Key term
CCEA AS-Level Biology 1010
Biological Molecules
Topic overviewWater as a solventInorganic ions and their rolesMonosaccharides and the glycosidic bondDisaccharides and polysaccharidesLipids, triglycerides and phospholipidsAmino acids and protein structureProtein shape, conjugated proteins and prionsNucleic acids: nucleotides, DNA and RNADNA replication and the Meselson–Stahl experimentBiochemical tests and paper chromatography
Enzymes
Topic overviewEnzymes as globular proteins and the active siteSpecificity, cofactors and coenzymesActivation energy and models of enzyme actionThe effect of temperature and pHThe effect of substrate and enzyme concentrationCompetitive and non-competitive inhibitionEnzymes as biomarkers of disease and inhibitors as drugsImmobilised enzymes and biosensors
Viruses and Cell Structure
Topic overviewBacteriophage and HIV structureViral replication in host cellsProkaryotic and eukaryotic cells comparedMembrane structure: the fluid mosaic modelFunctions of membrane componentsMitochondria and chloroplastsRibosomes, endoplasmic reticulum, Golgi apparatus and lysosomesThe nucleus, the cytoskeleton and plasmodesmataPlant, fungal and animal cellsMicroscopy, cell measurement and cell fractionation
Cell Physiology and Transport
Continuity of Cells
Topic overviewThe cell cycle: interphase and the gap phasesControl points in the cell cycle and cancerChromosome structure, haploidy and diploidyMitosis: the events of the four stagesCytokinesis and the significance of mitosisAnticancer drugs and the cell cycleMeiosis I and the first divisionMeiosis II and the significance of meiosisPreparing and examining slides of cell division
Tissues and Organs
Exchange Surfaces and Gas Exchange
Topic overviewSurface area, volume and the surface area to volume ratioFeatures of efficient exchange surfacesThe need for mass transport systemsFick's law and the rate of gas exchangeGas exchange in plants and the compensation pointGas exchange at the alveolusThe respiratory tree and the mechanism of ventilationThe effects of smoking on the breathing systemUsing a respirometer to measure gas exchange
Transport in Plants
Topic overviewEpidermis, endodermis and the tissues of the rootXylem vessels and their lignification patternsPhloem: sieve-tube elements and companion cellsWater and mineral ion uptake by root hairsThe apoplast and symplast pathwaysTranspiration and the factors affecting its rateCohesion-tension theory and the transpiration streamTranslocation of organic solutes in the phloemXerophytes and hydrophytes
The Circulatory System in Mammals
Topic overviewDouble circulation and the major blood vesselsThe structure and function of arteries, veins and capillariesAtherosclerosis, atheroma and the investigation of blood vesselsThe structure of the mammalian heartThe cardiac cycle and the operation of the valvesMyogenic stimulation and the electrocardiogramBlood cells and the stained blood filmPlasma, tissue fluid and blood clottingHaemoglobin and the oxygen dissociation curveThe Bohr effect, myoglobin and altitude
Adaptation and Biodiversity
Topic overviewAdaptation and the ways organisms meet environmental challengesEcological factors and the ecological nicheSampling procedures and sampling devicesEstimating abundance, density, frequency and percentage coverThe biochemical basis of life and the levels of biodiversityMeasuring species diversity with Simpson's indexHandling data: averages, spread and the t-testTaxonomy, nomenclature and the binomial systemThe concept of a speciesThe taxonomic hierarchy from genus to kingdomPhylogenetic taxonomy and molecular evidenceThe five kingdom system: prokaryotae, protoctista and fungiPlantae, animalia and alternative classification systems
Human Impact on Biodiversity
Topic overviewMonoculture, polyculture and intensive agricultureCrop rotation and hedgerow conservationPredator strips, pesticides and integrated pest managementOrganic pollution of waterways by slurry and silage effluentEutrophication and fertiliser run-offBiological oxygen demand and reducing aquatic pollutionConservation initiatives and habitat protectionGlobal warming, climate change and biodiversity
Exchange Surfaces and Gas Exchange
- 9 subtopics
- 27 things to know
- Unit AS 2
What Exchange Surfaces and Gas Exchange covers
Exchange Surfaces and Gas Exchange is examined in Unit AS 2, Organisms and Biodiversity, and drawn on again in Unit AS 3, the practical skills examination. It covers surface area, volume and the surface area to volume ratio, features of efficient exchange surfaces, the need for mass transport systems, Fick's law and the rate of gas exchange, gas exchange in plants and the compensation point, gas exchange at the alveolus, the respiratory tree and the mechanism of ventilation, the effects of smoking on the breathing system and using a respirometer to measure gas exchange.
Where it is assessed
Unit AS 2
Organisms and Biodiversity, and again in Unit AS 3, Practical Skills in AS Biology.
Check the CCEA specification ↗The 9 subtopics
Each one has its own page. CCEA AS Biology students sit this topic in the first year.
