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Glucose C6H12O6 - a single sugar which is produced in photosynthesis. ATP An activated nucleotide found in all living organisms, which is produced during respiration and acts as an energy carrier. ATP is produced during the light-dependent reaction of photosynthesis. metabolism the chemical processes that occur within a living organism in order to maintain life. Photosynthesis A complex metabolic pathway involving many intermediate reactions. Some energy in light is conserved in the form of chemical bonds. There are three main stages: capturing the light energy, the light-dependent reaction and light-independent reaction.
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Photolysis Light energy splits 2 water molecules into 4 electrons, 4 hydrogen ions (protons) and an oxygen molecule (light-dependent reaction). These electrons replace the electrons lost from a chlorophyll molecule when light strikes it. Oxidation Loss of electrons or loss of hydrogen or gain of oxygen with a substance Reduction Gain of electrons or gain of hydrogen or loss of oxygen from a substance
may have tubular extensions (intergranal lamellae) which join up with thylakoids in adjacent grana. Stroma Fluid-filled matrix where the light-independent stage of photosynthesis takes place. Chlorophyll Photosynthetic pigment inside thylakoids which absorbs light energy. Can become ionisied. Light-dependent reaction Stage of photosynthesis in which light energy is required to produce ATP and reduced NADP
Photoionisation Process by which a chlorophyll molecule becomes ionised. Caused by the chlorophyll molecule absorbing light energy and boosting the energy of a pair of electrons within a chlorophyll molecule, raising them to a higher energy level and they become so energetic they leave the chlorophyll molecule altogether and are taken up by an electron carrier. Thylakoid membrane Contains a transfer chain where electrons are passed along a number of electron carriers in a series of oxidation-reduction reactions. Where chemiosmotic theory happens - ATP is made. Proton pumps A protein which actively transports protons into the thylakoid using energy from electrons from chlorophyll. They mean a concentration gradient of protons is maintained across the thylakoid membrane with a high concentration inside the thylakoid space a low concentration in the stroma. Electron transfer chain How electrons are passed along a number of electron carriers in a series of oxidation-reduction reactions. Each new carrier is at a slightly lower energy level than the previous one in the chain, and so the electrons lose energy at each stage, which is used to combine an inorganic phosphate molecule with an ADP molecule to make ATP.
Light-independent reaction Stage of photosynthesis which does not require light energy directly, but does need the products of the light dependent reaction to reduce CO2 and form carbohydrate Calvin Cycle A biochemical pathway (part of the light-independent reaction) where CO2 is reduced to form carbohydrate. It takes 6 turns of the Calvin cycle (6 CO2, 18 ATP and 12 NADPH) to make one hexose sugar (because 1/6 molecules of TP are used to make useful substances e.g. glucose and 5/6 molecules of TP are used to make RuBP). 1 CO2 (1C) + 1 RuBP (5C) --> 2 GP (2 x 3C) + (2 NADPH + 2 ATP) --> 2 TP (2 x 3C) --> Glucose (6C) or RuBP (needs 1 ATP to make RuBP) (5C) Ribulose bisphosphate (RuBP) A 5 carbon sugar (in the Calvin cycle) which reacts with carbon dioxide in the stroma to produce two molecules of GP. This reaction is catalysed by rubisco (ribulose biphosphate caryboxylase). Glycerate 3 phosphate (GP)
A 3 carbon acid (in the Calvin cycle) which reduced NADP is used to reduce to TP using energy supplied by ATP. Triose Phosphate (TP) A 3 carbon sugar (in the Calvin cycle) which can be converted to organic substances that the plant requires such as starch, cellulose, lipids, glucose, amino acids and nucleotides, but most are used to regenerate ribulose biphosphate using ATP from the light-dependent reaction. Limiting factor A variable that limits the rate of a chemical reaction Aerobic Requires glucose, oxygen and produces carbon dioxide, water and up to 38 molecules of ATP ( from glycolysis, 2 from Krebs cycle and up to 34 from oxidative phosphorylation). Anaerobic Releasing energy from glucose without oxygen (produces lactate in animals and ethanol and carbon dioxide in plants and fungi) and 2 molecules of ATP.
