Topic 5 - Energy transfers Flashcards
state the two stages of photosynthesis
LDR (light dependent reaction)
LIDR (light independent reaction) - also known as the dark reaction
where does LDR occur
thylakoid membrane of chloroplast
where does LIDR occur
stroma of chloroplast
describe the structure of chloroplasts
did you mention:
double membrane (envelope), stoma containing thylakoid membrane, 70s ribosomes, circular DNA, starch granules, lamella, grana
describe photoionisation in the LDR
- chlorophyll absorbs light energy which exites its electrons (higher energy levels)
- so electrons are released from chlorophyll (chlorophyll becomes positively charged)
describes what happens after photoionisation in the LDR
some energy from electrons released in photoionisation is conserved in the production of ATP./reduced NADP:
- electrons move along electron transfer chain (electron carriers), releasing energy
- energy is used to actively pump pprotons from stroma into thylakoid
- protons move by facilitated diffusion down electrochemical gradient into stroma via ATP synthase
- energy used to join ADP and Pi to form ATP (photophosphorylation
- NADP accepts a proton and an electron to become reduced NADP
state 3 products of LDR
ATP, reduced NADP, half an O2 molecule
describe photolysis of water in the LDR
water splits to produce protons, electrons and oxygen (H2O –. 0.5 O2 + 2e- + 2H+)
electrons replace those lost from chlorophyll
what is the light independent reaction known as (2 names)
the dark reaction or the calvin cycle
where does the LIDR occur
stroma of the chloroplast
what 2 products of the LDR is used in the LIDR
reduced NADP and ATP
why are reduced NADP and ATP used in the LIDR
to reduce CO2
describe the LIDR
- CO2 reacts with ribulose bisphosphate (RuBP) and is catalysed by the enzyme rubisco
- this forms 2 glycerate 3-phosphate (GP) molecules [3C]
- GP is then reduced to triose phosphate (TP) [3C]. this uses reduced NADP oxidised into NADP and ATP reduced into ADP + Pi
- some TP is converted into useful organic substances e.g. glucose (6C)
- some TP is used to regenerate RuBP (5C) in the calvin cycle using energy from ATP (ATP is reduced into ADP + Pi)
does LIDR require light?
not directly
describe how temperature affects rate of photosynthesis
temperature increases = rate increases
above optimun temperature, rate decreases = fewer sucessful collisions and fewer ES complexes form
explain how temperature affects rate of photosynthesis
temp increases because enzymes like rubisco gain kinetic energy
enzymes will denature above optimun temperature. H bonds in tertiary structure break = fewer ES complexes form
describe how light intensity affects rate of photosynthesis
light intensity increases as rate increases but above a certain light intensity, rate stops increasing
explain how light intensity affects rate of photosynthesis
light increases as rate increases
LDR increases so more ATP and reduced NADP -produced so LIDR increases as more GP reduced to TP and more TP regenerates RuBP
above certain light intensity, rate stops increasing
another factor is limiting when light intensity rate stops increasing e.g. tmeperature or Co2 concentration
describe how CO2 conc affects rate of photosynthesis
as CO2 conc increases, rate increases
above certain CO2 conc, rate stops increasing
explain why CO2 conc affects rate of photosynthesis
rate increases as CO2 increases
LIDR increases as more CO2 combines w RuBP to form GP so more GP reduced to TP so more TP converted to organic substances and more RuBP regenerated
rate stopping after certain CO2 conc
another factor is limiting e.g. temp or light intensity
what is the law of limiting factors
when a process depends on two or more factors, the rate of that process if limited by the factor which is in shortest supply
what three factorrs can the rate of photosynthesis in a plant can be limited by
light intensity, conc of CO2, temperature
what happens to rate of photosynthesis when temeprature is too low
lower kinetic energy so fewer sucessful collision and fewer ES complexes form and a slower rate of reaction = lower rate of electron transport chain/lower rate of carboxylation by rubisco
what happen to rate of photosynthesis when temperature is high
