3.5 Energy Transfers In & Between Organisms Flashcards
what is the site of the light dependent stage of photosynthesis
the grana
describe the stroma
a fluid-filled matrix where the light independent stage of photosynthesis takes place. it contains a number of other structures like starch grains.
what does the chloroplast genome code for
ribosomal RNA
define community
all the living organisms that live in a habitat at the same time
define population
the number of the same species that live in a habitat at the same time
define ecosystem
a community in conjunction with the non living components of the environment
define abiotic
the non living, chemical and physical components of the ecosystem
define biomass
the total mass of living matter within an organism
define respiratory substrate
the organic molecules that can be oxidised by respiration, releasing energy to make molecules of ATP
define calorimetry
a technique used to measure the quantity of heat gained/lost by a system
the measure of biomass
dry mass of tissue per given area
use of calorimetry
to estimate the chemical energy store in dry biomass
what do the sugars synthesised by plants form
most are used as respiratory substrates and the rest make other groups of biological molecules which form the biomass
define gross primary production
the total quantity of the chemical energy store in plant biomass, in a given area or volume, in a given time
define net primary production
the chemical energy store which is left in plant biomass after respiratory losses to the environment have been taken into the account
what is NPP available for
plant growth, reproduction, to other trophic levels in the ecosystem such as herbivores/consumers and decomposers
the equation for net production of consumers
net = I - (F+R)
I = chemical energy store in ingested food
F = chemical energy store lost to the environment in faeces and urine
R = respiratory losses to the environment
explain the reasons why a low percentage of energy is transferred between trophic levels
some of the organism is not consumed
some parts cannot be digested
some energy lost in excretory materials
some energy lost as heat from respiration, lost to the environment
equation for percentage efficiency
energy available after transfer divided by energy available before transfer x 100
one aim of a farming practice and an example
to reduce respiratory losses in a human food chain in order to reduce energy loss and increase yield.
e.g keeping animals in confined spaces to reduce muscle movement and can keep them warm to reduce heat loss (ethical concerns)
second aim for farming practice and an example
to simplify food webs in order to reduce energy losses to non-human food chains.
e.g reduce/eliminate organisms that compete with the organism being farmed (crops compete with plants for water, space and light etc)
benefit of natural predators introduced into the ecosystem
crops lose less biomass and increase productivities
explain ammonification
- saprobiontic microorganisms feed off faeces, urine, and dead organisms
- this releases ammonia which forms ammonium ions in the soil
- the nitrogen returns to the non living component of the ecosystem
explain nitrification
oxidation reactions occurs which releases energy
oxidation occurs by free-living soil microorganisms known as nitrifying bacteria
first the oxidation of ammonium ions to nitrite ions
then the oxidation of nitrite ions to nitrate ions
the nitrifying bacteria need oxygen for these conversions
explain the farming practice of ploughing
nitrifying bacteria need oxygen for conversions of nitrate ions so lots of air spaces are preferable in the soil
explain nitrogen fixation
free-living nitrogen fixing bacteria reduce gaseous nitrogen to ammonia which they then manufacture into amino acids
when the bacteria decay/die, nitrogen rich compounds are released
mutualistic nitrogen fixing bacteria live on nodules on the roots of plants and obtain carbs from the plants
in exchange the plant gets amino acids from them.
explain denitrification
waterlogged soils means a decrease in oxygen concentration so there is a drop in aerobic nitrifying bacteria
therefore there is an increase anaerobic denitrifying bacteria which convert soil nitrates
how do farmers prevent build up of denitrifying bacteria
ensure well aerated land
define ammonification
the production of ammonia from organic nitrogen-containing compounds
define nitrification
the conversion of ammonium ions to nitrate ions
define nitrogen fixation
nitrogen gas is converted to nitrogen containing compounds
outline the phosphorous cycle
phosphorous exists mostly as phosphate ions in sedimentary rock but weathering/erosion dissolves the ions
the ions are then absorbed by plants and are incorporated into their biomass
animals obtain the ions when they feed on these plants
excess ions are excreted and may accumulated in waste material
decomposers break down these dead plants and animals which releases phosphate ions into the water and soil
some of the ions are left in remains such as bone or shell because it is slower to decompose
the phosphate ions are then released by decomposition or dissolve out of rocks and are transported by rivers/streams into lakes/oceans where they form sedimentary rock and complete the cycle
explain the role of mycorrhizae in nutrient cycles
fungi increase surface area for absorption of water/minerals
also acts as a sponge in the soil so holds water/minerals in the neighbourhood of the roots
this increases drought resistance and takes up inorganic ions more readily, improving the uptake of scarce phosphate ions
describe the relationship between mycorrhizae and plants
a mutualistic/symbiotic relationship
the fungi gets sugars and amino acids from the plant
the plant benefits from increased water/ion uptake
why does agriculture cause a loss in nutrients
when crops are harvested, minerals are removed and are not returned upon decomposition because the crops are taken away for consumption so minerals are not replaced by their remains/waste products
define fertilisers
they replace the lost materials so increase energy efficiency of the food chain
define natural fertilisers
organic matter such as manure, compost, sewage sludge, seaweed etc
define artificial fertilisers
inorganic matter such as pure chemicals (ammonium nitrate as powder/pellets)
describe the environmental issues with fertilisers
if more is added than can be used, the fertilisers are susceptible to leaching into waterways by rain or irrigation which can lead to eutrophication
when is leaching more likely and with which fertiliser
if the fertiliser is applied just before rainfall.
