TABLE 10-l Approximate Lipid Compositions of Different Cell Membranes PERCENTAGE OF TOTAL LIPID BYWEIGHT LIPID LIVER CELL RED BLOOD MYELIN MITOCHONDRION ENDOPLASMIC E cou PLASMA CELL PLASMA INNER AND RETICULUM BACTERIUM MEMBRANE MEMBRANE OUTER MEMBRANES) Cholesterol Phosphatidylethanolamine 7 18 Phosphatidylserine 7 2590 2 17 trace Phosphatidylcholine Sphingomyelin 8 0 Glycolipids trace trace Others 22
Phospholipid molecule CHOLINE CH2-NTICH3)3 PHOSPHATE GLYCEROL hydrophilic tail hh上 CH hH2c比 (hydro H, CH cis-double TH bon kLcl H
Four major phospholipids in mammalian plasma membranes ④NH3 ④NH3 CH3 CH CH3 CH3 CH3 CH2 -COOL CH2 CH2 CH2 CH2 CH H2 O=p-O⊙ O=p-0⊙ O=P-oO O=P-O⊙ CH2--CH-CH2 OH CH2--CH-CH2 CH2一CHCH2 CH-CH-CH2 =O C=O CH NH CH C-C Ha9 HO>E HQ> phosphatidy phosphatidyl ethanolamine serine phosphatidyl shingo choline myelin
Glycolipids are found on the surface of all plasma membranes Gal CH-CH-CH2 COC H NH Ic CH OH H H--CH-CH2 > CH NH HOH CHOH Ha> OH (A) galactocerebroside o 2 (C)sialic acid NANA (B)GM1 ganglioside
Cholesterol OH polar head group rigid steroid Ing CH3 CH3 structure CH2 CH nonpolar hydrocarbon tail 3 CH3