high kinetic energy breaks the hydrogen bonds in the tertiary structure of enzymes and proteins involved in the LDR and calvin cycle. enzymes + proteins lose their tertiary structure and change shape [denature] so cannot perform role in LDR or calvin cycle
lower rate of electron transport chain/lower rate of carboxylation by rubisco
what happens to rate of photosynthesis when CO2 is low
less CO2 so less RuBP to combine with and less GP produced. So less GP for the NADPH2 and ATP to convert into and less TP = less glucose
what happens to rate of photosynthesis when light intensity is lower
less light
less photoionisation which means less electrons are excited
so reduced electron transport chain = less NADPH2 and ATP produced
CO2 will combine with RuBP to produce GP but cannot change into TP as no NADPH2 or ATP so less TP converted into glucose
when there is a line with a gradient what does this mean regarding limiting factors
independent variable is limiting the rate of photosynthesis - xaxis
when there is a flat line what does this mean in limiting factor graphs
a factor other than the independent variable is limiting rate of photosynthesis = yaxis
what happens to rate of photosynthesis when there is a lack of chlorophyll
this is mainly due to being deficient iin Mg2+ so less light absorbed, less photoionisation, reduced electron transport chain = less NADPH2 and ATP so reduced production of TP and so less glucose
how does a lack of water affect rate of photosynthesis
less water split into two to replace the electrons lost in the Photosystem II and so reduced photolysis of water so cannot replace electrons so stays ionised and reduced electron transport chain. less NADPH2 and ATP produced so less GP turned into TP which means less glucose
why are fertilisers are used
- to replace nitrates/phosphates lost when plants are harvested and livestock are removed
- those removed from soil and incorporated into biomass can’t be released back into the soil through decomposition by saprobionts
- so improve efficiency of energy transfer = increase productivity/yield
faster growth, increased biomass, higher productivity (rate at which biomass is produced), higher yield and cheaper food
what are natural fertilisers made of
organic substances and ions are released during decompositioni by saprobionts e.g. manure, compost and sewage
what are artificial fertilisers made of
inorganic compounds of nitrogen, phosphorus and potassium
how do fertilisers increase productivity
nitrogen is an essential compound of amino acids, ATP and nucleotides in DNA all needed for plant growth. increased conc = plants develop quicker - greater leaf area, grow taller = more photosynthesis can occur and improved crop productivity
state 3 effects of using fertilisers
redeuced species diversity, leaching, eutrophication
state what happens in eutrophication
- rapid growth of algae in pond/river so light blocked
- submerged plants die as they cannot photosynthesise
- saprobionts decompose dead plant matter using oxygen in aerobic respiration
- so less oxygen for fish to aerobically respire, leading to their death
state how leaching affects it
phosphates/nitrates disssolve in water, leading to leaching of nutrients into lakes/river/oceans + eutrophication
pollutes watercourses
explain key advantages of using natural fertiliser over artificial fertiliser
- less water soluble so less leaching = eutrophication is less likely
- organic molecules require breaking down by saprobionts = slow release of nitrate/phosphate etc.
what is leaching
soluble mineral ions (nitrate ions) dissolve in rainwater and carry the ions deep into the ground beyond the reach of plant roots = mineral ions travel into watercourses (rivers and streams) via groundwater flow
state how fertilisers reduce species diversity
nitrogen rich soil favours the growth of grasses, nettles and other rapidly growing species which outcompete other species, leading to a reduced biodiveristy of plants = fewer plant speicies = reduced food sources and habitat options
what is eutrophication caused by
leaching of fertiliser into watercourses
what is eutrophication
soluble nitrates are washed into watercourse, algae absorb the nitrates and the opulation grows rapidly = alglal bloom which blocks aquatic plants so as they cannot photosynthesise, they die
lots of dead, organic material for bacteria to feed on = population grows rapidly = water is anoxic (lacking oxygen) due to anaerobic respiration.
