All steroids have a similar cyclic nucleus resembling phenanthrene (rings A, B, and C) to which a cyclopentane ring(D) is attached. The carbon positions on the steroid nucleus are numbered as shown in Figure 15–14. It isimportant to realize that in structural formulas of steroids, a simple hexagonal ring denotes a completely saturatedsix-carbon ring with all valences satisfied by hydrogen bonds unless shown otherwise; ie, it is not a benzene ring.All double bonds are shown as such. Methyl side chains are shown as single bonds unattached at the farther(methyl) end. These occur typically at positions 10 and 13 (constituting C atoms 19 and 18). A side chain atposition 17 is usual (as in cholesterol). If the compound has one or more hydroxyl groups and no carbonyl orcarboxyl groups, it is a sterol,and the name terminates in -ol.
Lipids need to be transported in plasma to tissues and organs to perform their metabolic functions. Given the hydrophobic nature of the neutral fats (TG and cholesterol esters), lipid transport via plasma would not be possible without some form of hydrophillic adaptation. The lipids are transported by a series of micelles called lipoproteins, which consist of an outer monolayer of protein (apolipoprotein) and polar lipids (phospholipid and unesterified cholesterol). The inner core consists of the hydrophobic lipids which is the cholesteryl esters & TAG.Lipoproteins function both to keep their component lipids soluble as they transport them in the plasma, and also to provide an efficient mechanism for transporting their lipid contents and to (and from) the tissues. NB. In humans the transport system is less perfect than in other animals, that is why they experience a gradual deposition of lipid especially cholesterol in tissues (atherosclerosis).
Chemistry of lipids cholestrol and lipoproteins ppt BIOCHEMISTRY email@example.com
Dr. Vijay Marakala, MBBS, MD.
SIMS & RC
No vegetable oil contains any cholesterol.
Cholesterol is the major sterol in animal tissues.
Only a little portion of the body cholesterol is derived
from diet. The bulk of it is synthesized in the body.
Unsaturated fatty acids lower blood cholesterol levels by
controlling cholesterol’s synthesis as well as its
elimination from the body.
Total 27 carbon atoms.
One hydroxyl group at the third
Double bond between carbon
atom 5 and 6
An 8 carbon side chain at position
Methyl side chains at positions
10 and 13
1. Major structural constituent of the cell membranes and lipoproteins
2. Precursor for Steroid hormones
d. Androgens & Estrogens
3. Formation of Bile acids and bile salts.
4. Synthesis of Vitamin D