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A Biology A Level > Topic 5 > Flashcards

Topic 5 Flashcards

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1
Q

What is the equation for photosynthesis?

A
  • 6H2O + 6CO2 → C6H12O6 + 6O2
  • Water + carbon dioxide → glucose + oxygen
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2
Q

What is ATP?

A
  • Adenosine triphosphate
  • Energy currency used to transfer and supply energy within cells
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3
Q

What is the structure of ATP?

A
  • Base adenine
  • Pentose sugar ribose
  • Three phosphate groups
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4
Q

How is ATP synthesised?

A
  • ADP + Pi → ATP
  • Condensation reaction requires energy and ATP synthase
  • Phosphorylation
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5
Q

How is ATP hydrolysed?

A
  • ATP → ADP + Pi
  • Dephosphorylation
  • Catalysed by ATPase
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6
Q

What are the roles of ATP?

A
  • Metabolic processes
  • Synthesise molecules
  • Movement
  • Active transport
  • Molecule activation
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7
Q

What is the structure of a chloroplast?

A
  • Double membrane filled with fluid known as the stroma.
  • Membrane consists of fluid filles flattened sacs known as the thylakoids
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8
Q

How is the structure of a chloroplast related to its function?

A
  • Stroma contains enzymes that catalyse photosynthesis reaction
  • Double membrane encloses components for photosynthesis
  • Grana has large SA, loads of photosystems and absorption of light
  • Thylakoids has space for accumulation of H+ ions.
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9
Q

What happens in the light dependent reaction?

A

-Light to photosystem II, excites electron in chlorphyll
- Photolysis to produce O, H, e-
- Electrons passed down electron transport chain
- Hydrogen ions are pumped in (Chemiosmotic gradient) and are pumped through ATP synthase
- Photophosphorylation of ADP to produce ATP.
- Photosystem I absorbs more light and the electron is passed down the electron transport chain.
- NADP picks up hydrogen or electrons to produce NADPH.

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10
Q

How does the structure of the grana relate to its function?

A
  • Grana formed from layers to increase SA for light absorption
  • Thylakoid membrane contains chlorophyll to absorb light
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11
Q

What is photolysis?

A
  • Light energy breaking bonds between oxygen and hydrogen in water
  • Produces 2H+ ions, 2 elections and one oxygen atom
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12
Q

What happens in non-cyclic photophosphorylation?

A
  • From Photosystem II to the end product.
  • Light energy hits photosystem II.
  • Two electrons gain energy and are excited, leaving PSII to travel on the electron transport chain.
  • This enables chemiosmosis.
  • Electrons passed to PSI and then combine with H+ ions from photolysis and coenzyme NADP to form reduced NADP (NADPH), which then passes to the light independent reaction
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13
Q

What happens in cyclic photophosphorylation?

A
  • Photosystem II to photosystem I
  • Light hits photosystem I.
  • Electrons excited and pass down ETC, driving chemiosmosis.
  • At the end of the electron transport chain, electrons re-join PSI in a complete cycle.
  • ATP produced joins light independent reaction
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14
Q

What products of the light dependent reaction are used in the light independent reaction?

A
  • Reduced NADP
  • ATP
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15
Q

What do membrane proteins do?

A
  • For electron transport
  • Move hydrogen ions across thylakoid membrane for ATP production
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16
Q

What happens in the light independent reaction?

A
  • Uses the products of ATP and reduced NADP from the light dependent reaction to form glucose.
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17
Q

How does chemiosmosis in the light dependent reaction catalyse the production of ATP?

A
  • H­­+ ions are actively pumped from a low conc in the stroma to a high conc in the thylakoid space (conc gradient)
  • H­­+ ions diffuse back across the thylakoid membrane into the stroma via ATP synthase
  • Movement of H­­+ ions causes the ATP synthase to catalyse the production of ATP
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18
Q

What are the steps of light independent reaction?

A
  • CO2 combines with RuBP (5C) and catalysed by RuBisCO to make 6C
  • Yields two 3C GP
  • GP is reduced to GALP using hydrogen from reduced NADP
  • For each molecule of CO2, ADP is produced
  • GALP converted back to RuBP by ATP hydrolysis
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19
Q

What is the role of RUBISCO?