lack of oxygen = reduced biodiversity as all organisms die
what can farmers do to increase growth
use greenhouses, propane burners, night lights, irrigation systems and pesticides
how does use of greenhouses increase growth in farming
increases radiation = increased LDR and increases temperature = increased KE
how does use of propane burners increase growth in farming
increase temperature = increased KE and increase CO2 = increased CAlvin cycle
how does the use of night lights increase growth in farming
more constant radiation = increased LDR
how does use of irrigation systems increase growth in farming
increased volume of water = increased LDR
how do pesticides increase growth in farming
kill pests which …..
leaves eaten = less photoionisation = reduced LDR
broken phloem tissue = reduced carbohydrates for respiration, storage and synthesis of molecules = reduced growth because reduced DNA reeplication, protein synthesis, cell division
damage root cells = reduced water and mineral ion absorption = reduced LDR and turgidity = reduced SA exposed so reduced LDR
mineral ion deficiency = reduced chlorophyll (less LDR), enzyme action, protein synthesis and ATP production
explain how crop farming practices increases efficiency of energy transfer
simplifying food webs to reduce energy/biomass losses to non-human food chains e.g.
- herbicides kill weeds = less competition for light so more energy to create biomass
- pesticides kill insects = reduce loss of biomass from crops
- fungicides reduce fungal infections = more energy to create biomass
fertilisers e.g. nitrates to prevent poor growth due to lack of nutrients
why are magnesium ions needed in fertilisers
required to synthesise chlorophyll molecules
why are nitrate ions needed in fertilisers
synthesises amino acids and mononucleotides = proteins, ATP, polynucleotides
why are potasssium ions needed in fertilisers
required for co-transport (NaK pump) = absorption of mineral ions by roots = generates osmotic pressure = movement of sucrose into the phloem
why are phosphate ions needed in fertilisers
to phosphorylate ADP into ATP, for phospholipids and nucleotides (mono and poly)
explain how livestock farming practices increase efficiency of energy transfer
reduce respiratory losses within a human food chain = more energy to create biomass:
- reduce movement and keep warm = less energy lost as heat from respiration
- slaughter animal while still growing/young when most energy is used for growth
- treated with antibiotics = prevent loss of energy due to pathogens
- selective breeding to produce breeds with higher growth rates
state 3 advantages of inorganic fertiliser
- can tailor the fertiliser to the specific needs of the soil/crop
- concentrated = large amount in small area
- soluble = easily spread in fields
state 2 disadvantages of inorganic fertilisers
favours the growth of fast growing plants (weeds) which results in reduced species diversity and doesn’t replace soil structure, leaving it vulnerable to wind and soil erosion. solubleeading to leeching and eutrophication
how is the mitrochondrion structure adapted to its function
- long and thin = large SA:V for movement of particles in and out of mitochondrion = short diffusion distance
- envelope = controls what enters and exits = H+ conc gradient to be set up
- cristae = high SA for attachment of respiratory proteins
- has its own DNA and ribosomes = make its own respiratory proteins
state the structures found in mitochondria
- inner and outer membrane (envelope)
- cristae
- matrix
- 70S ribosomes
- mitochondrial DNA
- intermembranal space
overall reaction for respiration
glucose + oxygen -> carbon dioxide + water + (38 ATP)
heat energy is also released = exothermic
chemical energy released initiates condensation reaction of ADP to ATP
define respiration
a chemical reaction that releases the chemical potential energy from molecules
what is the difference btwn respiration and breathing
respiration occurs ‘everywhere’ but breathing occurs in the lungs
what does ATP stand for
adenosine triphosphate
why ATP
- muscle contraction
- metabolic processes such as protein synthesis
- phosphorylation of molecules to make them more reaction
- active transport
- good energy carrier = invovles one step reaction = immediate source of energy which is released in small manageable amounts
- easily reformed in a condensation reaction
why is ATP a bad source of energy
