Transcript WELCOME TO BIOLOGY 2002

Announcements

Tomorrow’s quiz on NEJM paper

Bring two questions about NEJM

Exam I provided today
Which of the following enzymes work most
effectively at a very low pH?
A.
Salivary amylase
B.
Trypsin
C.
Pepsin
D.
Pancreatic amylase
E.
Pancreatic lipase
In zero gravity environment of space, how does food
swallowed by an astronaut reach her stomach?
A.
Swallowing hard
B.
Running around wheel creates -> artificial
gravity
C.
Involuntary muscle contractions
D.
IV administration of nutrients
Which of the following organs is incorrectly paired
with its function?
A.
Stomach –protein digestion
B.
Oral cavity -starch digestion
C.
Large intestine –bile production
D.
Small intestine –nutrient absorption
E.
Pancreas –enzyme production
Salivary glands
Secretes enzymes
that digest
carbohydrates
1. Mouth
Mechanical and
chemical processing
(chewing reduces size
of food; saliva digests
carbohydrates)
Liver
Secretes
molecules
required for
digestion of fats
2. Esophagus
Transports food
Gall bladder
Stores secretions
from liver; empties
into small intestine
4. Small intestine
Chemical processing
and absorption (digestion
of proteins, fats,
carbohydrates; absorption
of nutrients and water)
Pancreas
Secretes enzymes
and other materials
into small intestine
3. Stomach
Mechanical and
chemical processing
(digestion of proteins)
5. Large intestine
Water absorption
and feces formation
Stomach
End of esophagus
Sphincter seals off
stomach from esophagus
Sphincter seals off
stomach from small
intestine
Layers
of muscle
Beginning of
small intestine
Lumen
(interior)
Stomach lining
Canal empties to lumen
Parietal cells
(secrete HCl)
Chief cells
(secrete pepsinogen)
Secretion of HCI by parietal cells
HCl
to lumen
CO2
+
H 2O
H2CO3
To blood
H+
H+
HCO3–
Cl–
HCO3–
K+
H+/K+ pump
Cl–
Cl–
Cl–
Chloride channel
From blood
Parietal cell
Canal empties
to lumen
Enzymes, Hormones, other?
•Enzymes: pepsinogen (inactive)-> pepsin
(protease) from chief cells
•Other: HCl -> denature ECM bacteria, from
parietal cells, activator of pepsin
•Other: Mucins/mucus protective from goblet or
mucus cells
•Other: mechanical churning -> acid chyme
•Hormones: Gastrin (+), CCK/secretin (-),
enterogastrone (-- pyloric sphinct)
Enzymes, Hormones, other?
•Your turn
DIGESTION OF LIPIDS IN SMALL INTESTINE
Glycerol
Lipase
Fatty
acids
1. Large fat globules
are not digested
efficiently by lipase.
2. Bile salts
(produced in
liver) act as
emulsifying
agents.
3. Small fat droplets
result from
emulsification.
4. Lipase digests
the small fat
droplets into
glycerol and
free fatty acids.
Fold
Villi
115 µm
Cross-section of small intestine
Lumen of small intestine
Apical
side
Na+/glucose
cotransporter
H2O
Osmosis
Na+
Glucose
K+
GLUT-2
transport
protein
Na+/K+-ATPase
K+
ATP
Basolateral side
ADP
Blood
H2O
Osmosis
Na+
Glucose
Capillaries are small and extremely thin walled.
Glucose
Pancreas secretes
INSULIN
If glucose
levels too high
If glucose
levels too low
Pancreas secretes
GLUCAGON
Glycogen
Insulin causes cells in the liver and skeletal
muscle to synthesize glycogen; fat storage
cells synthesize triglycerides.
Glucose
levels fall
HOMEOTASIS
(normal glucose
levels in blood)
Glucose
levels rise
Glucagon causes cells in liver and skeletal
muscle to catabolize glycogen; fat storage
cells catabolize fatty acids.
Glycogen
Glucose