9C Plants and photosynthesis

9C Plants and photosynthesis 9CPlants and photosynthesis Green and growing Leaves and photosynthesis Photosynthesis and the environment

9C Plants and photosynthesis Green and growing

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?

9C The process of photosynthesis sunlight carbon dioxide oxygen photosynthesis glucose water Photosynthesis is a chemical reaction that happens in the leaf. TO AIR OR USED FOR RESPIRATION What are the reactants? PRODUCT REACTANT Where do they come from? FROM AIR What are the products of the reaction? PRODUCT USED BY PLANT What happens to the products? REACTANT FROM SOIL

9C Where does the sugar go? out of leafthrough stomata oxygen carbon dioxidefrom the air photosynthesis glucose waterfrom soil out of leafthrough stomata some oxygen and glucose used in respiration cellulose for cell walls oxygen proteins for growth and enzymes carbon dioxidefrom the air photosynthesis starch for storage glucose waterfrom soil fats and oils for storage Plants make glucose by photosynthesis. This is how they grow. 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? Glucose is a sugar. But a plant is not just sugar! It makes lots of other chemicals so it can grow.

9C All mixed up Match the reactants with their products to complete the word equations. Respiration oxygen + sugar carbon dioxide + water Photosynthesis light energy taken in carbon dioxide + water oxygen + sugar carbon dioxide sugar water oxygen

9C Faster photosynthesis oxygen collects test tube light source water pondweed (Elodea) beaker funnel 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? 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?

9C Faster photosynthesis Here are some results from the pondweed experiment. 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.

9C Photosynthesis myths? FALSE! They are vital to the plant but roots cannot carry out photosynthesis – they’re underground in the dark. Without light energy, the reactions of photosynthesis cannot work. TRUE! FALSE! Plants need carbon dioxide from the air and water from the soil to build sugars. Oxygen is produced in photosynthesis. FALSE! They take in carbon dioxide. Oxygen is produced by photosynthesis. TRUE! Photosynthesis produces glucose and oxygen, while respiration breaks them down to make carbon dioxide and water. TRUE! Chlorophyll absorbs all the colours in light except green – we see the green light because it is reflected from the plant. True or false? 3.Photosynthesis and respiration work in opposite directions. 4.Plants look green because they contain the chemical chlorophyll. 5.Roots carry out half the photosynthesis that takesplace in a healthy oak tree. 6. Plants give out carbon dioxide when they arephotosynthesising. 1.Photosynthesis only happens in the light. 2.Plants make food from oxygen and sunlight.

9C Plants and photosynthesis Leaves and photosynthesis

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?

9C Design a food factory Photosynthesis needs light. You are going to design a light-catching machine.

9C Design a food factory Chloroplasts use light to make sugar.Where would you put these to make the most of the light?

9C Design a food factory Photosynthesis needs carbon dioxide. How does this gas get into the leaf?

9C Design a food factory Photosynthesis needs water. How can you get it into the leaf?

9C Design a food factory tightly packed palisadecells 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 stomata to let carbon dioxide into the leaf If you’re a dynamite designer, you should have a food-making factory that looks something like this:

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.

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.

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.

9C Plants and photosynthesis Photosynthesis and the environment

9C Meet the energy twins Respiration and photosynthesis are like a pair of energy twins. oxygen + glucose sunlight energy 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?

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?

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?

9C Rainforest answers? 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. 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! How many future life-saving drugs have we already lost from the rainforests? How many unknown species have we made extinct? What do you think?

9C Plants and photosynthesis