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
Enzymes
- 8 subtopics
- 24 things to know
- Unit AS 1
What Enzymes covers
Enzymes is examined in Unit AS 1, Molecules and Cells, and drawn on again in Unit AS 3, the practical skills examination. It covers enzymes as globular proteins and the active site, specificity, cofactors and coenzymes, activation energy and models of enzyme action, the effect of temperature and pH, the effect of substrate and enzyme concentration, competitive and non-competitive inhibition, enzymes as biomarkers of disease and inhibitors as drugs and immobilised enzymes and biosensors.
Where it is assessed
Unit AS 1
Molecules and Cells, and again in Unit AS 3, Practical Skills in AS Biology.
Check the CCEA specification ↗The 8 subtopics
Each one has its own page. CCEA AS Biology students sit this topic in the first year.
- Enzymes as globular proteins and the active siteTerm active site, term biological catalyst and temporary structure formed when substrate binds to an enzyme.Open →
- Specificity, cofactors and coenzymesEnzyme specificity, term cofactor and inorganic cofactor.Open →
- Activation energy and models of enzyme actionTerm activation energy, lock and key hypothesis of enzyme action and induced fit hypothesis of enzyme action.Open →
- The effect of temperature and pHOptimum temperature of an enzyme, approximate optimum temperature of most human enzymes and shape of a graph of enzyme activity against pH.Open →
- The effect of substrate and enzyme concentrationWhy the rate stops rising at high substrate concentration and maximum rate of an enzyme-catalysed reaction.Open →
- Competitive and non-competitive inhibitionTerm enzyme inhibitor, how a competitive inhibitor slows a reaction and effect of raising the substrate concentration on competitive inhibition.Open →
- Enzymes as biomarkers of disease and inhibitors as drugsDescribing an enzyme as a biomarker of disease, three clinical samples in which enzyme biomarkers may be detected and active site-directed inhibitor.Open →
- Immobilised enzymes and biosensorsImmobilised enzyme, three types of support material used to immobilise enzymes and how an enzyme is immobilised in an alginate gel.Open →
What you need to know
Answer each one before you reveal it.
Your recallNot started
Process
Why does the rate stop rising as substrate is added, and what is limiting it at each stage?
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Define the term cofactor.
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Define the term activation energy.
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Describe how the rate of an enzyme-catalysed reaction changes as temperature rises to the optimum.
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Define the term enzyme inhibitor.
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What is meant by describing an enzyme as a biomarker of disease?
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What is meant by an immobilised enzyme?
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To which class of protein do enzymes belong?
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Give an example of an inorganic cofactor.
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Explain why lowering the activation energy allows reactions to run at body temperature.
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Define the optimum temperature of an enzyme.
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Describe the effect on reaction rate of increasing substrate concentration at low substrate levels.
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Where does a competitive inhibitor bind to an enzyme?
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Which enzyme released by white blood cells during respiratory infection damages the lung?
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Name three types of support material used to immobilise enzymes.
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Which level of protein structure creates the shape of the active site?
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Define the term coenzyme.
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Describe how forming an enzyme–substrate complex helps break a bond in the substrate.
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Explain what happens to an enzyme when it is heated well above its optimum temperature.
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Explain why the rate stops rising at high substrate concentration.
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What is the effect of raising the substrate concentration on competitive inhibition?
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Which lung protein is hydrolysed by elastase?
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Why is the activity of an immobilised enzyme usually lower than that of the free enzyme?
Take Enzymes further
The same content, four other ways.
Questions from this topic
Each one with the model answer underneath.
- 1
To which class of protein do enzymes belong?
Model answer
Enzymes are globular proteins.
- 2
Give two structural features of a globular protein that suit it to acting as an enzyme.
Model answer
It is compact with a precise three-dimensional shape, and its hydrophilic groups face outwards so it dissolves in the aqueous cytoplasm.
- 3
Define the term active site.
Model answer
The active site is a small region on the surface of an enzyme with a shape complementary to that of its substrate, to which the substrate binds.
- 4
Which level of protein structure creates the shape of the active site?
Model answer
The tertiary structure creates the active site, because folding brings particular R groups together on the surface.
- 5
What fraction of an enzyme molecule does the active site occupy?
Model answer
The active site occupies only a very small part of the molecule, typically a few amino acid residues out of hundreds.
- 6
Explain the role of the amino acids that lie outside the active site.
Model answer
They hold the chain in the folded shape that positions the active site residues correctly, so a change anywhere in the chain can alter the site.
What is inside Levo
Six ways to work the same material.
Enzymes revision questions
- Is Enzymes examined at AS in CCEA Biology?
- Yes. It sits in Unit AS 1, 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 Enzymes cover in CCEA AS-Level Biology?
- 8 subtopics: enzymes as globular proteins and the active site, specificity, cofactors and coenzymes, activation energy and models of enzyme action, the effect of temperature and ph, the effect of substrate and enzyme concentration, competitive and non-competitive inhibition, enzymes as biomarkers of disease and inhibitors as drugs and immobilised enzymes and biosensors. Each one has its own page with questions and model answers.
- How is Enzymes organised?
- By the CCEA 1010 specification, subtopic by subtopic, so it matches the order you are taught it in.
Every question in Enzymes, 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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