Key term
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
Cells
- 24 subtopics
- 71 things to know
- Papers 1 and 3
What Cells covers
Cells is examined on Paper 1 of AQA Biology, which covers topics 1 to 4, and on Paper 3, which can draw on any topic. 327 recall questions across 24 subtopics.
Where it is assessed
Papers 1 and 3
Topics 1 to 4, then the synoptic paper.
Check the AQA specification ↗The 24 subtopics
Each one has its own page.
- Cell-surface membrane, nucleus and mitochondriaRecall questions on the structure and function of the cell-surface membrane, the nucleus with its chromosomes, nucleolus and nuclear envelope, and the membranes and role of mitochondria.Open →
- Chloroplasts, Golgi apparatus and lysosomesRecall questions on the DNA and ribosomes of mitochondria and chloroplasts, the internal membranes of chloroplasts, the functions of the Golgi apparatus and its vesicles, lysosomes and ribosomes.Open →
- Ribosomes, endoplasmic reticulum, cell walls and vacuolesRecall questions on ribosome structure and location, rough and smooth endoplasmic reticulum, the cell walls of plants and fungi, and the structure and functions of the plant cell vacuole.Open →
- Cell specialisation, levels of organisation and organelle rolesRecall questions on how cells specialise and form tissues, organs and organ systems, what distinguishes eukaryotic from prokaryotic cells, and applying organelle functions to unfamiliar cases.Open →
- Prokaryotic cell structure and virus particlesRecall questions on the size, ribosomes, circular DNA, murein cell wall, plasmids, capsule and flagella of prokaryotic cells, and the capsid, genetic material and attachment proteins of viruses.Open →
- Optical and transmission electron microscopesRecall questions on how optical microscopes form images, their magnification, resolution and practical advantages, and how a transmission electron microscope forms an image and what it resolves.Open →
- Scanning electron microscopes, magnification and graticulesRecall questions on the scanning electron microscope, the limitations of electron microscopy, resolution and magnification, the magnification formula, and calibrating an eyepiece graticule with a stage micrometer.Open →
- Cell fractionation, homogenisation and ultracentrifugationRecall questions on cell fractionation, why the homogenising solution is cold and buffered, filtration, and how ultracentrifugation separates organelles into pellet and supernatant.Open →
- Order of sedimentation, artefacts and fractionation conditionsRecall questions on the order in which organelles sediment in differential centrifugation, artefacts in microscopy, and why the homogenate must be cold, isotonic and buffered.Open →
- The cell cycle, interphase and the stages of mitosisRecall questions on the cell cycle, DNA replication in interphase, and what happens to chromosomes, the nuclear envelope and spindle fibres in prophase, metaphase, anaphase and telophase.Open →
- Spindle fibres, cytokinesis and uncontrolled cell divisionRecall questions on the role of spindle fibres, cytokinesis, how uncontrolled cell division leads to cancer, how some cancer drugs stop cells dividing, and binary fission.Open →
- Binary fission, viral replication and root tip squashesRecall questions on how circular DNA and plasmids are shared in binary fission, how viruses replicate inside host cells, and preparing stained root tip squashes to find the mitotic index.Open →
- Mitotic index, mitosis stages and size calculationsRecall questions on calculating the mitotic index, the events of each stage of mitosis, and working with standard form, significant figures and estimates when calculating cell size and magnification.Open →
- The fluid-mosaic model and cholesterolRecall questions on the fluid-mosaic model of membranes, intrinsic and extrinsic proteins, glycoproteins and glycolipids, and how cholesterol affects membrane fluidity at high and low temperatures.Open →
- Simple diffusion, facilitated diffusion and membrane proteinsRecall questions on simple diffusion through the phospholipid bilayer and its limits, facilitated diffusion, and how channel and carrier proteins move specific molecules across membranes.Open →
- Osmosis, water potential and active transportRecall questions on osmosis and water potential, the water potential of pure water and solutions, and active transport by carrier proteins using energy from ATP hydrolysis.Open →
- Co-transport in the ileum and adaptations for rapid transportRecall questions on co-transport of sodium ions and glucose into ileum epithelial cells, how glucose reaches the blood, and how surface area, protein numbers and gradients speed transport across membranes.Open →
- Transport rates, dilution series and membrane permeabilityRecall questions on what limits the rates of diffusion, facilitated diffusion and osmosis, finding the water potential of plant tissue with a dilution series, and investigating membrane permeability.Open →
- Antigens, cell recognition and phagocytosisRecall questions on how surface molecules let the immune system identify pathogens, foreign cells, abnormal cells and toxins, antigens and antigen variability, and how phagocytes engulf pathogens.Open →
- Antigen-presenting cells, T cells and clonal selectionRecall questions on lysozymes, the cellular response, antigen-presenting cells, how helper T cells activate cytotoxic T cells, B cells and phagocytes, and clonal selection in the humoral response.Open →
- Antibody structure, agglutination and antigen-antibody complexesRecall questions on the heavy and light chains, variable and constant regions of an antibody, antigen-binding sites, antigen-antibody complexes, and how agglutination helps phagocytes destroy pathogens.Open →