A
  • RUBISCO is a catalyst in the Calvin cycle
  • It is involved in carbon fixation to form GP
  • GP is converted into GALP using ATP and NADPH
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20
Q

How much GALP is used in generation of organic molecules

A
  • For every 6 GALP, one organic molecule is produced
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21
Q

What is GP used to produce?

A
  • Amino acids (protein synthesis)
  • Fatty acids (lipid molecules)
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22
Q

What is GALP used to produce?

A
  • Hexose sugars eg. glucose
  • Glycerol
  • Nucleic acids
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23
Q

What happens to the growth of plants if there is an increase in CO2?

A
  • Carbon dioxide is a limiting factor
  • It is fixed to produce GALP
  • So more glucose is produced which leads to a greater rate of growth
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24
Q

How does GP synthesise starch?

A
  • GP to GALP using reduced NADP and ATP
  • GALP to glucose
  • Glycosidic bonds (1,4 and 1,6) form by condensation reaction
  • Amylose and amylopectin
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25
Q

What is a population?

A
  • All the individuals of one species in the same habitat
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26
Q

What is a community

A
  • All the populations living in the same area.
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27
Q

What is an ecosystem?

A
  • A community and its interactions with the non living (abiotic) and living (biotic) factors
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28
Q

What is an abiotic factor?

A
  • Non living factors
  • Eg. temperature, light intensity, pH
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29
Q

What is a biotic factor?

A
  • Living factors
  • Eg. predation, food availability
30
Q

What is a niche?

A
  • The way a species ‘uses’ its environment and interacts
31
Q

What are examples of a species role (niche)?

A
  • What it eats
  • What time it is active
  • Where in a habitat it lives
32
Q

Why must two species not occupy the same niche?

A
  • Creates competition for resources
  • Out-compete each other causing one to die out in that habitat
33
Q

What is abundance?

A
  • The number of individuals of a species living in a habitat
34
Q

What is distribution?

A
  • Where a species lives
35
Q

What is Gross primary productivity (GPP)?

A
  • Total quantity of all energy in biomass.
36
Q

What is net primary productivity (NPP)?

A
  • Total energy store after losses from respiration are accounted.
37
Q

What is the equation for NPP?

A
  • NPP = GPP - respiration
38
Q

What does primary productivity depend on?

A
  • Amount of sunlight energy
  • Ability of producers to use energy to synthesise organic compounds
  • Availability of other factors for growth of producers.
39
Q

Why is the transfer of energy not 100% efficient?

A
  • Energy is lost due to faeces, urine + respiration.
40
Q

What is a trophic level?

A
  • The stage in a food chain
41
Q

What are producers?

A
  • Organism which uses sunlight to photosynthesise and make their own energy
42
Q

What is the equation for biomass percentage efficiency?

A

% efficiency = energy after transfer/energy before transfer x 100

43
Q

Why is energy lost between trophic levels?

A
  • Not every single part is consumed eg. bones
  • Unable to digest all they ingest
  • Excretory materials
  • Energy lost via heat in respiration
44
Q

Why can’t all the suns light energy be absorbed?

A
  • Not all wavelengths can be used and absorbed
  • May not fall on chlorophyll
  • Sun gets reflected
  • Limiting factors eg. low CO2, temperature
45
Q

What is succession?

A
  • Processes that occur over time in a species to replace each other
46
Q

What is primary succession?

A
  • Colonisation of bare rock or barren terrain by living organisms, beginning an ecosystem
47
Q

What is the process of succession?

A
  • Colonised by a pioneer species which are adapted to hostile environments.
  • Change in environment, changes abiotic factors making it more hospitable
  • Dies increasing amount of organic matter + soil
  • Enables other species to colonise
  • Stability increases creating a climax community.
48
Q

Why does succession change the abiotic and biotic conditions?

A
  • New colonising species change the environment so it becomes less suitable for the previous species
49
Q

What are the common features of succession?

A
  • Abiotic features are less hostile
  • Increase in biodiversity
  • Greater number of habitats and niches
  • More complex food webs so increased biomass
50
Q

What is secondary succession?

