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Unformatted text preview: UNIT TWO: CELL BIOLOGY (Text from Modern Biology , Holt, Rinehart, and Winston) 1 Chapter Six (Photosynthesis) Chapter Six (Photosynthesis) Chapter Six (Photosynthesis) Chapter Six (Photosynthesis) SECTION ONE: THE LIGHT REACTIONS SECTION ONE: THE LIGHT REACTIONS SECTION ONE: THE LIGHT REACTIONS SECTION ONE: THE LIGHT REACTIONS OBTAINING ENERGY Organisms can be classified according to the way they obtain energy. Autotrophs Autotrophs Autotrophs Autotrophs are organisms that use energy from sunlight or inorganic substances to make organic compounds. They mostly use the process of photosynthesis photosynthesis photosynthesis photosynthesis to convert light energy from the sun into chemical energy. Animals and other organisms that have to get energy from food instead of directly from sunlight or other inorganic compounds are called heterotr heterotr heterotr heterotrophs ophs ophs ophs. Auto means self and hetero means other. So remember, auto trophs make food by themselves and hetero trophs need others for food. Photosynthesis involves a complex series of chemical reactions in which the product of one reaction is consumed by the net reaction. When such reactions are linked in this way, it is referred to as a biochemical pathway. OVERVIEW OF PHOTOSYNTHESIS The diagram to the left shows how autotrophs use photosynthesis to produce organic compounds from carbon dioxide (CO 2 ) and water. The oxygen (O 2 ) and some of the organic compounds produced are then used by cells in cellular respiration , where CO 2 and water are produced. Therefore, the products of photosynthesis are reactant of cellular respiration. This reaction goes both ways. Light energy Plants convert light energy to chemical energy. Caterpillars get energy by eating plants. Birds get energy by eating caterpillars. PHOTOSYNTHESIS by autotrophs CELLULAR RESPIRATION by autotrophs and heterotrophs Organic compounds and oxygen Carbon dioxide and water UNIT TWO: CELL BIOLOGY (Text from Modern Biology , Holt, Rinehart, and Winston) 2 Photosynthesis can be divided into two stages: 1. 1. 1. 1. Light Reactions Light Reactions Light Reactions Light Reactions in which light energy from the sun is converted into chemical energy, which is temporarily stored in ATP and NADPH, which is the energy carrier molecule. 2. 2. 2. 2. Ca Ca Ca Calvin Cycle lvin Cycle lvin Cycle lvin Cycle where organic compounds are formed using CO 2 and the chemical energy stored in ATP and NADPH. Photosynthesis can be summarized using the equation: CAPTURING LIGHT ENERGY The first stage of photosynthesis includes the light reactions light reactions light reactions light reactions, which require light to happen. This begins with light being absorbed in the chloroplasts chloroplasts chloroplasts chloroplasts of plant and algae cells. If you recall from Chapter 4, chloroplasts are surrounded by a double membrane....
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