Lipids Flashcards
What are lipids?
A heterogeneous group of water-insoluble (hydrophobic) organic molecules.
What do nonpolar solvents do?
Extract lipids from tissues.
What is the solubility of lipid?
And how is lipid stored and transported in the body?
Insoluble in aqueous solutions.
Body lipids+ membrane-associated lipids compartmentalized
Droplets of triacylglycerol in white adipocytes
Transported in plasma in association with protein, as in lipoprotein particles, or on albumin
What’s the function of lipids?
A major source of energy for the body
Provide the hydrophobic barrier that permits partitioning of the aqueous contents of cells and subcellular structures.
Some fat-soluble vitamins have regulatory or coenzyme functions and the prostaglandins and steroids hormones play major roles in the control of the body’s homeostasis.
What are the consequences of deficiencies or imbalances in lipid metabolism?
Can lead to some of the major clinical problems encountered by physicians, such as atherosclerosis and obesity.
How are dietary lipids processed in the stomach?
Lingual lipase- an acid-stable lipase that originates from glands behind the tongue. CATALYZES LIPIDS IN STOMACH
TAGs are the primary target for this enzyme. ESP short or medium length e.g fewer than 12 carbons such as found in milk fat.
These same TAGs are also degraded by a separate gastric lipase secreted by the gastric mucosa.
What is Cystic fibrosis (CF)?
This is the most common lethal genetic disease in Caucasians of Northern European ancestry and has a prevalence of about 1:3,000 births. This autosomal recessive disorder is caused by mutations to the gene for the CF transmembrane conductance regular (CFTR) protein that functions as a chloride channel on the epithelium. Defective CFTR results in decreased secretion of chloride and increased reabsorption of sodium and water. In the pancreas, the decreased hydration results in thickened secretions such that pancreatic enzymes are not able to reach the intestines, leading to pancreatic insufficiency. Treatment includes replacement of these enzymes and supplementation with fat-soluble vitamins. [Note: CF also causes chronic lung infections with progressive pulmonary disease.]
Describe the emulsification of lipids that occurs in the duodenum.
The critical process of emulsification of dietary lipids occurs in the duodenum. Emulsification increases the surface area of the hydrophobic lipid droplets so that the digestive enzymes, which work at the interface of the droplet and the surrounding aqueous solution, can act effectively. Emulsification is accomplished by two complementary mechanisms, namely, the use of the detergent properties of the bile salts, and mechanical mixing due to peristalsis.
Bile salts, made in the liver and stored in the gallbladder, are derivatives of cholesterol. They consist of a sterol ring structure with
a side chain to which a molecule of glycine or taurine is covalently attached by an amide linkage.
These emulsifying agents interact with the dietary lipid particles and the aqueous duodenal contents, thereby stabilizing the particle as they become smaller, and preventing them from coalescing. A more complete discussion of bile salt metabolism is given on.
