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Digestion Bio 391 2.9 – 2.11 Answer: QUESTION #1 • INGESTION Steps In Digestion – Putting food into the tube • DIGESTION – Mechanical and chemical breakdown of large food chunks • PERISTALSIS – Muscular contractions that move food chunks through the tube • ABSORPTION – Once food particles are small enough, diffusion through small intestine lining • DEFECATION – Removal of all the “undigestables” – leaves the tube DIGESTION breakdown of large food molecules into smaller ones MECHANICAL • Physical change • Breaking food into smaller parts by ripping, churning, crushing – – – – TEETH tear & crush STOMACH churns BILE separates Gizzard grinds (not in humans – birds, worms) • Increases surface area to help chemical digestion CHEMICAL • Chemical change • Enzymes break bonds of food molecules • Enzymes are made and used by organs – Each organ will produce different enzymes • Each enzyme is specific to a type of macromolecule – Carb, fat or protein Where does digestion occur in an organism? INTRACELLULAR EXTRACELLULAR • • • • Alimentary canal / GI tract Most animals, us too More complex = 1 way Carnivore vs. herbivores – Venus fly trap – Bread mold • Inside the cells • Plants – make own food, process within same cell • Single-celled organisms and simple animals – Diffusion of food molecules directly into cell 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 – Answer Q#2 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 production – 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 – protects tissues from chemical burns • Sphincters – muscle rings that prevent flow from one chamber to another Q4, Q5 4. Small Intestine Q3 • 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) • Carb digestion completed • Maltose glucose • Left over starch glucose • Liver & Gallbladder – Adds bile to the mix • Emulsifies (breaks up) 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 NUTRIENT DIGESTED Mechanical All Chemical Carbohydrates Mechanical All Stomach Chemical Protein Small Intestine Chemical All Mouth ENZYMES OF DIGESTION ENZYME SITE OF ACTION SITE of PRODUCTION NUTRIENT DIGESTED Amylase Mouth Salivary glands Carbohydrate Pepsin Stomach Lining of stomach Protein Lipase Small intestine Pancreas Fat Amylase Small intestine Pancreas Carb/Disaccharide Trypsin Small intestine Pancreas Polypeptide Peptidase Small intestine Lining of small intestine Polypeptide Maltase Small intestine Lining of small intestine Carbohydrate/d.s Sucrase Small intestine Lining of small intestine Carbohydrate/d.s Lactase Small intestine Lining of small intestine Carbohydrate/d.s OTHER SUBSTANCES INVOVLED IN DIGESTION SUBSTANCE SITE OF ACTION Saliva Mouth ACTION Moistens Food Esophagus, Stomach Helps food move easily Mucus Sm. & Lg. Intestines Protects organs Gastrin (H) Stomach Hydrochloric Acid (HCl) Secretin (H) Sodium bicarbonate Bile Helps breakdown food Kills bacteria Small Intestine Neutralizes acid so (NaHCO3made in pancreas) enzymes can function Small intestine Separates fat droplets, (made in liver, making them easier to stored in gall bladder) break down. Help breakdown food Bacteria Large Intestine Produce vitamin K