Topic 5 Flashcards
Light dependent reaction
- uses light energy to make ATP and NADPH
- takes place in the thylakoid membrane
- also called photophosphorylation
Light independent reaction
- uses products of light dependent reaction to make organic compounds
- takes place in the stroma
- called the Calvin cycle
Parts of a chloroplast
- lamellae
- Chloroplast DNA
- grana: stack of thylakoids
- thylakoid: Large SA, site of light dependent reaction
- starch grain: insoluble, no affect on water potential
- stroma: site of independent reaction
Stages of light dependent reaction
- called photophosphorylation
- photosynthetic pigments absorb light energy
- exists an electron that leaves the chlorophyll in P.S.1 (photoionisation)
- electrons move along the electron transport chain
- electron releases energy
- this energy is used to join ADP+Pi
- NADP is reduced to form NADPH
- photolysis of water produces protons, electrons and oxygen
Light independent reaction
Calvin cycle:
- CO2 combines with RuBP catalysed by the enzyme rubisco
- makes 2 molecules of GP
- both GP are reduced to for 2xTP - from 2xNADPH, 2xATP
- most TP is regenerated to form RuBP - using energy from ATP
- some of the TP is converted into useful organic compounds
Limiting factors of photosynthesis
- Light intensity
- CO2 concentration
- temperature
Light intensity as limiting factor
- the higher the light intensity the more energy there is for LDR so the faster the rate of photosynthesis
- light needs to be the right wavelength (looks green because the reflect green but absorb blue and red)
- different pigment absorbs different wavelengths
(Use light at night, green house allows light to pass in)
CO2 concentration as limiting factor
- CO2 is commonly the limiting factor
- CO2 is about 0.04% of atmosphere
- optimum CO2 concentration = 0.4%
- above 0.4% co2 has a negative effect on rate of photosynthesis
(Burn fossil fuels in a greenhouse, increase CO2 concentration)
Temperature as the limiting factor
- photosynthesis is controlled by enzymes
- if you increase temperature you increase the rate of reaction up to the optimum temperature
- beyond the optimum temperature the rate decreases
- high temperature causes stomata to close, low CO2 therefore low Calvin cycle
(Burner increases temp, greenhouse traps warm air, heating/ cooling to maintain optimum temp)
Aerobic respiration
- needs oxygen
- more efficient (more ATP per molecule of glucose)
- complete breakdown of glucose to form CO2, ATP
- slow
- glycolysis, link reaction, Krebs cycle, oxidative phosphorylation
Anaerobic respiration
- doesn’t need oxygen
- less efficient
- incomplete break down of glucose (makes harmful waste products)
- animals and bacteria = lactic acid
- plants and yeast = ethanol
- fast
- glycolysis
Glycolysis
- takes place in cytoplasm
- anaerobic
- net yield is 2ATP, 2NADH
- glucose is phosphorylated by adding ATP (glucose - glucose phosphate - hexose bisphosphate)
- triose phosphate is oxidises to form pyruvate
- pyruvate is actively transported into mitochondria for link reaction
Link reaction
- pyruvate is dehydrogenated and decarboxylated to form acetate
- in matrix of mitochondria
- acetate combines with coenzyme A to form acetyl coenzyme A
- products: per reaction = 1xCO2, 1xNADH/ per glucose = 2xCO2, 2xNADH
Krebs cycle
- matrix of mitochondria
- Acetyl COA joins a 4C compound to form a 6c compound
- coenzyme A is recycled (link reaction)
- 6C to 5C = decarboxylation
- dehydrogenation
- Substrate level phosphorylation = creation of ATP without ATP synthase, phosphate is added to ADP from another molecule
- lipids/ proteins can also be respired aerobically
- products per cycle = 3xNADH, 1xATP, 1xFADH, 2xCO2
Oxidative phosphorylation
- electrons and protons are released from reduced co enzyme = NADH (e-+H++NAD)/ FADH (e-,H++FAD)
- electrons flow along the electron transport chain in a series of redox reactions
- electrons release energy which is used to join ADP+Pi
- oxygen is the final electron acceptor (combines with electrons and protons to form water)
- oxidative phosphorylation makes most of the ATP in aerobic respiration
Anaerobic respiration - glycolysis in mammals and bacteria
Lactate fermentation:
glucose -(ATP-ADP)- glucose phosphate -(ATP-ADP)- hexose biosphosphate - 2xTP -(2ADP+Pi-ATP, NAD-NADH)- 2xPyruvate -(NADH-NAD) 2xLactate
Anaerobic respiration - glycolysis in plants and yeast
Alcoholic fermentation:
Glucose -(ATP-ADP)- Glucose phosphate -(ATP-ADP)- Hexose biosphosphate - 2TP -(2ADP+Pi-ATP, NAD-NADH)- 2Pyruvate -(-CO2)- 2Ethanal -(NADH-NAD)- 2Ethanol
Anaerobic respiration - glycolysis
- takes place in the cytoplasm
- less effeicient produce of ATP than aerobic respiration
- NAD is needed for glycolysis
- NAD is regeerated by reduced pyrivate
- mammals and bacteria = pyruvate - lactate