- easily hydrolysed
- cannot travel through the phospholipid bilayer as it is soluble = difficult to keep in one place. if kept in one place, affects water potential
what are the 4 main processes in aerobic respiration
substrate-level phosphorylation:
- glycolysis
- link reaction
- krebs cycle
- oxidative phosphorylation
what is the purpose of substrate-level phosphorylation
break down substrates to produce reduced co-enzymes to be used in oxidative phosphorylation
what does oxidative phosphorylation allow
create a H+ conc. gradient which allows phosphorylation of ADP to ATP
what is a co-enzyme
a non-protein compound necessary for the function on an enzyme
what co-enzymes are used in respiration
NAD, CoA, FAD
where does glycolysis occur
in the cytoplasm
where in the stage of respiration are co-enzymes used
reduced are used in the final stage of respiration (oxidative phosphorylation which produces a lot of ATP)
does glycolysis require oxygen
no
what happens in glycolysis
glucose is split into 2 molecules of pyruvate (a 3 carbon sugar) via phosphorylation
what two phases are there in glycolysis
energy pay off phase and energy investment (glucose -> triose phosphate -> pyruvate)
what are the resulting products of glycolysis
2 pyruvate molecules, net gain of 2 ATP molecules (4 overall gross gain of ATP molecules but 2 used in the reaction for phosphorylation to triose phosphate), 2 reduced NADP
where does the link reaction occur
matrix in the mitochondria
what happens in the link reaction
- pyruvate is produced in glycolysis is passed through the inner and outer membrane of the mitochondrion by active transport
- decarboxylatioin (CO2 removed from pyruvate) which requires enzyme decarboxylas
- CO2 diffuses out of the mitochondrion and cell
- dehydrogenation = hydrogen atom produced which is used by NAD to become reduced NADH
- coenzyme A picks up acetyl which results in acetyl coenxyme A (2C) which is then used in the Krebs cycle)
what occurs in the krebs cycle
- acetylee coenzyme A from the link reaction combines its acetyl group with oxalacetates (4C) to produce citrate (6C)
- citrate is decarboxylated and dehydrogenated to an intermediate 5C molecule
- futher decarboxylation and dehydrogenation produces an oxalacetate , 2 NADP molecules are reduced, FAD is reduced, ATP is produced and CO2 is produced.
- oxalacetate is now recycled with another acetyl coenzyme A to begin the cycle again
how many krebs cycles occur per glucose molecule
2
glucose > 2 triose phosphates > 2 pyruvates > 2 acetyl coenzyme As
what is produced in two link reactions which come from one glucose molecule
acetyl coenzyme A, 2 CO2, 2 NADH
what is produced in two krebs cycle from the one glucose molecule
4 CO2, 6 NADH, 2 FADH, 2 ATP
what is oxidative phosphorylation
it is the final stage of respiration where the majority of ATP is produced
where does oxidative phosphorylation occur
on the inner membrane of the mitochondria (cristae)
what does oxidative phosphorylation use and require to occur
it uses NADH, FADH and requires oxygen (known as the terminal electron acceptor)
what is oxidative phosphorylation also known as
the electron transport chain
give a brief description of what happens in oxidative phosphorylation
- hydrogen atoms are picked up and transported by NADH and FADH are split into H+ and e-
- electrons are passed down a series of electron transport carrier molecules (involves redox reactions) which releases energy that is then used to pump H+ into intermembranal space
- H+ diffuses down an electrochemical gradient (chemiosmosis) through ATP synthase which catalyses the condensation reaction of ADP and Pi
- once electrons have transferred their energy they combine with H+ in the mitochondrial matrix and oxygen to form water = oxygen is the terminal electron acceptor
4e- + O2 + 4H+ -> 2H2O
how many ATP molecules does NADH create
3
how many ATP molecules does FAD create
2
where is some energy lost in oxidative phosphorylation
heat
where in oxidative phosphorylation is energy released
electrons being passed from a higher energy carrier to a lower energy carrier = phosphorylate ADP to ATP
aerobic respiration requires oxygen, why is oxygen needed in oxidative phosphorylation
it is the terminal electron acceptor
what happens in oxidative phosphorylation if oxygen isn’t available
oxidative phosphorylation cannot occur and the reduced NAD and FAD cannot be oxidised so the link reaction and krebs cycle stops, leaving only glycolysis
