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Section 5 - Energy transfer in and between organisms - Coggle Diagram
Section 5 - Energy transfer in and between organisms
11 Photosynthesis
Light-dependent reaction
Absorption of light by chlorophyll in chloroplasts
Electrons become excited and leave the chlorophyll
Oxidation = loss of electron
Reduction = gain of electrons
Photoionisation of chlorophyll
Electrons are passed along electron carriers in the electron transfer chain within the thylakoid membrane
Electrons lose energy at each stage
This energy is used to make ATP
ADP and inorganic ion
Chemiosmotic theory
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Important products are ATP and reduced NADP
Light-independent reaction
Carbon dioxide reacts with ribulose bisphosphate (RuBP), a 5-carbon molecule
CO2 diffuses through stomata into the leaf
Catalysed by rubisco enzyme
Forms 2 glycerate 3-phosphate molecules (GP), a 3-carbon molecule
Does not need light directly
Calvin cycle
All within the chloroplasts
Occurs in the stroma
Structure is adapted to function
Occurs in the thylakoids (disc structures stacked together into grana)
Most of the triose phosphate is used to regenerate RuBP
Reduced NADP and ATP provides protons and energy to reduce GP into 2 triose phosphate molecules (3 carbon molecule)
NADP is returned to the light-dependent reaction
Some triose phosphate is converted into organic molecules e.g. starch, cellulose, amino acids
Products of light-dependent reaction are used in the light-independent reaction
12 Respiration
Glycolysis
A 6-carbon sugar is split into 2 pyruvate molecules (3-carbon molecules)
First stage of both aerobic and anaerobic respiration
Occurs in the cytoplasm
Glucose is phosphorylated
Requires ATP to supply phosphate groups and energy
Phosphorylated glucose splits into 2 triose phosphate molecules
Triose phosphate is oxidised
NAD is reduced
Produces 2 pyruvate molecules
2 molecules of ATP are formed per pyruvate molecule
Net gain of 2 ATP molecules per glucose
Products of glycolysis are 2 pyruvate, 2 ATP, and 2 reduced NAD
Aerobic respiration
Link reaction
Pyruvate is actively transported in mitochondrial matrix
Pyruvate us oxidised to acetate
Acetate + CoA = acetyl CoA
Reduced NAD and CO2 are produced
Acetyl CoA combines with 4-carbon molecule to make 6-carbon molecule
Krebs Cycle
Substrate-level phosphorylation produces ATP
CO2 lost
Generates reduced coenzymes NAD and FAD
Oxidation and reduction reactions
Oxidative phosphorylation
Electron transfer chain
Electrons provide energy for proton active transport
Movement of protons through ATP synthase
Chemiosmotic theory
Electrons from NAD and FAD
Anaerobic respiration
NAD is re-oxidised so it can continue to be used in glycolysis
Produces ethanol and carbon dioxide in plants and fungi
Produces lactate
Lactate can be converted back to pyruvate when oxygen is present
Lactate causes cramp and muscle fatigue
Produces only 2 ATP molecules per glucose (during glycolysis)
Occurs in absence of oxygen
13 Energy and ecosystems
Energy and ecosystems
Energy
Gross primary production
The chemical energy in the biomass of plants
NPP = GPP - R
Net primary production
Chemical energy left after accounting for respiratory losses
NPP is left over for plant growth and reprodution
NPP is also available to consumers e.g. herbivores
Secondary and tertiary consumers then obtain energy from primary consumers
Very little energy transferred at each stage for growth
Not all of the organism is consumed
Lost as heat
Lost in faeces and urine
Net production of consumers
N = I - (F + R)
Food chains are often not very long
Farming increases efficiency of energy transfer e.g. providing heating, restricting movement
Ecosystems
Producers
Plants synthesise organic substances using sunlight and carbon dioxide
Plants use the sugars for respiration and making biological molecules
Biological molecules comprise the biomass of the plant
Productivity
Rate of production of biomass in a given area in a given time
Biomass
Mass of living material
Fresh mass can be affected by water, so dry mass is used
The chemical energy in dry mass is estimated with calorimetry
Nutrient cycles
Fertilisers
Provides nitrates and phosphates to plants for growth
Improves productivity
Leaching
Eutrophication
Natural (organic) and artificial (ionorganic)
Nitrogen cycle
Nitrogen is required for proteins and nucleic acids
Producers and consumers die and excrete waste with nitrogen-containing compounds, which undergoes ammonification again
Ammonification - ammonia is produced from nitrogenous compounds e.g. urea, proteins
Saprobiontic fungi and bacteria release ammonia into soil
Nitrification - conversion of ammonia to nitrite ions, then to nitrate ions
Nitrifying bacteria and oxygen are required
Absorption of nitrate ions by plants
Mycorrhizae improves water and ion uptake in plants
Nitrogen fixation - conversion of nitrogen gas into nitrogen-containing compounds by bacteria
Denitrification - bacteria convert nitrates in soil into nitrogen gas
Occurs in anaerobic conditions
Phosphorus cycle
Found in ATP, proteins, and phospholipids
Phosphorus is mainly found as phosphate ions in rocks
Weathering and erosion of rocks
Phosphate ions become dissolved in rivers, oceans, and lakes
Plants absorb phosphate ions
Death of plants and animals with phosphorus-containing compounds
Remains are deposited and phosphates are returned to rocks
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