DigestionDigestionBio 391Bio 391

2.9 – 2.112.9 – 2.11

Answer: QUESTION #1

Steps In DigestionSteps In Digestion• INGESTIONINGESTION– Putting food into the tubePutting food into the tube

• DIGESTIONDIGESTION– Mechanical and chemical breakdown of large food chunksMechanical and chemical breakdown of large food chunks

• PERISTALSISPERISTALSIS– Muscular contractions that move food chunks through the tubeMuscular contractions that move food chunks through the tube

• ABSORPTIONABSORPTION– Once food particles are small enough, diffusion through small Once food particles are small enough, diffusion through small

intestine liningintestine lining• DEFECATIONDEFECATION– Removal of all the “undigestables” – leaves the tubeRemoval 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?

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– Diffusion of food molecules

directly into cell

Why specialized? 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

– 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 toanother

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. AbsorptionS.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

MouthMechanical

Chemical

All

Carbohydrates

StomachMechanical

Chemical

All

Protein

Small Intestine Chemical All

ENZYMES OF DIGESTION

ENZYME SITE OF ACTION SITE of PRODUCTION NUTRIENT DIGESTED

Amylase

Pepsin

Lipase

Amylase

Trypsin

Peptidase

Maltase

Sucrase

Lactase

Mouth

Stomach

Small intestine

Small intestine

Small intestine

Small intestine

Small intestine

Small intestine

Small intestine

Salivary glands

Lining of stomach

Pancreas

Pancreas

Pancreas

Lining of small intestine

Lining of small intestine

Lining of small intestine

Lining of small intestine

Carbohydrate

Protein

Fat

Carb/Disaccharide

Polypeptide

Polypeptide

Carbohydrate/d.s

Carbohydrate/d.s

Carbohydrate/d.s

OTHER SUBSTANCES INVOVLED IN DIGESTION

SUBSTANCE SITE OF ACTION ACTION

Saliva Mouth Moistens Food

MucusEsophagus, 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

BileSmall intestine

(made in liver,

stored in gall bladder)

Separates fat droplets,

making them easier to

break down.

Bacteria Large IntestineHelp breakdown food

Produce vitamin K