energy transfers in and between organisms Flashcards
where does LDR take place?
thylakoid membrane
where does LIR take place?
stroma
stages of LDR
- photolysis
- photoionisation of chlorophyll
- chemiosmosis
- production of ATP and NADPH
photolysis of water
- light energy is abosrbed by chlorophyll
- H2O -> 1/2O2 + 2e- + 2H+
- H+ is used to make NADPH
- e- passed along electron transport chain
- O2 used for respirartion
photoionisation of chlorophyll
light energy absorbed by chlorophyll excites electrons, raising them to a higher energy level, so they leave the chlorophyll
chemiosmosis/ETC in photosynthesis
- electrons move along photosystems
- electrons release energy and some is used to actively transport protons across chloroplast membrane into thylakoid space
- creates electrochemical gradient
- protons pass through ATP synthase which phosphorylates ADP into ATP
- protons phosphorylate NADP to become NADPH
LIR/calvin cycle
- carbon fixation (1c) with RuBP (5c) to form two molecules of GP (3c)
- this is catalysed by the enzyme RuBisCo
- GP is reduced into triose phosphate using 2ATP and oxidising 2NADPH
- 1/6 of triose phosphate carbon is used to make a hexose sugar
- rest of triose phosphate is used to regenerate RuBP using ATP
how many times must the calvin cycle happen to create a hexose sugar?
6
how does structure of chloroplast maximise the rate of LDR?
- ATP synthase channels within granal membrane
- large surface area of thylakoids
- photosystems position chlorophyll for maximum light absorption
how does structure of chloroplast maximise the rate of LIR?
- own DNA and ribosomes for synthesis of enzymes
- concentrations of enzymes and substrates in stroma is high
what is a limiting factor?
factor that can reduce the rate of photosynthesis, determining its maximum rate
limiting factors of photosynthesis
temperature, light intensity, carbon dioxide concentration
why is temperature a limiting factor of photosynthesis?
LIR is an enzyme controlled process, thus tempertaure increases rate until it becomes too high and denatures enzymes and no E-S complexes will be made
why is light intensity a limiting factor of photosynthesis?
light energy is needed in LDR for photolysis and photoionisation
why is carbon dioxide a limiting factor of photosynthesis?
carbon fixation in LIR
argicultural practices to remove limiting factors
- artificial light
- artifical heat
- addition of CO2
stages of aerobic respiration
- glycolysis
- link reaction
- krebs cycle
- oxidative phosphorlyation
process of glycolysis
- phosphorylation of glucose to make glucose phospahte, using ATP
- production of triose phosphate
- oxidation of triose phosphate to produce pyruvate using 2ATP and 2NADH
where does glycolysis occur?
cytoplasm
products of glycolysis
- 2 pyruvate
- net gain of 2 ATP
- 2 NADH
process of link reaction
- pryvuate and NADH are actively transported from cytoplasm into mitochondrial matrix
- pyruvate is oxidised into acetate, losing one molecule of carbon
- NAD is reduced
- acetate combines with coenzyme A to produce acetylcoenzyme A
where does the link reaction occur?
mitochondrial matrix
products of link reaction
- 2 acetyl CoA
- 2 CO2 released
- 2 NADH
process of krebs/citric acid cycle
- acetyl CoA reacts with oxaloacetic acid (4c), releaseing coenzyme A and producing citric acid (6c)
- in a series of redox reaction, krebs generates NADH, FADH, ATP (by substrate level phosphorlylation) and loses CO2
where does krebs occur?
mitochondiral matrix
products of krebs
per glucose
- 6 NADH
- 2 FADH
- 2 ATP
- 4CO2
process of oxidative phosphorlylation/electron transport chain
- H+ from coenzymes are oxidised into protons and electrons
- electrons pass through ETC
- when they pass through proteins they release energy for protons to move into intermembrane space
- this creates an electrochemical gradient where there is a high conc. of protons in IMS
- protons move down conc. gradient through ATP synthase by facilitated diffusion
- this phosphorylates ADP into ATP
- oxygen is the final electron acceptor
- oxygen picks up protons to create water in respiration
what two molecules can be used as alternative respiratory substrates?
amino acids from proteins
glycerol and fatty acids from lipids
lipids as a respiratory substrate
phosphorylation of glycerol = triose phosphate
fatty acid = acetate
proteins as a respiratory substrate
deamination produces 3c compounds (pyruvate) and 4c/5c compounds (krebs)
where does anaerobic respiration take place?
cytoplasm
process of anaerobic resipiration in animals
- glycolysis
- pyruvate is reduced to form lactate by gaining H+ from NADH
- oxidises NAD so it can be reused in glycolysis so more ATP is reduced
process of anaerobic respiration in plants
- glycolysis
- pyruvate is reduced to form ethanol and carbin dioxide by gaining H+
- oxidises NAD so it can be reused in glycolysis so more ATP is reduced
dangers of lactate
lactic acid build up causes muscles to fatigue and denaturation of enzymes (acidic pH)
dangers of ethanol
dissolves cell membranes
biomass
total dry mass of a tissue or carbon measured over a given time in a specific area
how do plants use sugars from photosynthesis?
