Download Chapter 38: Digestive System

Chapter 38: Digestive System
2 Major Patterns of Digestion
A. Intracellular
• Digestion occurs w/in cells
• Lysosomes release enzymes into food
vacuoles, breaks down occurs w/in these
vacuoles
- (lysis- splitting, some- body)
• Ex:
a. Sponges, unicellular organisms
b. Plants starch converts to simple
sugars (in every cell)
c. Cnidaria (hydra) partly intra/
extracellular
d. Humans some food in small intestine
(SI) undergoes final breakdown w/in cells
(proteins, lipids)
- BUT digestion largely
EXTRACELLULAR!
B. Extracellular
• Digestion outside the cell, usually w/in a cavity lined by these
cells
• Ex:
a.Molds, mushroom (other fungi)
b. Plants (Venus fly trap, pitcher plant) insectivorous
- Autotrophs, but have adaptations to trap insects- source of
nitrogen
c. Humans most food digested w/in digestive cavity (aka
alimentary canal)
Cont. Extracellular
d. Worms (Platyhelminthes) carnivorous
- Incomplete digestive tract- 1 opening that serves as mouth/ anus
– Food partially digested by pharynx (food tube) outside the body;
digestion completed w/in body
e. Starfish pushes out stomach; digest clam w/in shell
f. Earthworm complete digestive system- 2 openings
– Mouth pharynx crop gizzard intestine anus
– Food & soil enter mouth, pass through digestive system
– Wastes called “castings” sold commercially as “super stuff”/ fertilizer
enriches soil
C. Hydrolysis
• Chemical process in which larger molecules are broken
down into smaller soluble subunits by addition of water.
(+H2O)
1. Proteins -------------------- (+H2O) (hydrolysis) -----------------► Amino Acids
◄-------------------- (- H2O) (dehydration synthesis) --2. Polysaccharides --------- (+ H2O) ----------------► Monosaccharides
(Starches)◄---------------- (- H2O) ------------------- Simple sugars
3. Lipids ------------------------ (+ H2O) ---------------► 3 Fatty acids & glycerol
◄---------------------- (- H2O) ---------------4. Nucleic Acids -------------- (+H2O) ----------------► Nucleotides
(Cell nuclei)◄-------------- (- H2O) ------------------ (DNA- A, C, G, T)
(RNA- A, C, G, U)
Digestion- 2 Major Phases
A. Physical Phase: change in size or
movement of food molecules
•
Chewing- mastication
•
Swallowing- deglutition
•
Peristalsis- wave-like muscle
contractions through alimentary
canal; moves food from one area
to another
•
Segmentation- (small intestine)
mixes enzymes and food
•
Emulsification- (bile secreted by
liver into small intestine); physical
breakdown of lipids from larger
lipids to smaller sized lipidsfacilitates the chemical
breakdown of lipids by pancreatic
lipase
B. Chemical Phase: carried out by hydrolases- enzymes
which bring about hydrolysis
1. Protein + H2O ------------------------ Amino acids (soluble- can be absorbed into
(proteases)
cells)
2. Lipids + H2O --------------------- 3 Fatty acids & glycerol (soluble)
(lipases)
3. Carbohydrates + H2O --------------- Disaccharides (maltose, sucrose, lactose)
(amylases)
4. Disaccharides + H2O ---------------- Monosaccharides (simple sugars- soluble)
(disaccharases)
a. Sucrose- sucrase + H2O ------ glucose & fructose
b. Maltose- maltase + H2O ------- glucose & glucose
c. Lactose- lactase + H2O -------- glucose & galactase
5. Nucleic Acids + H2O ---------------- Nucleotides (ribose/ deoxyribose, +
(Pancreas- deoxyribonuclease)
nitrogen base + phosphate)
(Pancrease- ribonuclease)
(for DNA- A,C, G, T// for RNA- A, C, G, U)
Human Digestion
A. Essential Nutrients (6 types)
Energy foods
Non-energy foods
1. Amino acids (from protein)
1. Minerals
2. CHO (starches & sugars)
2. Vitamins (All 3 regulates body fxns)
3. Lipids (fats & oil)
3.