- Memory cells, vaccination and active and passive immunityRecall questions on plasma cells and memory cells, the primary and secondary immune responses, how vaccines give protection and herd immunity, and natural and artificial active and passive immunity.Open →
- HIV structure and replicationRecall questions on the lipid envelope, glycoprotein spikes, RNA and reverse transcriptase of HIV, how it infects helper T cells and integrates into the host genome, and how new particles leave.Open →
- AIDS, monoclonal antibodies, ELISA and clinical trialsRecall questions on how HIV causes AIDS, why antibiotics do not work on viruses, monoclonal antibodies in targeted drugs and diagnosis, the ELISA test, and the ethics and design of vaccine and antibody trials.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
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What happens during prophase of mitosis?
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What happens during metaphase, anaphase and telophase of mitosis?
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What are chromosomes composed of?
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How many nucleoli can be present within a nucleus?
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In which types of organisms are chloroplasts found, and what is their function?
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Describe the internal membrane system of a chloroplast.
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What is the composition and structure of a ribosome?
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Where can ribosomes be located within a eukaryotic cell?
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What is the correct sequence of organisation from cells to organ systems?
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What does cell specialisation involve?
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How does the size of prokaryotic cells compare to eukaryotic cells?
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How do the ribosomes of prokaryotic cells differ from those of eukaryotic cells?
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What is the resolution limit of an optical microscope, and why is it limited?
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Can optical microscopes be used to observe living cells?
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What type of image does an SEM produce?
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What is the resolution of a scanning electron microscope?
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Define cell fractionation.
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What is homogenisation in cell fractionation?
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Why do nuclei sediment before ribosomes during differential centrifugation?
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What is an artefact in microscopy?
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What is the role of spindle fibres during mitosis?
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Define cytokinesis.
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What happens to the circular DNA during binary fission?
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What happens to plasmids during binary fission?
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Do the membranes surrounding organelles in eukaryotic cells share the same basic structure as the cell-surface membrane?
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What is the fluid-mosaic model of membrane structure?
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Does simple diffusion require metabolic energy or carrier proteins?
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Which types of molecules can pass through the phospholipid bilayer by simple diffusion?
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What is water potential?
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What is the water potential of pure water?
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In the mammalian ileum, how is a sodium ion concentration gradient established across epithelial cells?
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How do sodium ions enter epithelial cells from the ileum lumen?
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How does the difference in water potential between two regions affect the rate of osmosis?
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How can a dilution series be used to determine the water potential of plant tissue?
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What types of molecules are found on cell surfaces that allow identification of different cell types?
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How do surface molecules enable the immune system to recognise pathogens?
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What are lysozymes and what is their role in phagocytosis?
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What is meant by the cellular response in immunity?
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What are monoclonal antibodies?
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Define the term antibody.
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What are plasma cells?
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Define memory cells.
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What does HIV stand for?
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How does HIV attach to helper T cells?
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What is AIDS?
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Why does the loss of helper T cells compromise the immune system?
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What is the nuclear envelope?
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What structural units make up the Golgi apparatus?
