Carbohydrates HUN3224 Major source of energy fuel in average diet total caloric intake o Polysaccharides starches dextrins o Monosaccharides simple sugars glucose galactose fructose o Some are digestible some are not Chemical structure below most simple carb o Simple glyceraldehyde o Complex glycogen Monosaccharides o Types based on of carbons 3 triose 4 tetrose 5 pentose made from hexoses helps made riboses 6 hexoses major energy source glucose galactose fructose 7 heptose Dietary Monosaccharides simple carbs o Glucose Most abundant of the three blood sugar o Fructose o Galactose Disaccharides o Formed from condensation of 2 monosaccharides Glucose glucose maltose Glucose galactose lactose Glucose fructose sucrose o High Fructose Corn Syrup 50 glucose 50 fructose sucrose Cane and beet sugar Table sugar processed foods HFCS 45 glucose 55 fructose lactose intolerance inability to break down lactose NOT a milk allergy Lquid made in lab Helps softer foods stay soft keeps processed food preserved Made from corn Sucrose less processed than HFCS Raffinose gal glu fruc Stachyose gal gal gluc fruc Found in beans peas and whole bran Sometimes fermented in gut using healthy bacteria unable to be enzymatically digested gas Fibers don t increase blood sugar Oligosaccharides o 3 10 monosaccharides Polysaccharides o Starch Storage form of carbs in plants Types we can digest these Amylose o Alpha 1 4 bonds of glucose units o Linear molecule Amylopectin o Branched alpha 1 6 chain polymer o Also has linear long straight chain alpha 1 4 o Glycogen Storage form of carbs in animals From all glucose Stored in liver and muscle Highly branched looks like amylopectin Energy source Get it when we are starving high epinephrine etc From glycogenolysis o Fiber Non digestible plant polysaccharides Defined by the USDA Dietary fiber found intact intrinsically in plant e g oats Functional fiber isolated extracted beneficial e g double fiber bread Metamucil Types Insoluble o Doesn t dissolve in water o Lower transit time moves through colon faster o Increases fecal bulk o Helps constipation o E g celluloses lignans some hemicelluloses Soluble o Dissolves in water o Increased transit time slower o E g pectin gum some hemicelluloses o Helps diarrhea Fermented by bacteria in colon Hydrogen methane gas CO2 short chain fatty acids o Short chain F A s Acetic acid butyric acid propionic acid o Functions of short chain F A s Stimulate water and sodium absorption into mucosa Provide colonocytes with energy Enhanced immune function Increases good bacteria in gut Decreases atrophy of gut Decreases cholesterol Excreted as fecal matter Carries bile with it soluble fiber does more than insoluble Sources DRI Fruits vegetables and whole grains o Men ages 19 50 38 g o Men older than 51 30 g o Women ages 19 50 25 g o Women older than 51 21 g Digestion of Carbs o Begins in mouth Salivary gland salivary amylase Digest alpha 1 4 bonds Amylose digestion Can totally digest it in mouth via amylase Branched starches Only breaks alpha 1 4 linkages not the alpha 1 6 bonds Action of salivary amylase is incomplete Alpha 1 6 bonds Time spent in mouth can determine how much is digested o Stomach HCl inactivates salivary amylase Does not digest carbs that much Mostly holds fod o Small intestine Pancreatic secretions Bicarbonate neutralizes chime Pancreatic amylase breaks only alpha 1 4 bonds Brush border enzymes Sucrase breaks down sucrose Lactase breaks down lactose Maltase breaks down maltose Absorption Transport o Location Small intestine o Mechanisms of transport Passive diffusion No energy needed Limited by concentration gradient Small molecules and solutes Facilitated diffusion Needs a carrier protein o Integral membrane protein o Functions as a transporter Rate determined by o Concentration gradient o Amount of carriers doors available o Rapidity of solute carrier interaction o Rapidity of conformation change of carrier Active transport Needs a carrier protein Requires energy in form of ATP Pumps against concentration gradient E g Na K pump o Carb Absorption Glucose Sodium dependent Active transport Transporter SGLT1 To maintain Na gradient Na must be pumped out of the cell K comes into cell Glucose enters hepatic portal system enterocyte capillaries portal system liver Galactose Same as glucose Can be converted to glucose to meet needs of enterocyte Fructose Facilitated diffusion GLUT5 Transported to liver Glucose Transporters GLUT1 erthyocytes placenta GLUT2 movement across basolateral membrane enterocytes fructose transport at liver GLUT3 brain GLUT4 muscle adipocytes GLUT5 fructose small intestine GLUT6 spleen brain GLUT7 unknown GLUT9 10 liver SGLT1 uptake of glucose galactose at lumen transporters that are insulin stimulated GLUT2 GLUT4 GLUT5 SGLT1 o Transport Portal circulation liver Facilitated diffusion o Fructose o Galactose o Glucose At typical intakes little to no fructose or galactose in peripheral blood Glucose not taken up by liver o Facilitated insulin dependent Skeletal muscle adipose tissue o Facilitated insulin independent Metabolic Pathways of Carbohydrates Kidney brain o Glycolysis Purpose oxidation of glucose energy production Location cytosol Types 2 Anaerobic no oxygen glucose pyruvate lactate Aerobic oxygen glucose pyruvate acetyl CoA Liver can take up extra glucose glycogen Muscle has to have a concentration gradient if more glucose in cell than outside then it stops taking anymore in o Glucokinase Functions in liver and pancreas Upregulated by insulin Liver doesn t remove large quantities of glucose from blood unless glucose levels are high o Hexokinase Functions in muscle adipose tissue and brain Downregulated by G6P Max enzyme activity at normal blood glucose levels o Anaerobic Glycolysis Energy production o ATP glucose G6P 1 ATP F6P F 1 6 BP 1 ATP 1 3 BPG 3PPG 2 ATP PEP Pyruvate 2 ATP G3P 1 3 BPG 2NADH Pyruvate Lactate 2 NADH o Net energy production 2 ATP o NADH o Aerobic Glycolysis Energy Production o ATP same as above o NADH 2 ATP G3P 1 3 BPG 2 NADH x3 6 ATP Pyruvate acetyl CoA 2 NADH x3 6 ATP o Net energy production 14 ATP CHO fats proteins can all enter and be completely oxidized into CO2 H2O and energy Provides precursors for synthesis pathways o Krebs Cycle TCA cycle citric acid cycle etc Amphibolic pathway Location mitochondrial matrix Products Co2 exhaled by lungs H2O Energy o GTP 1 ATP o FADH 2 ATP in reality b c of uncoupling 1 5 o NADH 3 ATP in reality b c of uncoupling 2 5 Energy Beginning w
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