11-24-2006, 05:36 AM
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Energy Metabolism
Alright so I couldn't figure out how to link my PowerPoint so I did the best I could by linking the images here. This took me a lot of time to get this set up and look semi-decent, so if you read this and find this useful let me know.
Basic Principles Available Substrates Body uses macronutrients – CHO, fats and proteins consumed daily to provide the necessary energy to maintain cellular activities both at rest and during exercise. CHO and fats = primary energy sources during exercise; protein plays minimal role Carbohydrate Composed of carbon, hydrogen and oxygen (CHO) Stored CHO = rapidly available source of energy Yield 4cal/gm Three forms: Monosaccharides Disaccharides Polysaccharides Monosaccharides = simplest form of CHO Glucose Fructose Galactose Disaccharides = 2 monosaccharides Maltose Lactose sucrose Polysaccharides = complex CHO Plant = starch Animal = glycogen Fats Same chemical elements as CHO, but the ratio of C to O2 in fats is much greater Most abundant energy source in body Yield 9cal/gm Found in both plants and animals Four general groups Fatty acids (FFA) Triglycerides (TG) Phospholipids steriods FFA stored as TG TG = 3 FFA + 1 glycerol backbone Primary storage site = adipose tissue Also stored in other organs (incl. ms) Phospholipids not used as an energy source – make up cell membranes and serve other biological functions Steroids not used for energy Most common steroid = cholesterol which is a component of cell membranes Cholesterol can be synthesized by every cell in the body and can also be consumed in foods (only animal sources) Cholesterol needed in various biological and physiological functions (eg. Synthesis of sex hormones – estrogen, testosterone etc) Proteins Composed of amino acids (a.a.) Formed when a.a. are linked by peptide bonds At least 20 different types of amino acids are needed by the body to form various tissues 9 a.a.=essential – must be consumed 11 a.a.=nonessential – body makes them Yield 4 cal/gm Generally does not contribute a lot to energy metabolism Proteins may contribute to energy during exercise under 2 situations: Starvation/low CHO diet Very prolonged exercise Energy Metabolism High Energy Phosphates ATP Adenosine triphosphate Immediate source of energy for ms contraction Structure: an adenine portion a ribose portion three linked phosphates  Formation occurs via: ADP + Pi --> ATP Energy is stored in the chemical bond joining ADP and Pi. When ATPase breaks this bond, energy is released. ATP ------> ADP + Pi + ENERGY ATP is the universal energy donor that drives the energy needs of the cell. Energy is released from the breakdown of foods (exergonic reactions). This energy is then used to make ATP (endergonic reactions). ATP is then used to drive the energy-requiring processes in the cell.  Bioenergetics Ms cells store limited amounts of ATP therefore metabolic pathways exist within the cell to provide a constant supply of ATP to provide energy for contraction. Metabolic pathways supplying ATP: phosphocreatine (PCr) breakdown anaerobic glycolysis aerobic glycolysis “Aerobic” with oxygen “Anaerobic” without oxygen Anaerobic ATP Production 1.Immediate Energy System = PCr System The most rapid method of producing ATP is from the PCr system. A phosphate group (Pi) is donated from the splitting of PCr. The Pi then binds with ADP to form ATP: 1. PCr--> Pi + Cr 2. Pi + ADP --> ATP + C Creatine Kinase catalyzes the reaction PCr System Ms cells store only a small amt of PCr, and the total amt of ATP that can be generated from this system is small. For every PCr broken down, 1 ATP molecule is created The ATP-PCr system provides energy for ms contraction at the onset of exercise and during very high intensity, short duration (<10 sec) exercise. PCr reformation requires ATP and can only occur during recovery from exercise Anaerobic ATP Production 2. Anaerobic Glycolysis involves the breakdown of glucose or glycogen (CHO only) to form 2 molecules of pyruvic acid or lactic acid   Anaerobic Glycolysis A series of enzymatically catalyzed, coupled reactions Produces 2 molecules of ATP per glucose molecule/3 ATP per molecule of glycogen 2 phases: energy investment energy generation Phase 1 - energy investment ATP is used at 2 points at the beginning of glycolysis ATP used to add phosphate groups to glucose and F-6-P Difference between glucose vs. glycogen 1 ATP invested vs 2  Phase 2 - energy generation 2 molecules of ATP are produced at 2 separate reactions near the end of the glycolytic pathway--> net gain of 2 ATP with glucose and 3 ATP with glycogen  H+ Carriers NAD=nicotinamide adenine