Key term
Edexcel A-Level Biology B 9BI0
Biological Molecules
Topic overviewMonosaccharides, disaccharides and polysaccharidesGlycosidic bonds and condensation reactionsStarch, glycogen and cellulose structureTriglycerides and phospholipidsSaturated and unsaturated fats and lipid propertiesAmino acid structure and the peptide bondPrimary, secondary, tertiary and quaternary structureFibrous and globular proteinsThe structure of DNADNA replication and gene mutationsThe structure of RNATranscription and translationEnzymes as globular proteinsFactors affecting enzyme activityMeasuring the rate of enzyme activityUnits, uncertainty and experimental errorEnzyme inhibitionInorganic ionsThe properties of water
Cells, Viruses and Reproduction of Living Things
Topic overviewCell theory and eukaryotic cell structureProkaryotic cells and Gram stainingMicroscopy, magnification and resolutionSignificant figures, estimates and mathematical symbolsVirus structure and classificationThe lytic cycle and latencyTreating viral disease and the ethics of untested drugsThe cell cycle and its regulationMitosis and the behaviour of chromosomesMitosis in growth, repair and root tip squashesMeiosis, genetic variation and chromosome mutationsGametogenesis in mammalsFertilisation and early embryo developmentPollen and embryo sac formationDouble fertilisation in flowering plantsInvestigating pollen tube growth
Classification and Biodiversity
Exchange and Transport
Topic overviewSurface area to volume ratioThe fluid mosaic modelDiffusion, osmosis and facilitated diffusionActive transport, endocytosis and exocytosisGas exchange in insects, fish and mammalsDissecting the insect gas exchange systemGas exchange in flowering plantsThe structure of the heart and blood vesselsThe double circulatory systemThe cardiac cycleMyogenic stimulation and ECG tracesThe composition of bloodThe functions of blood and clottingAtherosclerosis and its risk factorsHaemoglobin and the Bohr effectOxygen dissociation curvesFormation of tissue fluidThe lymphatic systemXylem and phloem structureApoplastic and symplastic pathwaysThe cohesion-tension theoryMeasuring transpiration with a potometerTranslocation and the mass flow hypothesis
Energy for Biological Processes
Topic overviewAn overview of aerobic respirationGlycolysisThe link reaction and the Krebs cycleThe electron transport chainChemiosmosis and ATP yieldAnaerobic respiration and ATP yieldMeasuring respiration with a respirometerAbsorption and action spectraPhotosynthetic pigments and chromatographyChloroplast structure and the light-dependent stageThe Calvin cycleLimiting factors in photosynthesis
Microbiology and Pathogens
Topic overviewCulturing microorganisms and aseptic techniqueMeasuring bacterial growthThe bacterial growth curveBacteria as pathogensThe action of antibioticsAntibiotic resistanceOther pathogenic agentsControlling endemic diseasePhagocytosis and the humoral responseThe cell-mediated immune responseMemory cells and the secondary responseNatural and artificial immunityVaccination and herd immunity
Modern Genetics
Origins of Genetic Variation
Topic overviewMutation, meiosis and random fertilisationGenotype, phenotype and monohybrid inheritanceDihybrid crosses and pedigree diagramsAutosomal linkage and sex linkageThe chi-squared test in geneticsSelection pressures and allele frequencyGenetic drift and the founder effectThe Hardy-Weinberg equation
Control Systems
Topic overviewHomeostasis and negative feedbackChemical control in mammalsPlant growth substancesAuxins, cytokinins and apical dominancePhytochrome and photomorphogenesisThe organisation of the nervous systemBrain regions and divisions of the peripheral nervous systemThe autonomic nervous systemResting potential and the action potentialPropagation and saltatory conductionSynaptic transmissionEffects of drugs on the nervous systemThe structure of the retina and rhodopsinRods, cones and visual acuityControl of heart rateKidney structure and ultrafiltrationSelective reabsorption and the loop of HenleADH and osmoregulationThermoregulation in endotherms
Ecosystems
Topic overviewEcosystems, habitats and nichesPyramids of numbers, biomass and energyEcological techniques for measuring distributionChoosing the right ecological techniquePresenting data in tables and graphsStatistical tests in ecologyProductivity and energy transfer efficiencyDecomposers and nutrient cyclingSuccessionBiotic and abiotic factors in population changeHuman influences on ecosystemsSustainability, resource management and peer review
Control Systems
- 19 subtopics
- 56 things to know
- Papers 2 and 3
What Control Systems covers
How mammals and plants keep conditions steady and respond to change: negative feedback, hormonal and plant chemical control, the nervous system from brain regions to synapse, the eye, the control of heart rate, and the kidney's role in osmoregulation.
Where it is assessed
Papers 2 and 3
Advanced Physiology, Evolution and Ecology, then the general and practical principles paper.
Check the Pearson Edexcel specification ↗The 19 subtopics
Each one has its own page.
