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Cellular Respiration Respiration: An Overview • The process by which cells break down food sources such as glucose, fats, and protein and release their stored energy. • Two main types – Anaerobic – no oxygen required – Aerobic – requiring oxygen • Both forms produce energy storage molecules called ATP – adenosine http://www.chemistry.wustl.edu/~courses/genchem/LabTutorials/Cytoc triphosphate. hromes/images/flowchart1.jpg Anaerobic Processes • No oxygen is required for these processes. • Includes glycolysis, the breakdown of glucose, and fermentation. • Some bacteria and yeast are examples of anaerobes. http://www.biol.vt.edu/research/images/C._perfringens_in_mac._jpg.jpg http://www.utoronto.ca/greenblattlab/images/a/yeast%201.jpg Glycolysis • Occurs in the cytoplasm. • Breaks down glucose into 2 molecules of pyruvate (3-carbon structures) • 2 ATP molecules are formed. • 2NADH energy shuttles are also formed. • This pyruvate is further metabolized during fermentation http://www.emc.maricopa.edu/faculty/farabee/BIOBK/enyld1.gif Fermentation • Pyruvate can be metabolized by: – Alcoholic fermentation – Lactic acid fermentation • AF produces ethyl alcohol and CO2 – yeast can ferment apple juice to fill a balloon. • LAF produces lactic acid. It can build up in muscles during strenuous exercise and cause burning and soreness. Aerobic Processes • Requires oxygen. • Most organisms are aerobes. • Equation for Aerobic respiration: C6H12O6 + 6O2 6CO2 + 6H2O + Energy http://www.oum.ox.ac.uk/thezone/animals/life/images/excrete.gif • Based on this equation – Why do we breathe? The Mitochondria • If O2 is present following glycolysis, pyruvate is modified and enters the mitochondria. • Here food is broken down completely into CO2. • Energy storage molecules like NADH and ATP are produced. This is why the mitochondria is called the power house of the cell. The Role of Oxygen • Energy carriers like NADH drop off electrons and as they “fall” to oxygen during metabolism energy is stored in a payload of ATP. • Oxygen picks up electrons and hydrogen ions to form water. Energy from electron s ATP ATP ATP O2 H2 O ATP: Adenosine Triphosphate • ATP is the cells energy currency. • Cellular work such as metabolism, transport, and movement is powered by the breakdown of ATP. ATP Structure – Ribose – a 5-carbon sugar – Adenine – a N-base – 3 phosphate groups ATP / ADP Cycle • ATP is constantly being used and remade in the cell. • Energy is released or stored by breaking or making a phosphate bond. http://www.columbia.edu/cu/biology/courses/c2005/purves6/figure06-09.jpg Summary of Cellular Respiration Respiration Process Where Process Occurs Anaerobic Glycolysis & Cytoplasm Fermentation Aerobic Krebs Cycle and Mitochondrion Electron Transport Net Gain of ATP Per Glucose 2 ATP 36 ATP