cholesterol
Introduction
Sphingolipids & cholesterol favor thicker bilayers, & are concentrated in plasma membranes. Little cholesterol is found in endoplasmic reticulum, nuclear & mitochondrial membranes. Cholesterol & its analogs is found in plasma membranes of eukaryotic cells in roughly equimolar amounts to the sum of all other lipids. Bacteria do not contain cholesterol.
Cholesterol may serve to decrease permeability of the plasma membrane to small molecules. Sites of unsaturation in phospholipid makes them difficult to pack together & allows for transient cavities in membranes to form, which in turn allows passage of small molecules.
Introduction of cholesterol into lipid bilayers has 2 main effects:
- Methylene groups 2-10 of unsaturated fatty acid chains abut against the fused ring of cholesterol making deformation more difficult & cause the membrane to become more ordered & tightly packed
- The cholesterol ordered segments of acyl chains lie perpendicular to the bilayer causing it to thicken.
About 85% of plasma membrane cholesterol is generally associated with the cytoplasmic leaflet.
The central nervous system makes up only 2% of the human body mass but contains about 25% of the body's unesterfied cholesterol.[2] Cholesterol in the brain is almost entirely derived from in situ synthesis, little is derived from peripheral tissue*. Allegedly, all cholesterol in the brain is produced by oligodendrocytes [no reference].
Oxidized cholesterol metabolites include:
* This is not so in mice.
More general terms
More specific terms
- 7-dehydrocholesterol
- 8-dehydrocholesterol
- cholesterol ester
- cholesterol sulfate
- desmosterol (24-dehydrocholesterol)
Additional terms
- cholesterol biosynthesis
- cholesterol in serum/plasma
- cholesterol ozonolysis metabolite
- oxysterol; hydroxysterol
- steroid biosynthesis
References
- ↑ Bretscher MS, Munro S. Cholesterol and the Golgi apparatus. Science. 1993 Sep 3;261(5126):1280-1. Review. PMID: https://www.ncbi.nlm.nih.gov/pubmed/8362242
- ↑ 2.0 2.1 Hartmann T. Cholesterol, A beta and Alzheimer's disease. Trends Neurosci. 2001 Nov;24(11 Suppl):S45-8. Review. PMID: https://www.ncbi.nlm.nih.gov/pubmed/11881745
- ↑ Vance JE. Dysregulation of cholesterol balance in the brain: contribution to neurodegenerative diseases. Dis Model Mech. 2012 Nov;5(6):746-55. Review. PMID: https://www.ncbi.nlm.nih.gov/pubmed/23065638 Free PMC Article