Section 7: Digestion and Absorption of Fats Flashcards
LA funeral director takes in about __ times as much fat as Japaneses coal miner
5
True or False? About 75% of consumed fats is absorbed.
F. nearly all
What percent of consumed fat is secreted in feces?
0%, excreted fats come from bacteria
What produces fat in the feces?
bacteria
Steatorrhea is more than __ gm/day of fat in the feces:
6gm/day
Organs involve in fat absorption and digestion:
liver, gallbladder, duodenum, ileum, portal blood supply
Most dietary fats are :
triglycerides
What are the 2 parts to fat digestion?
in lumen, in intestinal epithelial cells
In which part of the small intestines does the emulsification of fats take place?
the lumen
Bile salts + ? help emulsiy:
lecithin (phospholipid)
What aide in the emulsification of fats?
mixing by smooth muscle and HCO3- -rich fluid from pancreas and liver
Emulsification work best within this pH range?
6-8.5
Function of emulsification:
increases surface area
These are both secreted from the pancreas and function in fat digestion:
lipase and colipase
Functions of collapse:
aids in lipase attachment, allows lipase to work at lower pH, and prevent inactivation of lipase by bile salts
The long chain end of this compound is on the inside of the emulsion droplet:
lecithin
Lecithin and phoshoplipids involved in fat breakdown are secreted from:
the liver
emulsion droplets are broken down to:
glycerol, monoglycerides, and fatty acids
Amphiphilic molecules of fat digestion that can be incorporated into micelles:
detergent molecules, benzene, long-chain alcohol, conjugated trihyroxy bile sale, cholesterol, lecithin
True or False? Glycerol is fat soluble.
F. Water soluble
Contents of mixed micelles:
2-monoglycerides, free fatty acids and some fat-soluble vitamins
What favors the incorporation of fat digestion products into micelles?
high concentrations of amphiphilic compounds in bile
The concentration at which micelles form:
critical micelle concentration
When and where do mixed micelles form?
at very low concentrations of bile acids, cholesterol and lecithin in the lumen of the small intestine or in the lumen of the gallbladder (especially overnight when bile is concentrated)
Can micelles difuse through the unstirred layer?
Yes
High concentration of micelles mead rapid diffusion of fats through this layer to the epithelium
unstirred layer, into enterocyte via brush border
Compounds that can cross from the lumen into the intracellular space of epithelial cells:
glycerol, monoglyceride, fatty acid, lysolecitihin and cholesterol
Compounds that can combine to form chylomicrons in the intracellular space of epithelial cells:
triglycerides, lecithin, cholesterol esters, and free cholesterol
How do chylomicrons exit the epithelial cell of the lumen?
exocytosis, then pass through large inter endothelial channels of lymphatic capillaries and enter the lymph
fat soluble vitamins are absorbed via this pathway:
micelle-chylomicron pathway
True or False? Fat soluble vitamins are digested by lipase.
F
What’s left of micelles after absorption of fat digestion products, cholesterol and lecithin?
bile acids
Can conjugated, unconjugated, or both types of bile acids be absorbed in the ileum?
both, unconjugated: diffusion, conjugated: ASBT (apical sodium bile acid c-transporter)
ASBT stands for:
apical sodium bile acid c-transporter
Via which type(s) of transport does the absorption of bile acids in the ileum take place?
diffusion and secondary active transport
How do bile acids travel from the cells of the ileum to the liver
OSTalpha-OSTbeta (Farnesoid X Receptor?) on the basolateral membrane to the portal blood to the liver
What type of circulation is used for bile acids?
enterohepatic circulation
Bile acids enter ___ at from the ileum while fat and fat-soluble vitamins enter ___ at the earlier part of the lumen.
portal blood, lymph
Most plan and animal fats are thyroid gland made up of __ and ___ fatty acids.
C14 and C18
short chain fatty acids are fatty acids of less than __- carbon length.
12
Where do we get our supply of short chain fatty acids?
diet or produce by bacteria in the distal intestine.
In which part of our body do bacteria produce short chain fatty acids?
distal intestines
Are short chain fatty acids absorbed via the micelle-cyloiicron pathway?
no
Where are short chain fatty acids absorbed and list 3:
colon: acetate, proppionate, butyrate
How do short chain fatty acids get into the cell in the colon?
Either exchanger or diffusion, i.e. SCFA-/HCO3- or butyrate/ Cl-
the short chain fatty acids that enter the intracellular space of cells in the colon enter via this type of diffusion:
nonionic
True or False? Cholesterol and lecithin are both reabsorbed in the earliest part of the ileum.
F. latest part of the jejunum
List 3 ions that are absorbed past immediately past the stomach and before the entry of bile and pancreatic enzymes:
Ca2+, Mg2+, and Fe2+
normal dietary fat absorption is ___% efficient.
100%
True or False? Absorption of conjugated bile acids in the large intestines is active.
T
Immediately past the pancreas fats are hydrolyzed to free fatty acids and ____
2-monoglycerides
How many calories does one gram of fat contain?
9 calories
How many calories does 1 gram of carbohydrates/ protein have?
4
Drug that helps block fat absorption in the body and mechanism of action:
Xenical (orlistat), binds to lipase blocking triglycerides from absorption, creating a calorie deficiency, hydrogenated derivative of lipstatin
What is lipstatin a natural product of?
Streptomyces toxyricini
Common side effect of alli:
orange fatty discharge (looks like pizza grease), stomach pain, problems controlling bowel movements
What can a long term diet too low in fat cause?
depression, skin problems and battle hair and can block absorption of “good” fats like Omega-3’s
