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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
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
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