Process
AQA A-Level Biology 7402
Biological Molecules
Topic overviewMonomers, polymers, condensation and hydrolysisMonosaccharides, disaccharides and glycosidic bondsAlpha and beta glucose, amylose and amylopectinHow starch, glycogen and cellulose suit their functionsCellulose microfibrils and tests for sugars and starchTriglycerides, fatty acids and phospholipid structureProperties of lipids and the emulsion testThe general structure of amino acidsPeptide bonds, polypeptides and bonds in proteinsLevels of protein structure, the biuret test and chromatographyActivation energy, induced fit and enzyme specificityEnzyme and substrate concentration and inhibitionpH, temperature, initial rates and measurement uncertaintyDNA, RNA and the components of a nucleotideBase pairing in DNA and RNAPhosphodiester bonds and the DNA double helixDoubts about DNA, base ratios and RNA structureSemi-conservative replication, helicase and DNA polymeraseSteps of replication and the Meselson-Stahl experimentATP structure, hydrolysis and resynthesisWater as a metabolite, solvent and coolantHydrogen, iron, sodium and phosphate ions
Cells
Topic overviewCell-surface membrane, nucleus and mitochondriaChloroplasts, Golgi apparatus and lysosomesRibosomes, endoplasmic reticulum, cell walls and vacuolesCell specialisation, levels of organisation and organelle rolesProkaryotic cell structure and virus particlesOptical and transmission electron microscopesScanning electron microscopes, magnification and graticulesCell fractionation, homogenisation and ultracentrifugationOrder of sedimentation, artefacts and fractionation conditionsThe cell cycle, interphase and the stages of mitosisSpindle fibres, cytokinesis and uncontrolled cell divisionBinary fission, viral replication and root tip squashesMitotic index, mitosis stages and size calculationsThe fluid-mosaic model and cholesterolSimple diffusion, facilitated diffusion and membrane proteinsOsmosis, water potential and active transportCo-transport in the ileum and adaptations for rapid transportTransport rates, dilution series and membrane permeabilityAntigens, cell recognition and phagocytosisAntigen-presenting cells, T cells and clonal selectionAntibody structure, agglutination and antigen-antibody complexesMemory cells, vaccination and active and passive immunityHIV structure and replicationAIDS, monoclonal antibodies, ELISA and clinical trials
Organisms Exchange Substances with Their Environment
Topic overviewSurface area to volume ratio, metabolic rate and calculationsGas exchange in single-celled organisms, insects and fishLeaf gas exchange, insect water loss and xerophytesTrachea, bronchi, alveoli and lung dissectionInspiration, expiration and pulmonary ventilation rateLung disease, correlation, insect tracheae and Spearman's rankDigestion of carbohydrates and lipidsEndopeptidases, exopeptidases and dipeptidasesCo-transport of amino acids, micelles and chylomicronsHaemoglobin, red blood cells and the dissociation curveCooperative binding, the Bohr effect and different haemoglobinsDouble circulation and the major blood vesselsHeart chambers, the cardiac cycle and heart dissectionArteries, arterioles, veins and capillariesTissue fluid, cardiovascular risk factors and semilunar valvesXylem structure and the cohesion-tension theoryPhloem structure, companion cells and translocationMass flow from source to sink, tracers and ringingEvaluating mass flow, potometers and transpiration rate
Genetic Information, Variation and Relationships Between Organisms
Topic overviewProkaryotic and eukaryotic DNA, chromosomes and histonesDNA in mitochondria and chloroplasts, genes and lociFeatures of the genetic code, exons and intronsGenome, proteome, mRNA and tRNATranscription, RNA polymerase and splicingTranslation at the ribosome and the role of tRNAGene mutations, mutagens and chromosome non-disjunctionMeiosis, independent segregation and crossing overMeiosis compared with mitosis and random fertilisationGenetic diversity and the spread of advantageous allelesDirectional and stabilising selectionDefining adaptations and how antibiotic resistance spreadsSelection on birth weight, aseptic technique and antimicrobialsClassifying anatomical, physiological and behavioural adaptationsDefining a species, courtship and phylogenetic classificationThe taxonomic hierarchy, binomial names and molecular evidenceSpecies richness, the index of diversity and farmingComparing genetic diversity, standard deviation and the t-test
Energy Transfers in and Between Organisms
Topic overviewPhotoionisation and ATP from the light-dependent reactionChemiosmosis, photolysis and products for the Calvin cycleCarbon fixation, triose phosphate and limiting factorsGlasshouse conditions, pigment chromatography and DCPIPGlycolysis and its productsAnaerobic respiration and the oxidation of pyruvateAcetylcoenzyme A and the Krebs cycleOxidative phosphorylation, other substrates and respirometersBiomass and gross and net primary productionNet production of consumers and productivityFarming practices, transfer efficiency and the production equationsSaprobionts and the phosphorus cycleMycorrhizae, ammonification and nitrificationNitrogen fixation, denitrification and fertilisersLeaching, eutrophication and nutrient cycles reviewed
Organisms Respond to Changes in Their Internal and External Environments
