Louisa ScibelliMetabolism I Final Exam: Chapters in ReviewChapter 2: The Cell• Mitochondrion is the site of majority of metabolic energy produced in cells. o ATP ETC • Nucleus is the largest organelle; it initiates and regulates most cellular activities. o Nucleic acids: DNA and RNA. Made from nucleotides (C, G, A, U, T).• Protein synthesiso Cell replication: DNA replicates itself.o Cell transcription: mRNA copies the genetic information from DNA.o Cell translation: genetic information in RNA is converted into the AA sequence of a protein. • Apoptosis is the programmed death of a cell. Chapter 3: The Gastrointestinal Tract (Digestion and Absorption) • Functions: make nutrients available to cell, elimination of wastes, protect body from harmful substances, metabolic processes. • Oral cavity:o Saliva Salivary amylase: hydrolyzes ɑ-1, 4 linkages of amylose. Lysozymes: kill bacteria • Esophagus:o Movement of food via peristalsis. o Lower esophageal sphincter relaxes to let food into stomach. • Stomach:Louisa Scibellio Absorbs alcohol and aspirin. o Digestion: Lipids: limited hydrolysis via lingual lipase and gastric lipase. Proteins: some hydrolysis of small polypeptides via pepsin. • Pepsinogen (a zymogen) is secreted by chief cells in response to acetocholine. o Pepsinogen is activated by HCl (secreted by parietal cells) and pepsin (autocatalytic).• HCl regulation:o Gastrin (+): gastrin releasing peptide (GRP) in response to acetylcholine. o Acetylcholine (+): NT released by vagus nerve. Can act on parietal cells. o Histamine (+): produced by mast cells. Release by vagus nerve and gastrin. o Somatostatin (-): inhibits HCl release. Ach inhibits secretion of somatostatin; H+ promotes secretion. • GERD: Gastro Esophageal Reflux Disease; reflux of digestive juices from stomach into esophagus. • Pyloric sphincter regulates movement of food and acid from stomach to small intestine. • Small intestine o Digestion: In the lumen:• CH2O: hydrolysis of starch via pancreatic amylase (hydrolyzes ɑ-1,6 linkages). • Protein: pancreatic proteases are released and activated.Louisa Scibellio Trypsinogen (zymogen) trypsin (autocatalytic) via enteropeptidase.• Lipid: hydrolysis of TAG’s to MAG’s, FFA, and glycerol via pancreatic lipase. o Emulsification occurs via bile acids. Bile: synthesized in liver; stored in gallbladder. • CCK: stimulates constriction of gallbladder to release bile and releases zymogens from pancreas. Inhibits gastric emptying. • Secretin: stimulates release of bicarbonate. Inhibits gastric emptying. • GIP: inhibits gastric emptying. o Co-lipase: provides lipase access to TAG’s. o Micelles form which consist of bile acids and phospholipids. Transport end products across unstirred water layer to brush border. On brush border:• CH2O: hydrolysis of oligosaccharides to monosaccharides via oligosaccharidases. o Glucose and galactose: sodium dependent; active transport.o Fructose: sodium independent (GLUT 5); facilitated diffusion. • Protein: hydrolysis of oligopeptides to tri- and dipeptides and AA via aminopeptidases. • Lipid: long chain FA’s and MAG’s synthesized into TAG’s. o TAG’s, CE, free cholesterol, and phospholipids = chylomicrons.Louisa Scibelli• Mechanisms of absorptiono Active transport: glucose, galactose, and AA.o Facilitated diffusion: fructose (GLUT 5).o Diffusion: FA’s. • Transport away from intestinal cello Vascular system (portal vein): monosaccharides, AA, glycerol, and short chain FA’s. o Lymphatic system: TAG’s as a part of chylomicrons. • Colon o Absorption of water and electrolytes. • Factors affecting motility of GI tracto Rate of stomach emptying; volume of food, composition, hormones. o Intestinal motility; increased by motilin and fiber. Inhibited by peptide YY and secretin. Chapter 4: Fiber • Total fiber: non-digestible plant polysaccharides that contain β-1, 4 linkages which cannot be digested by humans. o Dietary fiber: found in foods.o Functional fiber: added to foods or taken as supplements. • Soluble fiber: soluble in hot water. Fermented by bacteria in GI tract. o Delays gastric emptying, increases transit time, decreases nutrient absorption. • Insoluble fiber: doesn’t dissolve in water. Not fermented by bacteria in GI tract. o Decreases transit time and increases fecal bulk. • Prebiotics are health promoting bacteria; found in fermentable fiber. • Disease and fiberLouisa Scibellio Heart disease: decreased serum cholesterol.o Diabetes mellitus: better regulation of blood glucose. o Obesity: increase satiety and decreases absorption of energy nutrients.o GI disorders: constipation, IBS, etc. o Important to drink lots of water!• AI = 25g/day for women and 38g/day for men. Chapter 5: Glycolysis• The oxidation of glucose to pyruvate (aerobic) or lactate (anaerobic). o Purpose is to produce energy from glucose. o Occurs in the cytoplasm. • Phosphorylation of glucoseo Hexokinase: all cells, any hexose, inhibited by G-6-PO4 (allosteric), low Km for glucose. o Glucokinase: liver and pancreas, glucose only, induced by insulin, high Km for glucose. • Allosteric modification: may be positive or negative. Regulation is irreversible. • Induction: increased synthesis of the enzyme, and increased amount of the enzyme. • Major rate controlling enzyme = PFK-1 (phosphofructokinase-1).o Regulated allosterically Inhibited by ATP and citrate Activated by AMP, ADP, fructose-2, 6-bisPO4. o Regulated by induction Insulin increases amount of PFK-1 synthesized. • Substrate level phosphorylation: transfer of PO4 from high energy compound to ADP to form ATP. Can occur in cytoplasm and mitochondria. ATP’s produced = 1.Louisa Scibelli• Oxidative phosphorylation: formation of ATP via ETC. Occurs in mitochondria. ATP’s produced = 3. • Energetics: 4 ATP’s produced and 2 NADH’s produced. • Malate shuttle: H’s attach to NAD to form NADH+H. 3 ATP’s formed. • Glycerol-3-PO4 shuttle: H’s attach to FAD to form FADH2. 2 ATP’s formed. • Cori cycle: lactate formed in muscle from anaerobic glycolysis may be sent to liver for synthesis of glucose. This glucose may be returned to muscle.Louisa ScibelliLouisa ScibelliChapter 6: Gluconeogenesis• Synthesis of glucose from pyruvate, lactate, glycerol or selected AA like alanine. o Occurs in liver; some in kidney during adapted starvation. o Energy required. • Most
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