Digestion INGESTION DIGESTION PERISTALSIS ABSORPTION DEFECATION Bio 391 2.9 – 2.11 Answer: QUESTION #1

DIGESTION  breakdown of large food molecules into smaller ones Why is it necessary? CHEMICAL MECHANICAL Physical change Breaking food into smaller parts by ripping, churning Increases surface area TEETH  tear & crush STOMACH  churns BILE  separates Gizzard  grinds 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? INTRACELLULAR EXTRACELLULAR Inside the cells Plants – make own food, process within same cell Single-celled organisms and simple animals Hydra Alimentary canal / GI tract Most animals, us too More complex = 1 way Carnivore vs. herbivores Venus fly trap Bread mold

Why specialized?

Human Anatomy

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 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 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) 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 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.

SUMMARY QUESTIONS What are the 2 types of digestion? Where does digestion begin? Where does MOST digestion happen? Where do nutrients enter the rest the of the body? (i.e.  leave the GI tract)

Where does Digestion occur? What Nutrient is Digested? ORGAN TYPE OF DIGESTION NUTRIENT DIGESTED Mouth Mechanical Chemical Stomach Small Intestine

ENZYMES OF DIGESTION ENZYME SITE OF ACTION SITE of PRODUCTION NUTRIENT DIGESTED Amylase Pepsin Lipase Trypsin Peptidase Maltase Sucrase Lactase

OTHER SUBSTANCES INVOVLED IN DIGESTION SITE OF ACTION ACTION Saliva Moistens Food Mucus Esophagus, Stomach Sm. & Lg. Intestines Gastrin (H)  Hydrochloric Acid (HCl) Helps breakdown food Kills bacteria Secretin (H)  Sodium bicarbonate Bile Bacteria