Section 7: Digestion and Absorption of Carbohydrates and Protein Flashcards
Which complex molecules can be absorbed directly across the epithelium
none, not through cell membranes or tight junctions
Enzyme locations for digestion and absotption of carbohydrates:
brush border and lumen
Final acts of digestion enzymes are here:
brush border
Which glucose bonds are harder to break?
1,6
Enzyme in carbohydrates breakdown:
alpha amylase of pancreas, alpha dextrinase and glucoamylase
Fructose + Glucose:
sucrose
2 transport proteins;
glucose carrier and fructose carrier
test of carrier mediated transport:
transported against concentration gradient, tube in rabbits stomach, infuse bolus of glucose solution, lumen of stomach now has high glucose concentration, glucose concentration higher in lumen than blood, no glucose after 90 minutes. Below dotted line = active transport
Glucose sugar levels:
90 mg percent (90 mMol)
What sugar will be absorbed preferentially over glucose?
galactose
Can provent functions of glucose carrier required for absorption:
oubain (poison), depeds on metabolic enegy, lumen Na+ depeneded
Glucose and galactose on this protien:
SGLT
What is SGTL:
cotransporter, one is not transported without the other
Glucose is moved out on the basolateral side via this:
GLUT 2
Ouabiain blocks:
the Na/K pump, Na increases in the cell, prevents glucose transport
True or False? Transport of glucose is concentration dependent.
F
fructose transport
can’t go against a concentration gradient, can’t be poisoned by oubain, no ATP involved, no sodium involved, ,
Which basolateral transporter moves fructose out of the cll?
GLUT 2, facilitated diffusion
True or False? lactose intolerabitliy leads to a decreases in luminal osmolarity.
F. increase
True or False? Fluid accumulates in the lumen of the stomach in people with lactose intolerance.
T
What are the more immediate issues that lead to diarrhea for lactose intolerant people?
luminal distension and enhanced peristalsis
Where do bacteria attack lactose in the gut?
small and large intestines
Liters of water entering the intestines each day:
8-10L (check)
True or False? High fructose corn syrup is worse for you than sugar.
F
Sugar is high in __ and low in ___:
calories, nutriiton
Dietary fibers:
cellulose, hemicelluose, or pectins
These enzymes don’t absorb cellulose, hemicelluose, or pectins
pancreatic or brush border enzymes
Organic anions of dietary fiber are:
osmoticaly active, less likely to be constipated
Bacteria break fibers dow to:
short chain fatty acids, H2, CO2, and methane
Short chain fatty acids that fiber is broken down to:
acetate, propionate, butyrate
True or False? None of the short chain fatty acids that are produced by the break down of fibers are absorbed.
F. Some are
Toxins produced by bacteria can cause:
secretory diarrhea
Protiens in the lumen:
125gm/day or 20% of the diet in U.S.
Amount of protein enzymes in the lumen per day:
30 mg/ day
This makes up 25 mg/day of the protein in the lumen:
dead epithelial cells
Turnover rate of epithelial cells in the lumen:
5 days
5 carriers in the proximal intestines:
Neutral AA’s, Basic AAs, Acidic AAs, Imido AA, Di- and tri-peptides
First real protease:
pepsin
What enzyme does most of the work of breaking proteins down?
pancreatic protease
Enzymes involved in protein digestion:
pancreatic protease and pepsin
Bile acids, and water soluble amino acids are returned via:
hepatic portal vein
What peptidases break down the smaller peptides?
intracellular
Characteristics of amino acids absorption:
transport aginst a concentration gradient, competition between amino acids, poisoned by ouabia (Na is involved), depends on metabolic energy to be absorbed, depend on luminal sodium
Amino acids absorption in the duodenum and jejunum:
Na coupled, proved by polarizing epithelial cells, Na/K pump always on the basolateral side
True or False? Amino acids acid absorption is always transported via this type of transport:
secondary active transport
Vitamin B12 is aka:
Cobalamin
Vitamin B12 is needed for:
making rbc
only thing the stomach does that is required for living
intrinsic factor secreted by parietal cells to absorb B12 in the blood
How is CBL broken down in the stomach
pepsin and the acidity of the stomach
Vitamin:
essential to live, you can’t make yourself
What cells secrete intrinsic factor?
parietal cells
What is secreted by gastric glands which then binds to cobalmin
Haptocorrin,
What is required for the absorption of B12?
intrinsic factor
Pernicious anemia:
large, odd red blood cells that get stuck in the capillaries, feed raw liver, they get better
When is CBL released into the small intestines?
proteolyic degradation of haptocorin
Why did the liver make the patients better?
store of B12 in the liver
What are absorbed in the jejunum?
Trigycerides, fat soluble vitamins, cholesterol, and lecithin
When is most absorption done?
mid jejunum
Why are fats harder to digest?
not water soluble
Reabsorbed in the ileum:
bile salts and V12
What sugars make up the largest and smallest components of our diet?
sucrose (30%) and lactose (6%)
