Lecture 3 Flashcards
What are lipids? 5 Common classes of lipids?
Heterogeneous group of water insoluble (hydrophobic) organic molecules
Fatty acids, triacylglycerol, glycerophospholipid, steroid, sphingoglycolipid
Where do lipids begin digestion and are catalyzed by?
Digestion of lipids begin in the stomach and are catalyzed by lipase. Primary target is TAGs
Emulsification of lipids occurs in what part of the small intestine and carried out by what?
Occurs in the duodenum and is carried out by bile salts
Different types of pancreatic enzymes along with what/how they degrade
Pancreatic lipase - TAG (Removes FAs at C1 and C3)
Cholesterol esterase - Cholesterol esters (Hydrolyzed to cholesterol and free FAs)
Phospholipase A2 - Phospholipids (Removes 1 FA from C2 leaving a lysophospholipid)
Lysophospholipase - Phospholipids (Removes the FA at C1 leaving a glycerophosphoryl base)
2 Hormones that control lipid digestion in small intestine and how they do so.
Cholecystokinin - triggers your gallbladder and pancreas to contract so they can deliver bile and enzymes to your duodenum to help break down the food for absorption (Food is held longer in stomach)
Secretin - regulation of gastric acid and stimulates the secretion of bicarbonate
Where is the primary site of lipid absorption of the enterocytes?
The brush border membrane
What is inside a mixed micelle?
Lipids along with bile salts and fat soluble vitamins
What is the activating enzyme of fatty acids? What is the activated form of that fatty acid?
Fatty acyl-CoA synthetase (Thiokinases) activates long-chain fatty acids into fatty acyl-CoA (Activated form)
Chylomicron contain what? What is the relative position of them to one another
Contains TAG and cholesterol ester with TAGs being on the outermost position (of the inside)
What does lipid malabsorption result in?
Causes steatorrhea (Lipid in the feces)
What are chylomicrons surrounded by?
-Phospholipids
-Unesterified cholesterol
-Apolipoprotein
How are particles released from enterocytes and into where?
Released by exocytosis and into the lacteals (lymphatic vessels originating in the villi of the small intestine)
Why do chylomicron particles not pass through blood vessel instead of the lymphatic system?
Chylomicron particles are too large to pass through blood vessels
Where are the dietary lipids used by the tissue?
-TAGs are broken down in capillary beds of skeletal muscle and adipose tissues
-Fatty acids are taken up by muscle cells and adipocytes
-Glycerol is used almost exclusively by the liver to produce G3P to enter glycolysis or gluconeogenesis by oxidation to DHAP
-Remaining chylomicron components are taken up by the liver and hydrolyzed to their component parts
What are the digestive products produced from the small intestine?
Free fatty acids (Short, medium, long-chains)
Cholesterol
2-Monoacylglycerol
Structure of fatty acid
Hydrophobic hydrocarbon chain with terminal hydrophilic carboxyl group
(Amphipathic molecule)
Monocarboxylic acids that typically contain hydrocarbon chains of variable lengths( between 12 and 20 or more)
-Numbered from the carboxylate end
More than 90% of the FAs found in plasma are in the form of what?
Fatty acid esters (primarily TAGs, cholesteryl esters, and phospholipids contained in circulating lipoprotein particles)
What does albumin do?
Albumin (water soluble protein) transport unesterified (free) fatty acids in the circulation
What are saturated and unsaturated fatty acids?
Saturated FA - contain only carbon-carbon single bonds
Unsaturated FA - contain one or more double bonds and can be cis (more common) or trans isomeric forms
Cis Unsaturated FA cause a inflexible kink so they don’t pack as tightly together and have lower melting point (liquid at room temp)
Longer the hydrocarbon chain, higher the melting point
If a fatty acid has more than one double bond, how is it oriented?
They are always spaced at 3 carbon intervals
How to identify Arachidonic acid, 20:4 (5,8,11,14)
Linoleic acid 18:2 ω-6
Arachidonic Acid:
20 Carbons long
4 Double bonds between C5-6, C8-9, C11-12, and C14-15
Linoleic acid:
18 Carbons long
2 Double bonds starting 6 carbons away from the end
Know palmitic acid, linoleic acid, a-linolenic acid, and arachidonic acid
Palmitic acid 16:0 (Structural lipids and TAGs contain primarily fatty acids of at least 16 carbons)
Linoleic acid 18:2 (9,12) (Omega 6) and a-Linolenic acid 18:3 (9,12,15) (Omega 3) - Essential fatty acids (not produced by body)
Arachidonic acid 20:4 (5,8,11,14) - Precursor of prostaglandins
Where does fatty acid synthesis occur in adults?
-Mainly in liver
-Lactating mammary glands
-Adipose tissue (to a lesser extent)
Where does fatty acid synthesis occur and where do the carbons come from?
Occurs in the cytosol and incorporates carbons from acetyl CoA using ATP and NADPH
Synthesized by the repetitive addition of two-carbon units to the growing end of the hydrocarbon chain