Topic overviewIAA, gravitropism and phototropismTaxes, kineses, reflex arcs and choice chambersThe Pacinian corpuscle and generator potentialsRods, cones, colour vision and visual acuityThe SAN, AVN, bundle of His and Purkyne tissueChemoreceptors, baroreceptors and cardiac outputMotor neurone structure and the resting potentialDepolarisation, action potentials and saltatory conductionThe refractory period and speed of conductionSynapse structure and the neuromuscular junctionTransmission at a cholinergic synapseAcetylcholinesterase, summation and inhibitory synapsesNeuromuscular junctions compared, agonists and antagonistsDrug effects and potassium channels in hyperpolarisationAntagonistic muscle pairs and muscle fibre structureSarcomere bands, actin, myosin and tropomyosinThe sliding filament cycle, ATP and phosphocreatineSlow twitch and fast twitch muscle fibresControl systems and why temperature, pH and glucose matterNegative and positive feedbackGlycogenesis, glycogenolysis and gluconeogenesisHow insulin, glucagon and adrenaline actThe second messenger model, diabetes and the sugar debateGlucose calibration curves and hormones affecting blood glucoseOsmoregulation, osmoreceptors and ADHNephron structure and ultrafiltrationThe proximal convoluted tubule and the loop of HenleThe distal tubule, collecting duct and urine concentration
Genetics, Populations, Evolution and Ecosystems
Topic overviewGenotype, phenotype and types of alleleMonohybrid and dihybrid crosses, sex linkage and autosomal linkageEpistasis, genetic diagrams and the chi-squared testGene pools, allele frequency and Hardy–WeinbergSources of variation and selection pressuresTypes of selection and allopatric and sympatric speciationGenetic drift, founder effects and the route to speciationCommunities, ecosystems, niches and carrying capacityCompetition, predation, quadrats and mark-release-recaptureMark-release-recapture assumptions and successionSuccession, conservation and evaluating the evidence
The Control of Gene Expression
Topic overviewTypes of gene mutation and mutagenic agentsSilent, frameshift, missense and nonsense mutationsTotipotent, pluripotent and induced pluripotent stem cellsTranscription factors, oestrogen, epigenetics and twin studiesDNA methylation, histone acetylation and cancerRNA interference and epigenetic drug targetsBenign and malignant tumours, suppressor genes and oncogenesAbnormal methylation, oestrogen and evidence on causes of cancerGenome projects, the proteome and sequencing methodsTransgenic organisms and making DNA fragmentsThe polymerase chain reactionPromoters, restriction endonucleases, sticky ends and ligaseTransformation, marker genes and uses of recombinant DNAThe humanitarian debate, cDNA and in vivo cloningDNA probes, hybridisation and screening for allelesGenetic counselling, personalised medicine and screening ethicsVNTRs, PCR and gel electrophoresisUsing and interpreting genetic fingerprints
Energy Transfers in and Between Organisms
- 15 subtopics
- 43 things to know
- Papers 2 and 3
What Energy Transfers in and Between Organisms covers
Energy Transfers in and Between Organisms is examined on Paper 2 of AQA Biology, which covers topics 5 to 8, and on Paper 3, which can draw on any topic. 223 recall questions across 15 subtopics.
Where it is assessed
Papers 2 and 3
Topics 5 to 8, then the synoptic paper.
Check the AQA specification ↗The 15 subtopics
Each one has its own page.
- Photoionisation and ATP from the light-dependent reactionRecall 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.Open →
- Chemiosmosis, photolysis and products for the Calvin cycleRecall 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.Open →
- Carbon fixation, triose phosphate and limiting factorsRecall 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.Open →
- Glasshouse conditions, pigment chromatography and DCPIPRecall 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.Open →
- Glycolysis and its productsRecall 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.Open →
- Anaerobic respiration and the oxidation of pyruvateRecall 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.Open →
- Acetylcoenzyme A and the Krebs cycleRecall 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.Open →
- Oxidative phosphorylation, other substrates and respirometersRecall 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.Open →
- Biomass and gross and net primary productionRecall 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.Open →
- Net production of consumers and productivityRecall 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.Open →
- Farming practices, transfer efficiency and the production equationsRecall 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.Open →
- Saprobionts and the phosphorus cycleRecall 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.Open →
- Mycorrhizae, ammonification and nitrificationRecall questions on how mycorrhizae help plants take up water and inorganic ions, ammonification by saprobionts, and the two stages of nitrification.Open →
- Nitrogen fixation, denitrification and fertilisersRecall 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.Open →
- Leaching, eutrophication and nutrient cycles reviewedRecall 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.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Process
What happens to carbon dioxide once it is fixed in the Calvin cycle?
Key term
Which environmental factors limit the rate of photosynthesis?
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What happens when chlorophyll absorbs light energy?
