Photosynthesis & Cellular Respiration

Photosynthesis & Cellular Respiration 2f. Students know plants use carbon dioxide (CO2) and energy from sunlight to build molecules of sugar and release oxygen. 2g. Students know plant and animal cells break down sugar to obtain energy, a process resulting in carbon dioxide (CO) and water (respiration). How Plants & Animals Get The Energy They Need What is Photosynthesis? • Photosynthesis is the process by which plants make food, using energy from sunlight to convert carbon dioxide and water into sugar. What is the Purpose of Photosynthesis? • • • To make food for the plant (food in the form of glucose, a type of sugar). All organisms get energy from food, but only plants can make food. Plants make food by a process called photosynthesis (photo = light and synthesis = putting together) • In photosynthesis, plants put together materials to make food with the energy of sunlight. FACT #1 It is the energy of sunlight that powers the process of photosynthesis! FACT #2 The process of photosynthesis “mostly” only happens in plants (along with algae and some bacteria) FACT #3 Photosynthesis takes place in the chloroplast, inside the plant cells. In most plants, this occurs in the outermost layer of the leaf (on the top part), though for a few other plants, like cactus, photosynthesis can happen in the cells that are on the stem. Analogy: Chloroplast as a Food Factory You can think of a chloroplast as a food factory. Carbon dioxide and water are the raw materials that go into that factory. Sunlight is the energy that changes the raw materials into the product of food, in the form of sugar (or glucose). Finally, the two by-products created in the process, oxygen and a little extra water, are released into the air as they are no longer needed by the plant. What are the three raw materials used in Photosynthesis? 1. Carbon Dioxide (CO2) from the air 2. Water (H2O) from the soil 3. Solar energy from sunlight What are the waste products (by-products) created during Photosynthesis? • • Water - a little extra water that is no longer needed Oxygen These two are released into the air by the plant through the stomata (tiny holes in the underside of leaves) What Sequence of Events Takes Place During Photosynthesis? • • • • • Sunlight is absorbed by chlorophyll in chloroplasts. That solar energy is then used to split apart water (H2O) molecules into hydrogen and oxygen. Later, during a series of chemical reactions, hydrogen (H) joins with carbon dioxide (CO2) to form a sugar called glucose (C6H12O6). In the process of making sugars, two by-products are formed, water (H2O) & oxygen (O2). Neither is no longer needed by the plant. These by-products leave the plant when they are released into the air through stomata (tiny leaf holes) What is Cellular Respiration? Cellular Respiration is the process by which cells, in plants & animals, use oxygen for breaking down sugar to release the stored energy. What is the Purpose of Cellular Respiration? To get cells the energy they need to function. Why is Cellular Respiration Necessary in Plants & Animals? The energy stored in sugar needs to be released so that it can be turned to a form useful to cells. If living things could not get the energy out of food, food would be absolutely worthless and all living thing would eventually die. What Living Things use Cellular Respiration? All living things FACT #1 The process of cellular respiration takes place in the Mitochondria of both plant and animal cells. FACT #2 Animals are able to store glucose very well. Yet animals are not able to store gases, such as oxygen and carbon dioxide. This is why animals need to breathe all the time! With every breath, you take in the oxygen gas that you need for cellular respiration. You also breath out carbon dioxide, the waste product of the process. What are the two raw materials used in Cellular Respiration? • • Glucose Oxygen What are the waste products (by-products) created during Cellular Respiration? • • Carbon Dioxide Water In animals these waste products are released into the blood. Carbon Dioxide is carried to the lungs, where it is exchanged for oxygen in the alveoli (and eventually exhaled). Water is carried to the kidneys, where it is removed in urine. What Sequence of Events Takes Place During Cellular Respiration? • • • Oxygen helps break down sugar… Releasing a lot of energy, which the cell traps in a molecule called ATP. In addition, the two by-products of carbon dioxide and water are produced. What is the Connection Between Photosynthesis and Cellular Respiration? • • • • • The two processes are almost the reverse of each other. Materials made during one process are the same as those needed for the other process. In other words they form a cycle. Together, photosynthesis and cellular respiration form the “Carbon Dioxide-Oxygen Cycle.” Here’s the “cycle”: Plants take in carbon dioxide (and some oxygen) and release oxygen into the air. Animals breathe in oxygen and release carbon dioxide into the air. The recycling of carbon dioxide and oxygen through the environment depends on two process, photosynthesis and cellular respiration. This cycle provides living things with the oxygen and carbon dioxide they need.