Unit 5 Flashcards
Stages of photosynthesis
-Light-dependent reaction (LDR)- thylakoid membrane of chloroplast.
-Light-independent reaction (LIR)- stroma of chloroplast.
Photoionisation of LDR
-Chlorophyll absorbs light energy which excites its electrons.
-Electrons are released from chlorophyll so it becomes positively charged.
Chemiosmosis
-Electrons move along electron transfer chain, releasing energy.
-Energy is used to actively pump protons 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 NADPH.
Photolysis of water
-Water splits to produce protons, electrons and oxygen.
-H2O –> 1/2 O2 + 2e- + 2H+
-Electrons replace those lost from chlorophyll.
Calvin cycle
-CO2 reacts with ribulose bisphosphate (RuBP).
-Catalysed by enzyme rubisco.
-Forming 2 glycerate 3-phosphate (GP) molecules.
-GP gets reduced to triose phosphate (TP).
-Using products from light dependent reaction- NADPH and energy from ATP.
-Some TP is converted to useful organic substances (e.g. glucose).
-Some TP is used to regenerate RuBP in the Calvin cycle (using energy from ATP).
How does temperature affect rate of photosynthesis?
-As temp increases, rate increases.
-Enzymes gain kinetic energy.
-So more ES complexes form.
-Above the optimum temp, rate decreases.
-Enzymes denature as H bonds in tertiary structure break.
-Fewer ES complexes form.
How does light intensity affect rate of photosynthesis?
-As light intensity increase, rate increases.
-LDR increases so more ATP and NADPH produced.
-More GP reduced to TP and more TP regenerates RuBP.
-After a certain light intensity, rate stops increasing.
-Another factor is limiting (e.g. temperature/ CO2 conc).
How does CO2 conc affect rate of photosynthesis?
-As CO2 conc increases, rate increases.
-LIR increases as more CO2 combines with RuBP to form GP.
-More GP reduced to TP.
-More TP converted to organic substances and more RuBP regenerated.
-Above a certain CO2 concentration, rate stops increasing.
-Another factor is limiting (e.g. temp/ light intensity).
Why is respiration important?
-Respiration produces ATP.
-For active transport, protein synthesis, etc.
Stages of aerobic respiration
-Glycolysis (cytoplasm)
-Link reaction (mitochondrial matrix)
-Krebs cycle (mitochondrial matrix)
-Oxidative phosphorylation (inner mitochondrial membrane)
Stages of anaerobic
-Glycolysis (cytoplasm)
-NAD regeneration (cytoplasm)
Process of glycolysis
-Glucose is phosphorylated to glucose phosphate.
-Using inorganic phosphates for 2ATP.
-Hydrolysed to 2x triose phosphate.
-Oxidised to 2 pyruvate.
-2 NAD reduced
-4 ATP regenerated (net 2)
What happens after glycolysis if conditions are anaerobic?
-Pyruvate converted to lactate or ethanol.
-Oxidising reduced NAD- NAD regenerated.
-So glycolysis can continue allowing continued production of ATP.
Why anaerobic respiration produces less ATP?
-Only glycolysis is involved which produces little ATP.
-No oxidative phosphorylation which forms majority of ATP.
Process of link reaction
-Pyruvate oxidised (and decarboxylated) to acetate.
-CO2 is produced.
-Reduced NAD produced.
-Acetate combines with coenzyme A, forming Acetyl Coenzyme A.
Process of Krebs cycle
-Acetyl coenzyme A (2C) reacts with a 4C molecules (oxaloacetate).
-Releasing coenzyme A.
-Producing a 6C molecule (citrate) that enters the Krebs cycle.
-In a series of oxidation-reduction reactions, the 4C molecules is regenerated and:
-2x CO2 lost
-Coenzymes NAD and FAD reduced.
-Substrate level phosphorylation (direct transfer of Pi from intermediate compound to ADP–> produced)
Oxidative phosphorylation
-NADH and FADH2 are oxidised to release H atoms meaning it is split into protons and electrons.
-Electrons transferred down the electron transfer chain (chain of carriers at decreasing energy levels).
-By redox reactions.