- yeast and plants = pyruvate - ethanal - ethanol
Why is there less ATP in anaerobic respiration
- products aren’t totally respired
- they still have chemical energy
- no oxygen as the final electron acceptor (no other stages of aerobic)
Why is there more CO2 produced in anaerobic respiration
- need a minimum amount of ATP to do metabolic processes
- only respire anaerobically you need to use more glucose to make necessary amount of ATP
- therefore you make more CO2 and more waste products as a result
- so less efficient
Respiratory substrate reaction
respiratory substrate +O2 > (many reactions catalysed by intra cellular enzymes) > H2O + CO2 + energy
Respiratory substrate reactions
- Carbohydrates = glucose (glycolysis - link reaction - acetyl COA - Krebs cycle - oxidative phosphorylation)
- lipids = triglycerides (acetyl COA - Krebs cycle - oxidative phosphorylation)
- proteins = amino acids (acetyl COA - Krebs cycle - oxidative phosphorylation)
Every cell respires
- respiration is essential to life
- ATP is needed for all metabolic processes
- every cell must respire
- minimum amount of ATP needed to maintain metabolism
- different respiratory substances have different energy values = Lipids > protein > carbs
- proteins only respire when there is no lipids or carbohydrates
Parts of a mitochondria
- mitochondrial DNA
- outer membrane
- inner membrane
- cristae: a fold in the inner membrane of a mitochondrion, to increase SA for oxidative phosphorylation
- matrix: link reaction, Krebs cycle
Net primary productivity equation
NPP=GPP-R
- NPP = Net primary productivity
- GPP = Gross primary production
- R = respiratory loss
Calculating energy transfer efficiency
Energy available after transfer/ energy available before transfer x 100
- kJm-2 yr-1
Net production equation
N=I-(R+F)
- N = net production
- I = total energy ingested
- R = Respiratory loss
- F = Faeces and Urine
Energy transfer - Sun
- very low
- long wavelength
- light hits non photosynthetic region
- light reflected
- lost as heat
Energy transfer - producer
- low
- respiratory loss (plant uses energy for metabolism
- lost as heat
- not all the plant may be eaten
- some food is not digested
Transfer efficiency - primary producer
- low
- respiratory loss (primary consumer uses energy for metabolism)
- lost as heat
- not all of the animal is eaten
- some of the food is digested
Energy transfer chain
Sun - (2%) - producer - (10%) - primary producer - (10-15%) - secondary producer
Energy transfer efficiency
- especially low for: old animals, herbivores, homeotherms, endotherms
Increasing energy transfer efficiency - plant crops
- shorten food web, reduce competition so the plant has energy to create biomass. (Herbicides, kill weeds. Fungicide, reduce fungal infections. Insecticide, chemical control of pests)
- fertilisers prevent growth being limited by lack if nutrients
Increasing energy transfer efficiency - animals/ likestock
- reduce respiratory loss (restrict movement = less respiration. Keep warm in winter = less respiration)
- slaughter animal while still growing
- keep predators away
- controlled diet = higher % of their food will be digested
Increasing energy transfer efficiency - plant and animals
- artificially select organisms with a high yield
Measuring dry biomass
- a sample of biomass is warmed on a scale until the mass remains constant (all water has evaporated)
- temperature must be low to avoid combustion
- amount of water in samples varies a lot (dry biomass gives a more representative sample)
- units: Kgm-2
Measuring mass of carbon
- organisms are made from organic compounds
- mass of carbon is a good indicator for biomass
- difficult to measure
- carbon is usually about 50% of the dry biomass
- units: Kgm-2 yr-1
Calculating energy stored in biomass
- burn a sample of biomass completely
- heat a known volume of water
- measure the temperature change of water
- calculate energy released
Nitrogen cycle stages
- ammonification
- nitrification
- nitrogen fixation
- denitrification
Nutrient cycle
- nutrients are taken up by producers as simple organic molecules
- producers incorporate the nutrients into the complex organic molecules
- producer is eaten and nutrients pass to the consumer
- nutrients pass along the food chain when animals are eaten by consumer
- producer and consumer die the complex molecules are broken down by saprobiontic microorganisms
Plants recycling nutients
- increases surface area of the roots
- increase the absorption of rare minerals and water
Fungi recycling nutrients
Plants exchange these for organic compounds
Fertilisers
- still need breaking down by saprobiotics
- slows release of Nitrogen and phosphate
- Benefits: aerate soil, less leaching, contain a wider range of elements, consume less energy
