GCSE›Edexcel GCSE Biology›Mind mapsPhotosynthesisEdexcel GCSE Biology: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsWhat it doesPlants and algae are producersLight energy becomes chemical energy in glucoseForms the base of biomass in ecosystemsThe reactionEndothermic: takes in energy6 COX2+6 HX2O→CX6HX12OX6+6 OX2\ce{6CO2 + 6H2O -> C6H12O6 + 6O2}6COX2+6HX2OCX6HX12OX6+6OX2Light absorbed by chlorophyllLimiting factorsTemperature, light intensity, CO₂ concentrationScarcest factor limits the ratePlateau means another factor is limitingHigh temperature denatures enzymesGrowers optimise all factors together, e.g. greenhousesPhotosynthesismaking glucoseCO₂O₂Core practicalPondweed at varying lamp distancesCount oxygen bubbles per minuteKeep temperature and CO₂ constantGas syringe more precise than countingLight intensityRate ∝ light intensity at low levelsIntensity ∝ 1d2\frac{1}{d^2}d21Doubling distance gives quarter intensity20 cm to 40 cm: ratio 14\frac{1}{4}41Exam tipsPhotosynthesis endothermic, respiration exothermicA plateau shows a different factor limitsName the scarcest factor, not just any factor