-Energy released by electrons used in the production of ATP from ADP + Pi (chemiosmotic theory).
-Energy used by electron carriers to actively pump protons from matrix to the intermembrane space.
-Protons diffuse into matrix down an electrochemical gradient via ATP synthase (which is embedded in the membrane).
-Releasing energy to synthesise ATP from ADP + Pi.
-In matric at end of ETC, oxygen is final electron acceptor- electrons can’t pass along otherwise.
-So protons, electrons and oxygen combine to form water.
Examples of other respiratory substrates
-Fatty acids from hydrolysis of lipids- converted to Acetyl Coenzyme A.
-Amino acids from hydrolysis of proteins- converted to intermediates in Krebs cycle.
How does energy enter an ecosystem and how is it transferred?
-Energy enters by photosynthesis of the producers.
-Photosynthesis makes organic matter which makes up the biomass of an organism.
-It is transferred from prey to predator when the prey is eaten.
Producers
Photosynthetic organisms that manufacture organic substances using light energy, water, carbon dioxide and mineral ions.
Consumers
Organisms that obtain their energy by feeding on (consuming) other organisms rather than using the energy of sunlight directly.
Saprobionts
-Decomposers
-A group of organisms that break down the complex materials in dead organisms into simple ones.
-In doing so, they release valuable minerals and elements into a form that can be absorbed by plants and contribute to recycling.
-Fungi and bacteria.
Food chain
Shows a feeding relationship where producers are eaten by primary consumers and they’re eaten by secondary consumers and so on.
Food web
Most animals do not rely on a single food source and within a single habitat, many food chains will be linked together.
Trophic level
-Each stage in the chain is known as a trophic level.
-Arrows represent the direction of energy flow.
Biomass
The total mass of living material in a specific area at a given time.
How is biomass measured?
-Measured using dry mass per given mass.
-g/m^2 (grams per square metre).
-Chemical energy store can be estimated using calorimetry.
Net Primary Productivity (NPP) equation:
-Chemical energy store in plant biomass after respiratory losses to environment taken into account.
-Gross Primary Production (GPP) - Respiratory losses (R)
-GPP- chemical energy store in plant biomass in a given area or volume in a given time.
NPP- importance
-Available for plant growth and reproduction.
-Available to other trophic levels in the ecosystem.
Primary/secondary productivity and units
-Rate of production.
-kJ/ha/year
How is energy lost in a food chain?
-Growth
-Some of the organism isn’t consumed.
-Some parts are consumed but can’t be digested so lost as faeces.
-Excretory materials, eg: urine.
-Heat loss from respiration.
Most of the Sun’s energy isn’t converted to organic matter because:
-Over 90% of the Sun’s energy is reflected back into space by clouds and dust or absorbed by the atmosphere.
-Not all wavelengths of light can be absorbed and used by photosynthesis.
-Light may not fall on chlorophyll.
-A factor, like low CO2 levels, may limit the rate of photosynthesis.
Net production of consumers equation:
N = I - (F+R)
N= net production
I= chemical energy store in ingested food
F= energy lost in faeces and urine
R= energy lost in respiration
Relative inefficiency between trophic levels explains why:
-Most food chains have 4 or 5 trophic levels because there is inefficient energy stores for further levels.
-Total mass of organisms in a particular place (biomass) is less at higher trophic levels.
-Total amount of energy available is less at each level as you move up.
Percentage efficiency equation:
Energy available after the transfer/ Energy available before the transfer x 100
How biomass is formed?
-During phototsynthesis, plants make organic compounds from atmospheric/ aquatic CO2.
-Most sugars synthesised are used by plants as respiratory substances.
-Rest used to make other groups of biological molecules, form biomass.
Dry mass measuring
-Sample dried in an oven.
-Sample weighed and reheated at regular intervals until mass remains constant (all water evaporated).
Calorimetry
-Known mass of dry biomass is fully combusted.
-Heat energy released heats a known volume of water.
-Increase in temp of water is used to calc chemical energy.
Calorimetry features
-Stirrer- evenly distribute heat energy.
-Air/insulation- reduces heat loss and gain to and from surroundings.
