Transcript lesson 2
Lesson 2: Leaves and Photosynthesis Lesson Aims To learn how to test leaves for the presence of starch and learn: • oxygen is a product of photosynthesis • factors needed for photosynthesis Learning outcomes By the end of the lesson you should: • know the reactants and products in photosynthesis • know how to safely test a leaf for starch • know how to safely collect and test for oxygen formed in photosynthesis Photosynthesis • Reactants How is glucose stored in plants? How can we test for • a) oxygen? • b) starch? Products Photosynthesis summary Chloroplast These are small structures that varychlorophyll. in They contain a green pigment called number and size. LIGHT Chlorophyll The Photosynthesis chlorophyll traps is thesunlight nameare of and the uses chemical energy reaction that Therefore, Chloroplasts where athis plant makes its toproduces drive the process plant’s of food. photosynthesis. ownthe food. Testing a leaf for starch http://lgfl.skoool.co.uk/content/keystage3/biolo gy/pc/learningsteps/TLSLC/launch.html SAFETY Risks Ethanol is flammable and must not be exposed to a naked flame. You must wear safety glasses. The Bunsen burner MUST be turned off BEFORE the ethanol is placed in the boiling tube. Method for testing a leaf for starch – – – – – – – – 1) Boil the leaf for a few minutes What does this do to the leaf? 2) Soak the leaves in alcohol What effect does this have on the leaf? 3) Dip the leaves in water What effect does this have? 4) Drop some iodine onto the leaf What do you see? Draw and explain your results Results Green Variegated Covered Leaf with leaf leaf leaf no CO2 (no light for for 2 days 2 days ) Starch present? Describe the method and write a conclusion: (Summarise each test ,your observations and what you found out ) Testing a leaf for oxygen production • Draw the apparatus • Write the method • Make a prediction What will happen? A: Light B: Dark Homework • Draw a cartoon strip/poster about how plants use energy from the Sun Do you? • know the reactants and products in photosynthesis • know how to safely test a leaf for starch • know how to safely collect and test for oxygen formed in photosynthesis Photosynthesis activity Photosynthesis We know that plants make their own food from sunlight. They are the producers in the food chain. This is done in the green parts of the plant, e.g. upper surface of the leaves. The reaction for this is: CARBON DIOXIDE + Taken in through holes in the leaves WATER Taken in through the roots With light and chlorophyll FOOD (GLUCOSE) Made by photosynthesis and stored as starch in leaves, roots, stems, etc. + OXYGEN waste product exhaled + ENERGY USEFUL!