Chapter 10 Reading Notes

Fatty Acids

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Don't forget DHA and EPA. Theie full names and short hand notations were given in class.

Sphingolipid metabolism

Synthesis and breakdown of sphingolipids is tightly controlled. This is very important in developing neural tissue.

Nieman-Pick disease: due to a defect in sphingomyelinase, the enzyme that cleaves phosphocholine from sphingomyelin. In these pateints, sphingomyelin accumulates in the brain, spleen, and liver. The result is impeded mental development and early death.

Tay Sach's disease: high prevalence (1 in 28) in people who are of Ashkenazic (Jewish people of Eastern European) descent. If both parents are carriers, the child has a 1 in 4 chance of getting the disease. The lysosomal enzyme hexosaminidase A is defective. This enzyme cleaves the bond between N-acetyl galactose and galactose in gangliosides. This results in a build up of paritially hydrolyzed gangliosides in the lysosomes: the swell up, burst and the lysosomal contents wreck havoc with the rest of the cell. This results in blindness, paralysis and death by age 3 or 4. Carriers can be indentified by assaying skin cells for hexosaminidase A, the carriers of the gene will have reduced levels of activity. They have functional enzyme, but it is present in reduced amounts.

Lipases

Phospholipase A1:cleaves the fatty acid from the first position on the glycerol backbone.
Phospholipase A2: cleaves the fatty acid from the second position on the glycerol backbone.
Phospholipase C: cleaves phosphotidyl derivative to release a phosphatylated derivative and diacyl glycerol
Phospholipase D: cleaves phosphotidyl derivative to release the free alcohol and diacyl glycerol phosphate.

Membrane lipids are involved in cellular signalling

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Phospholipase A2

Phospholipase A2 leaves aracadonic acid from membrane phospholipids. Aracadonic acid is the template for three classes of molecules: prostaglandins, thromboxanes and leukotrienes. The have hormone like effects, but they act locally, they are not transported through the blood to act a distant tissue. Prostaglandins were first isolated from prostrate glands. PGE2(ether soluble), PGF was soluble in fosfat buffer. These were first isolated by Bengt Samulson at the Carolina Institute in Sweden. Prostaglandins regulate the synthesis of cAMP, they regulate blood flow, the wake-sleep cycle, they control the responsiveness of tissues to hormones such as ephedrin and glucagon. They also elevate body temperature and cause inflammation.

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