biology T5 - energy transfers in and between organisms

• Acetyl coenzyme A


  A two-carbon molecule formed in the link reaction when acetate reacts with coenzyme A. It is oxidised in the Krebs cycle.
• Aerobic respiration


  1. Glycolysis

  2. Link reaction

  3. Krebs cycle

  4. Oxidative phosphorylation
• Overall equation for aerobic respiration: C6H12O6 + 6O2 ⟶ 6CO2 + 6H2O
• Ammonification


  The production of ammonia when saprobiontic microorganisms feed on organic nitrogen-containing compounds. Ammonium ions are formed and added to the soil.
• Anaerobic respiration


  1. In animals, lactate is produced

  2. In plants and microorganisms, ethanol and carbon dioxide are produced
• Anaerobic respiration produces less ATP than aerobic respiration
• Artificial fertilisers


  Man-made compounds generally containing nitrogen, phosphorus and potassium that are used to increase the mineral content of soils
• ATP synthase


  An enzyme found embedded in cellular membranes that phosphorylates ADP to form ATP as protons flow through it
• Biomass


  The total mass of organic material, measured in a specific area over a set time period. This can be calculated in terms of dry mass or mass of carbon per given area.
• Calorimetry


  A technique used to estimate the chemical energy store in dry biomass
• Carnivores


  Animals that prey on and eat other animals. They can be secondary or tertiary consumers.
• Chemiosmotic theory


  The synthesis of ATP through the movement of protons down their concentration gradient across a semipermeable membrane, catalysed by ATP synthase
• Chlorophyll


  A photosynthetic pigment located in the thylakoids of chloroplasts that absorbs light energy and becomes ionised
• Coenzymes


  Molecules that help enzymes carry out their function e.g. NAD, FAD, NADP
• Consumers


  Organisms that feed on other organisms to obtain energy
• Denitrification


  The conversion of nitrate ions to nitrogen gas by denitrifying bacteria
• Denitrifying bacteria


  Anaerobic microorganisms found in waterlogged soils responsible for the reduction of nitrate ions to nitrogen gas
• Ecosystem


  The community of organisms (biotic) and non-living (abiotic) components of an area and their interactions
• Efficiency of energy transfer

  The efficiency of energy transfer between trophic levels is calculated using: Energy transferred to next trophic level / Energy available at previous trophic level
• Electron acceptor


  Oxygen acts as the final electron acceptor in the electron transfer chain: ½O2 + 2e- + 2H+ ⟶ H2O
• Electron transfer chain


  A series of electron carrier proteins that transfer electrons in a chain of oxidation-reduction reactions
• Eutrophication


  When a body of water becomes excessively rich with nutrients (often from fertilisers)
• FAD


  A carrier molecule that becomes reduced when it takes up protons and electrons during the Krebs cycle, forming reduced FAD
• Food chain


  Describes the feeding relationships between organisms and the resultant stages of biomass transfer. It takes the form: producer ⟶ primary consumer ⟶ secondary consumer ⟶ tertiary consumer
• Glycerate 3-phosphate (GP)


  A three-carbon molecule which is reduced by reduced NADP in the light-independent stage of photosynthesis to form two molecules of triose phosphate (TP). This requires ATP.
• Glycolysis


  The first stage of aerobic and anaerobic respiration that takes place in the cytosol of the cell and breaks down glucose into two molecules of pyruvate. Two molecules of ATP and two molecules of reduced NAD are also formed.
• Gross primary production (GPP)


  The total amount of chemical energy stored in plant biomass in a set area or volume
• Krebs cycle


  A series of oxidation-reduction reactions in the matrix of the mitochondria in which acetyl coenzyme A is oxidised generating reduced NAD, reduced FAD, ATP and carbon dioxide.
• Light-dependent reaction


  The second stage of photosynthesis that uses light energy to produce ATP, reduced NADP and oxygen (by-product). It takes place in the thylakoids of the chloroplast.
• Light-independent reaction


  The third stage of photosynthesis, also known as the Calvin cycle, in which the products of the light-dependent stage and carbon dioxide are used to form a simple sugar. This stage does not require light energy and takes place in the stroma of the chloroplast.
• Link reaction


  The second stage of aerobic respiration that takes place in the mitochondrial matrix and converts pyruvate into acetyl coenzyme A and carbon dioxide. Reduced NAD is also formed. Overall: Pyruvate + NAD + CoA ⟶ acetyl CoA + reduced NAD + CO2
• Mycorrhizae


  Mutualistic associations between some species of fungi and the roots of many plants that retain water and minerals around the roots
• NAD


  A carrier molecule that becomes reduced when it takes up protons and electrons during aerobic respiration, forming reduced NAD
• NADP


  A carrier molecule that becomes reduced when it takes up protons and electrons during the light-dependent stage of photosynthesis, forming reduced NADP
• Natural fertilisers


  Dead and decaying organic matter used to increase the mineral content of soils
• Net primary productivity (NPP)


  The chemical energy store that remains when energy losses due to respiration are subtracted from the total energy store. This is used in plant growth or reproduction and is also available to other trophic levels.
• Nitrification


  The conversion of ammonium ions to nitrate ions by nitrifying bacteria. This takes place in two stages: ammonium ions are oxidised to nitrite ions; nitrite ions are oxidised to nitrate ions.
• Nitrifying bacteria


  Aerobic microorganisms found in the soil responsible for the oxidation of ammonium ions to nitrate ions
• Nitrogen cycle


  The cycle through which nitrogen moves between living organisms and the environment, involving ammonification, nitrification, nitrogen fixation and denitrification
• Nitrogen fixation


  The conversion of atmospheric nitrogen gas into nitrogen-containing compounds by nitrogen-fixing bacteria in the soil or root nodules of legumes