5. energy transfers in and between organisms P2 Flashcards
PHOTOSYNTHESIS
Describe how crop plants use light energy during the light-dependent reaction [5]
- the photolysis of water produces protons, electrons and oxygen.
- light excites electrons
- electrons move along electron transfer chain releasing energy.
- the energy is used to (pump protons from thylakoid to stroma creating an electrochemical gradient and then through ATP synthase via chemiosmosis) forming ATP from ADP and Pi.
- NADP reduces by electrons and protons.
PHOTOSYNTHESIS
explain the role of light in photolysis
light energy splits water molecules into protons, electrons and oxygen
PHOTOSYNTHESIS
what is the role of light in photoionisation in the light dependent stage of photosynthesis [2]
- chlorohyll absorbs light
- light excites electrons in chrolophyll
- electrons are lost
PHOTOSYNTHESIS
what happens in the electron transfer chain?
electrons released from chlorophyll move down a series of carrier proteins embedded in thylakoid membrane and undergo a series of redox reactions which releases energy
PHOTOSYNTHESIS
how is proton concentration gradient established during chemiosmosis?
some energy released from ETC is coupled to active transport of protons from stroma into thylakoid space
PHOTOSYNTHESIS
how does chemiosmosis produce ATP in light-dependent reaction?
protons move down concentration gradient from thylakoid space into stroma through ATP synthase.
ATP synthase catalyses ADP+Pi—>ATP
PHOTOSYNTHESIS
what happens to the products of photolysis of water?
protons move out of thylakoid space via ATP synthase and are used to reduce the coenzyme NAPD along with the electrons.
oxygen is used for respiration and diffuses out of leaf as waste gas
PHOTOSYNTHESIS
how and where is reduced NADP produced in the light dependent reaction?
NADP + proton + electron —> reduced NADP
PHOTOSYNTHESIS
name the three main stages in the calvin cycle
carbon fixation
reduction
regeneration
PHOTOSYNTHESIS
what happens during carbon fixation?
reaction between carbon dioxide and RuBP (ribulose biphosphate)
forms unstable 6 carbon molecule (2x GP)
PHOTOSYNTHESIS
what happens during reduction in the calvin cycle?
2 x GP is reduced to 2 x TP (triose phosphate) which requires reduced NADP and ATP for energy.
forms NADP and ATP
PHOTOSYNTHESIS
how does the light- independent reaction result in the production of useful organic substances
one carbon leaves the cycle
6 cycles to make glucose
PHOTOSYNTHESIS
what happens during regeneration in the calvin cycle?
after 1C leaves the cycle, 5C is used to regenerate RuBP using ATP
(ATP—>ADP +Pi)
PHOTOSYNTHESIS
state the roles of ATP and NADPH in the light independent reaction
ATP: reduction of GP to TP and provides energy to regenerate RuBP
NADPH: coenzyme transports electrons needed for the reduction of GP to TP
PHOTOSYNTHESIS
a decrease in the activity in the enzyme rubisco would limit the rate of photosynthesis. explain why.
Less Co2 reacts with RuBP, so less GP
PHOTOSYNTHESIS
where precisely is rubisco found in a cell?
stroma
PHOTOSYNTHESIS
The pigments in leaves are different colours. Suggest and explain the advantage of having different coloured pigments in leaves.
absorb different wavelengths of light for photosynthesis
PHOTOSYNTHESIS
describe the structure of a chloroplast
usually disc shaped, double membrane
thylakoids - flattened discs stack to form grana
lamellae- tubular extensions attach thylakoids in adjacent grana
stroma - fluid-filled matrix
PHOTOSYNTHESIS
in natural ecosystems, most of the light falling on producers is not used in photosynthesis. Give 2 reasons why
- light is reflected
- light is wrong wavelength
PHOTOSYNTHESIS
how does the structure of the chloroplast maximise the rate of the light dependent reaction?
ATP synthase channels within granal membrane
large surface area of thylakoid membrane for electron transport chain.
photosystems position chlorophyll to enable maximum absorption of light
PHOTOSYNTHESIS
how does the structure of the chloroplast maximise the rate of the light independent reaction?
own DNA and ribosomes for synthesis of enzymes (rubisco)
concentration of enzymes and substrates in stroma is high.