word equation for anaerobic respiration in animals
glucose -> lactate + (2 ATP)
word equation for anaerobic respiration in yeast (and plants)
glucose -> ethanol + carbon dioxide
how is pyruvate reduced in glycolysis in anaerobic respiration
reduced by the 2 NADs that come from glycolysis, recycling NAD, allowing further glycolysis to take place, converting it to lactate
what is pyruvate converted into in anaerobic respiration
lactate
what can happen to lactate when pyruvate is converted into it
- oxidised back to pyruvate, can be oxidised to release energy
- convert to glycogen as a store of carbohydrate
what occurs in anaerobic respiration as well as aerobic respiration
glycolysis
how is glycolysis able to occur when there is a lack of oxygen
oxygen isn’t needed and the NAD is recycled to form reduced NAD to convert pyruvate into lactate
where does the Krebs cycle occur
in the mitochondrial matrix
where does oxidative phosphorylation occur
inner mitochondiral membrane
where does NAD regernation of anaerobic respiration occur
cytoplasm
suggest why anaerobic respiration produces less ATP per molecule of glucose than aerobic respiration
only glycolysis is involved, produces little ATP. no oxidative phosphorylation which forms a majority of ATP
how does pyruvate travel from glycolysis to the next reaction step if respiration is aerobic
active transporte
how does the oxygen debt occur
extra oxygen is needed to oxidise lactate to turn back into pyruvate (on top of oxygen already needed in respiation)
what happens to pyruvate in anaerobic respiration of yeast n plants
it is decarobyxlated and reduced by reduced NAD to form ethanol
how can you measure the rate of a reaction
measure the rate at which reactants/products are used up/made
which would be the easiest reactant/product to measure aerobic respiration
oxygen uptake or carbon dioxide production
why are respirometers left for a time period to stabilise
to let temperature, pressure and the respiration to stabalise and reach equilibrium
why would the fluid move in a manometer
there is a pressure gradient
how would you calculate the respiratory quotient
volume of CO2 produced/ volume of O2 absorbed
what can lipids be metabolised into
glycerol -> triose phosphate -> energy pay off phase in glycolysis
fatty acids -> acetyl coenzyme A -> combines with oxalacetate in the krebs cycle
what happens to flucose after photosynthesis (4 things)
used in:
- respiration
- stored
- growth
- transport
how is glucose transported
transported as sucrose
how is glucose stored
as starch or as lipids
how is glucose used for growth
- cellulose (cell walls)
- amino acids (proteins)
- deoxyribose (DNA)
- riibose (RNA)
define biomass
the total mass of living material in a specific area at a given time
define food chain/web
a diagram that shows the flow of energy/biomass through thee ecosystem
define trophic level
the position an organism occupies in a food chain/web (usually no more than 5)
define producers
an organism that can synthesis its own biological molecules and therefore produce its own biomass e.g an autotroph
define consumers
an organism that cannot synthesis its own biological molecule and so needs to obtain its biomass from other organisms
define what it means by primary/secondary/tertiary/quaternary
terms given to the consumers in a good chain. food chains rarely possess more than 4 consumers due to less of energy btwn trophic levels
define saprobionts
organisms that feed through saprotrophic nutrition (extracellular enzymes are released and digestion occurs outside of the organisms body) and are responsible for decay and decomposition
4 reasons why biomass is not 100% transferred
- lost in chemical bonds of excretory products (urine and CO2)
- entire organisms are not ingested bone, nails, fur
- entire organisms are not digested, absorbed, assimilated - passed out in faeces
- energy lost as heat to surroundings
- used in respiration so chemical energy is lost
how do we measure biomass
mean mass of individual in species * number of individuals in an area
how would we sample animals in a species in a large area
mark, release, recapture
what is an advantage of using fresh biomass
it is easier to measure
what is a disadvantage of biomass
less reprodducible/repeatable because the amount of water in a living organism varires throughout the day and between species greatly
