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
Plant Structures and Their Functions
Limiting factors in photosynthesis
- 3 things to know
- Paper 2
Overview
What a limiting factor is, how light intensity, temperature and carbon dioxide concentration each affect the rate of photosynthesis, why the rate levels off in bright light and falls above about 45 °C, what limits a warm, brightly lit greenhouse, and what a flat section of a rate graph shows.
What you need to know
Answer each one before you reveal it.
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Key term
Explain why the rate of photosynthesis stops rising when light intensity is increased beyond a certain point.
Key term
Explain why the rate of photosynthesis increases when temperature rises from 10 °C to 25 °C.
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is meant by a limiting factor?
Model answer
A limiting factor is a condition in short supply that holds back the rate of a process even when every other condition is plentiful.
- 2
Describe the effect of increasing light intensity on the rate of photosynthesis when the light is dim.
Model answer
The rate rises steadily as light intensity rises, because more light energy is available to be absorbed.
- 3
Explain why the rate of photosynthesis stops rising when light intensity is increased beyond a certain point.
Model answer
Light is no longer the factor in shortest supply, so something else such as carbon dioxide concentration or temperature is holding the rate back.
- 4
Explain why the rate of photosynthesis increases when temperature rises from 10 °C to 25 °C.
Model answer
The enzymes and reacting molecules gain kinetic energy, so they collide more often and react more quickly.
- 5
Explain why the rate of photosynthesis falls sharply above about 45 °C.
Model answer
The enzymes controlling photosynthesis denature, so their active sites change shape and can no longer catalyse the reactions.
- 6
Describe the effect of increasing carbon dioxide concentration on the rate of photosynthesis.
Model answer
The rate increases as carbon dioxide rises, then levels off once a different factor becomes the one in shortest supply.
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