Key term
Edexcel GCSE Biology 1BI0
Key Concepts in Biology
Topic overviewEukaryotic and prokaryotic cellsSpecialised cells and their adaptationsMicroscopes and magnification calculationsSize, scale and units in cell biologyEnzyme action and denaturationFactors affecting enzyme activityEnzymes in synthesis and digestion, and rate calculationsFood tests and the energy in foodDiffusion, osmosis and active transportOsmosis in potatoes and percentage change in mass
Cells and Control
Topic overviewMitosis and the cell cycleWhy mitosis matters: growth, repair and cancerGrowth, differentiation and percentile chartsStem cells and their use in medicineThe structure and function of the brainNeurones, receptors and the reflex arcThe structure and function of the eyeEye defects and how they are corrected
Genetics
Topic overviewAsexual and sexual reproductionMeiosis and the formation of gametesDNA structure, genes and the genomeExtracting DNA from fruitMendel's work and the inheritance of blood groupsAlleles, genotype and phenotypeMonohybrid crosses and sex determinationProbability and ratios from genetic crossesCauses of variation: genes and environmentThe Human Genome ProjectGenetic variation and the effects of mutation
Natural Selection and Genetic Modification
Topic overviewDarwin, Wallace and the theory of evolutionNatural selection and antibiotic resistanceFossil evidence for human evolutionStone tool evidence for human evolutionThe pentadactyl limb and the three domainsSelective breedingTissue cultureGenetic engineering and modern agricultureBenefits and risks of GM organisms
Health, Disease and the Development of Medicines
Topic overviewHealth, disease and susceptibilityPathogens and common infectionsHow pathogens spread, and the virus life cycleSexually transmitted infectionsHow plants defend themselvesPhysical barriers and chemical defencesThe immune system, immunisation and herd immunityAntibiotics and developing new medicinesAseptic technique in culturing microorganismsTesting antiseptics and antibiotics on bacterial culturesLifestyle factors and non-communicable diseaseTreatments for cardiovascular disease
Plant Structures and Their Functions
Topic overviewPhotosynthesis as an endothermic reactionLimiting factors in photosynthesisLight intensity and the rate of photosynthesisRoot hair cells, xylem and phloemTranspiration and translocationLeaf structure for photosynthesis and gas exchangeFactors affecting the rate of transpirationPlant adaptations to extreme environmentsPlant hormones, phototropism and gravitropism
Animal Coordination, Control and Homeostasis
Topic overviewHormones, endocrine glands and homeostasisThe menstrual cycle and its hormonesHormonal and barrier contraceptionHomeostasis and thermoregulationControlling blood glucose, and type 1 diabetesType 2 diabetes and body massThe urinary system and the production of ureaThe nephron, filtration and selective reabsorptionTreating kidney failure: dialysis and transplants
Exchange and Transport in Animals
Topic overviewWhy multicellular organisms need exchange surfacesAlveoli and gas exchangeRate of diffusion and Fick's lawThe blood and its componentsArteries, veins and capillariesThe heart and the circulatory systemCellular respiration as an exothermic reactionAerobic and anaerobic respiration comparedInvestigating the rate of respirationCardiac output, stroke volume and heart rate
Ecosystems and Material Cycles
Topic overviewLevels of organisation and interdependenceAbiotic and biotic factors in a communityParasitism and mutualismSampling with quadrats and transectsEstimating population size from field dataEnergy transfer between trophic levelsHuman impact on ecosystems and biodiversityFood securityThe carbon cycleThe water and nitrogen cyclesFactors affecting the rate of decompositionCalculating the rate of decay
Exchange and Transport in Animals
Alveoli and gas exchange
- 3 things to know
- Paper 2
Overview
Alveoli as the site of gas exchange, how their number, one-cell-thick walls, capillary network, moist lining and ventilation keep the diffusion of oxygen and carbon dioxide fast, and the two cell layers oxygen crosses into the blood.
What you need to know
Answer each one before you reveal it.
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Key term
Explain how having millions of alveoli helps gas exchange.
Key term
Explain how the thickness of an alveolus wall helps gas exchange.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Name the tiny air sacs in the lungs where gas exchange takes place.
Model answer
Gas exchange takes place in the alveoli.
- 2
Explain how having millions of alveoli helps gas exchange.
Model answer
Together they provide a very large surface area, so far more oxygen and carbon dioxide can diffuse at the same time.
- 3
Explain how the thickness of an alveolus wall helps gas exchange.
Model answer
The wall is only one cell thick, giving a very short diffusion distance so gases cross quickly.
- 4
Describe the direction each gas moves in at an alveolus.
Model answer
Oxygen diffuses from the air in the alveolus into the blood, and carbon dioxide diffuses from the blood into the alveolus.
- 5
Explain how the capillary network wrapped around each alveolus keeps gas exchange fast.
Model answer
Flowing blood constantly carries oxygen away and brings carbon dioxide, which keeps the concentration gradients steep.
- 6
Explain why the inner lining of an alveolus is moist.
Model answer
Gases must dissolve in the film of moisture before they can diffuse across the alveolus wall.
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