Anatomy and Functions
Where are most nutrients absorbed?
Small intestine
HCl in the stomach breaks what kinds of bonds in proteins to linearize them?
Disulfide Bonds/Covalent Bonds
What is the sugar that we cannot break down?
Cellulose
(acceptable: lactose)
What are micelle shapes?
BONUS (x2): Why are they a challenge for digestion?
aggregates that form due to hydrophobic tails clumping vs. hydrophilic regions being exposed outside
BONUS (x2): ester bond being "protected"/hard to access
What are the pacemaker cells that induce intestinal contractions called?
cells of cajal
The basic functions of the stomach include absorption of _____, and protein ____.
BONUS (x2): What enzyme is secreted here?
Water (and some medications); digestion
BONUS (x2): Pepsin
What is the purpose of a microbial community in the large intestine?
( i know its not proteins but idc)
take uneaten food & "digest it in a sense" (have own enzymes & breaks down material) & releases nutrients back for us to absorb
Starch is digested (cleaved) by ____-ase.
Maltose is digested (cleaved) by ____-ase.
BONUS (x2): Glucose is digested by ______.
Starch is digested (cleaved) by amylase.
Maltose is digested (cleaved) by maltase.
BONUS (x2): trick question Glucose is absorbable.
What bond holds together glycerol and fatty acid tails?
Ester bond
What is the purpose of segmental contractions?
↑periodicity of contact of digestive material w/ lining of gut. there are microbes in lining that take uneaten food & "digest it in a sense" (have own enzymes & breaks down material) & releases nutrients back for us to absorb
Correctly match the following functions:
A) Duodenum B) Jejunum C) Ileum
1) Rich in Peyer's Patch 2) Primary site of absorption; membrane-bound enzymes 3) Starch, fat, protein digestion
A) Duodenum --> 3) Starch, fat, protein digestion
B) Jejunum --> 2) Primary site of absorption; membrane-bound enzymes
C) Ileum --> 1) Rich in Peyer's Patch
Give the function of each protease:
Pepsin
Trypsin
Carboxypeptidases
Aminopeptidases
Pepsin: endoprotease; secreted in stomach; breaks down into chunks
Trypsin: endoprotease; breaks into even smaller chunks
Carboxypeptidases: exoprotease; attack last AA on carboxyl side
Aminopeptidases: exoprotease; attack last AA on amino side
Fructose absorption only includes two transporters.
Order the transporters and define them as synporters/antiporters/neither.
GLUT5
GLUT2
1. GLUT5 neither
2. GLUT2 neither
Both are fructose "channels" and do not require anything to absorb fructose into the blood.
Where are bile salts secreted from? What do they do?
Gallbladder; insert selves into micelles to disrupt them > allow for enzymes (lipase) to come in
What do M cells on the epithelial layer do?
sample ilium fluid & pass antigens to immune cells
Enterocytes
Goblet Cells
Crypt-stem cells
Endocrine Cells
Enterocytes: Absorptive Cells
Goblet Cells: Secrete Mucus
Crypt-stem cells: Undifferentiated cells; always being renewed every 7 days
Endocrine cells: Regulation
There are three steps (transporters) in the absorption of amino acids from the intestinal tract to the blood. Put them in order:
Na+/AA synporter
Na+/K+ ATPase antiporter
Na+/AA antiporter
1. AA transported into enterocyte w/ Na+/AA synporter
2. AA transported across basolateral membrane by Na+/AA antiporter (AA into blood stream, Na+ into enterocyte)
3. Na+ goes out of enterocyte through Na+ K+ ATPase antiporter (Na+ out, K+ in.. uses ATP bc against gradient)
Glucose absorption includes three transporters.
Order the transporters and define them as synporters/antiporters/neither.
K+/Na+ ATPase
SGLT
GLUT2
1. SGLT (Na+/Glucose synporter)
2. GLUT2 (neither-- glucose "channel")
2. K+/Na+ ATPase (antiporter)
Fill in the blank:
Lipase is secreted by the _____ (organ) and breaks down fats by breaking the _____ bond between the _____ head and fatty acid tails. _/3 fatty acids are released and _/3 stay on the glycerol.
Lipase is secreted by the pancreas and breaks down fats by breaking the ester bond between the glycerol and fatty acid tails. 2/3 fatty acids are released and 1/3 stay on the glycerol.
