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9C Plants and photosynthesis 9C Plants and photosynthesis Green and growing Leaves and photosynthesis Photosynthesis and the environment © OUP: To be used solely in purchaser’s school or college 9C Plants and photosynthesis Green and growing © OUP: To be used solely in purchaser’s school or college 9C Photosynthesis matters Brian started with bare soil and a packet of seeds. Now he has tomatoes for his family all summer. The tomatoes contain lots of chemicals that were not there at the start. Where have they come from? What’s the role of the Sun in helping the tomatoes grow? © OUP: To be used solely in purchaser’s school or college 9C The process of photosynthesis Photosynthesis is a chemical reaction that happens in the leaf. What are the reactants? Where do they come from? oxygen REACTANT FROM AIR photosynthesis glucose PRODUCT USED BY PLANT water REACTANT FROM SOIL © OUP: To be used solely in purchaser’s school or college TO AIR OR USED FOR RESPIRATION PRODUCT carbon dioxide What are the products of the reaction? What happens to the products? sunlight 9C Where does the sugar go? Plants make glucose by photosynthesis. This is how they grow. out of of leaf leaf out through stomata stomata through cellulose for cell walls oxygen oxygen carbon dioxide dioxide carbon from the the air air from some oxygen and glucose used in respiration proteins for growth and enzymes photosynthesis photosynthesis water water from soil soil from Glucose is a sugar. But a plant is not just sugar! It makes lots of other chemicals so it can grow. © OUP: To be used solely in purchaser’s school or college glucose glucose starch for storage fats and oils for storage Starch is one chemical that a plant makes. A potato stores starch. How does the starch get there, when glucose is made in the leaf? 9C All mixed up Match the reactants with their products to complete the word equations. Respiration oxygen + sugar Photosynthesis carbon dioxide + water carbon dioxide © OUP: To be used solely in purchaser’s school or college carbon dioxide + water light energy taken in sugar oxygen + sugar water oxygen 9C Faster photosynthesis How fast does a plant photosynthesise? This question is very important to farmers and growers. We can use this apparatus to measure the rate of photosynthesis. How? oxygen collects light source test tube water pondweed (Elodea) beaker funnel We might count the oxygen bubbles per minute, or collect the gas given off in one minute and measure its volume. What would happen if we increased the light level? © OUP: To be used solely in purchaser’s school or college 9C Faster photosynthesis Here are some results from the pondweed experiment. light level bubbles of oxygen per minute very high 24 high 22 medium 15 low 7 very low 0 What effect does light have on the rate of photosynthesis? What would happen if we put a layer of oil on the water? This stops carbon dioxide from the air dissolving in the water. © OUP: To be used solely in purchaser’s school or college 9C Photosynthesis myths? True or false? 1. Plants 2. 3. 4. 5. 6. Photosynthesis Roots Plants carry make look give green out out food carbon only half and from because the respiration happens oxygen dioxide photosynthesis they inwhen and work contain thesunlight. light. they in opposite that the are chemical takes chlorophyll. directions. place photosynthesising. in a healthy oak tree. TRUE! Photosynthesis FALSE! Without Plants They take are need light vital energy, carbon to produces theall the dioxide plant reactions glucose but from roots and the ofincannot air Chlorophyll absorbs the colours light in carbon dioxide. Oxygen is oxygen, photosynthesis and carrywater out while photosynthesis from respiration cannot thesee soilwork. to breaks –build they’re sugars. them except green – we the green light produced by photosynthesis. down Oxygen underground to make carbon in the dark. in dioxide photosynthesis. and water. because itisisproduced reflected from the plant. © OUP: To be used solely in purchaser’s school or college 9C Plants and photosynthesis Leaves and photosynthesis © OUP: To be used solely in purchaser’s school or college 9C Food factories Plants are food factories! They are adapted to carry out photosynthesis quickly. How does this help them? Most photosynthesis happens in the leaves. Can you give three ways in which these leaves are adapted to be food factories? © OUP: To be used solely in purchaser’s school or college 9C Design a food factory Photosynthesis needs light. You are going to design a light-catching machine. © OUP: To be used solely in purchaser’s school or college 9C Design a food factory Chloroplasts use light to make sugar. Where would you put these to make the most of the light? © OUP: To be used solely in purchaser’s school or college 9C Design a food factory Photosynthesis needs carbon dioxide. How does this gas get into the leaf? © OUP: To be used solely in purchaser’s school or college 9C Design a food factory Photosynthesis needs water. How can you get it into the leaf? © OUP: To be used solely in purchaser’s school or college 9C Design a food factory If you’re a dynamite designer, you should have a food-making factory that looks something like this: tightly packed palisade cells full of chloroplasts spongy mesophyll with air spaces so gases can move around veins to bring water up from the roots, and also take sugar back down to the roots for storage © OUP: To be used solely in purchaser’s school or college stomata to let carbon dioxide into the leaf 9C Quiz 1. Leaves are adapted for… a) pollination b) photosynthesis c) photography. 2. Stomata are... a) holes in a leaf that can open and close to let gases in and out b) the cells that carry out photosynthesis c) small stones found in your stomach. © OUP: To be used solely in purchaser’s school or college 9C Quiz 3. Leaves are covered with a thin waterproof layer called the… a) popsicle b) cuticle c) waxicle. 4. Leaves have a large surface area to... a) increase the rate of reactions b) catch the maximum amount of sunlight c) look pretty in parks and gardens. © OUP: To be used solely in purchaser’s school or college 9C Quiz 5. Palisade mesophyll is in the upper part of the leaf because… a) it needs to capture as much sunlight as possible b) the lower areas were already full c) it stops the upper surface from collapsing. 6. Spongy mesophyll has large air spaces between the cells to... a) allow veins into the leaf b) cut down the amount of cellulose needed to build new cell walls c) give room for gases to move more easily. © OUP: To be used solely in purchaser’s school or college 9C Plants and photosynthesis Photosynthesis and the environment © OUP: To be used solely in purchaser’s school or college 9C Meet the energy twins Respiration and photosynthesis are like a pair of energy twins. sunlight energy oxygen + glucose photosynthesis respiration carbon dioxide + water energy released How do these energy twins work together to keep our atmosphere in balance? Where would we be without sunlight and green plants? © OUP: To be used solely in purchaser’s school or college 9C Food, medicines, and ... All of our food comes originally from plants. That’s true even if you only eat steak! Why? Many powerful drugs come from plants. Aspirin first came from the bark of willow trees. Powerful new anti-cancer drugs are made from yew trees. Wood, hay and bamboo are used all over the world for building. Linen and cotton are both fabrics made from plants. What else can we get from plants? © OUP: To be used solely in purchaser’s school or college 9C The rainforest question Rainforests are very complex ecosystems. Scientists estimate that thousands of unknown species live there. But the people living in rainforests need to live now. They cut down the trees for building and furniture. They grow crops on the land, but this destroys the soil. What does deforestation do to the atmosphere? What other problems does it cause? © OUP: To be used solely in purchaser’s school or college 9C Rainforest answers? Local people need money. They need to harvest the forests now. People in the rich world cut down all of their forests centuries ago – they can’t tell people in the developing world not to do the same! What do you think? © OUP: To be used solely in purchaser’s school or college Most of the money is earned by a few rich companies. The people who live in the forests get nothing – and they lose their homes. How many future lifesaving drugs have we already lost from the rainforests? How many unknown species have we made extinct?