3.5 Energy Transfers Flashcards
What is the role of producers and how is it limited?
Plants photosynthesise and form biological molecules to form biomass
Limited:
•not enough light hitting the chlorophyll
•light can be reflected off
•different wavelengths of light
How can biomass be measured?
•mass of carbon
•dry mass of tissue per given area, where its chemical energy is measured using calorimetry
How is energy lost between trophic levels?
•lost by respiration
•excretion where energy contained in faeces and urine is transferred to decomposers
•not all parts are digested = egestion
(Cannot sustain many trophic levels)
What is Gross and Net primary production? (+equation)
GPP= The chemical energy store in plant biomass, in a given area or volume, resulting from photosynthesis
NPP= The chemical energy store in the plant biomass, taking into account the energy lost due to respiration. (Represents dry mass of C)
NPP=GPP-R
What is the equation for net production of consumers?
N= I - (F + R)
I:chemical energy store in ingested food
F:chemical energy lost to environment in faeces/urine
R:respiratory losses
Why is rate of production measured in KJ ha-1 year-1?
•per unit area to standardise, allowing environments to be compared as it takes into account different environments will vary in size
•per year to take into account the impact of seasons on weather, providing an annual average to allow fair comparison between environments
What methods are used in intensive farming?
•temperature controlled so less respiration to maintain body temp.
•limited space so restricted movement so less respiration
•controlled nutrients/high protein
(Less biomass is wasted in respiration)
What are the disadvantages of intensive farming?
•infectious diseases can spread quickly so lots of antibiotics used which increases risk of antibiotic resistant bacteria
•unethical as animals get stressed
Why is the biomass of the primary consumer higher than the producer (sometimes in a pyramid)?
Producers are reproducing slower than they are being consumed
Why is intensive farming produce cheaper?
•faster rate of growth
•high survival rate so more plentiful food supply
Why does higher biodiversity compared to monoculture cause higher food yields?
•pests tend to be specific so will not destroy all crops
•different species have different root length so less competition for e.g water/mineral nutrients
Why does crop rotation lead to high crop yields?
•soils can regain mineral nutrients by e.g planting legumes (N-fixing bacteria)
•less spread of disease as different crops have different diseases
•different plants use different minerals so continued growth
What is nitrogen fixing?
Nitrogen fixing bacteria e.g in legumes root nodules will convert N2 gas into ammonium or nitrates
What is nitrification?
Nitrifying bacteria will turn ammonium into nitrites and then nitrates (aerobic conditions)
What is the role of saprobiotic bacteria in the nitrogen cycle?
They will do extracellular digestion to hydrolyse proteins (faeces/urea), forming ammonium (ammonification)
What is denitrification and what conditions does it need?
•Denitrifying bacteria converts nitrates into N2 gas
•waterlogged/poorly aerated (e.g no ploughing) so less O2 = anaerobic conditions
What is mycorrhizae?
•Mutualistic relationship= fungal association between plant roots and beneficial fungi
1.fungi increases SA for water/mineral absorption
2.mycorrhizae holds water/minerals around roots
3.plants is more drought resistant and able to take up more inorganic ions
What is the phosphorus cycle?
•sedimentary rocks are weathered/eroded to release PO4 3- into soils/water
•taken up by producers/consumers
•saprobionts will decompose dead matter/excretions to release into soil/oceans or to form sediment
Why are fertilisers used?
To replace nitrates and phosphate ions in soil, lost when plants are harvested + removed from nutrients cycles as crop
What are the advantages/disadvantages of natural fertilisers?
Ad:•cheaper/free as manure
•less soluble so less risk of leaching
Dis:•exact mineral proportion cannot be controlled
•smells
•unwanted material e.g fungal spores
What are the advantages/disadvantages of artificial fertilisers?
Ad:•control exact proportion of mineral nutrients
Dis: •more water soluble so higher risk of leaching
•expensive
What is eutrophication?
1.nitrogen fertiliser leaches into water
2.nitrates increase growth of algae and make a blanket on surface of water that blocks light
•plants below cannot photosynthesise and will die
•bacteria does microbial respiration as it decomposes dead matter
•decreases O2 content in water so organisms cannot respire and will die
Why do natural fertilisers cause less leaching?
1.made of organic matter
2.which needs to be broken down by microorganisms in soil before
3.it means the release of mineral nutrients is more controlled and it is less likely to be leached into ponds/rivers
What is the light dependent reaction and where does it occur?