artificial fertiliser is more soluble so more likely to leach
benefit of natural fertiliser being less soluble
the fertiliser is released slower and with more control so it is harder to add in excess, less leaching
relevance of phosphate-nitrate solubility
phosphates less likely to leach than nitrates as they are less soluble in water
explain eutrophication
Caused by excess nutrients leaching into waterways/oceans etc)
The leached excess minerals stimulate rapid growth of algae, naturally nitrate ions are a limiting factor for plant and algal growth as in low concentrations
The new large amount of algae block light reaching plants beneath them, light becomes the limiting factor for growth at lower depths
These plants cannot photosynthesise enough so die
Saprobiontic bacteria then feed on the dead plants, as lack of dead organisms is no longer a limiting factor, they use up all remaining oxygen through aerobic respiration
Fish and other organisms in the water die because there is not enough dissolved oxygen to survive, oxygen becomes the limiting factor for the aerobic organisms
Less competition for the anaerobic organisms now so their populations rise
They further decompose dead material releasing more nitrates and making the water putrid.
photolysis
a chlorophyll molecule absorbs a photon of light, splitting water into protons, electrons and oxygen
the electrons replace those lost due to photoionization
they provide energy for the proton pump and lead to chemiosmosis
photoionization of chlorophyll
When a photon of light is absorbed, a pair of electrons gain energy and are excited
They become unstable and are transferred to an electron chain acceptor
Results in production of atp and reduced nadp
chemiosmosis
Each electron carrier is at a lower energy level so electrons lose energy through the chain
This energy is used to transport protons from the stroma across into the thylakoid
Makes a concentration gradient of protons so they diffuse down the gradient through ATP synthase
This causes a change to the structure of ATP synthase and causes it to rotate, converts ADP and a Pi into ATP
production of ATP and reduced NADP
ATP and NADPH are results of photolysis producing electrons and photoionisation moving those electrons outside the chlorophyll, through the electron transfer chain
Then chemiosmosis occurs to get the protons on the stroma side, producing ATP and NADP
adaptations of the chloroplasts
Thylakoid membranes give a large surface area for the attachment of chlorophyll, electron carriers and enzymes for the LDR
Protein network in grana holds chlorophyll precisely to allow maximum light absorption
Granal membranes have ATP synthase to catalyze the production of ATP, selectively permeable to ensure a proton gradient
Contain dna and ribosomes to manufacturer some of the proteins involved in the LDR
cyclic electron pathway
A photon is absorbed by chlorophyll a in PSI
Two electrons in this molecule is excited and attains a higher energy level and becomes unstable so is transferred to an electron acceptor
Acceptor is reduced, molecule is oxidized (photoionisation)
These redox reactions occur along the electron transport chain until the electron is accepted by ferredoxin
Each new carrier is at a lower energy level so electrons lose energy at each stage
Ferredoxin transfers the electron to the cytochrome proton pump which transfers it back to PSI
Protons are pumped across the thylakoid membrane from the chloroplast stroma to the thylakoid lumen which creates a proton gradient
The protons flow through ATP synthase channel protein which changes the structure of the enzyme and causes it to rotate
This catalyses the addition of a phosphate and a proton to form ATP
Known as photo phosphorylation
non cyclic photophosphorylation pathway
A photon is absorbed by a molecule of water which breaks down into electrons, protons and oxygen
The electrons move into the reaction centre of PS2
The chlorophyll a molecule in PS2 absorbs a photon and an electron in this molecule is excited
The electron is donated between the electron acceptors, creating a series of redox known as the electron transfer chain
A section of the chain involves the transfer of the electrons between PS2 and PS1 which is performed by cytochrome proton pump
Protons are pumped across the thylakoid membrane from stroma to lumen, creating a gradient
High concentration inside the thylakoid space and low in the stroma
Protons flow through the channel protein associated with ATP synthase, causing the enzyme to rotate
Atp synthase catalyses the addition of ADP and a phosphate, forming ATP
Electron moves into reaction centre in PS1
The electron is excited again when P700 absorbs a photon and it is transferred between electron acceptors to ferredoxin
Electron transferred from ferredoxin to NADP, this cofactor also joins with a hydrogen ion to form reduced NADP
The electron in PS2 is replenished when another molecule of water is photolysed
How is carbon dioxide absorbed into the plant?
