energy transfers in and between organisms 3.5 Flashcards
aqa a level biology
what reaction occurs in the thylakoid?
light dependent reaction
what reaction occurs in the stroma?
light independent reaction
what are the four stages of LDR?
photolysis , photoionisation of chlorophyll, chemiosmosis and production of ATP and reduced NADP
what happens in photolysis of water?
- light energy absorbed by chlorophyll splits water into oxygen electrons and H+ ions
- H+ ions picked up by NADP to form reduced NADP and used in LIR
- electrons pass along chain of electron carrier protein
- oxygen is either used for respiration or diffuses out of stomata
what happens in photoionisation of chlorophyll?
- light energy absorbed by chlorophyll results in electrons becoming excited and raising an energy level to leave chlorophyll
- therefore chlorophyll ionised by light
- some of the energy released from electrons is used to make ATP and reduced NADP in chemiosmosis
what happens in chemiosmosis?
- electrons that gained energy and left the chlorophyll move along a series of proteins embedded within the thylakoid membrane
- as they move along they release energy and some of this energy is used to pump protons across the chloroplast membrane (stroma to thylakoid membrane)
- an electrochemical gradient is created, the protons pass through the enzyme ATP synthase via facilitated diffusion resulting in the production of ATP (phosphorylation of ADP)
- the proton comes back to stroma which then combines with co enzyme NADP to form reduced NADP
what enzyme is required in the Calvin cycle (LIR)?
RuBisCo
what happens in the LIR?
- CO2 reacts with 5C RuBP to form two molecules of 3C GP this reaction is catalysed by RuBisCo
- GP is reduced to TP using ATP energy and by accepting a H from reduced NADP
- one carbon from TP leaves cycle to be converted to useful organic substances
- rest of TP is regenerated back to RuBP with the use of ATP
what are the limiting factors of photosynthesis?
light intensity carbon dioxide and temperature
what are plants in the ecosystem?
producers
how can biomass be measured?
mass of carbon or dry mass of tissue remaining per given area
what is gross primary production?
chemical energy store in plant biomass in a given area or volume (total energy resulting from photosynthesis)
what is net primary production?
chemical energy store in plant biomass taking into account the energy that will be lost from respiration
what is the equation between GPP NPP and respiration?
NPP = GPP - R
what is NPP available for?
energy left over that is available for next trophic level to create new biomass and for plant growth/reproduction
what is the net production of consumers equation?
N = I - (F + R)
what does each letter stand for in N = I - (F + R)
N = net production of consumers
I = chemical energy store in ingested food
F = chemical energy lost to environment (faeces)
R = respiration loss
what are rates of productivity units?
kJ unit area-1 year-1
(unit area can be ha,m etc)
what does each symbol mean in the rates of productivity units?
kJ = units for energy
unit area to standardize the results so different areas can be compared
per year to take into account impact of each season provides average
what happens in ammonification?
saprobionts break down organic matter to ammonia and hydrolyse conplex proteins into amino acids etc
what are saprobionts?
bacteria and fungi that live on dead organisms and feed on them by extracellular digestion
what happens in nitrification?
nitrifying bacteria convert ammonia to nitrite than nitrates
what happens in denitrification?
when nitrate ions are converted into nitrogen gas by denitrifying bacteria
what happens in nitrogen fixation?
when nitrogen gas is converted to ammonia ions which dissolve to form ammonium ions to make nitrogen useable by plants
when does denitrification happen?
it wet areas with little oxygen (anaerobic areas)
how to calculate efficient energy transfers
energy after transfer/energy before transfer x 100
where is phosphorus released?
from sedimentary rocks as a result of weathering etc
what is mycorrhizae?
fungi associated between plant roots and beneficial fungi
why are mycorrhizae important?
- fungi increases surface area and mineral absorption
- hold water and ion around the roots
- makes plants drought resistant and able to take up more inorganic ion
what is the relationship between plants and myccorhizae?
mutualistic
why are fertilisers used?
to replace nitrates and phosphates lost in harvestation and removed from nutrient cycle
name a natural fertiliser
animal manure
name an artifical fertiliser
inorganic chemicals
what are the pros and cons of natural fertiliser?
+ very cheap
- unable to control proportion
what are the pros and cons of artifical fertiliser?
+ contain exact amounts of minerals
- very expensive
- very soluble so ions dissolve into surrounding waters of soil (impact of environment)
what are the environmental impacts of artifical fertilisers?
leaching and eutrophication + reduced species diversity
what is leaching?
when water soluble compounds are washed away into rivers and ponds etc
what is eutrophication?
- nitrates leached into pond increase growth of algae
- blocks light and so therefore less photosynthesis so plants die
- saprobionts feed and respire aerobically from dead plants
- use up majority of water so not enough oxygen for fish and other organisms so they die
what are the four key stages for aerobic respiration?
glycolysis
link reaction
krebs cycle
oxidative phosphorylation
where do the four key stages of aerobic respiration occur?
glycolysis - cytoplasm
link reaction - miochondrial matrix
krebs cycle - mitochondrial matrix
oxidative phosphorylation - mitochondrial cristae
what are the steps of glycolysis?