-Water- has high specific heat capacity.
Crop farming- increase efficiency
-Simplifying food webs to reduce energy losses to non-human food chains.
-Herbicides- kill weeds- less comp 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 prevent poor growth.
Lifestock farming- increase efficiency
-Reducing respiratory losses within a human food chain- more energy to create biomass.
-Restrict movement+ keep warm- less energy lost as heat from respiration.
-Treated with antibiotics- prevent loss of energy due to pathogens.
-Selective breeding to produce breeds with higher growth rates.
Nutrient cycle simple
-Nutrients are taken up by producers as simple, inorganic molecules.
-The producer incorporates the nutrient into complex organic molecules.
-When the producer is eaten, the nutrients are passed into the consumers.
-It is then passed along the food chain.
-When the producers and consumers die, complex molecules are broken down by saprobioants that release nutrients in the simplest original form.
Nitrogen cycle and stages
-Plants and animals require nitrogen in order to produce proteins and nucleic acids(RNA and DNA).
-78% of the atmosphere is nitrogen
-Bacteria convert atmospheric N2 into nitrogen containing compounds so it can be used in processes.
-Four stages are: nitrogen fixation, ammonification, nitrification and denitrification.
Nitrogen fixation
-Atmospheric nitrogen is converted into nitrogen-containing compounds.
-Carried out by nitrogen fixing bacteria (which are found in the root nodules of leguminous plants and free in the soil).
-Converts nitrogen into ammonia, which forms ammonium ions in solutions so it can be used by plants.
-Bacteria have a symbiotic relationship with the plant (rely on one another).
Ammonification
-Nitrogen compounds in waste products and dead organisms are decomposed into ammonia.
-This forms ammonium ions in the soil.
-By saprobionts which secrete enzymes for extracellular digestion.
Nitrification
-Uses nitrifying bacteria to convert ammonium ions into nitrogen containing compounds. Oxidation reaction.
-Turns them into nitrites (NO2-) then nitrates (NO3-).
-Oxidation reaction.
-Requires oxygen.
Denitrification
-Uses denitrifying bacteria.
-Bacteria use nitrates in respiration so it produces nitrogen gas.
-Anaerobic conditions.
Role of saprobionts in recycling elements
-Decompose organic compound.
-By secreting enzymes for extracellular digestion.
-Absorb soluble needed nutrients and release minerals ions.
Mycorrhizae
Symbiotic association between fungi and plant roots
Role of mycorrhizae
-Fungi act as an extension of plant roots to increase SA of root system.
-Increase rate of uptake of water and inorganic ions.
-In return, fungi receive organic compounds.
Ploughing- increasing fertility
-More ammounium converted into nitrite and nitrate- more nitrification/nitrifying bacteria.
-Less nitrate converted to nitrogen gas- less denitrification/denitrifying bacteria.
Phosphorus cycle
-Phosphate ions in rocks released by erosion/weathering.
-Phosphate ions taken up by producers/plants/algae and incorporated into their biomass,
-Rate of absorption increased by mycorrhizae.
-Phosphate ions transferred through food chains.
-Some phosphate ions lost from animals in waste products.
-Saprobionts decompose organic compounds releasing phosphate ions.
Why fertilisers?
-To replace nitrates/phosphates lost when plants harvested and lifestock removed.
-So improve efficiency of energy transfer- increase productivity/yield.
Artificial vs natural fertilisers
-Natural- organic- ions released during decomposition by saprobionts.
-Artificial- contains inorganic compounds of nitrogen, phosphorus and potassium.
Use of fertilisers- environmental issue
-Phosphates/nitrates dissolve in water leading to leaching of nutrients into lakes/rivers/oceans.
-Leads to eutrophication.
Eutrophication
-Rapid growth of algae in pond, so light blocked.
-Submerged plants die as they cannot photosynthesise.
-Saprobionts decompose dead plant matter using oxygen in aerobic respiration.
-Less oxygen for fish to respire leading to their death.
Advantage of using natural over artificial fertiliser.
-Less water soluble, less leaching, eutrophication less likely.
-Organic molecules require breaking down by saprobionts- slow release of nitrates etc.