PHOTOSYNTHESIS
explain why a decrease in the light-dependent reaction leads to a decrease in the light-independent reaction.
less ATP
less reduced NADP
PHOTOSYNTHESIS
name 4 environmental factors that could limit the rate of photosynthesis
light intensity (light dependent stage)
CO2 levels (light independent stage)
temperature (enzyme controlled steps)
mineral/ magnesium levels (maintain normal functioning of chlorophyll)
PHOTOSYNTHESIS
outline some common agricultural practices used to overcome the effect of limiting factors in photosynthesis
artificial light, especially at night
artificial heating
addition of CO2 to greenhouse atmosphere
PHOTOSYNTHESIS
why do farmers try to overcome the effect of limiting factors?
to increase yield
additional cost must be balanced with yield to ensure maximum profit
PHOTOSYNTHESIS
as light is increased, it then plateaus. explain why
all NADP has become reduced from the non-cyclic photophosphorylation (light-dependent)
PHOTOSYNTHESIS
as CO2 concentration increases, so does photosynthesis up to a point. why does it stop increasing?
no more RuBP available as all combines with CO2 or no more rubisco (all have formed ES complexes)
PHOTOSYNTHESIS
as temperature increases, so does photosynthesis, up to a point. explain why it stops increasing
changed to tertiary structure of ATP synthase/ rubisco
PHOTOSYNTHESIS
how do plants use the sugars from photosynthesis?
- primarily as respiratory substrates
- to synthesise other biological molecules e.g. cellulose
RESPIRATION
name the four main stages in aerobic respiration and where they occur
glycolysis - cytoplasm
link reaction - mitochondrial matrix
Krebs cycle - mitochondrial matrix
oxidative phosphorylation - cristae
RESPIRATION
describe the process of glycolysis
- glucose is phosphorylated using ATP to form hexose biphosphate
- this splits to form 2x triose phosphate
- 2x TP is oxidised to form pyruvate
- net gain of 2x reduced NAD and 2x ATP per glucose
RESPIRATION
outline the stages of the link reaction
- pyruvate is oxidised/ decarboxylated to acetate (NAD reduced)
- acetate combines with coenzyme A to form acetyl-coenzyme A
produces 2Co2, 2NADH and 2Acetyl coeunzyme A
RESPIRATION
give a summary equation for the link reaction
pyruvate + NAD + CoA —> acetyl CoA + NADH + CO2
RESPIRATION
outline the stages of the Krebs cycle
- acetyl CoA (2C) combines with oxaloacetate (4C) to form citrate (6c)
- CoA is released back to the link reaction to combine with acetate again
- citrate is decarboxilated, NAD is reduced and ATP is used for energy (ADP+pi)
- decarboxilated again to reform oxaloacetate. NAD is reduced and so is FAD
RESPIRATION
what is the electron transfer chain?
(oxidative phosphorylation)
series of carrier proteins embedded in membrane of the cristae of mitochondria
produces ATP through oxidative phosphorylation via chemiosmosis during aerobic respiration
RESPIRATION
what happens in the electron transfer chain (oxidative phosphorylation)
electrons released from NAD and FAD undergo redox reactions.
the energy released maintains a proton gradient (protons move from matrix to cristae)
oxygen acts as a final electron acceptor
RESPIRATION
how is a proton gradient established during chemiosmosis in aerobic respiration?
some energy released from the ETC is coupled to the active transport of H+ ions from the mitochondrial matrix to the cristae
RESPIRATION
how does chemiosmosis produce ATP during aerobic respiration?
H+ ions move down the electrochemical gradient from the cristae to the matrix via ATP synthase
ATP synthase catalyses ADP+Pi —> ATP
RESPIRATION
state the role of oxygen in aerobic respiration
final electron acceptor in ETC (produces water)
RESPIRATION
what is the benefit of an electron transport chain rather than a single reaction?
energy is released gradually
less energy is released as heat
RESPIRATION
name 2 types of molecule that can be used as alternative respiratory substrates
proteins
lipids
RESPIRATION
what happens during anaerobic respiration in animals?
pyruvate +NADH —> lactate +NAD
RESPIRATION
what happens in anaerobic respiration in plants and yeast cells?
pyruvate is decarboxilated to form ethanal.
ethanal is reduced to ethanol using NADH to produce oxidised NAD for further glycolysis
RESPIRATION
Explain why converting pyruvate to lactate allows the continued production of ATP by anaerobic respiration?
regenerates/ produces NAD so glycolysis can continue
RESPIRATION
compare aerobic and anaerobic respiration
both involve glycolysis
both require NAD
both produce ATP
RESPIRATION
describe the advantage of the bohr effect during intense exercise
increases dissociation of oxygen
for aerobic respiration at the tissues/muscles/cells
ENERGY
what is biomass?
total dry mass of tissue or mass of carbon per given area and time
ENERGY
how can the chemical energy store in dry biomass be estimated?
using Calorimetry
ENERGY
how could a student ensure that all water had been removed from a sample before weighing?
heat the sample and reweigh it until the mass reading is constant
ENERGY
give the formula showing the relationship between GPP and NPP
NPP = GPP - R
R = respiratory losses.
