Download Digestion

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