Key term
Eduqas A-Level Biology A400QS
Biological Molecules
Cell Structure and Organisation
Cell Membranes and Transport
Enzymes
Nucleic Acids and Their Functions
Importance of ATP
Photosynthesis
Respiration
Microbiology
Population Size and Ecosystems
Topic overviewPopulation growth and its measurementThe population growth curve and carrying capacityDensity dependent and density independent factorsSampling abundance and distributionEcosystems, habitats and communitiesEnergy transfer and pyramids of biomassSuccessionDecomposition and the carbon cycleThe nitrogen cycle and human interventionEutrophication and the effects of drainage
Human Impact on the Environment
Classification and Biodiversity
Topic overviewThe need for classification and the taxonomic hierarchyThe three domain and five kingdom systemsCharacteristic features of the five kingdomsAssessing relatedness by physical features and biochemistryThe species concept and the binomial systemBiodiversity, adaptation and natural selectionMeasuring biodiversity in a habitatGenetic and molecular measures of biodiversity
Mitosis and Meiosis
Sexual Reproduction in Humans
Sexual Reproduction in Plants
Inheritance
Variation and Evolution
Application of Reproduction and Genetics
Topic overviewThe Human Genome Project, other sequenced genomes and genomics in healthcareScreening embryos, stem cells and the ethical issuesGenetic fingerprinting, PCR and electrophoresis in forensic workRecombinant DNA and the production of human insulinGenetically modified crops and gene therapy
Adaptations for Gas Exchange
Topic overviewSurface area to volume ratio and gas exchange in small organismsSpecialised respiratory surfaces and the need for ventilationGills and counter current flow in bony fishThe human breathing system and its histologyVentilation and gas exchange in humansThe insect tracheal systemThe angiosperm leaf, stomata and gas exchange
Adaptations for Transport
Topic overviewVascular systems compared across animal groupsThe mammalian heart and blood vesselsThe cardiac cycle and its controlBlood, haemoglobin and dissociation curvesThe Bohr effect, chloride shift and tissue fluidThe root and the uptake of waterThe endodermis and the entry to the xylemXylem, transpiration and cohesion-tensionThe potometer and xerophytes and hydrophytesPhloem and translocation
Adaptations for Nutrition
Homeostasis and the Kidney
The Nervous System
Immunology and Disease: Disease and Its TransmissionImmunology
Immunology and Disease: AntibioticsImmunology
Immunology and Disease: The Immune ResponseImmunology
Human Musculoskeletal Anatomy: Skeletal TissuesMusculoskeletal
Topic overviewCartilage and its three typesThe composition and functions of compact boneBone remodelling and the Haversian systemRickets, osteomalacia, osteoporosis and brittle bone diseaseThe structure of skeletal muscleThe sliding filament theoryFast and slow twitch fibres, and energy for contraction
Human Musculoskeletal Anatomy: Structure and Function of the SkeletonMusculoskeletal
Human Musculoskeletal Anatomy: JointsMusculoskeletal
Neurobiology and Behaviour: The BrainNeurobiology
Neurobiology and Behaviour: NeuroscienceNeurobiology
Enzymes
Substrate and enzyme concentration
- 3 things to know
- Component 1
Overview
Recall questions on why the rate rises and then plateaus as substrate is added, what is limiting at each stage, the effect of enzyme concentration, the shape of each graph and why they differ, and how initial rate is measured.
What you need to know
Answer each one before you reveal it.
Your recallNot started
Key term
Explain why the rate levels off as substrate concentration keeps rising.
Key term
Define Vmax.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Describe the effect of increasing substrate concentration on the rate of reaction when the enzyme concentration is fixed.
Model answer
The rate rises steeply at first and then increases less and less, until it levels off at a maximum and rises no further.
- 2
Explain why the rate levels off as substrate concentration keeps rising.
Model answer
Every active site is occupied as soon as it becomes free, so the number of enzyme molecules present, not the amount of substrate, now limits the rate.
- 3
Define Vmax.
Model answer
The maximum rate a given concentration of enzyme can achieve, reached when all its active sites are saturated with substrate.
- 4
Describe the effect of increasing enzyme concentration when substrate is present in excess.
Model answer
The rate rises in direct proportion to the enzyme concentration, giving a straight line through the origin.
- 5
What happens to that straight-line relationship if the substrate begins to run short?
Model answer
The line bends and flattens, because substrate concentration rather than enzyme concentration has become the factor limiting the rate.
- 6
Why does the rate of an enzyme-controlled reaction fall as the reaction proceeds?
Model answer
The substrate is used up so collisions with active sites become less frequent, and accumulating product may also occupy sites or inhibit the enzyme.
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