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Module 16 - Metabolism .docx

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Western University
Physiology 2130
Paul Gillespie

Metabolism Definition of Metabolism • Metabolism o Chemical changes that within a cell to either  Manufacture energy  Store energy  Build new cell structures o Two types of metabolism  Anabolism • Creation of large molecules from small ones with the use of energy (ATP) • Breakdown of large molecules into small ones resulting in the release of energy (ATP) List the building blocks of all the main food groups as well as their storage forms in the body • (Fats) Triglycerides o Make up most of the fat found in the body o Consists of three fatty acid chains attached to one molecule of glycerol o Fats are stored as triglycerides inside fatty tissue called adipose tissue • Proteins o Consists of long chains of amino acids linked together o Amino acids become structural or functional proteins inside the muscle cells • Carbohydrates o Long chains of monosaccharides (like glucose) joined together o Carbohydrate glucose is stored inside muscle and liver cells in the form of glycogen Metabolism Describe the three chemical reactions/metabolic pathways in the body that produceATP. List how muchATPeach can form, which one requires oxygen, and where the reactions take place in the cell. Describe where each fuel source enters the metabolic pathways • Glycolysis (glycolytic pathway) o Serious of reactions that occurs in the cytoplasm o Does not require oxygen (anaerobic reaction) o Produces two molecules ofATP very quickly from one molecule of glucose o Glucose (as well as glycogen) enters glycolysis at the beginning of this reaction o Amino acids (AA) can be converted to pyruvate to enter glycolysis or can be converted to acetyl coenzymeA(acetyl CoA) to enter the citric acid cycle (CAC) to produceATP o Fats can be broken down to glycerol and free fatty acids  The glycerol molecules enter glycolysis  Fatty acids can be converted to acetyl CoAto enter the CAC • Citric acid cycle (CAC or Krebs cycle) o Inside the mitochondria o Requires oxygen (aerobic reaction) o Produce two molecules ofATP per molecule of glucose • Oxidative phosphorylation o Linked to the citric acid cycle o Reaction can produce 34 molecules ofATP from one molecule of glucose o Occurs in the mitochondria of the cell and also required oxygen Describe in detail the full metabolism of glucose by glycolysis and the citric acid cycle (in the presence of oxygen and without oxygen) • Glucose – monosaccharide (stored as glycogen) o Glycogen stores can be found in the liver and skeletal muscle o Glucose is a common fuel source for all the cells in the body o One of the only fuel sources for the brain (unlike other cells in the body, which can use fats and amino acids as well as glucose) o Liver stores glucose for the brain but doesn’t store when blood glucose levels get low • Glycolysis o All the reactions are reversible Metabolism o Starts with glucose entering a cell o Immediately converted to glucose-6-phosphate (G-6-P) o G-6-P can enter glycolysis to produceATP or it can be converted to glycogen and then stored o G-6-P will undergo a series of reactions that will result in the production of ATP and the end product of pyruvate o Pyruvate can then undergo two possible reactions  It can either enter the citric acid cycle (CAC) and produce lots of ATP (with the help of oxidative phosphorylation)  It can enter another shorter reaction to produce a small amount of ATP and the by-product lactate (lactic acid) o The reaction pyruvate take depends on whether oxygen is present or not  If there is sufficient oxygen, then most of the pyruvate will enter the CAC • Aerobic pathway  If not enough oxygen, CAC will not be running at full capacity and pyruvate will be converted to lactic acid o LacticAcid  During strenuous exercise, your cardiovascular system may not be able to supply sufficient oxygen to your working muscle cells to produceATP via the citric acid cycle (CAC)  Since glycolysis is anaerobic, this reaction can continue without oxygen to produceATP and the end product pyruvate  With insufficient oxygen, the CAC will not work at full capacity and pyruvate will start to accumulate  If too much pyruvate accumulates, then even glycolysis will be slowed  In order to glycolysis working so it can produceATP for the muscles, the pyruvate will be converted to lactic acid  Accumulation of lactic acid causes the “burning” sensation in the muscle and is believed to interfere with the contractile proteins causing fatigue • Accumulation of lactic acid will cause the blood vessels to dilate and the decreasing pH will unload more oxygen from hemoglobin  These mechanisms will help to increase blood flow and increase oxygen delivery to this working tissue to reduce the buildup of lactic acid o CitricAcid Cycle  Sufficient supply of oxygen, functions at full capacity  Pyruvate from glycolysis is converted to acetyl coenzyme (acetyl CoA), which then enters the CAC Metabolism  CAC in conjunction with oxidative phosphorylation together produce a total of 36 molecules ofATP from one molecule of glucose (2ATP from CAC and 34 from oxidative phosphorylation)  They also produce the by-products CO 2nd H O2  The CO 2ill diffuse into the blood and leaves the body at the lungs Describe in detail the full metabolism of fats and amino acids • Amino acids are stored in cells as proteins • Fats are mostly stored as tr
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