Students learn to. What Is Photosynthesis? 10 of 248. Page. form, or by any

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1 THEORY BOOKLET NAME: YEAR 111 CHEM ISTRY ENERGY LESSON 1: THE ORIGINS OF ENERGY SOURCES SAMPLE RESOURCES

2 1. Photosynthesis Students learn to outline the role of photosynthesis in transforming light energy to chemical energy and recall the raww materials for this process What Is Photosynthesis? Watch introductory video: The Simple Storyy of Photosynthesis Photosynthesis, meaning putting together byy light, is the process by which green plants and certain other organismss synthesisee glucose and oxygen from carbon dioxide and water using sunlight s as an energy source. 10 of 248

3 Write a balanced chemical equation for photosynthesis 1 : H = kj How much energy iss absorbed per gram off glucose? 2 The leaf is the primary site of photosynthesis inn plants andd it is the green pigment stored within chloroplasts, the chlorophyll molecule, whichh drives this process. The leaf can be thought of as a biological solar panel equipped with numerous tiny cells that carry out photosynthesis on a microscopic level. Plants do not directly usee the sun s light energy, but instead capture this energy and convert it through complex biochemical reactions into chemical energy in the form of chemical bonds. With glucose as a basic c building block, plants synthesise a numberr of complex carbon-based biochemicals used to grow and sustain life. These molecules, such as starch and cellulose, are termed carbohydrates because they are composed of thee elements carbon, hydrogen and oxygen. 11 of 248

4 Processs of Photosynthesis Photosynthesis is a two-stagtwo t different areas of these structures housee the individual processes. process. In organisms that have chloroplasts, A light-dependent process (called the light reaction) takes place in the grana, while a second light-independent process (dark reaction) subsequently occurs in the stroma of chloroplasts. In the first stage, or light reaction of photosynthesis (in the grana), water molecules are decomposed by photochemical oxidation into oxygen and hydrogen molecules. 2H 2 O (l) O 2(g) + 4H + (aq) + 4e - As this process is dependent upon the absorption of visible light, this process only occurs during daylight hours. In the second stage, or dark reaction of photosynthesis, the electrons and hydrogen which are transferred to the stroma convert c carbon dioxide into carbohydrate molecules. CH 2 O is the empirical formula for a carbohydrate. As this process is not dependent on the absorption of light, it continues throughout the night.. CO 2(g) + 4H + (aq) + 4e - CH 2 O (s) + H 2 O (l) Add both reactions too get the overall reaction of 248

5 Concept Check 1.1 Which of the following would NOT be a source of carbon dioxide? 4 (a) (b) (c) (d) aerobic respiration burning of fossil fuels volcanic eruptions photosynthesis Concept Check 1.2 The process of splitting water to release hydrogens and electrons occurs during which process? 5 (a) (b) (c) (d) light dependent light independent carbon fixation glycolysis Concept Check 1.3 Photosynthesis is the processs by which complex carbohydratess are synthesised by plants using sunlight as the energy source. Briefly describee this process; include all relevantt chemical equations. 13 of 248

6 2. Photosynthesis as an Energy Source Students learn to outline the role of the production of high energyy carbohydrates from carbon dioxide as the important step in the stabilisationn of the sun s energy in a form that can be used by animals as welll as plants Carbohydrates Carbohydrates are one of three macronutrientss that provide the body with energy (protein and fats being the other two). In order for the body to use carbohydrates for energy, e foodd must undergo digestion, absorption, and glycolysis. It is recommended that 55-60% of your dietary energy intake come from carbohydrates. What are some foods that contain carbohydrates? 6 Pure carbohydrates contain carbon, hydrogenn and oxygen atoms in the ratio C n (H 2 O) n. n However, this ratio only truly applies to thee monosaccharides, or simple sugars, such as glucose g andd fructose. Typical table sugar orr sucrose (CC 12 H 22 O 11 ) is a disaccharide composed of two monosaccharides boundd together. Below are three structural representations of glucose. They all have the t formula C 6 H 12 2O of 248

7 Plants use the products of photosynthesis to form cellulose and starch. Cellulose makes up to 50% of a plant s mass and is the most abundant polymer on earth. Cellulose functions as the structural support of the plant. Plants use starch as a store of glucose andd therefore chemical energy. Humans and other animals obtain carbohydrate es by eatingg foods thatt contain them. Our bodies contain enzymes that will breakk starch back down into glucose to fuel our bodies. We do not have the ability to break down cellulose. c 15 of 248

8 In order to use the energy contained in the carbohydrates,, organismss must metabolise or break down glucose during aerobic respiration. Write a balanced chemical equation for respiration. 7 H = kj How much energy iss released per gram of glucose? 8 16 of 248