The Endocrine Pancreas Cellular Respiration Pancreatic Anatomy Pancreas Head of Pancreas
Casteel, Sean, Contributing Writer has reference to this Academic Journal, PHwiki organized this Journal The Endocrine Pancreas Regulation of Carbohydrate Metabolism Nutritional Requirements Living tissue is maintained by constant expenditure of energy (ATP). Indirectly from glucose, fatty acids, ketones, amino acids, in addition to other organic molecules. Energy of food is commonly measured in kilocalories. One kilocalorie is = 1000 calories. One calorie = amount of heat required to raise the temperature of 1 cm3 of H20 from 14.5o to 15.5o C. The amount of energy released as heat when food is combusted in vitro = amount of energy released within cells through aerobic respiration. Metabolic Rate in addition to Caloric Requirements Metabolic rate is the total rate of body metabolism. Metabolic rate measured by the amount of oxygen consumed by the body/min. BMR: Oxygen consumption of an awake relaxed person 1214 hours after eating in addition to at a com as long as table temperature. BMR determined by: Age. Gender. Body surface area. Thyroid secretion.
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Anabolic Requirements Anabolism: Food supplies raw materials as long as synthesis reactions. Synthesize: DNA in addition to RNA. Proteins. Triglycerides. Glycogen. Must occur constantly to replace molecules that are hydrolyzed. Aerobic Requirements (continued) Catabolism: Hydrolysis (break down monomers down to CO2 in addition to H2O.): Hydrolysis reactions in addition to cellular respiration. Gluconeogenesis. Glycogenolysis. Lipolysis. How do we use food components in catabolic in addition to anabolic pathways Involves specific chemical reactions: – Each reaction is catalyzed by a specific enzyme. – Other compounds, besides those being directly metabolized, are required as intermediates or catalysts in metabolic reactions – adenosine triphosphate (ATP) – nicotinamide adenine dinucleotide (NAD+) – flavin adenine dinucleotide (FAD+) – Coenzyme A
ATP ATP is the energy currency of the cell The structure of ATP is similar to that of nucleic acids The energy in ATP is carried in the phosphate groups – to convert ADP into ATP requires energy – the energy is stored as potential energy in the phosphate group bond – removal of the third phosphate releases that energy NADH, FADH2 NAD+ can accept a hydrogen ion in addition to become reduced to NADH: NAD+ + 2[H+] + 2e- NADH + H+ The added hydrogen ion ( in addition to electrons) can be carried to in addition to used in other reactions in the body. FAD+ is similarly reduced to FADH2. NADH in addition to FADH carry hydrogen ions in addition to electrons to the enzymes in the electron transport chain of the mitochondria, allowing ATP production there. Coenzyme A The enzyme coenzyme A converts acetyl groups (2-carbon structures) into acetyl CoA, which can then be used in metabolic reactions During the course of acetyl CoA production, energy is released in addition to is used to convert NAD+ to NADH
Cellular Respiration Generating ATP from food requires glycolysis, the Krebs Cycle, in addition to the electron transport chain. Overall reaction: C6H12O6 + 6 O2-> 6 CO2 + 6 H2O + 38 ATP + heat The Main point: the break down of glucose releases LOTS of energy: – about 40% in usable as long as m (ATP) – about 60% as heat Glycolysis Glycolysis is the breakdown of glucose into pyruvic acid Two main steps are involved, occurring in the cytoplasm of cells (no organelles involved). The two main steps of glycolysis:
What happens to pyruvic acid In aerobic respiration (oxygen present): – pyruvic acid moves from cytoplasm to mitochondria – pyruvic acid (3 carbons) is converted to acetyl group (2 carbons), producing CO2 in the process – acetyl group is converted to acetyl CoA by coenzyme A – acetyl CoA is used in the Krebs cycle. Krebs Cycle Acetyl CoA combines with oxaloacetic acid, as long as ming citric acid A series of reactions then occurs resulting in: – one ATP produced – three NADH in addition to one FADH2 produced (go to electron transport chain) – two CO2 molecules produced Electron-transport Chain The main point: NADH in addition to FADH2 carry H+ ions to the electron-transport chain, resulting in production of ATP To do this, the H+ ions are moved along the transport chain, eventually accumulating in the outer mitochondrial compartment The H+ ions move back into the inner mitochondrial compartment via hydrogen channels, which are coupled to ATP production. At the end of the transport chain, four hydrogen ions join with two oxygen molecules to as long as m water: 4 H+ + O2 -> 2 H2O In the absence of oxygen, the transport chain stalls (no ATP production)
