Biology Reference
In-Depth Information
O
CH
3
CH
3
O
CH
3
H
*
CH
2
CH
3
O
n
O
UBIQUINONE (COENZYME Q)
HO
HO
--
O
HO
O
H
+
H
+
OH
O
--
O
O
O
fully reduced
dihydroquinone
quinone
anion
radical
semi-
quinone
radical
quinone
anion
fully
oxidized
quinone
FIGURE 5.27
Structure (top) and function (bottom) of coenzyme Q (ubiquinone, CoQ). CoQ is versatile as it
can carry 1 or 2 electrons and 1 or 2 protons and is a major component of the mitochondrial electron transport
chain.
(10 isoprene unit) anchoring chain. This molecule is often referred to as coenzyme Q10 or just
CoQ10. CoQ10 has recently been shown to be effective against Parkinson's Disease. Ubiqui-
none is the most abundant of all the mitochondrial electron carriers, being about 10X more
abundant than any other carrier. Ubiquinone is also the most versatile of all of the electron
transport components having the ability to carry either 1 or 2 electrons and 1 or 2 protons
as depicted in
Figure 5.27
.
SUMMARY
A major component of biological membranes is complex polar lipids, lipids that when
hydrolyzed release free fatty acids. Free fatty acids themselves are a minor component of
most membranes, as they can disrupt membrane structure. As a result, fatty acids are usually
esterified. Major animal membrane structural lipids can be classified into three basic types;
phospholipids, sphingolipids, and sterols. The major type of membrane lipids, phospho-
lipids, are divided into 7 structural classes. Each phospholipid has two esterified fatty acyl
chains, one saturated (
-2 chain), that control prop-
erties of the membrane interior. The second membrane lipid type is sphingolipids, so desig-
nated because they all contain the parent C-18 amino alcohol sphingosine. More than 60
different sphingolipids have been found in human membranes. The third major membrane
lipid type is sterols, particularly cholesterol. In mammalian plasma membranes cholesterol
sn
-1 chain) and the other unsaturated (
sn