Water
• Water makes most of cell volume/ main solvent
•70-90% depending on cell type
B. Anatomy of Human Digestive Tract
1. Alimentary Canal
•
•
Mouth esophagus stomach small intestine
(duodenum, jujenum, ileum) large intestine (colon)
rectum anus
These organs make DIRECT contact w/ food molecules
2. Accessory Organs
• DO NOT make contact with food/ secrete into
alimentary canal
a. Salivary glands (3 pairs)- parotid, submaxillary,
sublingual
b. Pancreas
c. Liver
d. Gallbladder
C. Small Intestine- Absorption of Digested Nutrients
•
•
•
•
Approx 16 ft long in adults
Surface area greatly increased by villi to allow for
maximum absorption of soluble food molecules into blood
& lacteals (lymph vessels)
Epithelial layer cells absorb soluble nutrients
Each villus contains capillaries & a lymph vessel
Cross-Section of S.I.
Capillaries absorb:
Lymph vessels (lacteal)
absorb:
1.
Monosaccharides
1. Fatty acids
2.
Amino acids
2. Glycerol
3.
Some glycerol
4. Minerals
5. Vitamins
6.
Water
*Cap 1-6 are carried to liver
by portal vein via hepatic
portal system
D. Hepatic Portal System
1. Portal System
– Venous system
which transports
blood through a
specific organ before
it is returned to the
heart
2. Hepatic Portal System
– Venous system
carrying digested
foods from the
digestive system to
the LIVER
– Main vein is the
portal vein which
enters the liver
3. Liver
-- Maintains the concentrations of organic nutrients in the
blood by converting 1 type of organic nutrients into others
•
Examples:
(Deamination)
----------------------- CHO
a. Amino Acids (AA) -------------------- - NH2 ----------------------- Lipids
(Amino group) ------------------- Urea excreted by kidney
(Amination)
b. CHO --------------------------------- + NH2 ------------------------ Nonessential AA
Lipids
c. CHO --------------------------------- Lipids
AA (- NH2)
Cont. Hepatic Portal
System
4. Essential Amino
Acids (8)
-Can’t be synthesized
by the body; acquire
through diet
5. Non-essential Amino
Acids (12)
- Can be synthesized
by the body
Hormones Which Regulate Digestion
Organ
Hormone
Target
Effect
1. Stomach
(pyloric region)
+ presence of
food
Gastrin
Stomach mucosa
a. Release H+ & Clinto cavity
forms HCl
b. Release
pepsinogen
2. Duodenum (1st
10 in of SI)
+ presence of
food
Secretin
Pancreas
NaHCO3 (baking
soda)
Pancreozymin
(cholecystokinin)
Pancreas, liver, &
gallbladder
* Bile release into
*Bile emulsifies lipids * Pancreatic lipase
duodenum causes
(causes physical
hydrolyzes lipids into
fatty acids & glycerol
relaxation of Spincter breakdown)
of Oddi
4 different type of
enzymes:
a. Amylase
b. Lipase
c. Proteases
d. Nucleases
The Digestive Enzymes **know which
Section 38-2
macromolecules
are broken down in each organ
Site
Enzyme
Role in Digestion
Mouth
Salivary amylase
Breaks down starches into
disaccharides
Stomach
Pepsin
Breaks down proteins into large
peptides
Small intestine
(from pancreas)
Amylase
Continues the breakdown of
starch
Trypsin
Continues the breakdown of
protein
Lipase
Breaks down fat
Maltase, sucrase, lactase
Breaks down remaining
disaccharides into
monosaccharides
Peptidase
Breaks down dipeptides into
amino acids.
Small intestine