Shared Flashcard Set

Details

Lipid Digestion and Absorption
Medical School Biochemistry
40
Biochemistry
Graduate
10/19/2011

Additional Biochemistry Flashcards

 


 

Cards

Term
What is the major caloric source of fat in our diets?
Definition
Triglycerides
Term
What is the source of Phospholipids, sterols, sphingolipids, galactolipids, and carotenoids that we ingest?
Definition
Membranes of cells that we eat
Term
What is the average U.S. fat intake?
Definition
120-140 grams a day
Term
How long does it take to absorb dietary fat into the circulatory system?
Definition
Between 2-3 hours
Term
Where are Acid lipases found?
Definition
Lingual glands and Gastric mucosa
Term
The pancreas secrets which lipases?
Definition
Pancreatic lipase-colipase, Carboxy ester lipase, and Phospholipase A2
Term
Acid lipases account for how much lipid digestion in a normal adult?
Definition
between 10-30%
Term
What is the action of acid lipase on triglycerides?
Definition
Tend to cleave one ester bond of a triglyceride leaving a fatty acid and a diglyceride.

Important to note is that the acid lipases can cleave more then one bond but typically only achieve the above action due to timing (compensatory digestion occurs in patients with pancreatic deficiency)
Term
How does the fat emulsify so that acid lipases can work efficiently?
Definition
Hydrophobic interactions combined with gastric contractions help to emulsify the fat
Term
What triggers the release of CCK?
Definition
Fatty acids from acid lipase lipolysis
Term
What is the function of CCK?
Definition
To trigger release of pancreatic juice and bile salts
Term
How do newborns digest fat, given that they do not have high levels of pancreatic enzymes?
Definition
Compensatory action from acid lipases as well as human milk lipase
Term
In patients with pancreatic insufficiency, what happens to enzymatic activity?
Definition
Compensatory action from acid lipases allows for some absorption of fat (not as efficient as pancreatic lipases, but higher activity than normal)
Term
What type of action does the Pancreatic lipse-colipase system have?
Definition
This enzyme will only cleave the 1 or 3 ester bond making 2 fatty acids and a 2-monoglyceride
Term
What is the optimal pH for Acid lipases?
Definition
4
Term
What is the optimal Ph for Pancreatic and milk lipases?
Definition
7
Term
Gastronoma's can have what effect on lipolysis enzymes?
Definition
Gastronoma's can end up secreting gastric acids in areas of pancreatic digestion. This can denature the pancreatic enzymes
Term
What is the effect of bile salts on Pancreatic lipase?
Definition
Diminishes action of Pancreatic lipase
Term
What is the function of colipase?
Definition
To help reintroduce pancreatic lipase when displaced by bile salts
Term
What is the action of Carboxyl esterase?
Definition
Non-specific like acid lipases. The end result of lipolysis by Carboxyl esterase is 3 fatty acids and glycerol. This enzyme can also lipolzye cholesterol esters
Term
What is the action of phospholipase A2?
Definition
Will work on phospholipids cleaving off one fatty acid
Term
What is the effect of bile salts on Carboxyl ester lipase and phospholipase A2?
Definition
activity increases because the enzymes cannot to favorably reach the bonds until they are in micelles
Term
What do bile salts disperse?
Definition
the PRODUCTS of lipolysis. You will not find triglycerides in bile salts
Term
Besides helping Carboxyl ester lipase and phospholipase A2, what other important effect do bile salts have on fat digestion?
Definition
Greatly increase the water solubility of fatty acids
Term
What other important factors can "hitch a ride" on the fatty core of bile salt micelles?
Definition
cholesterol, drugs, carcinogens, etc
Term
What is the effect of consuming plant sterols on dietary cholesterol absorption?
Definition
Plant sterols compete with cholesterols reducing the amound of cholesterols that are taken up
Term
What happens in the cyle of bile salts?
Definition
Highly conserved, very low levels of bile salts are lost in the feces but the liver readily replaces it
Term
Where is active absorption of bile salts taking place?
Definition
Distal ileum
Term
Where is active absorption of fat occuring in the intestine?
Definition
No where, it is all passive absorption
Term
What are the three enzymes of TG Synthase?
Definition
Acyl-Coa Synthetase, MG-acyltransferase, DG acyltransferase
Term
What is the function of Acyl-Coa synthethase?
Definition
Attaching an SCoA to a fatty acid, making an "Active fatty acid"
Term
What are the two pathways of triglyceride synthesis?
Definition
Via TG synthethase or via Phosphatidic Acid
Term
What is the path of Chylomicrons?
Definition
Travel along lymphatic system and dump into the subclavian vein where they then make their way towards the liver
Term
How do fat soluble vitamins and carcinogens travel across the intestinal membrane?
Definition
Via the bil-salt micelles
Term
What are the three general ways you can have fat malabsorption?
Definition
Intraluminal

Mucosal

Lymphatics
Term
What are the common intraluminal defects?
Definition
Lipase/colipase deficiency

miceller dispersion
-bile salt issues
pH regulation
Term
Whats the most common cause of chronic pancreatitis?
Definition
chronic alcoholism
Term
What are the effects of chronic pancreatitis?
Definition
decreased pancreatic HCO3 causing pH disregulation

pancreatic enzymatic insufficiency
Term
What percent of lipase action do you need to lose before you have an noticable effect on fat absorption?
Definition
More than 80% percent
Term
What is unique about fat absorption of medium chain length fatty acids?
Definition
Can pass through the membrane via diffusion and therefore do not need to be converted
Supporting users have an ad free experience!