Chapter 29 Lipid Metabolism Flashcards
What is the role of bile salts in lipid digestion?
They act as detergents, binding to the globules of dietary fat as they are broken up by the peristaltic action of intestinal muscle. The emulsified fat has increased surface area for subsequent attack by pancreatic enzymes.
What hormones are effected when acidic stomach content enters the duodenum of the small intestine, and what are their roles?
The gut hormone cholecystokinin is secreted by intestinal cells when stomach content enters the intestine. The peptide hormone secretin is also released by the small intestine in response to acidic materials. Secretin signals the liver, pancreas, and certain intestinal cells to secrete bicarbonate, which raises the pH of the intestinal lumen to ~6, optimal for intestinal digestive enzymes.
What pancreatic enzymes digest triglycerides and how?
Pancreatic lipase cleaves triacylglycerol at positions 1 and 3, producing free fatty acids and 2-monoacylglycerol. Cholesterol esterase removes fatty acids from compounds (such as cholesterol esterases), and phospholipase A2 digests phospholipids to a free fatty acid and a lysophospholipid.
Describe the pathway for bile salt synthesis and recycling in the digestive system.
Bile salts are synthesized in the liver, stored in the gallbladder, secreted into the small intestine, resorbed in the ileum, and returned to the liver via enterohepatic circulation.
What is the biochemical significance of the lower Km of the LPL in the capillaries of muscle cells than adipose LDL?
Muscle cells can obtain fatty acids from blood lipoproteins whenever they are needed for energy, even if the concentration of lipoproteins is low.
Where does the main route for digestion of triacylglycerols occur and what does it involve?
Occurs in the lumen of the intestine and involves hydrolysis to fatty acids and 2-monoacylglycerol
What do lingual and gastric lipases hydrolyze?
short and medium chain fatty acids from dietary triacylglycerols
The contraction of the gallbladder and secretion of pancreatic enzymes are stimulated by what gut hormone?
Cholecystokinin
An increase in pancreatic lipase may indicate what diagnosis?
acute pancreatitis
What are chylomicrons major component?
triacylglyceride derived from the diet
also contain cholesterol, and fat soluble viatmins
What are the fat soluble vitamins?
A,D,E and K
What is the major apolipoprotein associated with chylomicrons as they leave the intestinal cells?
B48
What is Olestra and what effects does it have on the body?
Olestra is an artificial fat substitute that is supposed to make food taste good without having the calories of fat. Olestra is resistant to hydrolysis so it passes through the digestive system unimpeded & carries fat-soluble vitamins with it. Olestra is supplemented with these vitamins but the side effects of cramping and diarrhea decrease the popularity.
Why is isolated heparin frequently used as an anticoagulant?
BEcause it binds to antithrombin III (ATIII) and the activated ATIII then binds factors necessary for clotting and inhibits them from working.
