Digestion of carbohydrates Begins in mouth Salivary glands produce salivary amylase Digests alpha 1 4 bonds Cause straight line don t break down Amylose digestion Does not break down alpha 1 6 bonds because they are branches so they The way digestion works with carbohydrates is they start out as polysaccharides and are broken down to disaccharides and finally they break down to monosaccharides which are absorbed into the blood so the body can use them You start chewing so food is broken down into smaller pieces and your mouth begins producing saliva This saliva contains amylase which is a digestive enzyme that mixes with your food and begins this breakdown into monosaccharides Branched starches Action of salivary amylase is incomplete Alpha 1 6 bonds Time spent in mouth Stomach Small intestine Where you really start to digest carbs Pancreatic secretions small intestine from the stomach Pancreatic amylase HCL inactivates salivary amylase because amylase works well at a pH of 7 but inside the stomach the gastric juices cause the pH of the solution to drop significantly This denatures the amylase so it doesn t function normal Bicarbonate is a base and critical for neutralizing the acid coming into the Branch border enzymes involved in the terminal process of the digestion of carbs and proteins Sucrase sucrose Glucose fructose Lactase lactose glucose galactose Maltase maltose glucose glucose Absorption and transport Location Small intestine Mechanisms of transport into cell Passive diffusion Facilitated diffusion Active transport Passive diffusion of solute through membrane No energy required and is limited by concentration gradient movement through membrane Small molecules and solutes Facilitated diffusion Needs a carrier protein integral membrane protein that functions as a transporter Rate is determined by Concentration gradient Amount of carrier available Rapidity of solute carrier interaction Rapidity of conformation change of carrier Active transport Needs a carrier protein Requires energy ATP Pumps against conc gradient Ex Na K pump Carbohydrate absorption Glucose Requires ATP since its active transport so it requires sodium SGLT1 To maintain Na concentration gradient Na must be pumped out of cell Enters hepatic portal system from gut straight to liver Galactose Fructose Same as glucose Can be converted to lucose to meet needs of enterocyte Doesn t require ATP so it goes across by facilitated diffusion Crosses via GLUT 5 Transported to liver Some is converted to glucose in enterocyte Glucose transporters transport at liver GLUT2 Movement across basolateral membrane of enterocytes fructose GLUT4 Insulin stimulated uptake of glucose at muscle heart and adipocytes GLUT5 Absorption of fructose at small intestine Transport SGLT1 Uptake of glucose and galactose from lumen Portal circulation liver Facilitated transport Fructose Galactose Glucose At typical intakes little to no fructose or galactose in peripheral blood Glucose not taken up by liver Facilitated insulin dependent Skeletal muscle and adipose tissue Facilitated insulin independent Kidney and brain Metabolic pathways of carbohydrates Glycolysis PFK rate controlling enzyme that utilizes an ATP to convert F 6 P to F 1 6 BiP Induced by ATP Oxidation of glucose Energy production Purpose Location Cytosol Types Glucokinase Functions in liver and pancreas Upregulated induced by insulin Liver does not remove large quantities of glucose from blood unless blood glucose levels are high Hexokinase Functions in muscle adipose brain Downregulated inhibited by glucose 6 P Maximum enzyme activity at normal blood glucose levels Aerobic vs anaerobic glycolysis Anaerobic glycolysis Energy production Aerobic glycolysis Energy production ATP Glucose Glucose 6 phosphate 1ATP F6P F 1 6 BisP 1 ATP 1 3 BPG 3 PG 2 ATP PEP Pyruvate 2 ATP NADH can produce 3 ATP ATP NADH Glucose Glucose 6 phosphate 1ATP F6P F 1 6 BisP 1 ATP 1 3 BPG 3 PG 2 ATP PEP Pyruvate 2 ATP G 3 P 1 3 BPG 2NADH Pyruvate lactate 2NADH Net energy 2 ATP Krebs cycle AKA Tricarboxcylic Acid Cycle TCA Citric Acid Cycle Amphilbolic pathway that CHO fats and proteins enter to be complete oxidized in CO2 H20 and energy Provides precursors for synthesis pathways Location Mitochondrial matrix Products CO2 Exhaled by lungs H2O Energy Energy from krebs cycle Beginning with Acetyl CoA 3 NADH 9ATP 1 FADH 2ATP 1 GTP 1 ATP Net 12 ATP Beginning with pyruvate 4 NADH 12 ATP 1 FADH 2 ATP 1 GTP 1 ATP Net 15 ATP Total energy production from 1 molecule of Glucose Energy Molecule ATP NADH FADH GTP Glycolysis Krebs Total ATP 2 4 6 2 2 2 10x3 2x2 2 2 30 4 2 38ATP The shuttle systems Malate aspartate shuttle Moves NADH into mitochondria ETC Active in liver kidney heart It s a mechanism that regenerates NAD to NADH How it works electrons in the reduced NADH outside cytoplasm are transferred to the oxaloacetate OAA to form malate which enters the inner mitochondrial matrix Electrons are used to reduce NAD to NADH while the malate is converted back into oxaloacetate The OAA is then aminated to aspartate and pumped out of the matrix Glycerol 3 Phosphate shuttle NADH FADH enters complex II of ETC FADH yields only 2 ATP Active in muscle and brain How it works G 3 P dehydrogenase converts dihydroxacetone phosphate to glycerol 3 phosphate by oxidizing one molecule of NADH to NAD Then G 3 P gets converted back to dihydroxyacetone phosphate by a membrane bound mitochondrial glycerolphosphate dehydrogenase which reduces one molecule of FAD to FADH2 FADH2 reduces to coenzyme Q ubiquinone which enters into oxidative phosphorylation and enters the electron transport chain Electron transport chain Wednesday May 20 2015 10 22 PM Purpose production of mitochondrial ATP Concepts o Oxidation phosphorylation reactions Oxidation loss of electrons or hydrogen o Phosphorylation addition of phosphorus Proton gradient Proton pumps o Uncoupling means there are reactions that don t completely finish o Particles diffuse from an area of higher concentration to lower concentration o Must maintain a higher concentration of protons in outer mitochondrial space o Complexes which remove electrons form coenzymes located in the inner mitochondrial space and or pump protons into the outer mitochondrial space Complex I NADH Dehydrogenase complex Complex III cytochrome B C complex Complex IV Cytochrome oxidase complex Electron transporters o Transport electrons between complexes in the electron transport chain Uniquinone complex II also known
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