Carbon dioxide from the atmosphere diffuses into the leaf through stomata, it dissolves in water around the mesophyll cell walls.
Then diffuses through the cell surface membrane, cytoplasm and chloroplast membranes into the stroma of the chloroplast.
How is carbon dioxide then incorporated into organic molecules?
It reacts with ribulose bisphosphate (RuBP 5C), the carboxylation catalysed by Rubisco.
This reaction produces two molecules of glycerate 3-phosphate (GP 3C.)
Reduced NADP from the LDR reduces GP to Triose phosphate (TP 3C) using energy supplied by ATP.
What then happens to the NADP and TP?
The NADP is reformed and goes back to a reactant in the LDR to be reduced again
Some TP is converted to organic substances needed by the plant e.g starch, cellulose and amino acids
Most TP is used to regenerate RuBP using ATP from the LDR.
Adaptations of the chloroplasts for the LIDR:
Stroma fluid contains all the necessary enzymes
Products of the LDR can readily diffuse into the stroma as the stroma fluid surrounds the grana
Contains dna and ribosomes so can manufacture proteins involved in the LIDR
Generates ATP
both
photolysis
non cyclic
ps2
non cyclic
ps1
both
produces oxygen
non cyclic
reduced NADP
non cyclic
proteins in thylakoid
both
Describe the role of RuBP in the Calvin cycle
combines with carbon dioxide to form two GP molecules
State how the reduced NADP from the LDR is used in the LIDR
Reduces the GP to TP
Which other product of the LDR is used in the LIDR
ATP provides the energy for the reduction reactions
State precisely where in a plant cell the enzymes involved in the calvin cycle are found
in the stroma
Light is not required for the calvin cycle to take place. Explain therefore why the calvin cycle cannot take place for long in the absence of light.
Reduced NADP and ATP, products from the LDR, are important components in the calvin cycle. With no more being produced, reduction of GP to TP cannot occur and the cycle will come to a halt.
Why can plants not use the LDR as their only source of ATP? Suggest two reasons:
When it is dark, the plant will not be able to produce any ATP and will not make any glucose. Also, the LDR might not be efficient enough to produce ATP at the requirements of the plant. Cells without chlorophyll cannot produce ATP in this way and ATP cannot be transported around the plant
define limiting factor
a factor that when in short supply will prevent photosynthesis from occurring at its’ maximum possible rate
limiting factors
temp, co2 concentration, light intensity
short supply of water impact
the plant closes its stomata to prevent water loss so carbon dioxide concentration is affected
method of chlorophyll chromatography
Finely cut up some leaves and fill a mortar to about 2 cm depth.
Add a pinch of sand and about six drops of propanone from the teat pipette.
Grind the mixture with a pestle for at least three minutes.
On a strip of chromatography paper, draw a pencil line 3 cm from the bottom.
Use a fine glass tube to put liquid from the leaf extract onto the centre of the line. Keep the spot as small as possible.
Allow the spot to dry, then add another spot on top. Add five more drops of solution, letting each one dry before putting on the next. The idea is to build up a very concentrated small spot on the paper.
Attach the paper to the pencil using sellotape so that when placed in the beaker, the paper is just clear of its base.
Place no more than about 10 cm3 of propanone in the beaker and hang the paper so it dips in the propanone. Ensure the propanone level is below the spot.
Avoid moving the beaker in any way once the chromatography has started.
Leave the experiment until the propanone has soaked near to the top, and then remove the paper from the beaker.
Mark how high the propanone gets on the paper with a pencil and let the chromatogram dry.
what do saprobionts do and what does this allow to happen
they feed on remains of dead plants, animals + waste products to break them down
how do saprobionts digest their food
saprobionts secrete enzymes and digest their food externally then absorb soluble molecules (nutrients) they need. this is extracellular digestion
role of water in LDR
provides protons for reduction and a source of electrons for the electron transfer chain
advantage of using standard deviations rather than ranges
shows if difference between the data is significant and reduces the effect of anomalies
how do microorganisms contribute to the increase in temperature during processing of organic waste
respiration/metabolism/ammonification releases heat
why is the rate of oxygen production a measure of the rate of photosynthesis
oxygen is a product of the LDR. the faster oxygen is produced, the faster the LDR
explain the effect of a faster production of ATP and reduced NADP
more LIDR can occur so more sugars are produced to be used in respiration so there is more energy for growth
how does nitrogen fixing bacteria allow crops in low concentrations of nitrate ions to grow
the bacteria convert nitrogen to ammonia which is used to produce proteins
how does oxygen in the roots allow take up of nitrogen containing substances
uptake of the substances is by active transport which requires aerobic respiration
