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ATP and Energy, Enzymes SOME BASIC ENERGY CONCEPTS Energy makes the world go around. But what is energy? Energy is defined as the capacity to perform work. Kinetic energy is the energy of motion. Potential energy is stored energy. 2 basic types of energy Machines and organisms can transform potential energy stored in matter to kinetic energy. •Swimming motion of sperm •Muscles producing contraction •Solar radiation is converted to chemical energy in green plants forming sugars In all such energy transformations, total energy is conserved. Energy cannot be created or destroyed. This is the principle of conservation of energy. Energy conversions Every energy conversion releases some randomized energy in the form of heat which increases the entropy or randomness of the universe. Heat is a Type of kinetic energy (energy of movement) is always a “waste” product of all energy conversions Fuel Energy conversion Waste products 25% of energy is actually used! 40% of energy is actually used (humans) 1 ATP and Energy, Enzymes How do living things manipulate energy? Sunlight Plants store Animals store (radiant energy) (chemical energy) (chemical energy) ATP used in metabolic processes Heat as waste product Conversion to carbohydrates by Photosynthesis Sunlight One of the types of Conversion to ATP during cellular respiration radiant or electromagnetic energy coming from the sun Plants, algae, and some cyanobacteria are able to use by mean of photosynthesis ATP used in metabolic processes Heat as waste product Conversion to ATP during cellular respiration Chemical Energy Potential energy stored in matter, is released or stored when molecules are changed from one type to another All living things use chemical energy to stay alive… in a process called “cellular respiration”, the energyreleasing chemical breakdown of fuel molecules, that provides energy for cells to do work What units we use to measure chemical energy? Calories (Cal or Kcal) A calorie is the amount of energy that raises the temperature of one gram of water by 1 degree Celsius. Food Calories are kilocalories, equal to 1,000 calories. The average Calories needed by a human being are 2,000 2 ATP and Energy, Enzymes ATP and Cellular Work ATP works like an energy shuttle It is a short term storage place for energy obtained from food Releases it later as needed Transport work (cell transport) ATP energizes other molecules by transferring phosphate groups, this energy helps cells perform… Mechanical work (muscles) Chemical work (enzymatic reactions) The ATP Cycle Cellular work spends ATP. ATP is recycled from ADP and a phosphate group through cellular respiration. A working muscle cell spends and recycles about 10 million ATP molecules per second. Food (animals, fungi, protozoa, most bacteria) Sunlight + CO2 + H2O (plants, algae, cyanobacteria) 3 ATP and Energy, Enzymes ENZYMES Metabolism is the total of all chemical reactions in an organism. Most metabolic reactions require the assistance of enzymes, special proteins that speed up chemical reactions. Why do we need to speed up reactions using enzymes? Activation Energy (Ea) Synthesis and breakdown of molecules and energy conversion processes requires energy to initiate the breakdown of nutrients (octet rule… chemical bonds… remember?) Extra energy required to destabilize existing chemical bonds and initiate a chemical reaction between two or more molecules Enzymes reduce the energy of activation! Without enzymes With enzymes How Enzymes Work… Every enzyme is very selective, catalyzing a specific reaction. A reactants B+C products Each enzyme recognizes only one substrate, a specific reactant molecule. The enzyme fits to the substrate, and the enzyme changes shape slightly. This interaction is called induced fit. Enzymes are substrate specific! Enzymes remain unchanged! Enzymes can be reused billions of times, one single enzyme can convert millions of substrate molecules per second! ACTIVE SITE: Is the part of the enzyme, where the energy of activation is lowered by the enzyme so the reaction can happen 4 ATP and Energy, Enzymes Factors that affect the enzymes activity… 1) Temperature Optimum (temperature range at which the speed of product generation is maximum) The speed of the reaction, or the number of molecules of substrate that one enzyme can react with in a given time, decreases as temperature moves right or left from the optimum range. At higher or lower temperatures than the optimum, Enzymes can lose their configuration (be completely unfolded and only retain the primary structure) and be no longer active Enzyme Denatured Enzyme (1ry structure = sequence of amino acids) Denaturation Loss of the structures of a protein, only the primary structure remains 2) pH Is important in defining the final shape of proteins each enzyme reaches it maximum activity level at a given pH Changes in pH determine the number of H+ ions available in the enzyme environment these H+ may interact with exposed side-chains of the polar enzyme molecule enzyme activity changes Denaturation 3) Enzyme-Substrate concentration Loss of the structures of a protein, only the primary structure remains With all other variables fixed Rate of product formation is defined by the enzyme characteristics With huge amounts of substrate present the rate of product generation can only be increased by adding more enzymes! 5 ATP and Energy, Enzymes Enzyme Inhibitors… Enzyme inhibitors can prevent metabolic reactions by binding to the active site. Enzymes regulation… Negative feedback Is a regulatory mechanism in which a 'stimulus' causes an opposite 'output' in order to maintain an ideal level of whatever is being regulated The amount of one or more products in the sequence of reactions regulate the activity of an enzyme in a previous reaction of the sequence 6