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NAME ________________________ PHOTOSYNTHESIS WILBERT DATE ___________ 7 _____ PHOTO (Greek “light”) SYNTHESIS (Greek “putting together”) PHOTOSYNTHESIS IS THE PROCESS THAT ALLOWS PLANTS TO CAPTURE LIGHT ENERGY AND CHANGE IT INTO CHEMICAL (FOOD) ENERGY. THE PROCESS Photosynthesis takes place in plant cells that have structures called chloroplasts. FOOD MAKING HAPPENS IN THESE CELL STRUCTURES. (A single plant cell can have 20-100 chloroplasts.) Inside the chloroplasts are molecules that capture the energy in sunlight. These molecules are called pigments. The main pigment in chloroplasts is chlorophyll (which is green). The captured energy from the sun gets photosynthesis started. Water, from the soil, is absorbed by the roots. It is transported to the leaves and into the chloroplasts. Carbon dioxide, a gas from the air, enters the plant leaves through microscopic openings. The carbon dioxide will find its way into the chloroplasts. Inside the chloroplasts the water and carbon dioxide molecules are used to make food. Making food is powered by solar energy. As a result, a sugar called glucose is made. Glucose is the name of the food that plants make. About 50% of the glucose is used by the plant for its own energy supply. The rest is changed into other molecules for building things such as wood, leaves, stems, roots, flowers, seeds, fruits, etc. When water molecules are taken apart to make food, the oxygen in H2O is released into the air through microscopic openings in the leaves. A little water vapor (H2O in the gas state) is also released into the air, too. SUMMARIZING PHOTOSYNTHESIS WITH A CHEMICAL EQUATION 6CO2 + 6H2O carbon dioxide water + Light Energy light captured by chlorophyll C6H12O6 makes sugar called glucose + 6O2 oxygen gas released Explanation: The light energy absorbed by chlorophyll is used to break water (H 2O) down into hydrogen and oxygen. The hydrogen is the combined with carbon dioxide (CO 2) from the air to make a sugar called glucose (C6H12O6). The oxygen that is split off from the water molecule and one from carbon dioxide can be used directly by the plant or released into the atmosphere. The little numbers are called subscripts and tell you how many atoms of each element are needed. The large numbers are called coefficients. They tell you how many of each molecule is needed to BALANCE the equation. These means the total number of atoms should be equal on each side of the arrow. THE IMPORTANCE OF PHOTOSYNTHESIS FOOD FOR OTHERS Plants are important because they are the key organisms, on our planet, that can capture sun energy and change it into food energy. Nearly all living organisms get energy either directly or indirectly from energy captured during photosynthesis. For example, animals cannot make their own food. To get their energy supply (food) they must eat plants directly or eat other animals which have eaten plants directly or indirectly. OXYGEN MAKERS Photosynthesis is also essential for the oxygen you breathe. Most living things need oxygen to survive. About 21% of Earth’s atmosphere is oxygen— thanks to plants and other organisms that carry out photosynthesis (some bacteria and protists). Please understand that plants need some oxygen to carry out their life activities.