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How Plants Make Food Photosynthesis = the process by which plants make food Takes place mainly in the leaves Photo = light Synthesis = putting together Cells in the leaf have most of the chloroplasts that contain chlorophyll Chlorophyll takes in light energy from the sun and changes it into chemical energy Xylem and phloem tubes (veins) carry water from the roots to the chloroplasts AND carry food from the chloroplasts back to the stem and roots. Veins help a plant keep its shape and keep it from wilting The adaptation of a leaf being thin and flat helps the leaf take in as much sunlight as possible Epidermis = the upper layer of a leaf that protects the inner cells like skin on a person . Sunlight can pass easily through the epidermis The upper epidermis helps the leaf not lose water through the surface Palisade Layer = layer of cells below the epidermis made of long, thin, packed tight cells. Lots of chloroplasts in these cells Most photosynthesis takes place here Spongy layer is next Sometimes there is a waxy covering called a cuticle on the leaf that also helps the leaf not lose water Loosely packed cells with lots of air spaces Air spaces allow carbon dioxide to pass through to get to the chloroplasts Have chloroplasts in the spongy layer but not as much as the palisade layer Lower epidermis is the underside of the leaf Stomata are in this layer surrounded by guard cells Guard cells can change shape to allow the stomata to open and close Stomata open = carbon dioxide can enter the leaf and oxygen can leave Stomata closed = not much water and no photosynthesis takes place Photosynthesis begins when the sun hits a leaf Light is taken in by chlorophyll in the chloroplasts and is changed from light energy to chemical energy 2 reactions take place in the chemical energy 1. 2. Water is split into hydrogen and oxygen Hydrogen combines with carbon dioxide to make glucose and oxygen Glucose is used by the plant for food and some is stored as starch Oxygen is released into the air Most of the food that a plant produces is used by that plant for it to growth, repair, and reproduce Cellular Respiration = plants releasing the energy in food to carry on the life process Plants store food to use when they can’t make food (cloudy days or dry periods) Stored food is starch. When the plant needs food, it can turn this starch back into glucose Plants use 90% of their food. They give 10% to animals who eat it Animals use most of food they eat to survive (90%) Energy stored in the food is released by cellular respiration Energy from the sun passes to the plant and then to the animal Oxygen combines with glucose to form carbon dioxide and water and produce energy 10% of the food an animal eats is stored in their body When an animal eats another animal, it gets stored energy from that animal. All energy can be traced by to the SUN!!