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Module 16- Metabolism Good notes, organized by colour, great diagrams, all the material you need to know for this module

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Physiology 1021
Tom Stavraky

March Physiology: Module 16 2011 Metabolism Metabolism is defined as the chemical changes that occur within a cell to manufacture energy, store energy, or build new cell structures. The two types of metabolism: 1. Anabolism is the creation of large molecules from small ones with the use of energy (ATP) 2. Catabolism is the breakdown of large molecules into small ones resulting in the release of energy (ATP). The Building Blocks Triglycerides (make up most of the fat found in the body) consist of three fatty acid chains attached to one molecule of glycerol. Proteins consist of long chains of amino acids linked together Carbohydrates are long chains of monosaccharides (like glucose) joined together. Glycogen: the carbohydrate glucose that is stored inside muscle and liver cells Fats are stored as triglycerides inside fatty tissue called adipose tissue. The amino acids become structural or functional proteins inside the muscle cells. Glucose -1% of the total energy requirements of the body -its reserves (in the form of glycogen) can last for roughly a day -monosaccharide -stored as glycogen (in most cells of the body) -found in the liver and skeletal muscle -common fuel source for all the cells; one of the only fuel sources for the brain (stored in the liver) Fatty acids -contribute to 77% of the total energy produced -can last for up to two months depending on the individual Amino acids -stored as proteins -not usually used to create energy -can account for 22% of the body’s fuel requirements if absolutely necessary Glucose Glucose enters cell and converted to glucose-6-phosphate (G-6-P). G-6-P can enter glycolysis to produce ATP OR can be converted to glycogen & stored. When necessary, glycogen can be converted back to G-6-P to enter glycolysis to produce energy. In glycolysis, G-6-P will undergo a series of reactions that will result in the production of ATP and the end product of pyruvate. Pyruvate can either: 1. Enter the citric acid cycle (CAC) and produce lots of ATP (with the help of oxidative phosphorylation) 2. Enter another shorter reaction to produce a small amount of ATP and the by- product lactate (lactic acid). Physiology: Module 16 March 2011 Which reaction will pyruvate take? If O2 is present: most of the pyruvate will enter the CAC If not enough O2 present: pyruvate will be converted to lactic acid During strenuous exercise, your cardiovascular system may not be able to supply sufficient oxygen to your working muscle cells to produce ATP via the citric acid cycle (CAC). Glycolysis (anaerobic: can continue without oxygen to produce ATP; end product: pyruvate) With insufficient oxygen: CAC will not be able to work at full capacity & pyruvate accumulates. If too much pyruvate accumulated, glycolysis is slowed. To keep glycolysis working (so it can produce ATP), pyruvate will be converted to lactic acid. Accumulation of lactic acid causes dilation The accumulation of of blood vessels and the decreasing pH will lactic acid causes the unload more oxygen from hemoglobin and "burning" sensation in thus, increasing blood flow & increasing the muscle and is oxygen delivery to this working tissue to believed to interfere reduce the build-up of lactic acid. with the contractileNote: if oxygen is restored, proteins causing fatigue. lactic acid can be converted back to pyruvate to enter the citric acid cycle and pyruvate can be turned back into glycogen through G-6-P and stored for later use. Sufficient supply of oxygen: Citric acid cycle (CAC) can function [at full capacity] and the pyruvate from glycolysis is converted to acetyl coenzyme A (acetyl CoA), which then enters the CAC. The CAC in conjunction with oxidative phosphorylation together produce: -a total of 36 molecules of ATP from one molecule of glucose -2 ATP from CAC -34 ATP from oxidative phosphorylation They also produce the by-products CO2 and H2O. The CO2 will diffuse into the blood and leaves the body at the lungs. Amino Acids -stored in cells as proteins -can be metabolized to create ATP by cells (each one enters the metabolic pathways at different points) Physiology: Module 16 March 2011 -can be converted to either pyruvate or acetyl CoA to enter glycolysis or the citric acid cycle (CAC) (respectively) These molecules can either produce ATP or can be converted to glycogen and stored in the cell in much the same way as glucose. The FED and Fasted State Fed state (absorptive state): the condition the body is in after a meal (nutrient levels in the blood are high). During this period, the body's goal is to store this new fuel (amino acids, fats, and glucose) for later use. Fasted state (or post absorptive state): the condition the body is in
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