- Homeostasis and negative feedbackRecall questions on receptors, the control centre and effectors, negative feedback, and why positive feedback is the exception.Open →
- Chemical control in mammalsRecall questions on endocrine glands and target cell receptors, and the two modes of hormone action: second messengers for water-soluble hormones such as adrenaline, and direct binding to transcription factors for lipid-soluble hormones such as oestrogen.Open →
- Plant growth substancesRecall questions on auxins, cytokinins and gibberellins as plant growth substances, how gibberellin stimulates amylase production in germinating cereals, and the starch agar assay used to investigate it.Open →
- Auxins, cytokinins and apical dominanceRecall questions on how auxin promotes cell elongation and root growth, apical dominance, and how the antagonistic balance of auxin and cytokinin controls the growth of lateral buds.Open →
- Phytochrome and photomorphogenesisRecall questions on phytochrome as a photoreceptor pigment, photomorphogenesis and flowering, the interconversion of Pr and Pfr by red and far-red light, Pfr as the active form, and how its reversion in darkness lets plants measure day length.Open →
- The organisation of the nervous systemRecall questions on the central and peripheral nervous systems, the brain and spinal cord, grey and white matter in the spinal cord, and the sensory and motor neurones of the dorsal and ventral roots.Open →
- Brain regions and divisions of the peripheral nervous systemRecall questions on the roles of the medulla oblongata, cerebellum, cerebrum and hypothalamus, and the division of the peripheral nervous system into the voluntary and autonomic nervous systems.Open →
- The autonomic nervous systemRecall questions on the sympathetic and parasympathetic divisions of the autonomic nervous system, their fight-or-flight and rest-and-digest effects on heart and breathing rate, and why antagonistic control allows fine adjustment.Open →
- Resting potential and the action potentialRecall questions on the resting potential, the sodium-potassium pump and potassium leak channels, threshold, depolarisation through voltage-gated sodium channels, repolarisation through potassium channels, and hyperpolarisation.Open →
- Propagation and saltatory conductionRecall questions on local currents and the propagation of action potentials, the refractory period, Schwann cells, nodes of Ranvier and saltatory conduction, and why myelinated axons conduct faster.Open →
- Synaptic transmissionRecall questions on the sequence at a cholinergic synapse, the role of calcium, and summation and inhibition.Open →
- Effects of drugs on the nervous systemRecall questions on agonists and antagonists, and on how named drugs alter synaptic transmission.Open →
- The structure of the retina and rhodopsinRecall questions on the photoreceptor, bipolar and ganglion cell layers of the retina, the path of light, the pigment epithelium, the optic nerve and blind spot, and how light converts retinal and bleaches rhodopsin.Open →
- Rods, cones and visual acuityRecall questions on the distribution and connections of rods and cones, and how they explain acuity and sensitivity.Open →
- Control of heart rateRecall questions on the cardiovascular centre, the effect of the sympathetic and parasympathetic nerves, and the role of baroreceptors and chemoreceptors.Open →
- Kidney structure and ultrafiltrationRecall questions on the cortex, medulla and nephron, the glomerulus, Bowman's capsule and podocytes, how high hydrostatic pressure drives ultrafiltration through the filtration barrier, and deamination and urea formation in the liver.Open →
- Selective reabsorption and the loop of HenleRecall questions on reabsorption in the proximal tubule, and on how the counter-current multiplier concentrates the medulla.Open →
- ADH and osmoregulationRecall questions on the long loops of Henle of the kangaroo rat, osmoreceptors in the hypothalamus, ADH release from the posterior pituitary, aquaporins in the collecting duct, and osmoregulation as negative feedback.Open →
- Thermoregulation in endothermsRecall questions on the hypothalamus, vasodilation and vasoconstriction, sweating and shivering, and behavioural responses.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Process
What would happen to cells if water potential were not maintained?
Process
Where are hormones produced and how do they travel to reach their target cells?
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Describe how cereal seeds are set up in a starch agar assay to test the effect of gibberellin.
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Describe the relationship between cytokinin and auxin in controlling apical dominance.
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Explain how the balance of auxin and cytokinin determines lateral bud development.
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What are the two main divisions of the mammalian nervous system?
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Describe the arrangement of grey and white matter in a cross-section of the spinal cord, and what each contains.
Process
What type of drug action does nicotine exhibit at acetylcholine receptors?
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If a neurone is treated with lidocaine, what happens when a stimulus is applied?
Process
Explain the mechanism by which parasympathetic stimulation affects the pacemaker region of the heart.
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What is the Bowman's capsule and where is it located within the nephron?
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Explain how high hydrostatic pressure is generated in the glomerulus.
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Explain what occurs in the ascending limb of the loop of Henle and why water cannot follow the ions.
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What structural adaptation of the kangaroo rat's nephrons allows survival in arid environments?
Process
How do osmoreceptors detect a fall in blood water potential and bring about increased water reabsorption?