Net Result of Glycolysis, Citric Acid Cycle, in addition to Electron Transport Chain: Production of ATP (stored, potential energy as long as chemical reactions in the body; 40% of energy released). Production of heat (maintains body temperature; 60% of energy released). Also, production of CO2 in addition to H2O. Storage in addition to Utilization of Glycogen Excess glucose can be stored as glycogen. Stored glycogen can be utilized, by glycogenolysis. Glycogenolysis: -glycogen is broken down into glucose 6- phosphate – liver trans as long as ms glucose 6-phosphate to glucose, maintaining blood glucose levels Lipid Metabolism Over 95% of stored energy in the body is in the as long as m of triacylglycerol During lipid catabolism (lipolysis), triacylglycerol is broken down into free fatty acids in addition to glycerol Free fatty acids are metabolized by beta-oxidation: 1) fatty acid (18 C) + coenzyme A 2) fatty acid (18 C)-coA 3) fatty acid (16 C) in addition to acetyl-coA Acetyl-CoA used in citric acid cycle This reaction also yields NADH => electron transport chain Excess acetyl-CoA as long as ms ketone bodies
Lipid Metabolism (cont.) The glycerol is converted into glyceraldehyde 3-phosphate, which is converted to pyruvic acid Pyruvic acid is metabolized under aerobic conditions into acetyl-coA While lipids are major storage as long as m of energy, accessing lipids as long as metabolism takes time – water insoluble – less efficient energy source – potential as long as keto-acidosis Protein Metabolism Amino acids are NOT stored as long as energy However, protein can be broken down, in addition to amino acids can be modified in addition to utilized to create glucose or as long as metabolism Modification of amino acids to produce substrate as long as energy involves oxidative deamination Oxidative Deamination Oxidative deamination removes the amino group from the amino acid, as long as ming ammonia, NADH, in addition to a keto acid: NADH => electron transport chain ammonia => liver, converted to urea keto acid => acetyl-coA => citric acid cycle
Proteins in addition to Energy Utilization of proteins as long as quick energy is not very efficient: – more difficult to break apart (multiple proteases) – toxic byproduct (ammonia) – can get accumulation of keto acids – proteins are important structural in addition to functional components of cells Interconversion of Nutrients Lipogenesis: once glycogen stores are filled, glucose in addition to amino acids are converted to lipids Rate limiting enzyme: acetyl CoA carboxylase acetyl CoA carboxylase Interconversion of Nutrients (cont.) Gluconeogenesis: amino acids in addition to glycerol can be used to produce glucose (liver) More glucose is produced via gluconeogenesis than glycogenolysis Rate-limiting enzyme: phosphoenolpyruvate carboxykinase PEPCK
Importance of Blood Glucose Homeostasis Blood glucose levels must be maintained as a nutrient source as long as nervous tissue (no glucose stores) What mechanisms regulate blood nutrient levels in tissues in addition to blood glucose levels The Endocrine Pancreas: Regulation of Nutrient Metabolism Located on the posterior abdominal wall, retroperitoneal. Exocrine portion: secretes digestive enzymes via pancreatic duct, to small intestine. Endocrine portion: pancreatic islets (of Langerhans), involved in regulation of blood glucose levels. Pancreatic Anatomy Gl in addition to with both exocrine in addition to endocrine functions 15-25 cm long 60-100 g Location: retro-peritoneum, 2nd lumbar vertebral level Extends in an oblique, transverse position Parts of pancreas: head, neck, body in addition to tail
Pancreas Head of Pancreas Includes uncinate process Flattened structure, 2 3 cm thick Attached to the 2nd in addition to 3rd portions of duodenum on the right Emerges into neck on the left Border b/w head in addition to neck is determined by GDA insertion SPDA in addition to IPDA anastamose between the duodenum in addition to the right lateral border Neck of Pancreas 2.5 cm in length Straddles SMV in addition to PV Antero-superior surface supports the pylorus Superior mesenteric vessels emerge from the inferior border Posteriorly, SMV in addition to splenic vein confluence to as long as m portal vein Posteriorly, mostly no branches to pancreas
Treatment in Diabetes Change in lifestyle: Increase exercise: Increases the amount of membrane GLUT-4 carriers in the skeletal muscle cells. Weight reduction. Increased fiber in diet. Reduce saturated fat. Hypoglycemia Over secretion of insulin. Reactive hypoglycemia: Caused by an exaggerated response to a rise in blood glucose. Occurs in people who are genetically predisposed to type II diabetes. Insert fig. 19.13 Metabolic Regulation Anabolic effects of insulin are antagonized by the hormones of the adrenals, thyroid, in addition to anterior pituitary. Insulin, T3, in addition to GH can act synergistically to stimulate protein synthesis.
Casteel, Sean Contributing Writer
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