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Cell Respiration Releasing Chemical Energy Introduction • All organisms must have energy to carry out life processes. • Where does this energy come from? Autotrophs collect energy from the sun and store it as organic compounds. The Need for Energy • No Energy = no work •Energy = Work Respiration: An Overview • Metabolism is all of the chemical reactions in the body. These reactions are either: 1. Synthesis – combining small molecules to make complex molecules OR A + B ---> AB 8 Fe + S8 ---> 8 FeS 2. Decomposition reactions – breaking down molecules into simpler forms. AB ---> A + B 2 H2O ---> 2 H2 + O2 Reactions Continued • Synthesis reactions require energy – example photosynthesis. • Decomposition reactions release energy. • This energy can be used to make ATP • ATP is a small, useable packet of energy. Cellular Respiration • Cell Respiration is a decomposition reaction that provides the energy cells need to function. • In this series of reactions, sugars, proteins, and lipids are broken down (decomposed) and energy is released. Types of Cellular Respiration • There are two types of cell respiration – aerobic and anaerobic. 1. Aerobic respiration occurs in the presence of oxygen. 2. Anaerobic respiration occurs in the absence of oxygen. Raw Materials for Cell Respiration • What are the raw materials for cell respiration? Carbohydrates, proteins, and lipids • How does the food become the raw materials? •Food is digested into carbohydrates, lipids, and proteins. Glucose and Glycogen • Glucose is the form in which animals transport carbohydrates through the blood stream. • Glycogen is the form in which it is stored in animals. • Glycogen is stored in the liver and muscles. Mitochondria • Mitochondria are the energy factories of the cells. Mitochondria • Cellular Respiration occurs in the mitochondriaan organelle in the cytoplasm of cells. They have: • an outer membrane that encloses the entire structure • an inner membrane that encloses a fluid-filled matrix • between the two is the intermembrane space • the inner membrane is elaborately folded with shelf-like cristae projecting into the matrix. Stages of Cell Respiration 1. Glycolysis 2. Kreb’s Cycle 3. Electron Transport System Glycolysis • Glycolysis happens in the cytoplasm. • Glucose is split into 2 three-carbon molecules. • Enzymes partially oxidize glucose and this partial oxidation releases energy that forms a small amount of ATP. • This is an anaerobic process and 2 net ATP are generated. • This ATP is used to start the Kreb’s Cycle. Glycolysis Animations http://www.copernicusproject.ucr.edu/ssi/HSB iologyResources.htm Kreb’s Cycle • The Kreb’s cycle completes the decomposition and oxidation of glucose to carbon dioxide. • The carbon dioxide is released as a gas. • The oxidation of one glucose molecule yields up to 38 ATP molecules under ideal conditions (this occurs infrequently) • The reaction of acetyl CoA with oxaloacetate starts the cycle by producing citrate (citric acid). • In each turn of the cycle, two molecules of CO2 are produced as waste products, plus three molecules of NADH, one molecule of GTP, and one molecule of FADH2. • The number of carbon atoms in each intermediate is shown in a yellow box. (see picture next slide) Krebs Cycle Animations • http://www.science.smith.edu/departments/ Biology/Bio231/krebs.html • http://www.wiley.com/legacy/college/boyer/ 0470003790/animations/tca/tca.htm The Electron Transport Chain • It is composed of the mitochondrial enzymes that transfer electrons from one complex to another, eventually resulting in the formation of ATP. • In the first part, electrons are transferred from protein to protein and energy is lost as free energy along the way. ATP Synthetase • This free energy is used to move protons into the matrix of the mitochondria. • As they pass through the matrix, they pass through the ATP –synthetase enzyme. • This causes a charge differential (gradient) which drives the forming of ATP from ADP. Electron Transport • http://www.wiley.com/legacy/college/boyer/ 0470003790/animations/electron_transport/ electron_transport.htm • http://www.science.smith.edu/departments/ Biology/Bio231/etc.html • http://www.sp.uconn.edu/~terry/images/ani m/ETS.html ATP Synthesis • http://telstar.ote.cmu.edu/biology/animation/ ATPSynthesis/biochem.html • http://www.sp.uconn.edu/~terry/images/ani m/ATPmito.html