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What distinguishes rough endoplasmic reticulum from smooth, and what is its function?
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What key feature distinguishes eukaryotic cells from prokaryotic cells?
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Where is the DNA located within a prokaryotic cell?
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What type of images do optical microscopes produce in terms of colour?
Process
Describe the preparation steps required for electron microscope specimens.
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Why must the solution used in cell fractionation be kept cold?
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Why must the homogenate be kept cold during cell fractionation?
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Do all cells in a multicellular organism retain the ability to divide?
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What is the outcome of cytokinesis?
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How many copies of circular DNA does each daughter cell receive after binary fission?
Numbers
State the formula for calculating the actual size of a cell.
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Why is the cell membrane described as 'fluid'?
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Why can't large molecules, charged molecules and ions pass through the phospholipid bilayer by simple diffusion?
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What happens to water potential when solutes are added to pure water?
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How does glucose enter epithelial cells from the ileum lumen?
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At what solution concentration is the water potential of plant tissue equal to that of the surrounding solution?
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What allows the immune system to distinguish between cells from your own body and cells from another person?
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How do T lymphocytes recognise antigens presented by antigen-presenting cells?
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How many heavy chains does an antibody molecule contain?
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Why is the secondary immune response faster and greater in magnitude than the primary response?
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What happens after the HIV envelope fuses with the helper T cell membrane?
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What types of conditions do people with AIDS become susceptible to?
Take Cells further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Magnification vs Resolution
Magnification: how many times larger an image is than the object. Resolution: the ability to distinguish two close points separately.
Prokaryotic cell vs Eukaryotic cell
Prokaryotic cell: a small cellular form lacking membrane-bound organelles. Eukaryotic cell: a cellular form containing a nucleus and membrane-bound organelles.
Active transport vs Facilitated diffusion
Active transport: movement against a concentration gradient using energy and carrier proteins. Facilitated diffusion: passive movement down a concentration gradient through membrane proteins.
Questions from this topic
Each one with the model answer underneath.
- 1
What is the primary function of the cell-surface membrane?
Model answer
It controls the entry and exit of substances into and out of the cell.
- 2
Describe the basic structure of the cell-surface membrane.
Model answer
It is a partially permeable barrier composed of a phospholipid bilayer with embedded proteins.
- 3
What two key roles does the nucleus perform in a eukaryotic cell?
Model answer
It contains the genetic material and controls cell activities.
- 4
What are chromosomes composed of?
Model answer
Linear DNA bound to proteins.
- 5
How many nucleoli can be present within a nucleus?
Model answer
One or more nucleoli.
- 6
What is the function of the nucleolus?
Model answer
It is the site of ribosome production.
What is inside Levo
Six ways to work the same material.
Cells revision questions
- What does Cells cover in AQA A-Level Biology?
- 24 subtopics: cell-surface membrane, nucleus and mitochondria, chloroplasts, golgi apparatus and lysosomes, ribosomes, endoplasmic reticulum, cell walls and vacuoles, cell specialisation, levels of organisation and organelle roles, prokaryotic cell structure and virus particles, optical and transmission electron microscopes, scanning electron microscopes, magnification and graticules, cell fractionation, homogenisation and ultracentrifugation, order of sedimentation, artefacts and fractionation conditions, the cell cycle, interphase and the stages of mitosis, spindle fibres, cytokinesis and uncontrolled cell division, binary fission, viral replication and root tip squashes, mitotic index, mitosis stages and size calculations, the fluid-mosaic model and cholesterol, simple diffusion, facilitated diffusion and membrane proteins, osmosis, water potential and active transport, co-transport in the ileum and adaptations for rapid transport, transport rates, dilution series and membrane permeability, antigens, cell recognition and phagocytosis, antigen-presenting cells, t cells and clonal selection, antibody structure, agglutination and antigen-antibody complexes, memory cells, vaccination and active and passive immunity, hiv structure and replication and aids, monoclonal antibodies, elisa and clinical trials. Each one has its own page with questions and model answers.
- How is Cells organised?
- By the AQA 7402 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Cells, 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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