Key term
AQA GCSE Biology 8461
Bioenergetics
Cell Biology
Topic overviewEukaryotes and prokaryotesAnimal and plant cellsCell specialisation and differentiationMicroscopyGrowing bacteria and aseptic techniqueCalculating bacterial growth, and testing antiseptics and antibioticsChromosomes, mitosis and the cell cycleStem cells in embryos, adults and meristemsTherapeutic cloning, its risks, and cloning plantsDiffusion and the factors affecting its rateSurface area to volume ratio and exchange surfacesOsmosisActive transport
Ecology
Topic overviewLevels of organisation in an ecosystem, and what organisms needCompetition, interdependence and stable communitiesAbiotic factorsBiotic factorsAdaptationsProducers, food chains and sampling with quadrats and transectsPredators, prey and measuring population sizeHow materials are cycledDecompositionWaste management and biodiversityLand use, deforestation and global warmingMaintaining biodiversityTrophic levels and pyramids of biomassTransfer of biomassFactors affecting food securityFarming techniques and sustainable fisheriesRole of biotechnologyImpact of environmental change
Homeostasis and Response
Topic overviewHomeostasisThe nervous system and the reflex arcThe structure of the eye and accommodationMyopia, hyperopia and how they are correctedThe brain and the control of body temperatureHuman endocrine systemInsulin, glucagon and diabetesWater and ion loss, and the production of ureaThe kidneys, ADH and treating kidney failureHormones in human reproductionContraceptionThe use of hormones to treat infertilityNegative feedbackPlant hormones and their uses
Infection and Response
Topic overviewCommunicable (infectious) diseasesViral diseasesBacterial diseasesFungal and protist diseasesHuman defence systemsVaccinationAntibiotics and painkillersDiscovery and development of drugsProducing monoclonal antibodiesUses of monoclonal antibodiesDetection and identification of plant diseasesPlant defence responses
Inheritance, Variation and Evolution
Topic overviewSexual and asexual reproductionMeiosisAdvantages and disadvantages of sexual and asexual reproductionDNA and the genomeDNA as a polymer of four nucleotidesProtein synthesis and complementary base pairingMutations, protein shape and non-coding DNAGenetic terms, dominant and recessive allelesPunnett squares, probability and genetic crossesInherited disorders and sex determinationVariationEvolutionSelective breedingWhat genetic engineering is, and what it is used forGM crops, their risks, and the steps of the processCloningDarwin, Lamarck and the acceptance of evolutionSpeciationThe understanding of geneticsEvidence for evolution, and extinctionFossilsResistant bacteriaClassification of living organisms
Organisation
Topic overviewLevels of organisation, and how enzymes workAmylase, proteases and lipasesBile, food tests and the effect of pH on amylaseThe heart, the lungs and double circulationThe pacemaker, the blood vessels and the bloodCoronary heart disease: a non-communicable diseaseHealth issuesRisk factors and causal mechanisms in diseaseSampling, correlation and interpreting risk dataCancerPlant tissues, and transpiration and its rateRoot hair cells, xylem, phloem and stomata
Cell Biology
Osmosis
- 3 things to know
- Paper 1
Overview
Osmosis and partially permeable membranes, plant tissue in pure water and sugar solution, percentage change in mass and water uptake, the potato cylinder method and its variables, accuracy, precision, repeatability and reproducibility, systematic, zero and random errors, gradients and y = mx + c, and a hypothesis.
What you need to know
Answer each one before you reveal it.
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Key term
What is a partially permeable membrane?
Key term
Describe what happens to a piece of plant tissue placed in pure water.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Define osmosis.
Model answer
The diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane.
- 2
What is a partially permeable membrane?
Model answer
A membrane that lets water molecules pass through but not larger solute molecules.
- 3
Describe what happens to a piece of plant tissue placed in pure water.
Model answer
Water moves into the cells by osmosis, so the tissue gains mass and becomes firm.
- 4
Describe what happens to a piece of plant tissue placed in a concentrated sugar solution.
Model answer
Water moves out of the cells by osmosis, so the tissue loses mass and becomes limp.
- 5
How is the percentage change in mass of a piece of tissue calculated?
Model answer
Divide the change in mass by the starting mass and multiply by 100.
- 6
A potato cylinder of mass 4.0 g has a mass of 4.6 g after soaking. Calculate the percentage change in mass.
Model answer
A gain of 15%.
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