Key term
CCEA A-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
Homeostasis and Excretion
Topic overviewPrinciples of homeostasis and negative feedbackExcretion, osmoregulation and nitrogenous wasteGross structure of the kidney and the urinary systemStructure of the nephron and its blood supplyEpithelia of the nephron and their adaptationsThe glomerular filterUltrafiltration and the forces that drive itSelective reabsorption in the proximal convoluted tubuleThe loop of Henlé and the medullary salt gradientADH, osmoreceptors and the control of water balance
Immunity
Topic overviewNatural barriers to infectionAntigens, antibodies and the antigen–antibody reactionAntibody-mediated immunity and B-lymphocytesCell-mediated immunity and T-lymphocytesActive immunity, passive immunity and vaccinationTransplant rejection and immunosuppressionBlood group polymorphism and the rhesus factorTransfusion compatibility and its consequencesAntibiotic resistance and the search for new antimicrobialsELISA and the detection of disease biomarkers
Co-Ordination and Control
Topic overviewPhytochromes and the control of floweringPlant growth substances and stem elongationThe structure of a neuroneResting potential, threshold and the action potentialImpulse propagation and the speed of conductionSynapse structure and chemical transmissionExcitatory and inhibitory post-synaptic potentialsGross structure of the eye and accommodationThe retina, rods and conesSkeletal muscle and the sliding filament theory
Populations and Communities
Topic overviewPopulation growth curves, carrying capacity and environmental resistancer-selected and K-selected speciesInteractions between populationsBiological control of pest speciesPopulation dynamics and changes in population sizeEstimating population size in the field and the laboratoryCommunities and ecosystemsSuccession and climax communities
Ecological Energetics and Nutrient Cycling
Topic overviewFood chains, food webs and detritus food chainsTrophic levels, gross and net primary productionEcological pyramids and their usefulnessEnergy transfer efficiency between trophic levelsWhy energy is lost at each trophic levelImplications for agriculture and intensive farmingThe carbon cycleThe nitrogen cycle and the role of bacteria
Respiration
Topic overviewATP and the ATP/ADP cycleGlycolysisThe mitochondrion and the sites of aerobic respirationThe link reaction and the Krebs cycleThe electron transport chain and oxidative phosphorylationATP yield from one molecule of glucoseAnaerobic respiration in animals, plants and fungiAerobic and anaerobic respiration compared, and oxygen debtRespiratory quotient and measuring respiration
Photosynthesis
Topic overviewChloroplast structure and the sites of photosynthesisPhotosynthetic pigments and paper chromatographyAbsorption spectra and action spectraPhotosystems, photoactivation and the Z-schemePhotolysis of water, reduced NADP and redox indicatorsCarbon dioxide fixation and rubiscoReduction of glycerate phosphate and regeneration of ribulose bisphosphateLimiting factors, the compensation point and measuring photosynthesis
DNA as the Genetic Code
Topic overviewGenes and the nature of the genetic codeExons, introns and RNA splicingComparing DNA and RNATranscription and RNA polymeraseTransfer RNA, ribosomes and the sites of translationTranslation and polypeptide synthesisOne gene, one polypeptide and the control of the phenotypeEpigenetics, methylation and histone modification
Gene Technology
Topic overviewThe polymerase chain reactionDNA probes and genetic markersMicroarrays, pharmacogenetics and personalised medicineGenetic fingerprinting and gel electrophoresisThe stages of gene transferGenetically modified microorganismsTransgenic animals and plantsGene therapyGenome sequencing and the Human Genome ProjectGene inactivation and knockout organismsSocial, ethical and ecological issues of gene technology
Genes and Patterns of Inheritance
Topic overviewGenotype, phenotype and the environmentChromosomes, genes and allelesMonohybrid inheritance and Mendel's first lawCodominance, multiple alleles and lethal allelesTest crossesDihybrid inheritance and Mendel's second lawAutosomes, sex chromosomes and sex determinationGene interaction and epistasisPolygenic inheritance and continuous variationThe chi-squared test
Population Genetics and Evolution
Evolutionary Trends in Plants
Homeostasis and Excretion
- 10 subtopics
- 30 things to know
- Unit A2 1
What Homeostasis and Excretion covers
Homeostasis and Excretion is examined in Unit A2 1, Physiology, Co-ordination and Control, and Ecosystems, and drawn on again in Unit A2 3, the practical skills examination. It covers Principles of homeostasis and negative feedback, excretion, osmoregulation and nitrogenous waste, gross structure of the kidney and the urinary system, structure of the nephron and its blood supply, Epithelia of the nephron and their adaptations, the glomerular filter, ultrafiltration and the forces that drive it, selective reabsorption in the proximal convoluted tubule, the loop of Henlé and the medullary salt gradient and ADH, osmoreceptors and the control of water balance.
Where it is assessed
Unit A2 1
Physiology, Co-ordination and Control, and Ecosystems, and again in Unit A2 3, Practical Skills in Biology.
Check the CCEA specification ↗The 10 subtopics
Each one has its own page.
