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Energy transfers official content
Energy transfers official content develops AQA A-Level Biology knowledge through Photosynthesis, Respiration, Energy and ecosystems, Nutrient cycles. Students should connect molecular detail, cell-level mechanisms, organism-level outcomes and ecological or genetic consequences where relevant, rather than treating each objective as an isolated definition. The topic overview should help learners locate every learning objective, recognise the main command words and prepare for data-led questions. Focus on precise biological vocabulary, cause-and-effect chains, and evidence from practical work or experimental observations. Useful revision links include Describe, light-dependent, reaction, including, chlorophyll, photoionisation,, electron, transfer,, production,, reduced. Strong answers should state the biological principle, apply it to the named context, interpret any data carefully and finish with a clear consequence or evaluation. Common mistakes include giving GCSE-level descriptions, missing the scale of organisation, or using a correct term without explaining why it matters in this A-Level context.
20
Objectives
10
Flashcards
10
Questions
90 min
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Syllabus checklist
What you need to know
20 objective pages available
Photosynthesis7 objectives
- Describe the light-dependent reaction including chlorophyll photoionisation, electron transfer, ATP production, reduced NADP and photolysis.
- Describe the Calvin cycle using RuBP, GP, triose phosphate, ATP, reduced NADP and rubisco.
- Identify environmental factors limiting photosynthesis.
- Evaluate data on agricultural practices used to overcome limiting factors.
- Required practicals 7 and 8: investigate leaf pigments by chromatography and dehydrogenase activity in chloroplast extracts.
- Required practical 7: use chromatography to investigate pigments isolated from leaves.
- Required practical 8: investigate dehydrogenase activity in chloroplast extracts.
Respiration5 objectives
- Describe glycolysis, the link reaction and the Krebs cycle in respiration.
- Explain oxidative phosphorylation using electron transfer, proton gradients and ATP synthase.
- Explain roles of NAD and FAD in respiration.
- Compare aerobic respiration with anaerobic respiration in mammals and yeast.
- Required practical 9: investigate the effect of a named variable on respiration rate in cultures of single-celled organisms.
Energy and ecosystems4 objectives
- Explain biomass transfer through food chains and food webs.
- Calculate gross production, net production and respiratory loss where data are provided.
- Explain why energy transfer between trophic levels is inefficient.
- Evaluate ways to increase productivity in agricultural systems.
Nutrient cycles4 objectives
- Explain decomposition by saprobionts and nutrient release.
- Describe nitrogen-cycle processes including ammonification, nitrification, nitrogen fixation and denitrification.
- Describe phosphorus cycling through rocks, soil, organisms and decomposers.
- Explain effects of environmental conditions on decomposition and nutrient cycling.
Key terms
Exam tips
- Use diagrams to illustrate processes: When describing processes like the light-dependent reactions, include labeled diagrams to enhance clarity.
- Use diagrams to illustrate processes: When describing the Calvin cycle, draw a diagram to show the flow of carbon and the role of different molecules.
Common mistakes
- Confusing photolysis with respiration: Remember that photolysis occurs during photosynthesis and is specifically the splitting of water, while respiration involves the consumption of oxygen.
- Confusing GP with triose phosphate: Remember that GP is an intermediate product that is converted into triose phosphate, which can then be used to synthesize glucose.
Practice preview
- What is the primary role of chlorophyll in the light-dependent reactions of photosynthesis?
- Describe the process of photolysis in the light-dependent reactions of photosynthesis.
- A scientist measures the rate of oxygen production in a plant under different light intensities. Explain how the light-dependent reactions contribute to the observed changes in oxygen production.
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