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How are zones of starch digestion measured in a starch agar assay?
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Into which two systems is the peripheral nervous system divided?
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Which subdivision of the autonomic nervous system is associated with 'fight or flight' responses?
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Which subdivision of the autonomic nervous system is associated with 'rest and digest' responses?
Process
By what process do sodium ions enter the axon during depolarisation?
Process
Define saltatory conduction.
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Define spatial summation.
Process
What happens to rhodopsin following the shape change of retinal, and what does this trigger?
Process
Explain how reduced neurotransmitter release from rod cells leads to visual signals being transmitted to the brain.
Process
What happens to sodium ion channels in the rod cell membrane when light is absorbed?
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Which types of photoreceptor are found in the fovea?
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What three variables do chemoreceptors detect changes in?
Process
Define an endotherm.
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Which division of the nervous system controls involuntary physiological responses to temperature changes?
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How do hormones exert their effects on target cells?
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Which region of the brain is responsible for controlling breathing rate?
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What is the approximate resting potential of an axon, and which side of the membrane is negatively charged?
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What must happen to the membrane potential for an action potential to be initiated?
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What happens to voltage-gated sodium channels during repolarisation?
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Define the renal pelvis and state its function.
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Define homeostasis.
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What determines which hormones can affect a particular cell?
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Explain the role of gibberellin during seed germination in cereals.
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What effect does auxin have on plant cells that leads to growth?
Process
How does the slow reversion of Pfr to Pr in darkness allow plants to respond to day length?
Process
How does phytochrome control flowering?
Key term
Which division of the mammalian nervous system connects the CNS to the rest of the body?
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State the brain region that controls heart rate.
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Name the two subdivisions of the autonomic nervous system.
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What type of transport does the sodium-potassium pump use, and what energy source does it require?
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What type of ion channels open during the depolarisation phase of an action potential?
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What happens to voltage-gated potassium channels during repolarisation?
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At what general level do drugs affect the nervous system?
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Which type of cell forms the photoreceptor layer of the human retina?
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What change in membrane potential occurs in rod cells when sodium channels close in response to light?
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What do baroreceptors detect?
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What are the two main structural regions of the mammalian kidney, and what surrounds the entire organ?
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What is the proximal convoluted tubule and what is its position in the nephron?
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What happens when osmoreceptors detect a decrease in blood water potential?
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Define deamination and state the products formed.
Take Control Systems further
The same content, four other ways.
Commonly confused
Pairs that lose marks when they are blurred together.
Endocrine signalling vs Nervous signalling
Endocrine signalling: chemical communication through hormones carried in blood. Nervous signalling: rapid communication through electrical impulses and neurotransmitters.
Depolarisation vs Repolarisation
Depolarisation: membrane-potential change making the cell interior less negative. Repolarisation: membrane-potential change restoring the negative resting value.
Osmoregulation vs Thermoregulation
Osmoregulation: control of water potential and solute balance. Thermoregulation: control of core body temperature.
Questions from this topic
Each one with the model answer underneath.
- 1
Define homeostasis.
Model answer
The maintenance of a state of dynamic equilibrium.
- 2
What does 'dynamic equilibrium' mean in the context of homeostasis?
Model answer
Conditions fluctuate around a set point rather than remaining absolutely constant.
- 3
Why must pH be maintained within narrow limits in living organisms?
Model answer
Enzymes have optimal pH ranges; outside these ranges enzymes denature, preventing metabolic reactions from occurring.
- 4
Explain why maintaining a constant temperature is essential for enzyme function.
Model answer
Enzymes have optimal temperatures; temperatures that are too low reduce kinetic energy and slow reaction rates, while temperatures that are too high cause enzyme denaturation.
- 5
What would happen to cells if water potential were not maintained?
Model answer
Cells would gain or lose water by osmosis, causing lysis (bursting) if too much water enters or crenation (shrinkage) if too much water leaves.
- 6
Define negative feedback.
Model answer
A control mechanism where a deviation from the set point triggers a response that returns the system towards the set point.
What is inside Levo
Six ways to work the same material.
Control Systems revision questions
- What does Control Systems cover in Edexcel A-Level Biology B?
- 19 subtopics: homeostasis and negative feedback, chemical control in mammals, plant growth substances, auxins, cytokinins and apical dominance, phytochrome and photomorphogenesis, the organisation of the nervous system, brain regions and divisions of the peripheral nervous system, the autonomic nervous system, resting potential and the action potential, propagation and saltatory conduction, synaptic transmission, effects of drugs on the nervous system, the structure of the retina and rhodopsin, rods, cones and visual acuity, control of heart rate, kidney structure and ultrafiltration, selective reabsorption and the loop of henle, adh and osmoregulation and thermoregulation in endotherms. Each one has its own page with questions and model answers.
- How is Control Systems organised?
- By the Edexcel 9BI0 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Control Systems, 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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