In the thylakoid membrane
1.photoionisation=chlorophyll absorbs light energy and an e- is excited, lost and passed onto an e-acceptor
2.the e- will be transferred across an e-transport chain and will release energy in a series of redox reactions in the thylakoid membrane
3.energy is used to actively transport H+ from the stroma to the membrane which produces an electrochemical gradient
4.H+ will diffuse back to the stroma via ATP synthase that will catalyse ADP + Pi = ATP
5.NADPH forms when NADP picks up H+ and an e-
What is photolysis?
Light energy is absorbed by chlorophyll to split water into H+ , e- and O2
•chlorophyll will become oxidised as it loses e-
What is the light independent reaction?
Calvin cycle=
1.CO2 reacts with RuBP to from 2x GP. Catalysed by rubisco
2.ATP = ADP + Pi to release energy and NADPH release H+ and e- which are needed to reduce GP to triose phosphate
3.some triose phosphate is used to regenerate RuBP and some is converted to useful organic substances
4.This occurs in the stroma
Why does the Calvin cycle slow down when there is low light energy?
•less NADPH and ATP will form in the light dependent reaction
•so less GP converts into Triose phosphate
•less RUPB is regenerated to join with co2
Where and what occurs in glycolysis?
•cytoplasm
•phosphorylation of glucose to glucose phosphate, using x2 ATP= ADP
•2 triose phosphate are made
• x2 TP is oxidised to pyruvate (2x ADP +Pi = ATP and NAD to NADH)
What is the net gain in glycolysis?
2 ATP
2 NADH
2 pyruvate
Where and what happens in the link reaction?
•mitochondrial matrix
•pyruvate (3C) is oxidised to acetate
(2C)(NAD to NADH) by releasing CO2
•acetate will combine with coenzyme A to form acetyl coenzymeA (2C)
What is the net gain in the link reaction?
2 NADH
2CO2
2 acetyl coenzyme A
Where and what happens in the kreb’s cycle?
•mitochondrial matrix
•acetyl coenzyme A (2C) reacts with 4C to form 6C compound.
•The 6C is decarboxylated and dehydrogenated
•6C into 5C by loss of CO2 and NAD being reduced to NADH
•5C to 4C by loss of CO2, 2NAD into 2NADH, FAD into FADH and forming of ATP
What is the net gain in the Kreb’s cycle?
•2 ATP
•6 NADH
•2 FADH
•4 CO2
What occurs in oxidative phosphorylation?
•NADH/FADH is oxidised and releases an e- which is transferred to e- carriers in the inner membrane
•the e- are passed down a chain of e- carriers in a series of redox reactions, releasing energy
•this energy is used to actively transport H+ from the matrix to the intermembrane space (electrochemical gradient)
•H+ move back to matrix via ATP synthase, which catalyses ATP from ADP + Pi
•O2 is the last e- acceptor and will combine with H+ and e- to form H2O (recycles NADH and FADH)
What happens in anaerobic respiration and where?
Cytoplasm:
•Pyruvate formed in glycolysis is reduced to from ethanol/CO2 (plants) or lactate (animals) by gaining H from NADH
•NAD can be reused in glycolysis so ATP production continues
Why is anaerobic respiration useful and why can it not continue for long?
When no O2 is present, ATP is still released but lots of lactic acid/ethanol can denature enzymes in glycolysis
How can lipids and proteins be used as substrates in respiration?
Lipids:
•3C glycerol enters glycolysis to be converted to pyruvate
•fatty acids = 2C to from acetyl coA
Proteins:
•amino group in aa is removed (deamination), so C part of aa can be converted to pyruvate or enter kreb’s cycle
Why are lipids and carbs preferably used in respiration over proteins?
Many proteins have essential structural functions in body, so breakdown can cause health problems and even death
What happens to lactate after production?
•oxidised back to pyruvate to enter link
•converted to glycogen for storage in liver
Why is the apparatus left for 10 mins to calibrate in a respirometer?
1.reach equilibrium
2.allow for pressure change in apparatus
3.allow for respiration rate to stabilise
Why does aerobic respiration yield fewer ATP than maximum theoretical yield?
•some ATP used to actively transport pyruvate into mitochondria
•some energy is lost in the e- transport chain as heat
•not all NADH is fed into the e- transport chain
Why is having more cristae useful?
•increased SA for more enzyme activity so higher rates of oxidative phosphorylation so more ATP synthesised
