The Working Cell BIO100 Page Baluch A handful of peanuts contains enough energy to boil a quart of water It takes about 10 million ATP molecules per second to power an active muscle cell About 75 of the energy generated by a car s engine is lost as heat You d have to run about 14 miles to burn the calories from a pepperoni pizza BIOLOGY AND SOCIETY STONEWASHING WITHOUT THE STONES The sturdy cotton fabric denim has been worn because of its toughness and appeal Stonewashing jeans with pumice stone can damage the fabric Recently the enzyme cellulase has been used to achieve better results Figure 5 1 SOME BASIC ENERGY CONCEPTS Energy makes the world go around What is energy Conservation of Energy Energy is defined as the capacity to perform work Energy can be changed from one form to another However it cannot be created or destroyed This is the conservation of energy principle Potential energy is stored energy Kinetic energy is the energy of motion 2 1 High potential energy Conversion of kinetic energy to potential energy 3 Conversion of potential energy to kinetic energy 4 Low potential energy Figure 5 2 Heat Heat is A type of kinetic energy A product of all energy conversions Randomized molecular motion Entropy Scientists use the term entropy as a measure of disorder or randomness All energy conversions increase the entropy of the universe Chemical Energy Chemical energy Is a form of potential energy Is found in food gasoline and other fuels Living cells and automobile engines use the same basic process to make chemical energy do work Fuel rich in chemical energy Gasoline Waste products poor in chemical energy Heat energy Carbon dioxide Combustion Kinetic energy of movement Oxygen Water a Energy conversion in a car Energy Production in Cells Heat energy Food Oxygen Cellular respiration Energy for cellular work Carbon dioxide Water b Energy conversion in a cell Figure 5 3b Light energy ECOSYSTEM Cells require transfusions of energy from outside sources to perform their many tasks Organic O 2 molecules CO2 H2O ENERGY Flows into an ecosystem as SUNLIGHT and leaves as HEAT ATP Heat energy Light energy ECOSYSTEM ATP is the immediate energy source for almost all organism function life s currency Organic O 2 molecules CO2 H2O ATP Heat energy Photosynthesis Photosynthesis Transformation of solar light energy trapped by chloroplasts into chemical bond energy stored in sugar and other organic molecules Uses CO2 as the carbon source and light as the energy source CO2 H2O Energy light Glucose O 2 Directly or Indirectly supplies energy for almost all living things 6CO2 6H2O Energy light glucose Balanced Equation C 6H12O6 6O2 The breakdown of organic molecules is catabolism and is exergonic Catabolic pathways yield energy due to the transfer of electrons down energy gradients Specifically Catabolic pathways yield energy by oxidizing organic fuels Cellular respiration To keep working Cells must regenerate ATP Cellular respiration The most prevalent and energetically efficient catabolic pathway Consumes oxygen and organic molecules such as glucose Yields ATP REDOX REACTIONS In oxidation Transfer electrons from one reactant to anothe by oxidation and reduction A substance loses electrons or is oxidized In reduction A substance gains electrons or is reduced Example of a redox reaction becomes oxidized loses electron Na Cl Na becomes reduced gains electron Cl Products Products Reactants Reactants becomes becomes oxidized oxidized CH4 CH4 2O2 2O2 CO2 Energy 2 H2O CO2 Energy 2 H2O becomes becomes reduced reduced O O C O H O O H H H C H Methane reducing agent Oxygen oxidizing agent Carbon dioxide Water H Oxidation of Organic Fuel Molecules During Cellular Respiration becomes oxidized C6H12O6 6O2 6CO2 6H2O Energy becomes reduced An overview of CELLULAR RESPIRATION Electrons carried via NADH and FADH2 Electrons carried via NADH Glycolysis Pyruvate Glucose Cytosol Citric acid cycle Oxidative phosphorylation electron transport and chemiosmosis Mitochondrion ATP Substrate level phosphorylation ATP Substrate level phosphorylation ATP Oxidative phosphorylation Food Calories A calorie is the amount of energy that raises the temperature of 1 gram of water by 1 degree Celsius The kilocalorie is 1 000 calories The unit used to measure the energy in food Figure 5 4a The energy of calories in food is burned off by many activities Figure 5 4b ATP AND CELLULAR WORK The chemical energy of organic molecules is released in cellular respiration to make ATP in the mitochondria The Structure of ATP ATP adenosine triphosphate Consists of adenosine plus a tail of three phosphate groups Is broken down to ADP accompanied by the release of energy Energy Adenosine Adenosine Phosphate transferred to other molecules Phosphate Transfer ATP can energize other molecules by transferring phosphate groups This energy can be used to drive cellular work Motor protein Protein moved a Mechanical work Transport protein Solute Solute transported b Transport work ATP Reactants Product made c Chemical work Figure 5 6 The ATP Cycle Cellular work spends ATP ATP is recycled from ADP and phosphate through cellular respiration ATP functions in what is called energy coupling or the ATP cycle Cellular respiration chemical energy harvested from fuel molecules Energy for cellular work Figure 5 7 ENZYMES Metabolism is defined as the many chemical reactions that occur in organisms Few metabolic reactions occur without the assistance of enzymes Activation Energy Activation energy Is the energy that activates the reactants Triggers a chemical reaction Lower the activation energy for chemical reactions Enzymes Enzyme Activation energy barrier Reactants Products a Without enzyme b With enzyme Induced Fit Each enzyme is very selective It catalyzes specific reactions Each enzyme recognizes a specific substrate The active site fits to the substrate and the enzyme changes shape slightly This interaction is called induced fit Enzymes can function over and over again This is a key characteristic of enzymes Substrate sucrose 1 Enzyme available with empty active site 2 Substrate binds Active site to enzyme Enzyme sucrase Fructose Glucose 4 Product are released 3 Substrate is converted to products Enzyme Inhibitors Enzyme inhibitors Substrate Can inhibit a metabolic reaction Bind to the active site as substrate impostors Inhibitor Substrate Active site Active site Enzyme a Normal enzyme action Enzyme b Enzyme inhibition by a substrate imposter Other inhibitors Bind