- glucose is phosphorylated to form glucose phosphate using 2xATP
- glucose phosphate converted to triose phosphate
- triose phosphate oxidised to produce pyruvate by dehydrogenase enzyme
- this also forms ATP and NADH
what are the products of glycolysis?
2 x pyruvate
net gain of 2 x ATP (4 produced)
2 x NADH
what happens in the link reaction?
- pyruvate actively transported to matrix
- it is oxidised to form acetate and CO2
- acetate combines with coenzyme A to form acetylcoenzyme A
what are the products of link reaction?
2 x acetylcoenzyme A (CoA)
2 x CO2
2 x NADH
what happens in the Krebs cycle?
- acetylcoenzyme A combines with 4C oxaloacetate to form 6C citrate
- 6C citrate decarboxylated using decarboxylase enzyme removing CO2
- also H is removed by dehydrogenase enzyme and that is used to form NADH
- 5C compound goes through same thing
- 4C compound formed and is changed to another 4C compound
, ADP is phosphorylated to form ATP - 4C compound is dehydrogenated twice each H used to form FADH and NADH
- 4C oxaloacetate regenerated so krebs cycle can continue
what are the products of kreb cycle PER cycle?
1x ATP
3x NADH
1x FADH
2x CO2 released
what are the products of krebs cycle for each glucose overall?
2x ATP
6x NADH
2x FADH
4x CO2 released
what happens in oxidative phosphorylation?
- NADH and FADH are oxidised, H removed by dehydrogenase enzyme
- this H splits into protons and electrons
- electrons pass along the electron transfer chain and release energy
- this energy used to pump protons from matrix into intermembrane space
- electrochemical gradient is set (higher conc in intermembrane space)
- protons diffuse down electrochemical gradient through ATP synthase channel
- ADP + Pi -> ATP (phosphorylated)
- final accepter is oxygen and combines with electrons and protons to form water (chemiosmosis)
what is produced in anaerobic respiration in plants and animals?
ethanol and carbon dioxide (plants)
lactate (animals)
what happens in anerobic respiration?
pyruvate reduced to lactate to produce NAD which is used in glycolysis again
what type of muscle is a skeletal muscle?
antagonistic
what is the structure of myofibrils?
sarcomere
sarcoplasm
sarcolemma
sarcoplasmic reticulum
what proteins are myofibrils made off?
actin and myosin (form sarcomeres)
what is the sliding filament theory?
- when action potential reaches a muscle fibre it triggers Ca2+ release from sarcoplasmic reticulum to sarcoplasm
- Ca2+ binds to tropomyosin causing it to move and expose actin binding site
- with ADP and Pi still attached myosin head binds to actin binding site forming actinomyosin cross bridge
- once cross bridge forms myosin head bends pulling actin filament along (power stroke) releasing ADP + Pi and causing actin to slide over myosin
- a new ATP molecule binds to myosin head causing it to detach from actin filament
- within sarcoplasm ATPase hydrolyses ATP into ADP and Pi the energy released is used to reposition myosin head into original state
- if Ca2+ levels remain high cycle continues and when simulation stops Ca2+ actively transported back into sarcoplasmic reticulum and tropomyosin blocks binding sites again
what key roles do ATP have in sliding filament theory?
- break actinomyosin bridges
- to move/bend myosin heads
- for active transport of Ca2+ ions back into sarcoplasmic reticulum
what is the role of phosphoceratine in sliding filament theory?
if not enough ATP, phosphoceratine acts as rapid ATP source donating phosphate group to ADP ensures ATP produced in intense activity
what is the role of glycogen granules in skeletal muscles?
- store of glucose
- glucose used as respiratory substrate to provide ATP
what is the role of Ca2+ ions in muscle contraction?
bind to tropomyosin to expose binding sites on actin
what is the A band in sarcomere?
distance of myosin
what are Z lines in sarcomere?
start and end points
what is I band in sarcomere?
section of actin NOT overlapping with myosin
what is the H zone in sarcomere?
section of myosin with NO overlaps with actin
what happens when a muscle contracts?
H zone and I band decreases and Z lines come closer together
what are slow twitch fibres?
they contract slower to sustain aerobic respiration
produce ATP slowly but more ATP per glucose
large supply of myoglobin, lots of blood supply and mitochondria
for marathon running
what are fast twitch fibres?
contract faster for short bursts of energy powerful contractions
produce ATP faster but less ATP per glucose
uses anaerobic respiration
thicker more myosin filaments, large glycogen store and store of phosphoceratine
what is the neuromuscular junction?
where motor neurone meets skeletal muscle
what happens when an nerve impulse reaches skeletal muscle?
- nerve impilses arrives at presynaptic neurone
- depolarisation of membrane occurs
- Ca2+ channels open causes synaptic vesicles to diffuse and fuse with the membrane
- ACH is released and binds to receptors on sarcolemma
- Na+ channels open and Na+ diffuse in sarcolemma depolarise creates AP
- AP leads to voltage gated Ca2+ in membrane of sarcoplasmic reticulum
- Ca2+ diffuse out of sarcoplasmic reticulum
- enables muslce contraction
differences between neuromuscular and choligernic synapse?
neuromuscular is only excitatory and is the end point unlike choligernic
