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Glucose Production Noadswood Science, 2012 Tuesday, May 23, 2017 Glucose Production • To understand how plants store and use the glucose produced during photosynthesis Equations The word equation for photosynthesis is carbon dioxide + water glucose + oxygen The symbol equation for photosynthesis is 6CO2 + 6H2O C6H12O6 + 6O2 Glucose & Starch • During photosynthesis glucose is produced (a simple sugar) • However, plants cannot store glucose, so they convert it into starch (many small glucose molecules are joined together) • Starch is insoluble, meaning it can be stored easily (when you wash some rice you can see the starch wash off) Glucose • Glucose can be used to make long chains of starch… Glucose molecules Starch molecule • This glucose is then used by the plant as a store of energy and some of it may be used for respiration • The energy released from respiration can be used to make amino acids or to build up fats and oils as a food store in seeds Proteins • Glucose is combined with nitrate ions (NO3-) (absorbed from the soil) to make amino acids which are then made into proteins… Starch Test • How can we test for starch? • How can we relate the presence of starch to the amount of photosynthesis taking place? • Iodine tests for starch – it turns blue/black in the presence of starch • If a plant photosynthesis a lot, then there should be more starch present (as more glucose would have been made and converted into starch) Experiment • Your task is to look at two different types of leaf –one normal leaf, and one which has been kept in the dark • You need to find out how much starch is present in each leaf… • Follow the leaf starch experiment worksheet Starch Experiment Boiling & Ethanol • Why do we need to boil the leaf first, and then add it to the ethanol? • Boiling the plant damages the cell wall, and the ethanol extracts the chlorophyll from the leaf allowing us to test if any starch is present Explanation • Explain your results for the leaf in the light and the leaf in the dark • The leaf in the light has a good store of starch (photosynthesis has taken place, converting the glucose produced to starch) • The leaf in the dark cannot photosynthesize, but has been respiring (using up the starch supply) Storage • Why store the glucose as starch? • Remember, the starch is insoluble, so the plant can store it conveniently without it getting dissolved within the cell which is much more convenient than the soluble glucose Minerals • How do plants absorb the minerals they need? • Roots are adapted to absorb the minerals needed to remain healthy (although some plants have adapted some special ways to get more minerals, e.g. a Venus fly trap) • Venus fly traps often live in areas where minerals are scarce – to compensate they can trap and digest insects, getting valuable minerals from them Minerals • There are 3 essential minerals: • Nitrates – needed for protein manufacture • Phosphates – needed for respiration and photosynthesis • Potassium – needed for enzymes involved in respiration and photosynthesis • Iron and magnesium are also needed in trace amounts for chlorophyll production Photosynthesis Photosynthesis