Lecture 3 Flashcards
Primary source of lipids in humans come from ___
Diet
Outside of Diet, what are other sources of lipids?
Endogenous biosynthesis
Synthetic lipid sources
intra-lipids
What are esterases
Digestive enzymes that digest lipid via hydrolysis of ester bonds
3 types of esterases
Lipases (TG)
Phospholipases (phospholipids)
Cholesterol esterases (cholesteryl esters)
Where is lingual lipase found?
In serrous gland under the tongue
Where is gastric lipase formed?
By chief peptic cells
Lingual and gastric lipase are important for what two things?
Milk fat digestion and cystic fibrosis (
In cystic fibrosis whats the issue?
No pancreatic enzymes
Lingual and gastric lipase are stable under what ph
4-6
Milk TAG are esterified at the what position?
sn-3
When Milk TG are esterified what is formed?
DAG, MAG, and a FFA
Does emulsification occur in stomach?
Some
What is slightly emulsified in stomach?
GLycolipid action
dietary proteins
phospholipids
Undigested fat in the stomach causes release of what?
Secretin
What does secretin do?
Stimulate pancrease to release digestive enzymes out the acinar cell, and slow down gastric motility and emptying
Name exocrine portion of pancreas
Acinar cells
Duct cells
Is insulin beta or alpha?
beta
Where is bile made?
Liver
When gallbladder contracts bile is released where?
Into cystic duct which joins the common bile duct
What does bile do?
emulsify fat
What part of small intestine absorbs bile and returns to liver via hepatic portal vein?
illeum
Stimulation of lipase is secreted how?
neural (sympathetic agonists)
Dietary (high fat)
Mechanical (suckling and swallowing)
Fats are emulsified via what action?
hydrolysis
Does emulsification increase or decrease surface area of lipid droplets?
Increase
2 things that digest fat?
Intestinal endopeptidases and pancreatic lipase
What stimulates gallbladder contraction and release of bile salt?
CCK
WHen is CCK released
presence of lipids and proteins
Does CCK increase or decrease gastric motility?
decrease
What makes secretin?
S-cell
S-cell causes release of what?
sodium bicarbonate to alkalyze fat
What type of properties does bile salt have?
Amphipathic
Emulsification occurs via what?
peristalsis and detergent effect
Bile emulsifies fat forming what?
micelles
TAG are too large to be taken up by enterocytes and are acted upon by what?
esterases and pancreatic lipases
When TAG are broken down by pancreatic lipases and esterases it removes FA at what points?
C-1 and C-3
Forming DAG, FFA, and then 2 monoacylglycerols
Pancreatic protein which anchors pancreatic lipase
Colipase
What is colipase’s zymogen?
and what activates it?
procolipase
Trypsin in the lumen of duodnum
cholesterol in food are in what form?
Free and nonesterified
What blocks enzymes to prevent fat abosrption and cause weight reduction?
Orlistat
What does orlistat do?
prevent fat absorption
What does cholesterol esterase from pancreas do?
Hydrolyze cholesterol ester and to cholesterol and FFA
Phospholipase 2 turns to what and activated by what?
phospholipid degradation
trypsin
Phospholipid degradation does what?
Removes FA from carbon 2 on phospholipid forming lysolecithin (lysophopholipid)
What forms micelle?
cholesterol
FFA
Lysophospholipid
2monoacylglycerol
are micelles positive or negatively charged?
negative
What do micelles interact with?
Microvilli and empty their contents into enterocytes
FFA, medum and short chain FA are absorbed how?
directly into enterocytes and into portal blood to bind to albumin which takes the to liver
MAG, DAG, and FFA that enter enterocyte (Diffusion) are carried where?
Endoplasmic reticulum where acyltransferase transfers CoA-FA onto them
When cholesterol is absorbed and facilitated by transfer proteins such as Niemann Pick C1 transporter, what drug has showed inhibition of cholesterol absorption?
ezetimibe
How are TG resynthesized
Acyl-CoA syhtetase (thiokinase) adds acyl co-a on FA (loves LCFA)
The 2 MAG is converted by TAG synthase using acyl-coa
What esterifies Cholesterol in ER
Acyl-CoA (ACAT1 and ACAT 2)
don’t esterify plant sterols only cholesterol
What converts lysophopholipids to phospholipids?
Acyl-transferase
TAG in liver can be made in enterocytes by what?
A-glycerophosphate
How is A-glycerophosphate made?
adding PO4 to glycerol or from reducing DHAP
Where are fat soluble vitamins resynthesized?
ER
exported from enterocyte via exocytosis as portion of chylomicrons
Once micelles are packaged in ER they are tagged with what inside the enterocyte?
Apo B-48 and then Apo A-4
then transferred to HDL
Once micelle leave ER it goes where?
Golgiapparatus where CHO is added
FABP is needed for what?
synthesis of TAG,MAG,DAG
chylomicrons enter what?
Via exocytosis lacteals thoracid duct left subclavian circulation
where are apolipoproteins made?
liver
HDL with chylomicron attach what to it?
Apo C2 and Apo E
Apo C2 and Apo E are recognized by what?
lipoprotein lipase on adipocytes and liver cell receptors
What breaks down TG in chylomicron?
lipoprotein lipase in skeletal muscle and adipocytes
also in kidney heart and liver
what makes lipoprotein lipase?
skeletal muscles and adipocytes