Topic 5 Flashcards
What is the equation for photosynthesis?
- 6H2O + 6CO2 → C6H12O6 + 6O2
- Water + carbon dioxide → glucose + oxygen
What is ATP?
- Adenosine triphosphate
- Energy currency used to transfer and supply energy within cells
What is the structure of ATP?
- Base adenine
- Pentose sugar ribose
- Three phosphate groups
How is ATP synthesised?
- ADP + Pi → ATP
- Condensation reaction requires energy and ATP synthase
- Phosphorylation
How is ATP hydrolysed?
- ATP → ADP + Pi
- Dephosphorylation
- Catalysed by ATPase
What are the roles of ATP?
- Metabolic processes
- Synthesise molecules
- Movement
- Active transport
- Molecule activation
What is the structure of a chloroplast?
- Double membrane filled with fluid known as the stroma.
- Membrane consists of fluid filles flattened sacs known as the thylakoids
How is the structure of a chloroplast related to its function?
- 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.
What happens in the light dependent reaction?
-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.
How does the structure of the grana relate to its function?
- Grana formed from layers to increase SA for light absorption
- Thylakoid membrane contains chlorophyll to absorb light
What is photolysis?
- Light energy breaking bonds between oxygen and hydrogen in water
- Produces 2H+ ions, 2 elections and one oxygen atom
What happens in non-cyclic photophosphorylation?
- 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
What happens in cyclic photophosphorylation?
- 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
What products of the light dependent reaction are used in the light independent reaction?
- Reduced NADP
- ATP
What do membrane proteins do?
- For electron transport
- Move hydrogen ions across thylakoid membrane for ATP production
What happens in the light independent reaction?
- Uses the products of ATP and reduced NADP from the light dependent reaction to form glucose.
How does chemiosmosis in the light dependent reaction catalyse the production of ATP?
- 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
What are the steps of light independent reaction?
- 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
What is the role of RUBISCO?
- 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
How much GALP is used in generation of organic molecules
- For every 6 GALP, one organic molecule is produced
What is GP used to produce?
- Amino acids (protein synthesis)
- Fatty acids (lipid molecules)
What is GALP used to produce?
- Hexose sugars eg. glucose
- Glycerol
- Nucleic acids
What happens to the growth of plants if there is an increase in CO2?
- 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
How does GP synthesise starch?
- 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
What is a population?
- All the individuals of one species in the same habitat
What is a community
- All the populations living in the same area.
What is an ecosystem?
- A community and its interactions with the non living (abiotic) and living (biotic) factors
What is an abiotic factor?
- Non living factors
- Eg. temperature, light intensity, pH
What is a biotic factor?
- Living factors
- Eg. predation, food availability
What is a niche?
- The way a species ‘uses’ its environment and interacts
What are examples of a species role (niche)?
- What it eats
- What time it is active
- Where in a habitat it lives
Why must two species not occupy the same niche?
- Creates competition for resources
- Out-compete each other causing one to die out in that habitat
What is abundance?
- The number of individuals of a species living in a habitat
What is distribution?
- Where a species lives
What is Gross primary productivity (GPP)?
- Total quantity of all energy in biomass.
What is net primary productivity (NPP)?
- Total energy store after losses from respiration are accounted.
What is the equation for NPP?
- NPP = GPP - respiration
What does primary productivity depend on?
- Amount of sunlight energy
- Ability of producers to use energy to synthesise organic compounds
- Availability of other factors for growth of producers.
Why is the transfer of energy not 100% efficient?
- Energy is lost due to faeces, urine + respiration.
What is a trophic level?
- The stage in a food chain
What are producers?
- Organism which uses sunlight to photosynthesise and make their own energy
What is the equation for biomass percentage efficiency?
% efficiency = energy after transfer/energy before transfer x 100
Why is energy lost between trophic levels?
- Not every single part is consumed eg. bones
- Unable to digest all they ingest
- Excretory materials
- Energy lost via heat in respiration
Why can’t all the suns light energy be absorbed?
- Not all wavelengths can be used and absorbed
- May not fall on chlorophyll
- Sun gets reflected
- Limiting factors eg. low CO2, temperature
What is succession?
- Processes that occur over time in a species to replace each other
What is primary succession?
- Colonisation of bare rock or barren terrain by living organisms, beginning an ecosystem
What is the process of succession?
- 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.
Why does succession change the abiotic and biotic conditions?
- New colonising species change the environment so it becomes less suitable for the previous species
What are the common features of succession?
- Abiotic features are less hostile
- Increase in biodiversity
- Greater number of habitats and niches
- More complex food webs so increased biomass
What is secondary succession?
- Recolonisation of an area after earlier community is removed/destroyed
What is deflected succession?
- Human halt of succession as ecosystem is prevented from developing further. (plagioclimax)
What is the pattern of growth of species?
- 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
What is a carrying capacity?
- It is the maximum population size that can be maintains over a period in a habitat
What limiting factors slow the rate of natural processes?
- Temperature
- Light
- Water
- Predation
- Parasites
What is sustainability?
- Meeting demands of today without compromising the future
How can humans help sustainability?
- Replanting trees
- Ensure ecosystems are functional
- Local people have to be benefited.
What happens in the carbon cycle?
- 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.
What evidence is there for climate change caused by human activities increasing the concentrations of greenhouse gases?
- 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
What is a greenhouse gas?
- Gas that absorbs re-radiated radiation to trap it in its earths atmosphere contributing to the greenhouse effect
What is the greenhouse effect?
- 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
How can studying pollen grains in peat bogs provide evidence for climate change?
- 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
How does dendrochronology show changes to climate over the years?
- Tree trunks grow in diameter each season as they produce more vascular tissue
- Trees grow faster when conditions are warmer
Why are anthropogenic emissions of greenhouse gases affecting the climate?
- Human activity such as deforestation and burning fossil fuels
- Increase amount of CO2 or methane
- Mean increase in surface/atmospheric temp
What is extrapolation?
- Using existing data to make predictions about what will happen in the future
What are the limitations to climate change models based on extrapolated data?
- 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
What effect does climate change have?
- More extreme weather events
- Changes to ocean currents which alters local climate
- Change in rainfall pattern
What is the evidence for changes in climate patterns due to climate change?
- warming climate cause species migration
- water availability in habitats changing
- seasonal cycles changing
- polar ice and glaciers retreating
- sea levels rising
What effects do higher temperatures have on enzyme reactions?
- Reactions speed up
- More kinetic energy
- More enzyme-substrate complexes as collide more frequently
What happens when an enzyme is denatured?
- Weakened hydrogen and ionic bonds so they start to break
- Permanently damages the active site, preventing substrate from binding
How can we reduce carbon emissions?
- Biofuels over fossil fuels
- Renewable energy sources
What are the pros + cons of renewable energy?
Pros - cheaper and efficient, no CO2 released
Cons - Dependent on natural processes, visual damage
What are the pros + cons of biofuels?
Pros - Made of biomass, cheaper than oil, renewable, carbon neutral
Cons - Vast amount of land needs to be grown, loss of biodiversity