Leaching
- when soluble compounds are washed off land by rain
- more common in artificial fertilisers
- rainwater dissolves soluble nutrients
- carried deep into the soil, beyond the roots
- enter the watercourse
Eutrophication
Process by which nutrient concentrations increases in water
1) nitrate/ phosphate ions leach into fresh water
2) algal bloom
3) blocks out the light
4) plant can’t photosynthesise - die
5) sabrobionts break down dead plants
6) respire aerobically - use up oxygen/ increase demand
7) oxygen concentration decreases as nitrates increase
8) oxygen become limiting factor so fish etc die
9) without aerobic organisms less competition for anaerobic organisms
10) anaerobic organisms further decompose dead material releasing more nitrate and toxic waste
Harvesting crops/ livestock
- removes N and P from their cycles
- soil N and P becomes depleted
- add fertiliser to replace N+P
- too much fertiliser can be harmful eg change water potential
Phosphorus cycle
- phosphorous ions in the form of sedimentary rock deposits
- weathering and erosion of rocks helps phosphate ions to become dissolved and available for absorption by plants
- excess phosphate ions are excreted and accumulate in waste material
- when plants and animals die, decomposers break them down releasing phosphate ions into water or soil
- some phosphate ions will remain in bones and shells, which take longer to break down
- dissolved phosphate ions are transported by streams and rivers to lakes and oceans and form sedimentary rocks
Ammonification
- production of ammonia from organic nitrogen containing compounds
- compounds: Urea, protein, nucleic acid, vitamins
- saprobiontic microorganisms feed on faeces/dead organisms releasing ammonia, leading to the formation of ammonium ions in the soill
Nitrification
- bacteria obtain their energy from chemical reactions involving inorganic ions
- one reaction is the conversion of ammonium ions to nitrate ions > oxidative reaction, which releases energy
- bacteria area called nitrifying bacteria
- the conversion occurs in two stages: oxidation of ammonium ions to nitrite ions, oxidation of nitrite ions and nitrate ions
- oxygen is required for these reactions, they require soil with many air spaces
Nitrogen fixation
- nitrogen gas converted into nitrogen-containing compounds
- this can occur industrially or naturally when lightning pass through the atmosphere
- two microorganisms: free-living and mutualistic
- free living: reduces gaseous nitrogen to ammonia, used to manufacture amino acids
- mutualistic: live in nodules on the roots of plants, obtain carbohydrate from plants, plant acquires amino acids from bacteria
Denitrification
- when soil is waterlogged and has a low oxygen concentration, the type of microorganism present changes
- fewer aerobic nitrifying and nitrogen fixing bacteria and an increase in anaerobic denitrifying bacteria
- these bacteria convert soil nitrates into gaseous nitrogen, reduces the availability of nitrogen for plants
Mycorrhizae
- mutual symbiotic associations between certain fungi and the roots of the vast majority of plants
- the fungi acts like extensions of the roots increasing surface area for absorption
- they hold water and minerals around the roots
- helps to survive droughts
- mutualistic as plant receives water and inorganic ions from fungi and fungi receives organic compounds from the plant
Organic fertilisers
- contain dead and decaying remains of plants and animals
- can also contain manure, slurry and bone meal
Inorganic fertilisers
- mined from rocks and deposits
- converted into different forms and blended together to give different quantities of minerals for specific crops
- compounds containing nitrogen, phosphorus and potassium are always present
- mixture of the two gives the greatest impact and greatest increase in productivity
- an increase in minerals will not impact productivity
How do fertilisers increase productivity
- nitrogen required for amino acids, ATP and nucleotides in DNA, needed fo plant growth
- nitrate ions are in good supply, plants develop earlier, grow taller and leaves have a greater surface area. Increase photosynthesis and improve crop productivity
Negative effect of fertilisers
- reduced species diversity
- leaching
- eutrophication
Reduced species diversity from fertilisers
- nitrogen rich soil: favour growth of grasses, nettles ad other rapidly growing species
- species then outcome other species, causing them to die
- for an area to be species rich: nitrogen levels need to be sufficiently high, but low enough so that other species can compete
Leaching problems
- lower concentrations available to plants
- enter watercourse that are drinking sources, prevent efficient oxygen transport in babies, cause stomach cancer in humans
