Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
21 Cards in this Set
- Front
- Back
|
۞ ----- Dietary lipids
|
• Triacylglyceride most common dietary fat
• Glycerol backbone esterified with mostly long chain fatty acids • Western diet average intake > 100 gms fat/day > 900 calories from fat/day • Average 40% calories from fat • Recommendation is < 30% calories from fat • Include dietary fat soluble vitamins – A, D, E, K • cholesterol intake usually less than 1 gram • more cholesterol is made in the body than eaten |
|
|
۞ -----Digestion of lipids
STOMACH |
• Stomach
* gastric lipase action (acid lipase) highest activity at low pH ** Hydrolyzes triglycerides – medium chain faster than long chain *** Milk contains a lot of short and medium chain fatty acids that are broken down by acid lipase **** Acid lipase does not hydrolyze cholesterol or phospholipid esters ***** Lipid droplets enter the small intestine at less than 0.5 mm diameter |
|
|
۞ ----- digestion of lipids
Small intestine. DUODENUM |
* acid lipase is still active at pH of 6-7 and continues to hydrolyze fatty acids
** acid lipase prefers to cleave the fatty acid in position 3 leaving diglycerides *** grinding and mixing help emulsify the fat o Pancreatic lipase works primarily esterified fatty acids on position 1 and 3 of the glycerol backbone leads to monoglycerides Bile salts block pancreatic lipase Cofactor colipase helps bind the lipid and pancreatic lipase in the presence of bile salts |
|
|
۞ -----digestion of lipids
SM INT PHOSPHOLIPIDS |
• Phospholipids are digested by phospholipase A
o Release fatty acid from 2 position |
|
|
۞ -----digestion of lipids
SM cholesterol |
* Only free cholesterol can be absorbed (10-15%). The rest is the cholesterol ester
* Cholesterol esterase hydrolyzes cholesterol ester to free cholesterol ** Cholesterol esterase pancreatic enzyme *** Cholesterol esterase has non-specific activity: hydrolyzes • All 3 fatty acids positions in triglycerides • Cholesterol esters • Phospholipid esters • Esters of vitamin A and D • Activity stimulated by bile salts |
|
|
۞ -----digestion of lipids
Uptake of lipid by enterocytes |
• Digestion of triglycerides, phopholipids and cholesterol esters leaves;
o Monoglycerides o Fatty acids o lysophosphatidylcholine o cholesterol • lipids must pass through a water layer over the villi to be absorbed – more vigorous mixing increased absorption • lipids are solubilized in bile salt micelles (mixed micelles)– natural detergents cross the unstirred water layer (***this makes the free cholesterol and phospholipids soluble in the water layer) |
|
|
۞ -----digestion of lipids
Uptake of lipid by enterocytes 2 |
• Two methods of uptake by the enterocyte
o Passive uptake o Carrier mediated uptake • Once inside the enterocyte passive diffusion of lipids to the intracellular compartment • Rapid reesterification of lipids to triglycerides, phopholipids and cholesterol esters occurs by enzymes in the endoplasmic reticulum – this favors continued uptake of lipids by passive diffusion • Prepared for export as chylomicrons • Glycerol and scfa are taken up by diffusion • There appears to be binding proteins that may help in the uptake of lipids but true role is not known at this time |
|
|
۞ -----digestion of lipids
Fat soluble vitamins |
• Solubilized in mixed bile salt micelles
• Taken up either diffusion or could be a specific carrier (unknown) |
|
|
۞ -----digestion of lipids
Intestinal Lipoproteins |
• Lipid-protein complex prepared in the intestine and liver for transport of lipids from these organs
|
|
|
۞ -----digestion of lipids
Types of lipoproteins |
1. chylomicrons
2. VLDL very low density lipoprotein are triglyceride rich 3. HDL, high density lipoprotein |
|
|
۞ -----digestion of lipids
Apoproteins |
helpers signaling lipids how to go and where to
|
|
|
۞ -----digestion of lipids
lipoproteins |
Chylomicrons and VLDL are made in the small intestine. After high fat meal;
• Amount of chylomicrons and VLDL remains constant • Enterocyte fills each chylomicron with more triglyceride making them larger and lighter |
|
|
۞ -----digestion of lipids
DETERMINATION |
Intestinal lipid malabsorption
• Determine the amount of fat in stool • Normal < 6 gms/24 hrs or <5% of fat consumed |
|
|
۞ -----digestion of lipids
Conditions that lead to fat malabsorption |
celiac/ sprue
pancreatic deficiency bile salt deficiency abetalipoproteinemia chylomicron retention disorder |
|
|
۞ -----digestion of lipids
Conditions that lead to fat malabsorption • Celiac/sprue |
intestinal lesions caused by gluten
|
|
|
۞ -----digestion of lipids
Conditions that lead to fat malabsorption • Pancreatic deficiency |
o Abdominal pain and steatorrhea (large, pale, frothy stools)
o Removal of pancreas or due to disease o Low fat diet and pancreatic enzymes |
|
|
۞ -----digestion of lipids
Conditions that lead to fat malabsorption • Bile salt deficiency |
liver disease or gall stone disease
|
|
|
۞ -----digestion of lipids
Conditions that lead to fat malabsorption • Abetalipoproteinemia |
Apo B is needed for formation and secretion of B-containing lipoproteins – genetic defect. Apo-B is made but doesn’t work
|
|
|
۞ -----digestion of lipids
Conditions that lead to fat malabsorption • Chylomicron retention disorder |
failure to release pre-chylomicrons from the golgi –derived vesicles into the intercellular space through exocytosis. Absence of chylomicrons in the intercellular spaces
|
|
|
۞ -----digestion of lipids
Intestinal injury |
• lcfa can lead to injury in developing intestine. Injury reversible. (shown in pigs)
|
|
|
۞ -----digestion of lipids
Satiety of fat |
evidence that intake of fat leads to satiety and inhibition of food intake
• ******mainly lcfa which are transported via chylomicrons while mcfa are transported via the portal blood***** • fatty acids added to the small intestine have a greater effect than fatty acids given peripheral vein • satiety is abolished by orlistat an inhibitor of pancreatic lipase • apo-IV synthesis and secretion stimulated by digestion of fat o it acts on CNS to give feeling of satiety o also has a role in digestion; inhibits gastric emptying and gastric acid secretion |
