7 - Lipids 1 Flashcards
What is a lipid generally?
What types of lipids are there most commonly in the body?
What is the difference between saturated and unsaturated fatty acids?
The omega nomenclature is almost exactly the same as the delta nomenclature, the only differences being: Carbons are counted from the methyl (omega) end instead of the carboxylic acid end. The omega symbol is used instead of the delta symbol.
What is the structure and function of triacyglycerols?
*The storage form of lipids
* Obtained from diet or synthesized
* Formed by a process called esterification
*triacylgycerols stored in solid form as fat in adipose tissue
What is the structure and function of phospholipids?
Phospholipids have clinical significance with use in liposomes.
What is the structure and function of Cholesterol?
Explain the digestion and absorption of fat in detail.
Dietary fat is mainly comprised of:
* Triacylglycerol (roughly 90%)
* Cholesterol
* Cholesterol esters
* Phospholipids
* Non-esterified fatty acids * Digestion of triacylglycerol to fatty acids begins in the stomach
and is completed in the small intestine
* Medium- and short-chain fatty acids are directly absorbed into
the portal vein
* Long-chain fatty acids need to be resynthesized to triacylglycerol
Ingested fats forms a large structure called fat globules in the small intestine
* Fat globules limit the action of water-soluble digestive enzymes
* Pancreatic lipase (hydrophilic) breaks down triacylglycerols
* Dietary fats need to be emulsified before digestion.
* Liver produces bile
* Bile includes Bile salts, Phospholipids, Cholesterol, Amino acids, and Steroids.
Where and when is fatty acid synthesis performed?
How is fatty acid synthesis performed?
Addition of 2 carbons per synthetic cycle. It is a two-stage process: Stage 1: Uses acetyl-CoA to form malonyl-CoA Stage 2: Elongation of the fatty acid chain (Fatty acid synthase)
Synthesis beyond 16 carbons occurs in the endoplasmic reticulum with Palmitic acid (16:0) serves as main substrate
-10 carbons or more
-Unsaturated fatty acids
Fatty acid elongase enzymatic complex
-Similar to fatty acid synthase
-CoA instead of ACP
* Goal: to produce elongation of very-long-chain fatty acids (22-24 carbons)
Chain Desaturation:
Fatty acyl-CoA desaturase enables the addition of double bonds in long-chain fatty acids.
How is Acetyl Co-A transported to the cytosol for fatty acid synthesis?
malate shuttle
How are triacyglyercols synthesized and stored in the body?
Dietary and endogenous fatty acid are converted to triacylglycerol and mostly
stored in adipose tissue.
* Dietary fatty acid is synthesized into triacylglycerol which is transported by chylomicrons
* Endogenous (De novo process) fatty acid synthesized to triacylglycerol is transported by
Very-low-density lipoprotein (VLDL)
* Production of triacylglycerol requires adding a phosphate group to glycerol and involves phosphatic acid as an intermediate.
* The source of glycerol 3-phosphate in both liver and adipose tissue comes
from glucose metabolism, but adipose tissue lacks glycerol kinase, becoming unable to convert free glycerol
Enzyme: Phosphatidic acid phosphatase forms Diacylglycerol
Enzyme: Diacylglycerol acyltransferase forms triacylglycerol
Endogenous triacylglycerols packed into VLDL
VLDL assembled in the
endoplasmic reticulum and released into blood stream to deliver triacylglycerols to adipose tissue
How are triacylglycerols transported in the body?
- Chylomicrons (dietary fat) and VLDL (endogenous fat) systemically travels to
deliver triacylglycerol to adipose tissue. - Chylomicrons and VLDL are acted upon an enzyme called Lipoprotein Lipase
(LPL). - LPL is synthesized and secreted by the adipose tissue → Insulin regulates this mechanism.
- Interestingly, skeletal muscle
has LPL, but insulin inhibits its
activity.
