- 8.1 Metabolism
- 8.2 Cell respiration
- 8.3 Photosynthesis
This pages gives outline details of the content of the topic together with essential questions and student skills and applications. Helpful for revision.
- A chain or a cycle of enzyme-catalysed reactions makes a metabolic pathway.
- Enzymes catalyse chemical reactions by lowering the activation energy.
- Competitive inhibitors for example in medicine - ethanol and Fomepizole used as competitive inhibitors for antifreeze poisoning.
- Non-competitive inhibitors. E.g. Drugs for treatment of malaria.
- End-product inhibition can control metabolic pathways - e.g. In the pathway that converts threonine to isoleucine.
- The use of databases to identify potential new anti-malarial drugs. In the ER role play: students will have seen this
- In the Enzyme inhibition experiment students will calculate and plot rates of reaction from raw experimental results.
- They will also distinguish different types of inhibition from graphs at specified substrate concentration.
Introduction to reactions in respiration
- Cell respiration involves:
- the oxidation and reduction of electron carriers.
- the phosphorylation of molecules which makes them less stable.
- decarboxylation removes a carbon atom from a molecule
Glycolysis & the Krebs cycle
- Glycolysis is the conversion of glucose to pyruvate in the cytoplasm giving a small net gain of ATP(without the use of oxygen.)
- Aerobic cell respiration converts the pyruvate by decarboxylation and oxidation, into an acetyl compound.
- In the link reaction acetyl is attached to coenzyme A to form acetyl coenzyme A.
- In the Krebs cycle,
- the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating carbon dioxide.
- reduced NAD and FAD (NADH+H+ and FADH+) carry energy released by oxidation reactions to the cristae of the mitochondria.
The electron transport chain & Mitochondrion structure.
- the electron transport chain in the membrane of the cristae is coupled to proton pumping.
- oxygen is the final electron acceptor.
- In chemiosmosis protons diffuse through ATP synthase to generate ATP.
- Oxygen binds with the free protons to maintain the hydrogen gradient and resulting in the formation of water.
- The structure of the mitochondrion is adapted its function. Annotate a diagram of a mitochondrion to show these adaptations
- Active mitochondria have been studies using electron tomography - images.
- students will be able to identify where decarboxylation and oxidation reactions occur in diagrams of the pathways of aerobic respiration.
- The names of the intermediate compounds in gylcolysis and the Krebs cycle are not required.
- Happen in the thylakoid membranes and in the space inside them.
- Reduced NADP (NADPH2) and ATP are produced in the light-dependent reactions.
- Light absorbed by photosystems generates excited electrons.
- Photolysis of water generates electrons for use in the light-dependent reactions.
- Excited electrons are transfered between carriers in the thylakoid membranes.
- Excited electrons from Photosystem II are used to generate a proton gradient.
- ATP synthase in the thylakoids generates ATP using the proton gradient.
- Excited electrons from Photosystem I are used to reduce NADP to NADPH2.
- Take place in the stroma.
- RuBP carboxylase enzyme catalyses the carboxylation of ribulose bisphosphate (RuBP).
- Glycerate 3-phosphate is reduced to triose phosphate using "reduced NADP" (NADPH2) and ATP.
- Triose phosphate is used to regenerate RuBP and produce carbohydrates.
- Ribulose bisphosphate (RuBP) is regenerated using ATP.
- The structure of the chloroplast is adapted to its function in photosynthesis.
- to recognise details of Calvin’s experiment to elucidate the carboxylation of RuBP.
- to be able to annotate a diagram showing the adaptations of a chloroplast to its function.
This topic covers the way enzyme pathways form a cell's metabolism as well as specific examples of these pathways. The action of enzymes and their substrates is required as well as the way in which competitive and non-competitive inhibitors change the rate