dinucleotide FAD=flavin adenine dinucleotide Both transport H+ and their associated energy to be used for later generation of ATP in the mitochondria via aerobic process. Continuation of glycolysis Must have adequate NAD to accept H+ NAD + H ? NADH Then NAD must be reformed to continue the shuttling of H+ Reformation of NAD from NADH: 1. Sufficient O2 available H+ from NADH can then be shuttled into the mito of the cell and used for the aerobic production of ATP 2. Insufficient O2 available Pyruvic acid accepts the H+ from NADH and forms lactic acid and reforms NAD Need 1 or 2 to take place so glycolysis can continue Summary of glycolysis = the breakdown of glucose into pyruvic acid or lactic acid Effect of glucose or glycogen on ATP production Glucose = 6 C molecule ? 2 x 3-C molecules of pyruvic acid or lactic acid Compartment of Cell Immediate energy system Anaerobic Glycolysis Glycolysis as aerobic or anaerobic? Summary ATP = immediate source of energy ATP ? ADP + Pi + ENERGY (via ATPase) Anaerobic vs. Aerobic Metabolism 3 metabolic pathways: ATP-PC System Glycolysis Oxidative Phosphorylation Aerobic ATP Production Oxidative Phosphorylation Cell compartment 2 cooperating metabolic pathways 1. Krebs Cycle (citric acid cycle) (tricarboxcylic acid cycle – TCA) The complete oxidation (hydrogen removal) of CHO, fats and proteins using NAD and FAD as hydrogen carriers Importance of H+ removal Role of O2 2. Electron Transport Chain (ETC) Energy potentiated from the removal of H+ in the Krebs cycle is used in the ETC to combine ADP+Pi?ATP O2 is the final hydrogen acceptor at the end of the ETC ? formation of H20 3 stages of aerobic ATP production: 1. generation of acetyl CoA 2. oxidation of acetyl CoA in KC 3. ETC 1. Formation of Acetyl CoA Occurs from macronutrient breakdown Need sufficient O2 Pyruvic acid ? acetyl CoA (CHO and protein) Irreversible process Cytoplasm?mitochondria 2. Krebs Cycle Primary function Remove hydrogens from various substrates in the cycle Completes oxidation of CHO, proteins, fats Supplies electrons to ETC to provide energy for aerobic production of ATP Note: for every molecule of glucose oxidized (a 6-C molecule), 2 molecules of pyruvate are created ? 2 molecules of acetyl CoA Impact on KC??? 3. Electron Transport Chain Metabolic pathway responsible for the aerobic production of ATP Uses the potential energy available in NADH and FADH (that were generated from glycolysis and the KC) to rephosphorylate ADP?ATP Electrons which are removed from the H+ atoms are passed down a series of electron carries = cytochromes O2 is the final electron acceptor at the end of the ETC ? H2O Summary Aerobic ATP production occurs in mito Interaction between KC and ETC KC – oxidize substrates to form NADH and FADH to enter ETC End result of ETC = ATP formation and H2O Energy release from CHO Glycolysis – glucose vs. glycogen Oxidative phosphorylation – glucose vs. glycogen Energy release from fats Metabolic pathway = beta-oxidation Occurs in mitochondria TG = storage form of fat TG?FFA (lipases) FFA? acetyl CoA via B-oxidation  Primary role of B-oxidation Only occurs during aerobic metabolism Structure of FFA (even carbon atoms) Cycles of B-oxidation Cont’d Catabolism of glycerol Glycolysis accepts glycerol at level of 3-phosphoglyceraldehide ? pyruvate? acetyl CoA?KC?ETC Yields 19 ATP molecules ATP production from fat Depends upon length of FFA chain Only aerobic Application Why is it said that fats burn in a CHO flame?   Interaction of Energy Systems ATP production also due to the interaction of aerobic and anaerobic metabolism Key word = PREDOMINATE In general, the shorter the activity, higher the intensity, the more anaerobic. Longer duration, lower intensity activities ?higher aerobic contribution         
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04-15-2007, 03:50 PM
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well maybe its just me but im a total nerd , i love reading stuff like this. ^_^ Reminds of my bio class which was my ultimate fav. class, i remember learning about the citric acid cycle and the breaking down of all the macromolecules, interesting stuff :yes
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04-15-2007, 04:31 PM
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I'm glad you like it, I'm working on getting out a few more write ups sometime soon.
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07-23-2007, 07:15 PM
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It's a great read if you ever want to check up on anything. But if you have any specific questions just post it up. We'll be glad to answer it.
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