what is the advantage of using dry biomass
it is more accurate
what are the disadvantages of using dry biomass/carbon
it kills the organism because we dry them out in a kiln so only small sample sizes which may not be as representative
how would we change fresh biomass into dry biomass
kill the sample humanly and dry in a kiln. monitor the dry sample until the mass on longer decreases for a set time period
for 2D habitats what unit do we measure biomass in
g m^-2
for 3D habitats what unit do we measure biomass in (aqautic habitats)
g m^-3
how do we measure chemical potential energy in biomass
burn the sample in a bomb calorimeter:
- dry biomass is burnt in pure oxygen in a sealed chamber which is then surrounded by a water bath
- use equation E= mcdeltaT
state 4 inorganic nitrogen containing compounds
NO3- , NO2-, NH3/NH4+, N2
state 4 organic nitrogen containing compounds
DNA, RNA, amino acids, proteins
state the equation used to calculate net production of consumers
N = I - (F +R)
where
- N = net production
- I = chemical energy store
- F = biomass lost in faeces and excretory products
- R = biomass/energy lost from respiration (heat energy)
state the equation used to calculate the net primary production
NPP = GPP - R
where
NPP = net primary production : resultant quantity of chemical potential energy found in biomass of the plant
R = stored chemical potential energy lost from respiration
GPP = gross primary production, total quantity of light converted into chemical potential energy
in natural ecosystems, most of the light falling on producers is not used in photosynthesis. state 5 reasons why
- Reflected back into space by earths atmosphere, absorbed by atmosphere
- Not all of suns light falls on photosynthetic organisms
- Some light does not hit a chlorophyll molecules
- Some wavelengths of light not absorbed
- Another factor could be limiting rate of photosynthesis
state 4 features of the bomb calorimeter which can ensure a valid measurement of the total heat energy released
- thermometer
- stirrer distributes the heat
- insulation reduces amount of heat lost
- water has a high specific heat capacity
state the 4 types of bacteria that are in the nitrogen cycle
they act as saprobionts, nitrifying bacteria, denitrifying bacteria, nitrogen-fixing bacteria
what is the role of saprobionts in the nitrogen cycle
- they decompose organic compoiunds (urea, DNA, proteins) in dead matter/organic waste
- secrete enxymes for extracellular digestion (saprobiotic nutrition)
- absorb soluble nutrietns and release mineral ions e.g. ammonium
what is the role of nitryfying bacteria
nitrification: the oxidation of ammonium ions intro nitrites and nitrates in aerobic conditions
NH4+ -> NO2- -> NO3-
what is the role of denitrifying bacteria
denitrification
- the reduction of nitrates to nitrogen gase in anaerobic conditions
NO3- -> N2
what is the role of nitrogen-fixing bacteria
nitrogen fixation
- converts nitrogen gas into ammonium ions
N2 - > NH4+
describe the role of bacteria in nitrogen fixation
nitrogen gas is converted into ammonia which forms ammonium ions in soil by nitroggen-fixing bacteria which may be found in root nodules
suggest why ploughing (aerating) soil increases fertility
- more ammonium is converted into nitrite and nitrate/more nitrification/more nitrifying bacteria
- less nitrate is converted to nitrogen gase/less denitrification/fewer nitrifying bacteria
state 9 biological molecules that contain phosphorus
phospholipids, DNA, RNA, ATP, ADP, TP, GP, RuBP
describe the phosphorus cycle
- phosphate ions in rocks are relased by erosion/weathering
- phosphate ions taken up by producers and incorporated into their biomass (absorption helped by mycorrhizae)
- phosphate ions are transferred through food chain e.g. as herbivores eat producers
- some phosphate ions lost from animals in waste products (excretion)
- saprobionts decompose organic compounds e.g. DNA in dead matter/organic waste, releasing phosphate ions
define mycorrhizae
the mutualistic symbiotic associations btwn fungi and plant roots
how do mycorrhizae benefit plants
- increase SA available for the absorption of water and minerals
- can hold water and dissolved minerals in the surrounding area of a root system
what does mycorrhizaee enable
- faster rate of growth due to an increased absorption rate of mineral ions
- plant able to resist drought conditions due to its sponge-like structure
