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8.1 Energy and Life, Pages 226-229 8.2 Photosynthesis: An Overview, Pages 230-234 8.3 The Process of Photosynthesis, Pages 235-241 http://www.kideos.com/video/photosynthesis-song Slide 2 8.1 Adenosine triphosphate Heterotroph Autotroph Photosynthesis 8.2 Pigment Chlorophyll Thylakoid Stroma NADP+ Light-dependent reactions Light-independent reactions 8.3 Photosystem Electron transport chain ATP synthase Calvin Cycle Slide 3 Energy is the ability to do work. Your cells are busy using energy to build new molecules, contract muscles, and carry out active transport. Without the ability to obtain and use energy, life would cease to exist. Slide 4 One of the most important compounds that cells use to store and release energy is adenosine triphosphate (ATP). ATP consists of adenine, a 5-carbon sugar called ribose, and three phosphate groups. Slide 5 Adenosine diphosphate (ADP) looks almost like ATP, except that it has two phosphate groups instead of three. ADP contains some energy, but not as much as ATP. When a cell has energy available, it can store small amounts of it by adding phosphate groups to ADP, producing ATP. ADP is like a rechargeable battery that powers the machinery of the cell. http://www.youtube.com/watch?v=4Elr8GO HI9A&feature=related Slide 6 Cells can release the energy stored in ATP by breaking the bonds between the second and third phosphate groups. Because a cell can add or subtract these phosphate groups, it has an efficient way of storing and releasing energy as needed. Slide 7 ATP is not a good molecule for storing large amounts of energy over the long term. It is more efficient for cells to keep only a small supply of ATP on hand. Cells can regenerate ATP from ADP as needed by using the energy in foods like glucose. Slide 8 Some heterotrophs get their food by eating plants. Other heterotrophs, such as this cheetah, obtain food from plants indirectly by feeding on plant-eating animals. Still other heterotrophs, such as mushrooms, obtain food by decomposing other organisms. Slide 9 Plants, algae, and some bacteria are able to use light energy from the sun to produce food. The process by which autotrophs use the energy of sunlight to produce high-energy carbohydrates that can be used for food is known as photosynthesis. Slide 10 Energy from the sun travels to Earth in the form of light. Sunlight is a mixture of different wavelengths, many of which are visible to our eyes and make up the visible spectrum. Our eyes see the different wavelengths of the visible spectrum as different colors: red, orange, yellow, green, blue, indigo, and violet. Slide 11 Plants gather the suns energy with light-absorbing molecules called pigments. The plants principal pigment is chlorophyll. The two types of chlorophyll found in plants, chlorophyll a and chlorophyll b, absorb light very well in the blue-violet and red regions of the visible spectrum, but not in the green region. * Leaves reflect green light, which is why plants look green. Slide 12 Photosynthesis happens here: Slide 13 8.2 Photosynthesis-An Overview Pages 230-234 http://www.youtube.com/watch?v=LgYPeeABoUs http://www.youtube.com/watch?v=1gLa5EWn9OI&feature=related Slide 14 The light-dependent reactions use energy from sunlight to produce ATP and NADPH. These reactions take place within the thylakoid membranes of the chloroplast. Water is required as a source of electrons and hydrogen ions. Oxygen is released as a byproduct. Slide 15 When chlorophyll is hit by light, electrons become excited. They will move around in the thylakoid until they reach a special carrier called NADP which becomes NADPH. Oxygen is given off and ATP is also made. Slide 16 ATP and NADPH molecules produced in the light-dependent reactions are used to produce high- energy sugars from carbon dioxide. No light is required to power the light-independent reactions. The light-independent reactions take place outside the thylakoids, in the stroma. Slide 17 Photosynthesis uses the energy of sunlight to convert water and carbon dioxide into high- energy sugars and oxygen. In symbols: 6 CO 2 + 6 H 2 O C 6 H 12 O 6 + 6 O 2 In words: Carbon dioxide + Water Sugars + Oxygen Slide 18 Plants use the sugars generated by photosynthesis to produce complex carbohydrates such as starches, and to provide energy for the synthesis of other compounds, including proteins and lipids. Slide 19 The light-dependent reactions directly involve sunlight and occur in the thylakoids of chloroplasts. The products are oxygen, ATP and NADPH. ATP and NADPH provide the energy for the Light- Independent Reactions. Slide 20 During the light-independent reactions, commonly referred to as the Calvin cycle, plants use the energy that ATP and NADPH contains to build stable high-energy carbohydrate compounds that can be stored for a long time. Slide 21 The two sets of photosynthetic reactions work togetherthe light-dependent reactions trap the energy of sunlight in chemical form, and the light-independent reactions use that chemical energy to produce stable, high-energy sugars from carbon dioxide and water. In the process, animals, including humans, get food and an atmosphere filled with oxygen.