- respiratory substrates
- synthesis of biological molecules (cellulose)
how can the chemical energy store in dry biomass be estimated?
calorimetry
what is GPP?
gross primary production- total chemical energy in plant biomass in a given area or volume
what is NPP?
net primary production- total chemical energy available for plant growth, plant reproduction and energy transfer to other trophic levels after respiratory losses
mathematical relationship of GPP and NPP
NPP = GPP - R
where R is respiratory losses
why is most of the sun’s energy not converted to organic matter?
- most solar energy is abosorbed by atmosphere or reflected by clouds
- photosynthetic pigments can’t absorb all wavelengths of ligtht
- not all light falls on chlorophyll
- energy lost as carbon dioxide or heat during respiration/photosynthesis
calculation for net production of consumers
N = I - (F + R)
I- chemical energy in ingested food
F- energy lost in excretion
R- respiratory losses
why does biomass decrease along a food chain?
- energy lost to excretion
- not all of an organism is consumed
- energy lost to surroundings as heat (e.g respiration)
primary and secondary productivity
primary and secondary productivity is the rate of primary or secondary production, respectively. it is measured as biomass in a given area in a given time eg kJ ha–1 year–1
farming practices that increase energy transfer
- restriction of movement
- exclusion of predators
- artificial heating
efficiency calculation
energy converted to a useful form (J)/ total energy supplied (x100)
why is the length of food chains limited?
energy is lost at each trophic level so there is insufficient energy to support a higher trophic level
what is phosphorous used for?
DNA/RNA, ATP and phospholipid bilayer
what are mycorrhizae?
fungal associations between plant roots and beneficial fungi that form symbiotic relationships
role of mycorrhizae
- fungi made up of long strands called hyphae that connect to plant roots
- hyphae increase surface area of plant’s roots to absorb more water and ions (phosphorous)
- in turn, fungi obtain organic compounds (glucose) from the plant
phosphorous cycle process
- plants absorb phosphate ions in ocean and soil by active transport (increased by mycorrhizae)
- animals digest this
- some animal excretion containing the ions goes back into the ocean and soil
- other excretion and decomposition goes into guano, bones and shells
- these will erode back into oceans and soil
- some of this will deposit and form phosphate into rocks
- rocks can erode back into ocean (weathering) and addition of fertilisers in land can go into ocean
- sediment from oceans can form rocks containing phosphate ions
what is nitrogen used for?
DNA/RNA, ATP and proteins (amino acids)
role of saprobiotic bacteria
use enzymes to decompose proteins/DNA/RNA/ATP to produce ammonia
stages of nitrogen cycle
- nitrogen fixation
- nitrification
- ammonification
- denitrification
ammonification
- nitrates in soil are actively transported into plants
- assimilated into cells
- animals digest this
- excretion contains ammonia
- when plants and animals die, saprobiotic bacteria digest proteins and DNA and ammonify them
nitrogen fixation
nitrogen fixing bacteria in plant legume root nodules and soil react with atmospheric nitrogen and convert it into ammonium
nitrification
nitrifiying bacteria converts ammonium into nitrites then nitrates
ammonification in nitrogen cycle
- nitrates are absorbed into plants by active transport then assimilated into the cells
- animals will eat the plants
- animals produce waste containing ammonia which can be nitrified
- when animals and plants die, saprobiotic bacteria digest and ammonify proteins, DNA etc
denitrification
denitrifying bacteria in soil convert nitrates back into atmospheric nitrogen
what are the agricultural issues of denitrification?
loss of nitrifying compounds
how to avoid denitrification?
denitrifying bacteria are anaerobic so soil needs to be aerated
two types of fertiliser
natural (manure) and artificial (inorganic chemicals)
evaluation of natural fertiliser
- cheap and often free as farmer owns the animal
- exact minerals and proportions cannot be controlled
evaluation of artificial fertiliser
- know exact proportions of minerals
- water soluble so ions dissolve in soil
- high water solubility can cause leaching
what is leaching?
when water soluble compounds are washed away into rivers and ponds, possibly leading to eutrophication
process of eutrophication
- nitrates leached from fertilised fields stimulate growth of algae in pond
- excessive growth of algae creates an algal bloom which blocks out light
- plants can therefore not photosynthesise and die
- bacteria in water feed and respire on dead plant matter
- results in an increase of bacteria which all respire and use up oxygen
- fish and other aquatic organisms die due to lack of dissolved oxygen in water
why does a respirometer have to be air tight?
prevent air entering or leaving as this will change volume and therefore pressure
why does the liquid in a respirometer move to the left?
- respiring organisms take in oxygen through respiration
- the carbon dioxide it releases is absorbed by potassium hydroxide
- the volume of gas therefore decreases in the experimental tube and pressure is lower
- so the liquid moves to the experimental tube
what units would you use for the rate of respiration in a respirometer?
unit for volume, time and mass
(volume/timexmass)
why must the origin line of chromotography paper be done in pencil?
ink from the pen will dissolve in the solvent and run
why should you measure the rf value from the middle of the pigment?
standardise measurements to allow for comparison
why should chromotography paper be kept verticle?
pigments can move straight up the paper to avoid the running off the side or being washed off
efficiency of energy transfer
energy available after transfer/energy avaialble before transfer x100
how would you measure the biomass of a field of wheat?
- large random sample of wheat
- heat wheat sample in oven
- weigh it
- repeat until the mass is constant (all water is evaporated)
