Energy transfers in and between organisms — AQA A-Level Biology
In summary: Energy transfers in and between organisms is a key topic in AQA A-Level Biology. Key exam tip: Use the formula NPP = GPP - R to structure answers regarding biomass productivity.
Exam Tips for Energy transfers in and between organisms
- Use the formula NPP = GPP - R to structure answers regarding biomass productivity.
- When describing chemiosmosis, always mention the proton gradient and ATP synthase.
- Be precise with terminology: use 'saprobionts' rather than 'decomposers' where appropriate.
- Ensure you can link the structure of mitochondria and chloroplasts to their specific functions.
- Practice interpreting data on limiting factors in photosynthesis.
Common Mistakes
- Confusing the roles of ATP and reduced NADP in the light-independent reaction.
- Failing to distinguish between GPP and NPP, or omitting respiratory losses (R).
- Misunderstanding the role of oxygen in aerobic respiration (as the final electron acceptor).
- Inaccurate descriptions of the nitrogen cycle, particularly confusing nitrification with nitrogen fixation.
- Confusing the location of specific stages (e.g., glycolysis in cytoplasm vs. Krebs in matrix).
Marking Points
- Photoionisation of chlorophyll and the role of the electron transfer chain in ATP production.
- The light-dependent and light-independent reactions of photosynthesis.
- Stages of aerobic respiration: glycolysis, link reaction, Krebs cycle, and oxidative phosphorylation.
- The role of ATP synthase and chemiosmotic theory in both photosynthesis and respiration.
- Calculation of GPP, NPP, and net production of consumers.
- The nitrogen and phosphorus cycles, including the role of saprobionts and mycorrhizae.
- Environmental impacts of fertilisers, specifically leaching and eutrophication.
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