- Principles of homeostasis and negative feedbackJob of the sensor in a homeostatic mechanism and negative feedback.Open →
- Excretion, osmoregulation and nitrogenous wasteRecall questions on the difference between excretion and egestion, deamination in the liver and the ornithine cycle, why urea rather than ammonia is excreted by a mammal, and the role of the kidney in balancing water as well as removing waste.Open →
- Gross structure of the kidney and the urinary systemOuter region of the kidney in which the glomeruli lie, renal pyramids and position and the function of the renal pelvis.Open →
- Structure of the nephron and its blood supplyShape of the Bowman's capsule, shape and the position of the loop of Henlé and vasa recta.Open →
- Epithelia of the nephron and their adaptationsEpithelium lines the proximal convoluted tubule, basal invaginations of a proximal tubule cell and epithelium lines the descending limb of the loop of Henlé.Open →
- The glomerular filterEndothelium of a glomerular capillary and two components of blood that are not filtered.Open →
- Ultrafiltration and the forces that drive itTwo forces that oppose ultrafiltration in the glomerulus, how the solute potential of the glomerular blood opposes filtration and back pressure of the filtrate.Open →
- Selective reabsorption in the proximal convoluted tubuleSelective reabsorption and renal threshold for glucose.Open →
- The loop of Henlé and the medullary salt gradientOverall purpose of the loop of Henlé and salt gradient that exists in the medulla.Open →
- ADH, osmoreceptors and the control of water balanceRecall questions on the osmoreceptors of the hypothalamus, the posterior pituitary and the release of antidiuretic hormone, the change in collecting duct permeability, and the full negative feedback loop after drinking and after dehydration.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
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What happens when blood glucose rises above the renal threshold, and why does the urine volume rise with it?
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What does homeostasis mean?
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Define excretion.
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What is the glomerulus?
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What kind of epithelium lines the proximal convoluted tubule?
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What are podocytes?
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Define ultrafiltration.
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What is the overall purpose of the loop of Henlé?
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Where in the body are the osmoreceptors that monitor the blood?
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Why must a mammal hold its internal conditions steady rather than let them follow the environment?
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Which two nitrogenous waste products does the mammalian kidney remove from the blood?
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Name the outer region of the kidney in which the glomeruli lie.
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Which vessel brings blood into the glomerulus, and which vessel takes it away?
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How does a brush border help reabsorption?
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Which layer of the glomerular filter actually decides what is held back?
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What provides the main driving force for ultrafiltration in the kidney?
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Define selective reabsorption.
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What happens to the filtrate as it moves down the descending limb?
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Where is ADH synthesised?
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Name the three components that every homeostatic control system must have.
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From which substance is creatinine produced?
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Name the region of the kidney that lies between the cortex and the pelvis.
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Describe the shape of the Bowman's capsule.
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What are the basal invaginations of a proximal tubule cell?
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What is the basement membrane of the glomerulus made of?
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How does the diameter of the afferent arteriole compare with that of the efferent arteriole?
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In which part of the nephron is most of the filtrate reabsorbed?
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At which point in the loop of Henlé is the filtrate most concentrated?
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Where is ADH stored, and from where is it released?
Take Homeostasis and Excretion further
The same content, four other ways.
Questions from this topic
Each one with the model answer underneath.
- 1
What does homeostasis mean?
Model answer
Homeostasis is the maintenance of a constant internal environment inside an organism despite changes in external conditions.
- 2
Why must a mammal hold its internal conditions steady rather than let them follow the environment?
Model answer
Enzymes and other proteins work properly only within narrow ranges of temperature, pH and water potential, so cells can function reliably only if those conditions are held close to the optimum.
- 3
Name the three components that every homeostatic control system must have.
Model answer
A homeostatic system needs a sensor or receptor that monitors the factor, a control centre that compares it with the norm, and a corrective mechanism that restores it.
- 4
What is the job of the sensor in a homeostatic mechanism?
Model answer
The sensor monitors the factor being controlled and detects any deviation of it from the normal value.
- 5
What does a corrective mechanism do?
Model answer
A corrective mechanism brings about changes that push the factor being controlled back towards its normal value, so the factor is regulated.
- 6
Define negative feedback.
Model answer
Negative feedback is a control response in which a deviation from the norm triggers changes that reverse that deviation and restore the original value.
What is inside Levo
Six ways to work the same material.
Homeostasis and Excretion revision questions
- What does Homeostasis and Excretion cover in CCEA A-Level Biology?
- 10 subtopics: principles of homeostasis and negative feedback, excretion, osmoregulation and nitrogenous waste, gross structure of the kidney and the urinary system, structure of the nephron and its blood supply, epithelia of the nephron and their adaptations, the glomerular filter, ultrafiltration and the forces that drive it, selective reabsorption in the proximal convoluted tubule, the loop of henlé and the medullary salt gradient and adh, osmoreceptors and the control of water balance. Each one has its own page with questions and model answers.
- How is Homeostasis and Excretion organised?
- By the CCEA 1010 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Homeostasis and Excretion, 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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