Energy Transfers in and Between Organisms | AQA A-Level Biology (7402)

Energy Transfers in and Between Organisms

195 questions
15 subtopics
Paper 2, and available on Paper 3
Paper 2 and Paper 3

Energy Transfers in and Between Organisms is examined on Papers 2 and 3 of AQA Biology, which draw on topics 5 to 8.

156 recall questions across 15 subtopics.

Sample questions from Energy Transfers in and Between Organisms

Answer each one closed book first, then open the answer.

Photoionisation and ATP from the light-dependent reaction

Define photoionisation in the context of photosynthesis.

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Photoionisation is the process by which chlorophyll loses electrons after absorbing light energy.
Chemiosmosis, photolysis and products for the Calvin cycle

Define photolysis.

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Photolysis is the splitting of water molecules using light energy.
Glasshouse conditions, pigment chromatography and DCPIP

How are the electrons lost from chlorophyll during photoionisation replaced?

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Electrons from photolysis of water replace the electrons lost from chlorophyll.
Glycolysis and its products

What happens to triose phosphate in the third stage of glycolysis?

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Triose phosphate is oxidised to pyruvate
Acetylcoenzyme A and the Krebs cycle

What happens to coenzyme A when acetylcoenzyme A reacts with the four-carbon molecule?

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Coenzyme A is released
Oxidative phosphorylation, other substrates and respirometers

Why is a respirometer left in a water bath for several minutes before the tap is closed and readings begin?

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So that the apparatus and gases reach the water bath temperature; otherwise gas expansion or contraction would move the liquid.
Net production of consumers and productivity

In the consumer production equation N = I − (F + R), what does I represent?

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The chemical energy store in ingested food
Farming practices, transfer efficiency and the production equations

Why is energy lost in faeces considered unavailable to the consumer that produced it?

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Because faeces contain undigested material that was never absorbed, so the chemical energy it contains is lost to the environment rather than being used by the consumer

The 15 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
Photoionisation and ATP from the light-dependent reaction	Recall questions on how light causes photoionisation of chlorophyll, how energy from the released electrons makes ATP and reduced NADP, and the electron transfer chain, proton movement and ATP synthase.	8
Chemiosmosis, photolysis and products for the Calvin cycle	Recall questions on where ATP synthase sits in the chloroplast, chemiosmotic theory, the protons, electrons and oxygen produced by photolysis of water, and how ATP and reduced NADP supply the light-independent reaction.	8
Carbon fixation, triose phosphate and limiting factors	Recall questions on carbon dioxide reacting with RuBP catalysed by rubisco, the reduction of GP to triose phosphate, its uses, and how light, carbon dioxide and temperature limit photosynthesis.	10
Glasshouse conditions, pigment chromatography and DCPIP	Recall questions on raising carbon dioxide and temperature in glasshouses, the Calvin cycle, separating leaf pigments by chromatography and calculating Rf values, and using DCPIP to measure dehydrogenase activity in chloroplasts.	32
Glycolysis and its products	Recall questions on respiration as the source of ATP, glycolysis in the cytoplasm as the stage shared by aerobic and anaerobic respiration, the phosphorylation of glucose, triose phosphate, net ATP and reduced NAD.	9
Anaerobic respiration and the oxidation of pyruvate	Recall questions on pyruvate becoming ethanol in yeast or lactate in muscle, why regenerating oxidised NAD matters, and pyruvate's active transport into the mitochondrial matrix and oxidation to acetate.	9
Acetylcoenzyme A and the Krebs cycle	Recall questions on acetate combining with coenzyme A in the link reaction, acetylcoenzyme A reacting with a four-carbon molecule, and the oxidation reactions, ATP and carbon dioxide of the Krebs cycle.	10
Oxidative phosphorylation, other substrates and respirometers	Recall questions on the electron transfer chain, chemiosmosis and ATP synthase in oxidative phosphorylation, lipids and amino acids as respiratory substrates, and measuring the rate of respiration of yeast.	22
Biomass and gross and net primary production	Recall questions on how plants use the sugars they make, measuring biomass as dry mass or mass of carbon, estimating its energy by calorimetry, and the equation linking net and gross primary production.	11
Net production of consumers and productivity	Recall questions on how net primary production is used, the equation for net production of consumers, primary and secondary productivity and their units, and how farming raises energy transfer efficiency.	10
Farming practices, transfer efficiency and the production equations	Recall questions on simplifying food webs and reducing respiratory losses in farm animals, calculating the efficiency of energy transfer, and applying the equations for net primary and consumer production.	13
Saprobionts and the phosphorus cycle	Recall questions on nutrient cycles, how saprobionts digest dead matter extracellularly, and how phosphate passes from rocks to soil, plants, animals and the sea, including guano.	16
Mycorrhizae, ammonification and nitrification	Recall questions on how mycorrhizae help plants take up water and inorganic ions, ammonification by saprobionts, and the two stages of nitrification.	10
Nitrogen fixation, denitrification and fertilisers	Recall questions on why nitrifying bacteria need aerated soil, nitrogen fixation, denitrification in waterlogged soil, and why natural and artificial fertilisers replace nitrates removed by harvesting.	10
Leaching, eutrophication and nutrient cycles reviewed	Recall questions on leaching and each stage of eutrophication from algal bloom to oxygen depletion, and on reviewing nitrification and the importance of the phosphorus cycle.	17

Energy Transfers in and Between Organisms is 195 of the 1,977 questions in the guide.Get the guide, £8

How the guide is worked

Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.

Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.

Read the full method, the return schedule and the research behind it.