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Digestion Bio 391 2.9 – 2.11 Answer: QUESTION #1 INGESTION DIGESTION PERISTALSIS ABSORPTION DEFECATION DIGESTION breakdown of large food molecules into smaller ones Why is it necessary? • • • • • • • MECHANICAL Physical change Breaking food into smaller parts by ripping, churning Increases surface area TEETH tear & crush STOMACH churns BILE separates Gizzard grinds CHEMICAL • Chemical change • Enzymes break bonds of food molecules • Enzymes are made and used by organs – Not always the same • Each enzyme is specific to a type of macromolecule – Carb, fat or protein Where does digestion occur? EXTRACELLULAR • • • • Alimentary canal / GI tract Most animals, us too More complex = 1 way Carnivore vs. herbivores – Venus fly trap – Bread mold INTRACELLULAR • Inside the cells • Plants – make own food, process within same cell • Single-celled organisms and simple animals – Hydra Why specialized? 1. Mouth • Physical digestion • Chemical digestion – Saliva, salivary glands – Starts carbohydrate digestion – Amylase • Starch complex smaller sugars (maltose) • Saliva’s pH at 6.0-7.4 – Short time in mouth lots left undigested 2. Esophagus & Epiglottis • Esophagus connects mouth to stomach – Peristalsis – wavelike contrxns force food down – Mucus secreted • Epiglottis – “trap door” prevents food “going down the wrong way” 3. Stomach • Physical digestion • Chemical digestion – Presence of food triggers gastrin release • Hormone, controls juice prodxn – Gastric juice • HCl + mucus + pepsinogen • pH 1.0 – 3.5 • Pepsinogen pepsin once in acid (inactive) (active) – Protein digestion begins – Proteins polypeptides • Chyme • Mucus lining • Sphincters 4. Small Intestine • All digestion completed, nutrients absorbed • S.I. secretions – Secretin – presence of acid stimulates SI cells to release hormone to pancreas via blood stream • Stimulates pancreas to release NaHCO3 – Carbohydrases (ex: maltase) • Carbo digestion completed • Maltose glucose • Left over starch glucose • Liver & Gallbladder – Adds bile to the mix • Emulsifies fats S. I. Digestion via pancreatic secretions • Pancreas adds pancreatic juice – Shifts pH from acidic to basic – WHY? – Protein digestion completed • Trypsinogen trypsin (inactive) (active) – Polypeptides amino acids – Fat digestion completed • Lipases – Lipids fatty acid + glycerol – Pancreatic amylase • Carbo’s (maltose) glucose S.I. Absorption • Large surface area – Villi & Microvilli – Capillaries enter each 5. Large Intestine • Waste condensation – Water absorption – Feces • Bacterial symbionts – Synthesize vitamins – Vitamins absorbed • Also has villi • Diarrhea & constipation • Undigested food leaves through anus – Cellulose, fiber, etc. DISORDERS • Heartburn stomach acid enters esophagus because of weak cardiac sphincter • Peptic Ulcer Hole in stomach wall caused by Helicobacter pylori. The pain is caused by the acid. • Diarrhea Not enough water is absorbed • Constipation Too much water is absorbed • Diabetes Glucose cannot enter cells of body very well, therefore glucose cannot get turned into energy!! Diabetes • 6th killer in America (and rising) • Pancreas cannot produce insulin or the body does not use it properly • Insulin is a hormone that decreases the amount of sugar in the blood by helping it enter the cells of the body. – Glucose does not enter cells easily, insulin must “act like a butler” and bind to a cell membrane protein to help it in. Where does Digestion occur? What Nutrient is Digested? ORGAN TYPE OF DIGESTION Mechanical Mouth Chemical Mechanical Stomach Chemical Small Intestine Chemical NUTRIENT DIGESTED ENZYMES OF DIGESTION ENZYME Amylase Pepsin Lipase Amylase Trypsin Peptidase Maltase Sucrase Lactase SITE OF ACTION SITE of PRODUCTION NUTRIENT DIGESTED OTHER SUBSTANCES INVOVLED IN DIGESTION SUBSTANCE SITE OF ACTION Saliva ACTION Moistens Food Esophagus, Stomach Mucus Gastrin (H) Hydrochloric Acid (HCl) Secretin (H) Sodium bicarbonate Bile Bacteria Sm. & Lg. Intestines Helps breakdown food Kills bacteria