- Surface area, volume and the surface area to volume ratioRecall questions on why the ratio falls as an organism grows, worked ratios for cubes and spheres, why a small organism needs no transport system, and how flattening, folding and projections restore the ratio a larger body would otherwise lose.Open →
- Features of efficient exchange surfacesRecall questions on large surface area, a short diffusion distance, a moist surface and a maintained concentration gradient, how the leaf and the alveolus each achieve them, and why gases must dissolve before they can cross a membrane.Open →
- The need for mass transport systemsMass transport system and why diffusion becomes impractically slow over long distances.Open →
- Fick's law and the rate of gas exchangeRecall questions on the relationship between surface area, concentration difference and thickness, what happens to the rate when each is changed, and how a ventilation and a blood supply keep the gradient steep.Open →
- Gas exchange in plants and the compensation pointNet gas exchange of a plant at night, role of the air space system of the spongy mesophyll and why the mesophyll surface must be moist.Open →
- Gas exchange at the alveolusRecall questions on the structure of the alveolar wall and the capillary beside it, the short diffusion path, the surfactant and the moist lining, and how the blood supply and ventilation together maintain the gradient.Open →
- The respiratory tree and the mechanism of ventilationMuscles that act on the ribcage during breathing, position and structure of the diaphragm and muscle activity that produces a quiet expiration.Open →
- The effects of smoking on the breathing systemNormal function of the cilia lining the airways, why a smoker develops a persistent cough and why emphysema reduces the rate of gas exchange.Open →
- Using a respirometer to measure gas exchangeRespirometer used to measure, chemical placed in a respirometer to absorb carbon dioxide and purpose of the control tube in a respirometer experiment.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
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What decides whether a leaf takes in or gives out carbon dioxide, and what happens at the compensation point?
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Compare the diffusion distance across a capillary wall with that across a multi-layered tissue.
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Define the volume of an organism in terms of its tissues.
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Why do large multicellular organisms need mass transport systems?
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State the three factors related in Fick's law.
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Name the tissue that forms the wall of an alveolus.
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List the parts of the respiratory tree in the order that air passes through them.
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What is the normal function of the cilia lining the airways?
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Name the chemical placed in a respirometer to absorb carbon dioxide.
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Why does the volume of metabolically active tissue set an organism's demand for metabolites?
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Name the two groups of organisms whose mass transport systems are studied
Who and when
According to Fick's law, what happens to the rate of diffusion if the surface area is doubled and nothing else changes?
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Which two gases are exchanged between a leaf and the atmosphere?
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Name the tissue that forms the wall of a blood capillary surrounding an alveolus.
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What keeps the trachea open when the pressure inside it falls?
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How does tobacco smoke damage the ciliated epithelium of the airways?
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Explain what the volume change in a respirometer measures when potassium hydroxide is present.
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How does surface area influence the supply of metabolites to an organism's tissues?
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How is a concentration gradient across an exchange surface maintained in a living organism?
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Give the mass transport system that carries water in a flowering plant.
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What happens to the rate of diffusion if the diffusion path is made twice as thick?
Process
Which two processes in a plant determine the net exchange of gases at any moment?
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Why is the outer surface of an alveolus kept moist?
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Which two structures does the trachea divide into?
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Why does cilia damage make a smoker more prone to lung infections?
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How is carbon dioxide production calculated from two respirometer readings?
Take Exchange Surfaces and Gas Exchange further
The same content, four other ways.
Questions from this topic
Each one with the model answer underneath.
- 1
What is meant by the surface area of an organism when exchange with the environment is being considered?
Model answer
It is the total area of cells that are in direct contact with the surrounding environment.
- 2
Define the volume of an organism in terms of its tissues.
Model answer
Volume is the total three-dimensional space occupied by the metabolically active tissues of the organism.
- 3
Why does the volume of metabolically active tissue set an organism's demand for metabolites?
Model answer
Every respiring cell within that volume consumes oxygen and nutrients, so the greater the volume of active tissue the greater the total demand.
- 4
How does surface area influence the supply of metabolites to an organism's tissues?
Model answer
The surface area determines how quickly materials can be absorbed, so a larger surface allows a faster rate of supply.
- 5
What happens to the surface area to volume ratio of an organism as its body size increases?
Model answer
The ratio falls, because volume increases more steeply than surface area.
- 6
Calculate the surface area to volume ratio of a cube of side 1 cm.
Model answer
The surface area is 6 cm² and the volume is 1 cm³, so the ratio is 6:1.
What is inside Levo
Six ways to work the same material.
Exchange Surfaces and Gas Exchange revision questions
- Is Exchange Surfaces and Gas Exchange examined at AS in CCEA Biology?
- Yes. It sits in Unit AS 2, which you take in the first year, so it is on the AS paper as well as counting towards the full A level.
- What does Exchange Surfaces and Gas Exchange cover in CCEA AS-Level Biology?
- 9 subtopics: surface area, volume and the surface area to volume ratio, features of efficient exchange surfaces, the need for mass transport systems, fick's law and the rate of gas exchange, gas exchange in plants and the compensation point, gas exchange at the alveolus, the respiratory tree and the mechanism of ventilation, the effects of smoking on the breathing system and using a respirometer to measure gas exchange. Each one has its own page with questions and model answers.
- How is Exchange Surfaces and Gas Exchange organised?
- By the CCEA 1010 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Exchange Surfaces and Gas Exchange, 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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