A
  • Recolonisation of an area after earlier community is removed/destroyed
51
Q

What is deflected succession?

A
  • Human halt of succession as ecosystem is prevented from developing further. (plagioclimax)
52
Q

What is the pattern of growth of species?

A
  • Lag phase - few organisms acclimatising to their environment
  • Log phase - resources are plentiful so rapid growth
  • Stationary phase - population has levelled out, death rate equals reproduction rate
53
Q

What is a carrying capacity?

A
  • It is the maximum population size that can be maintains over a period in a habitat
54
Q

What limiting factors slow the rate of natural processes?

A
  • Temperature
  • Light
  • Water
  • Predation
  • Parasites
55
Q

What is sustainability?

A
  • Meeting demands of today without compromising the future
56
Q

How can humans help sustainability?

A
  • Replanting trees
  • Ensure ecosystems are functional
  • Local people have to be benefited.
57
Q

What happens in the carbon cycle?

A
  • Animals respire to release CO2 into the air
  • Plants take up this CO2 and use it in photosynthesis
  • Plants get eaten by animals so CO2 transferred
  • All die so decomposed to release CO2 into the air.
  • Fossil fuels are harvested, releasing CO2 in combustion.
58
Q

What evidence is there for climate change caused by human activities increasing the concentrations of greenhouse gases?

A
  • Records of atmospheric C02 levels
  • Records of average global temperatures
  • Records of changing plant communities by sampling pollen grains in peat bogs
  • Records of tree growth in dendrochronology
59
Q

What is a greenhouse gas?

A
  • Gas that absorbs re-radiated radiation to trap it in its earths atmosphere contributing to the greenhouse effect
60
Q

What is the greenhouse effect?

A
  • Sun radiates energy towards earth and some is absorbed by ozone or reflected.
  • Surface of the earth reflects back the absorbed energy as infrared light into space.
  • But some is absorbed by gases in atmosphere, warming up the earth’s surface
61
Q

How can studying pollen grains in peat bogs provide evidence for climate change?

A
  • Pollen is preserved in peat bogs
  • Climate affects the type of plants growing
  • Depth of peat correlates with period of time since pollen was produced.
  • Changes in pollen indicate changes in climate
62
Q

How does dendrochronology show changes to climate over the years?

A
  • Tree trunks grow in diameter each season as they produce more vascular tissue
  • Trees grow faster when conditions are warmer
63
Q

Why are anthropogenic emissions of greenhouse gases affecting the climate?

A
  • Human activity such as deforestation and burning fossil fuels
  • Increase amount of CO2 or methane
  • Mean increase in surface/atmospheric temp
64
Q

What is extrapolation?

A
  • Using existing data to make predictions about what will happen in the future
65
Q

What are the limitations to climate change models based on extrapolated data?

A
  • don’t know which scenario for the future is most likely
  • don’t know if future technologies will be successful at removing greenhouse gases
  • global climate patterns are complex and hard to predict
  • unknown exactly how CO2 affects global temp
66
Q

What effect does climate change have?

A
  • More extreme weather events
  • Changes to ocean currents which alters local climate
  • Change in rainfall pattern
67
Q

What is the evidence for changes in climate patterns due to climate change?

A
  • warming climate cause species migration
  • water availability in habitats changing
  • seasonal cycles changing
  • polar ice and glaciers retreating
  • sea levels rising
68
Q

What effects do higher temperatures have on enzyme reactions?

A
  • Reactions speed up
  • More kinetic energy
  • More enzyme-substrate complexes as collide more frequently
69
Q

What happens when an enzyme is denatured?

A
  • Weakened hydrogen and ionic bonds so they start to break
  • Permanently damages the active site, preventing substrate from binding
70
Q

How can we reduce carbon emissions?

A
  • Biofuels over fossil fuels
  • Renewable energy sources
71
Q

What are the pros + cons of renewable energy?

A

Pros - cheaper and efficient, no CO2 released
Cons - Dependent on natural processes, visual damage

72
Q

What are the pros + cons of biofuels?

A

Pros - Made of biomass, cheaper than oil, renewable, carbon neutral
Cons - Vast amount of land needs to be grown, loss of biodiversity

A Biology A Level (8 decks)

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