, with some organisms living in it, including spores and seeds, but the existing community has been destroyed so the soil is bare.
  • e.g. after a forest fire, on an abandoned agricultural land. due to the presence of some soil and organisms, secondary succession occurs much faster than primary
70
Q

what equation is used in mark-release-recapture to calculate population size?

A

(total no. of individuals in first sample x total no. of individuals in second sample) / number of marked individuals recaptured.

71
Q

state and explain methods used to conserve habitats and species

A
  • Managing succession: managing succession in a way that prevents change to the next stage, so the climax community is not reached
  • Seed banks: prevent species of plants from going extinct
  • Captive breeding: encourages endangered animals to breed and increase the numbers that exist e.g. pandas
  • Fishing Quotas: prevents fishes from being overhunted. maintains biodiversity of the sea
  • Protected Areas: maintains the natural diversity of the land e.g. National Parks. Protects landscapes and habitats from being destroyed
72
Q

food chain

A

a linked series of living organisms each of which is the food for the next level, showing energy flow through the ecosystem

73
Q

food web

A

the complex interactions between food chains in an ecosystem

74
Q

producers

A

an organisms producing its own food from simple inorganic materials e.g by photosynthesis

75
Q

autotrophs

A

green plants and some bacteria that makes their own food

76
Q

consumers

A

heterotrophs, which obtain nourishment by feeding on other organisms

77
Q

heterotrophs

A

an organism obtaining food by feeding on complex organic matter i.e consumer

78
Q

trophic level

A

the position an organism occupies in a food chain

79
Q

gross productivity

A

total energy fixed during photosynthesis

80
Q

net productivity

A

energy available for the next trophic level after respiration

81
Q

respiration

A

process whereby cells release energy from organic molecules

82
Q

biomass

A

the dry mass of organisms

83
Q

population

A

all the organisms of the same species living together in a particular habitat

84
Q

habitat

A

a place within an ecosystem where a population lives

85
Q

abiotic factors

A

physical and chemical features of the environment that have an effect on a population of organisms

86
Q

biotic factors

A

biological features of the environment that have an effect on a population of organisms

87
Q

intraspecific competition

A

individuals of the same species attempt to make use of the same scarce resources

88
Q

interspecific competition

A

individuals of more than one species attempt to make use of the same scarce resources

89
Q

pioneer

A

a plant species found in the early stage of succession

90
Q

sere

A

name given to each stage in a succession

91
Q

climax community

A

end stage in a succession

aqa bio (5 decks)

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