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Topic 5 - ID, Energy transfer - Coggle Diagram
Topic 5 - ID
Photosynthesis
Chloroplast Structure
Thylakoid membrane - folded membranes which contain photosynthetic proteins (chlorophyll) and electron carrier proteins are embedded within membranes which are both used in LDR.
Granum - stack of thylakoid membranes.
Stroma - fluid center which contains enzymes involved in LIR.
Inner and outer membrane control what can enter and leave the organelle.
Light dependent reaction
LDR occurs in the thylakoid membrane or grana.
Light energy and water are used to create ATP and reduced NADP which are needed in the LIR.
Photolysis of water
Light energy is absorbed by Chlorophyll and splits water into oxygen, H+ and e-.
2(H20) = O2 + 4e- + 4H+
The H+ is picked up by NADP to form NADPH.
The e- are passed along a chain of electron carrier proteins.
The O2 is either used for respiration or diffuses out of the leaf via stomata.
Photoionisation of Chlorophyll
Light energy is absorbed by the chlorophyll and the energy results in electrons becoming excited and raising up an energy level to leave chlorophyll.
Therefore, the chlorophyll has been ionised by light.
Some of the energy from the released electrons is used to make ATP and reduced NADP in chemiosomsis.
Chemisomosis
The electrons that gained energy and left the chlorophyll (PSII) move along a series of proteins embedded within the thylakoid membrane.
As they move along they release energy and some of the energy from the electrons is used to pump protons across the chloroplast membranes.
An electrochemical gradient is created. The protons diffuse through the enzyme ATP synthase which results in the production of ATP.
The protons combine with the co-enzyme NADP to become reduced NADP. Electrons accepted by PSI & ones lost from PSII are replaced by those produced in photolysis.
Because the protons move from a high to low concentration gradient this is known as chemiosmosis.
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The light-independent reaction
The light-independent reaction is the calvin cycle.
The calvin cycle occurs in the stroma, and this fluid contains the enzyme RuBisCo which catalyses this reaction. This stage is temperature sensitive.
LIR (Calvin cycle)
Carbon dioxide reacts with ribulose bisphosphate (RuBP) to form two molecules of glycerate phosphate (GP). This reaction is catalysed by the enzyme Rubisco.
GP is reduced to triose phosphate (TP) using energy from ATP and by accepting a H from reduced NADP.
Some of the carbon from TP leaves the cycle each turn to be converted into useful organic substances - hexose sugar (glucose).
The rest of the molecule is used to regenerate RuBP with the energy from ATP.
Whilst Glucose is the product, this monosaccharide can join to form dissacharides such as sucrose, and polysaccharides such as celluose and starch. It can also be converted into glycerol and therefore combine with fatty acids to make lipids for the plant.
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Limiting Factors
Factors that reduce the rate of photosynthesis.
These could be temperature, carbon dioxide concentration or light intensity.
For maximum photosynthesis, and therefore plant growth, common agricultural practices incorporate techniques to remove limiting factors.
E.g artificial lights to maximise light intensity; heating a greenhouse to increase temperature & burning fuel** to release more carbon dioxide.
The extent that each technique is used needs to be considered in terms of profit - cost effectiveness in comparison to growth.
Respiration
Aerobic respiration
GlycolysisFirst stage of anaerobic and aerobic respiration.It occurs in the cytoplasmSTEPS:
- Phosphorylating glucose to glucose phosphate, using ATP (ADP by-product)
2.Glucose biphosphate splits in to triose phopshate.
- Oxidation of triose phosphate to produce pryuvate using NAD and 2 ATP.
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Anaerobic respirationIn the absence of oxygen respiration occurs anaerobically. It occurs in the cytoplasm only.The pyruvate produced in glycolysis is reduced to form:
- Ethanol and carbon dioxide - in Plants and Microbes.
- Lactate in animals.
by gaining the hydrogen from NADH.
This oxidises NADH producing NAD so that it can be reused in glycolysis and ensure more ATP is produced.
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Nitrogen cycle
The importance of the Nitrogen cycleThe air is 78% nitrogen. however plants and animals cannot obtain nitrogen through gas exchange.Nitrogen gas contains a triple bond. Microorganisms are required to convert nitrogen gas into nitrogen containing substances that plants and animals can absorb.Molecules containing nitrogen:
- Proteins
- ATP
- Nucleic acids
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Energy transfer
In any ecosystem, plants are the producers in a food web as they are able to produce their own carbohydrates using carbon dioxide in the atmosphere and water.
Between each trophic level in a food web the majority of the energy is lost due to respiration and excretion. The remaining energy is used to form the biomass.
The amount of biomass remaining in an organism can be measured in terms of mass of carbon or dry mass of tissue per given area.
Net production of consumers
N = I - F + R
I = The chemical energy store in ingested food.
F = The chemical energy lost to the environment in faeces or urine.
R = respiratory loss.
Rates of productivity
Rates of productivity are recorded using units KJ ha-1 year-1
KJ is the unit of energy, but these units also include per unit area and per year.
It is recorded per unit area to standardize the results to enable environments to be compared - it takes into account that different environments will vary in size.
The units are also per year to take into account the impact of seasons will have on rain, light and heat - it provides an annual average to allow fair comparisons between enviroments.
NPP & GPP
How productive an ecosystem is depends on the abiotic and biotic factors. Plenty of water, light, warmth and green plants will maximise the rates of photosynthesis and therefore result in more carbohydrates being produced in the plants.
This can be quantified using GPP and NPP.
Gross Primary production (GPP) is the chemical energy store in plant biomass, in a given area or volume. It is the total energy resulting from photosynthesis.
Net Primary Production (NPP) is the chemical energy store in plant biomass taking into account the energy that will be lost due to Respiration (R)
NPP = GPP - R
