Digestion Bio 391 2.9 – 2.11 Answer: QUESTION #1

Steps In Digestion INGESTION DIGESTION PERISTALSIS ABSORPTION 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 CHEMICAL 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 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 Inside the cells Plants – make own food, process within same cell Single-celled organisms and simple animals Diffusion of food molecules directly into cell Alimentary canal / GI tract Most animals, us too More complex = 1 way Carnivore vs. herbivores Venus fly trap Bread mold

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 Q4, Q5 Physical digestion Chemical digestion Chyme 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

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 Bacterial symbionts 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 Mouth Mechanical Chemical All Carbohydrates Stomach Protein Small Intestine

ENZYMES OF DIGESTION ENZYME SITE OF ACTION SITE of PRODUCTION NUTRIENT DIGESTED Amylase Pepsin Lipase Trypsin Peptidase Maltase Sucrase Lactase Mouth Stomach Small intestine Salivary glands Lining of stomach Pancreas Lining of small intestine Carbohydrate Protein Fat Carb/Disaccharide Polypeptide Carbohydrate/d.s

OTHER SUBSTANCES INVOVLED IN DIGESTION SITE OF ACTION ACTION Saliva Mouth Moistens Food Mucus Esophagus, Stomach Sm. & Lg. Intestines Helps food move easily Protects organs Gastrin (H)  Hydrochloric Acid (HCl) Stomach Helps breakdown food Kills bacteria Secretin (H)  Sodium bicarbonate Small Intestine (NaHCO3made in pancreas) Neutralizes acid so enzymes can function Bile Small intestine (made in liver, stored in gall bladder) Separates fat droplets, making them easier to break down. Bacteria Large Intestine Help breakdown food Produce vitamin K