Describe the 3 patterns for contractions:
1. migrating motor complex
2. peristalsis
3. segmental contractions
1. migrating motor complex: empty gut at night during "starvation" period
2. peristalsis: moves food/bolus unidirectionally (think: toothpaste tube)
3. segmental contractions: (in LI) cause mixing
Correctly order the digestive tract:
Duodenum, Ascending colon, Stomach, Descending Colon, Ilium, Jejunum, Transverse colon, Pancreas*, Liver*, Gall Bladder*, Mouth, Esophagus
*separate from the main tract but where do they connect along the tract?
Mouth, Esophagus, Stomach, Duodenum (Liver/Gall Bladder/Pancreas), Jejunum, Ilium, Ascending Colon, Transverse Colon, Descending colon
Fill in the blank for the cascade after eating a proteinaceous meal:
*stomach*
1. Gastrin (hormone) upregulates (1) chief cells secreting _____ & (2) _____ cells secreting HCl, therefore increasing breakdown of protein
*goes to duodenum (surrounded by pancreas)*
2. In the pancreas, _____ cells secrete enzymes & _____ (buffer; controls pH levels) into the duodenum.
3. The ________ (organ) secretes bile salts to help w/ digestion of fats.
4. Duodenum tissue secretes hormones ______ (upregulates bile production + acinar cells) & secretin (upregulates ____ cells)
1. Gastrin (hormone) upregulates (1) chief cells secreting pepsin & (2) parietal cells secreting HCl, therefore increasing breakdown of protein
*goes to duodenum (surrounded by pancreas)*
2. In the pancreas, acinar cells secrete enzymes & bicarb (buffer; controls pH levels).
3. The gallbladder (organ) secretes bile salts to help w/ digestion of fats.
4. Duodenum tissue secretes hormones CCK (upregulates bile production + acinar cells) & secretin (upregulates acinar cells)
Fill in the blanks:
1. Glucose molecules bound by ____ bonds come in as _____ (polymer)
2. Amylase (in mouth & _____) cuts α 1-4 bonds, breaking down starch into disaccharides (e.g. maltose)
3. Maltase: enzyme that breaks up disaccharide maltose into ______
4. Now absorbed through _______ (type of cell) into bloodstream
1. Glucose molecules bound by α 1-4 bonds come in as starch (polymer)
2. Amylase (in mouth & pancreas) cuts α 1-4 bonds, breaking down starch into disaccharides
3. Maltase: enzyme that breaks up disaccharide maltose into glucose molecules
6. Now absorbed through enterocytes into bloodstream
Order the following for emulsification in relation to bile salts:
reassemble back into triaclyglycerides inside enterocyte; these + cholesterol combine w/ proteins to form chylomicrons
free fatty acids diffuse across membrane of enterocyte (no channel bc soluble in membrane) (2 fatty acids, 1 bound to glycerol)
lipase moves in & breaks apart fatty acids note: bile salts recycled in large intestine
exocytosis of chylomicrons into lymph system then blood then liver for redistribution
bile salts insert selves into & disrupt micelles
cholesterol enters by facilitated diffusion (uses special channel)
bile salts insert selves into & disrupt micelles
lipase moves in & breaks apart fatty acids note: bile salts recycled in large intestine
free fatty acids diffuse across membrane of enterocyte (no channel bc soluble in membrane) (2 fatty acids, 1 bound to glycerol)
cholesterol enters by facilitated diffusion (uses special channel)
reassemble back into triaclyglycerides inside enterocyte; these + cholesterol combine w/ proteins to form chylomicrons
exocytosis of chylomicrons into lymph system then blood then liver for redistribution
Fill in the blanks for the formation of HCl in the parietal cells of the stomach:
1. Water dissociates into __ & OH-
2. H+ moves out by ___ into stomach lumen, K+ comes in (from interstitial space)
3. K+ goes back out by _____
4. Carbonic anhydrase forms _____ from CO2 and OH-.
5. HCO3- exchanged out for __ in (from interstitial space).
6. Cl- exits the parietal cell through _____.
7. HCl formed in stomach lumen from accumulated H+ & Cl-.
Water dissociates into H+ & OH-
H+ moves out by HKA into stomach lumen, K+ comes in (from interstitial space)
K+ goes back out by channel
Carbonic anhydrase forms HCO3- from CO2 and OH-
HCO3- exchanged out for Cl- in (from interstitial space).
Cl- exits the parietal cell through a channel/simple diffusion.
HCl formed in stomach lumen from accumulated H+ & Cl-