Digestion and Absorption of Lipids Flashcards
what are molecules of fat?
triglycerides, cholesterol, phospholipids
what does aqeous chyme leaving the stomach contain?
coarse emulsion of large fat droplets
what does bile salts do in small intestine?
increase surface area for enzymatic fat digestion
Bile salts are amphipathic what does this mean?
hydrophic and hydrophilic region
what is enzymatic fat digestion carried out by?
lipases - remove 2 fatty acids from each triglyceride molecules
How does bile salt coating intestinal emulsion complicate digestion?
lipase cant penetrate bile salts
what does fat digestion require?
colipase a protein cofactor secreted by the pancreas it displaces some bile salts allowing lipase access
what are phospholipids digested by?
pancreatic phospholipase
What fat is not digested but absorbed?
free cholesterol
What does digestion of fats coalesce to make?
small micells
What do micelles do?
enter unstirred aqueous at edge of brush border
how are fatty acids and monoglycerides absorbed?
simple diffusion as move out of micelles and diffuse across enterocyte
what does ezetimibe drug do?
inhibit cholesterol absorption by blocked NPC1L1 transporters
where do monoglycerides in enterocytes move to?
SER to recombine to triglycerides which join cholesterol to form chylomicrons
How are chylomicrons transported?
Packaged into vesicles by golgi and leave cell by exocytosis
What are chylomicrons absorbed by?
lacteals the lymph vessels of the villi into the venous blood
where does most water absorption take place?
in small intestine and 0.5L in the colon
Where does absorption of nutrients do?
moves solute from the lumen of intestine to the ECF creating an osmotic gradient that allows water to flow
what do enterocytes and colonocytes absorb?
na using 3 membrane proteins
How does K and H2O absorption occur?
in the intestine by paracellular pathway
what is route for most drugs?
non-ionised form absorbed by simple passive diffusion
What are osmotic factors for fluid accumulation in intestinal lumen?
faulty nutrient digestion and absorption which increase osmotic pressure in lumen
What is faulty water absorption due to?
from defective ion transport
what is active fluid secretion due to?
capacity of colon to absorb
how to treat acute diarrhoea?
oral rehydration therapy 8 tsp of sugar, 1 tsp salt and 1 litre of water
