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
Diffusion and the factors affecting its rate
- 3 things to know
- Paper 1
Overview
The definition of diffusion and net movement, substances such as oxygen, carbon dioxide and urea that diffuse into and out of cells, and how concentration gradient, temperature and membrane surface area affect the rate.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Name two gases moved in and out of cells by diffusion during gas exchange.
Key term
In which direction does oxygen diffuse at a respiring cell, and why?
Questions from this subtopic
Each one with the model answer underneath.
- 1
Name the process by which many dissolved substances and gases pass through cell membranes without energy being used.
Model answer
Diffusion.
- 2
Define diffusion.
Model answer
The spreading out of particles of a substance in solution, or of a gas, giving a net movement from a higher to a lower concentration.
- 3
What is meant by a net movement of particles?
Model answer
Particles move in both directions, but more move one way than the other, so overall there is movement in that direction.
- 4
What happens to the net movement of a substance once its concentration is the same on both sides of a membrane?
Model answer
There is no net movement, although the particles continue to move randomly in both directions.
- 5
Name two gases moved in and out of cells by diffusion during gas exchange.
Model answer
Oxygen and carbon dioxide.
- 6
Which waste substance diffuses out of cells into the blood plasma?
Model answer
Urea.
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