ENERGY
define gross primary production (GPP)
Total chemical energy in plant biomass within a given volume or area
ENERGY
define net primary productivity(NPP)
chemical energy store in plant biomass after respiratory losses to the environment have been taken into account
ENERGY
why is most of the suns every not converted to organic matter?
most solar energy absorbed by atmosphere or reflected in clouds.
photosynthetic pigments cannot absorb some wavelengths of light.
energy is lost as heat during respiration/photosynthesis.
ENERGY
how can the net production of consumers (N) be calculated?
N = I - (F+R)
I = chemical energy lost by ingested food
F= chemical energy lost by faeces.
R= respiratory losses to environment.
ENERGY
why does biomass decrease along a food chain?
- energy lost in urine and faeces.
- some of the organism isn’t consumed
- energy lost to surroundings as heat.
ENERGY
define primary and secondary productivity
- rate of primary/ secondary production.
- measured by biomass in a specific area over a given time period.
ENERGY
outline some common farming practices used to increase the efficiency of energy transfer
- simplifying food webs (exclusion of predators) to reduce energy lost to non-human food chains
- artificial heating: reduce energy lost to maintain constant body temperature.
ENERGY
give the equation for % efficiency
energy converted to a useful form/
total energy supplied x100
ENERGY
explain why the length of food chains is limited
energy is lost at each trophic level
so there is insufficient energy to support a higher trophic level.
NUTRIENT CYCLES
name the 4 main stages of the nitrogen cycle
nitrogen fixation
ammonification
nitrification
denitrification
NUTRIENT CYCLES
outline the role of bacteria in nitrogen fixation
nitrogen fixing bacteria consume nodules of legumes for energy.
NUTRIENT CYCLES
outline the role of bacteria in ammonification
saprobionts
NUTRIENT CYCLES
describe the role of saprobionts in the nitrogen cycle
bacteria that decompose proteins which produces ammonium
NUTRIENT CYCLES
eutrophication can cause water to become cloudy. describe how you would obtain a quantitative measurement of their cloudiness.
- use of colorimeter
- measure absorbance of light
- standardised method, e.g. same volume of water, same wavelength of light etc.
NUTRIENT CYCLES
what is mycorrhizae?
symbiotic relationship between fungi and roots. Increases the surface area of roots
NUTRIENT CYCLES
what is nitrogen fixation?
nitrogen gas is converted into ammonium ions using nitrogen fixing bacteria
NUTRIENT CYCLES
what is ammonification?
dead organisms broke down (e.g. into amino acids). ammonia is released into the soul.
NUTRIENT CYCLES
what are the two stages of nitrification?
conversion of ammonium ions into nitrites
conversion nitrites into nitrates
using nitrifying bacteria
NUTRIENT CYCLES
what is denitrification?
nitrates being converted into nitrogen gas using denitrifying bacteria, in anaerobic conditions such as waterlogged soil or reduced O2
NUTRIENT CYCLES
other than biological nitrogen fixation, what are two other ways nitrogen can get into an ecosystem?
lighting
artificial fertilisers
NUTRIENT CYCLES
why do plants and animals need phosphorus?
to make ATP, DNA, RNA, phospholipids
NUTRIENT CYCLES
Freshwater marsh soils are normally waterlogged. This creates anaerobic conditions.
Suggest why these soils contain relatively high conc of ammonium and low conc of nitrite/nitrate ions.
Less nitrification, less conversion of ammonium ions to nitrite and nitrate ions. More denitrification
use your knowledge of NPP to explain why freshwater marshes have a high carbon use efficiency and the advantage of this
low respiration
more biomass
suggest one way in which an increase in the uptake of phosphate could increase plant growth.
used to produce ATP in cells
give two examples of bio molecules containing nitrogen that would be removed when a crop is harvested
proteins
DNA/ RNA