FAD
A hydrogen carrier molecule which is important in the Krebs cycle. Pyruvate 2 molecules of this are produced by glycolysis. If there is no oxygen present then it will be converted into either lactate or ethanol during anaerobic respiration. If oxygen is present it will be actively transported into the matrix of the mitochondria where it is oxidized to acetate. Link reaction Process linking Glycolysis to the Krebs Cycle (in the matrix of the mitochondria), where the 2 molecules of pyruvate are converted to CO2 and acetylcoenzyme A. 2 NAD molecules are reduced to form reduced NAD. Pyruvate + NAD + CoA --> acetyl CoA + reduced NAD + CO Acetyl coenzyme A Formed in the link reaction when coenzyme A combines with acetate (2C). Kreb's cycle
A series of aerobic biochemical reactions in the matrix of mitochondria of most eukaryotic cells by which energy is obtained through introducing acetylcoenzyme A into a cycle of oxidation- reduction reactions (in the matrix of the mitochondria). Acetyl CoA combines with a 4C molecule to produce a 6C molecule. This then loses 2 CO2 and hydrogen to give a 4C molecule and ATP due to substrate level phosphorylation. The 4C molecule then combines with acetyl CoA to continue the cycle. Per glucose molecule it produces 2 molecules of ATP and 6 reduced NAD and 2 reduced FAD. 2 acetyl CoA + 6NAD+ + 2FAD + 2ADP + 2H3PO4 --> 4CO2 + 6 NADH + 6H+ + 2FADH2 + 2ATP Substrate level phosphorylation Happens in plant and animal cells when phosphate groups are transferred from donor molecules to ADP to form ATP. Oxidative phosphorylation The formation of ATP in the electron transport system of aerobic respiration. Happens in the mitochondria within the inner folded membrane (cristae). It involves the transfer of electrons down a series of electron carrier molecules which form an electron transfer chain.
Theory of oxidative phosphorylation. As electrons flow along the chain, they release energy which causes the active transport of protons across the inner mitochondrial membrane which means a concentration gradient of protons is maintained with a higher concentration of protons in the inter-membranal space than in the mitochondrial matrix. They then diffuse back into the mitochondrial matrix through ATP synthase channels which forms ATP. Proton pump A protein which actively transports protons into the inter-membranal space using energy from the energy released by electrons as they flow along the chain. They mean a concentration gradient of protons is maintained across the inner mitochondrial membrane with a high concentration in the inter-membranal space and a lower concentration in the mitochondrial matrix. Electron acceptor Oxygen acts as the final acceptor of electrons in the electron transfer chain. Oxidation-reduction A chemical reaction in which electrons are transferred from one substance to another substance. The substance losing electrons is oxidized and the substance gaining the electrons is reduced.
Biomass The total mass of living material in a specific area at a given time. Usually measured in gm-2. Fresh mass is quite easy to assess, but varies depending on the water content. Measuring dry mass overcomes this problem but the organism must be killed, it is usually only a small sample and may not be representative. Calorimetry The chemical energy store in a dry mass can be estimated using this technique. When a sample of dry material is weighed and then burnt in pure oxygen within a sealed container (bomb). The bomb is surrounded by a water bath and the heat of combustion causes a temperature rise. This can be used to work out the energy released from the mass of burnt biomass. Producer Photosynthetic organism that manufacture organic substances using light energy, water, carbon dioxide and mineral ions.
GPP
Gross primary production which is the total quantity of the chemical energy store in plant biomass, in a given time. Plants use 20-50% of this energy in respiration. NPP Gross primary production - respiratory losses. The chemical energy store which is left when these losses to respiration have been taken into account. This is available for plant growth and reproduction and available to other trophic levels in the ecosystem (such as consumers and decomposers). Respiratory losses Taken away from GPP to calculate NPP. Food chain
Describes a feeding relationship in which the producers are eaten by primary consumers, which are eaten by secondary consumers, which are then eaten by tertiary consumers. These could then be eaten by quarternary consumers. Each stage is referred to a trophic level. Food web How food chains link together in a habitat to form a food web. Pyramid of Number A pyramid drawn with bar lengths proportional to the numbers of organisms present Pyramid of Biomass A pyramid drawn with bar lengths proportional to the mass of plants/animals
Percentage efficiency Can be calculated by dividing the energy available after the transfer by energy available before the transfer x 100. Biological control Controlling pests by introducing predators Selective breeding Breeding of organisms by human selection of parents for certain characteristics Ecosystem All the living and non-living components of a particular area. Saprobiontic microorganism Also known as saprophyte - an organism that obtains its food from the dead or decaying remains (detritus) of other organisms. Detritivores
Organisms that help saprophytes do their job. They feed on pieces of dead and decaying material and finely break it up increasing its surface area. Decomposer Any organism which breaks down organic matter. Include saprophytes and detritivores. Nitrogen cycle Four main stages: ammonification, nitrification, nitrogen fixation and denitrification. This is because all living organisms require a source of nitrogen from which to manufacture proteins, nucleic acids and other nitrogen-containing compounds. Nitrogen fixation Conversion of nitrogen gas into nitrogen-containing compounds. Carried out by free-living nitrogen fixing bacteria and mutualistic nitrogen-fixing bacteria which live in nodules on the
