Presentation on theme: "A summary of what you should know"— Presentation transcript:
1 A summary of what you should know photosynthesisA summary of what you should know
2 PHOTOSYNTHESIS Check out what you remember. Some could Revision of third form photosynthesisCheck out whatyou remember.Some couldcome up in the GCSE
3 CARBON DIOXIDE AND WATER PHOTOSYNTHESISPhotosynthesisWhat happens to the glucose formed in photosynthesis?Required to make plant cell walls. It is made of 100s of glucose molecules bonded together.STARCHCELLULOSELIPIDSPROTEINSCARBON DIOXIDE AND WATERPHOTOSYNTHESISGLUCOSEGlucose is chemically converted to fatty acids and glycerol to make lipids, which are needed to make plant cell membranes and seed storage oils.Is used by roots and leaves to store excess glucose in an osmotically inactive form. It is made of 100s of glucose molecules.Using nitrate ions absorbed by plant roots, glucose is converted first to amino acids then to protein.respirationATPThe carbon dioxide can be used again in photosynthesis or may diffuse out of the leaf via the stomata
4 temperature (degrees C) PHOTOSYNTHESISFactors necessary for photosynthesisFactors affecting the rate of photosynthesisThe effect of light intensity on photosynthetic rateThe main external factors affecting the rate of photosynthesis are:The rate is limited by another factor such as carbon dioxide concentrationlight wavelengthlight intensitytemperaturecarbon dioxideLight intensity limiting.Increasing light intensity increases the energy entering chlorophyll and thus the amount of ATP and produced to drive photosynthesislight intensityNotice how increasing the light intensity beyond a certain point causes no further increase in rate of photosynthesis. Something else is now ‘holding the reaction back’. Light is no longer the limiting factor.The effect of temperature on photosynthetic rateOptimumRate of photosynthesisEnzyme protein denatures. They lose their catalytic ability to catalyse photosynthesisHeat energy increases kinetic energy. More collisions, with more force, thus the rate increasesPhotosynthetic sugar production is catalysed by enzymes. If the temperature is raised too high the enzymes denature and photosynthesis stops.temperature (degrees C)
5 temperature (degrees C) Rate of photosynthesis Factors necessary for photosynthesisLimiting factorsAt low light intensities increasing the temperature has little effect on the rate of photosynthesis.The effect of temperature and lightAt high light intensities the rate of photosynthesis increases much more rapidly over the same temperature range.High light intensityThis is an example of the law of limiting factors.Rate of photosynthesisTHE LAW OF LIMITING FACTORS If a process is influenced by more than 1 factor, the rate will be limited by the factor nearest its lowest valueLow light intensitytemperature (degrees C)25O C and 0.4% CO2Here is another example of the law of limiting factorsWhat 3 factors are limiting in regions A, B, C respectively?Rate of photosynthesis25O C and 0.04% CO2ABCANSWERS:At A CO2 limiting15O C and 0.04% CO2At B temperature limitingAt C light limitingLight intensity
6 PHOTOSYNTHESIS Plant mineral requirements Plants require small quantities of minerals for healthy growthMinerals are absorbed by the root hairs, either by diffusion or active transport, depending on their concentration in the soil – see next topic.The most important minerals for plants are:NitrogenPotassiumMagnesiumIronPhosphoroususually as nitrate, nitrite or ammonium ions, NO3- , NO2-, NH4+often in the form of phosphate ions, PO4- ions.in the form of K+ ions.in the form of Mg2+ ionsin the form of Fe2+ ions
7 REMEMBER THESE ARE REQUIRED IN IONIC FORM! PHOTOSYNTHESISMineral requirements of plantsNitrogen (nitrate ions: Needed to make proteins and chlorophyllDeficiency: Poor growth and leaf yellowingNO3-Potassium: Helps enzymes in photosynthesis and respirationDeficiency: Yellow leaves with dead spotsK+Phosphorous: Required for photosynthesis and respirationDeficiency: Poor root growth and purple younger leavesPO4-Magnesium is required as part of the chlorophyll moleculeDeficiency: Yellowing of leaves and poor growthMg+Iron is required by the enzymes that make chlorophyllDeficiency: Leaf yellowingFe2+REMEMBER THESE ARE REQUIRED IN IONIC FORM!
8 WHAT YOU SHOULD KNOW AT THE END OF THIS UNIT PHOTOSYNTHESISWHAT YOU SHOULD KNOW AT THE END OF THIS UNITREVIEWThe photosynthesis word equation. That light energy is absorbed by chlorophyll in chloroplasts and used to make sugar from carbon dioxide. Oxygen is a bye-product.The rate of photosynthesis may by limited by: low temperature, shortage of carbon dioxide, shortage of light.The glucose produced in photosynthesis may be converted to insoluble starch. Start does not attract water by osmosis.Plant cells use some of the photosynthetic glucose for respiration. In addition, nitrates, absorbed by the roots, are needed for healthy growth.Any 1 of light, temperature and carbon dioxide will be limiting the rate of photosynthesis at any particular time.The energy from respiration is used to build smaller molecules into larger ones, including: sugars into starch, sugars into cellulose for cell walls, sugars, nitrates and other nutrients into amino acids and then proteins. Sugars into lipids for seed storage.For healthy growth plants need mineral ions including: nitrate for protein synthesis, phosphate and potassium for photosynthesis and respiration.Symptoms shown by mineral ion-deficient plants include:Stunted growth and yellow older leaves if nitrate ions are deficientPoor root growth and purple younger leaves if phosphate ions are deficientYellow leaves with dead spots if potassium ions are deficient.