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Where is ATP synthase located within the chloroplast?
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What does chemiosmotic theory explain?
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How can chromatography be used to compare different plant species?
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What is the Calvin cycle?
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Does glycolysis require oxygen?
Process
What happens to glucose in the first stage of glycolysis, and what is required for this?
Key term
Where does pyruvate move to from the cytoplasm during aerobic respiration?
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What molecule is formed when acetate combines with coenzyme A?
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At the start of the Krebs cycle, acetylcoenzyme A reacts with a molecule containing how many carbon atoms?
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What is the role of the electron transfer chain in oxidative phosphorylation?
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During oxidative phosphorylation, across which membrane do protons pass?
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From what source do terrestrial plants obtain the carbon they use to synthesise organic compounds?
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Define biomass.
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What is net primary production available for within the plant itself?
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Which other trophic levels can access net primary production?
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What does simplifying food webs involve in agricultural practice?
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How is the efficiency of energy transfer between trophic levels calculated?
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Name two examples of nutrient cycles that recycle elements in natural ecosystems.
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Define the term saprobiont.
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What is a mycorrhiza?
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Define ammonification.
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Define nitrogen fixation.
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Where can nitrogen-fixing bacteria be found?
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Define leaching in the context of soil chemistry.
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What is eutrophication?
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What is released from chlorophyll molecules during photoionisation?
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What protons are produced during photolysis of water?
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What happens when carbon dioxide reacts with ribulose bisphosphate?
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How many carbon atoms does GP contain, and how is it formed?
Process
What happens to triose phosphate in the third stage of glycolysis?
Key term
What happens to coenzyme A when acetylcoenzyme A reacts with the four-carbon molecule?
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Where is ATP synthase located in the mitochondrion?
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State one way biomass can be measured.
Numbers
State the equation used to calculate net production of consumers.
Key term
Explain the distinction between GPP and NPP.
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Where does digestion occur when saprobionts break down organic molecules?
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Which organisms carry out ammonification?
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What is denitrification?
Process
What triggers the process of eutrophication in aquatic ecosystems?
Take Energy Transfers in and Between Organisms further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
The light-dependent reaction vs The light-independent reaction
The light-dependent reaction: the stage in the thylakoid membranes that uses light to make ATP and reduced NADP, splitting water. The light-independent reaction: the stage in the stroma that fixes carbon dioxide using the products of the first stage.
Glycolysis vs The link reaction
Glycolysis: the splitting of glucose into two molecules of pyruvate in the cytoplasm, with a small net yield of ATP. The link reaction: the conversion of pyruvate to acetylcoenzyme A in the mitochondrial matrix, releasing carbon dioxide.
Gross primary production vs Net primary production
Gross primary production: the total chemical energy a plant converts from light in a given area. Net primary production: the chemical energy store in plant biomass after respiratory losses to the environment have been taken into account.
Questions from this topic
Each one with the model answer underneath.
- 1
What happens when chlorophyll absorbs light energy?
Model answer
Chlorophyll absorbs light energy, which causes photoionisation of chlorophyll molecules.
- 2
What is released from chlorophyll molecules during photoionisation?
Model answer
Electrons are released from chlorophyll molecules.
- 3
Define photoionisation in the context of photosynthesis.
Model answer
Photoionisation is the process by which chlorophyll loses electrons after absorbing light energy.
- 4
How is some of the energy from electrons released during photoionisation conserved?
Model answer
Some energy is conserved in the production of ATP.
- 5
Besides ATP, what other molecule is produced using energy from electrons released during photoionisation?
Model answer
Reduced NADP.
- 6
What role does the electron transfer chain play in ATP production during the light-dependent reaction?
Model answer
Electrons are transferred down the electron transfer chain, and this process is coupled to ATP production.
What is inside Levo
Six ways to work the same material.
Energy Transfers in and Between Organisms revision questions
- What does Energy Transfers in and Between Organisms cover in AQA A-Level Biology?
- 15 subtopics: photoionisation and atp from the light-dependent reaction, chemiosmosis, photolysis and products for the calvin cycle, carbon fixation, triose phosphate and limiting factors, glasshouse conditions, pigment chromatography and dcpip, glycolysis and its products, anaerobic respiration and the oxidation of pyruvate, acetylcoenzyme a and the krebs cycle, oxidative phosphorylation, other substrates and respirometers, biomass and gross and net primary production, net production of consumers and productivity, farming practices, transfer efficiency and the production equations, saprobionts and the phosphorus cycle, mycorrhizae, ammonification and nitrification, nitrogen fixation, denitrification and fertilisers and leaching, eutrophication and nutrient cycles reviewed. Each one has its own page with questions and model answers.
- How is Energy Transfers in and Between Organisms organised?
- By the AQA 7402 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Energy Transfers in and Between Organisms, on a schedule.
Attempt a question from memory, write the correct version, then attempt it again. Levo records the jump between your first attempt and your last, and brings each question back on the day you are due to forget it.
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