3 polar head groups cholesterol- stiffened region more fluid region 0 Figure 10-9. Cholesterol in a lipid bilayer. Schematic drawing of a cholesterol molecule interacting with two phospholipid molecules in one leaflet of a lipid bilayer
Figure 10-9. Cholesterol in a lipid bilayer. Schematic drawing of a cholesterol molecule interacting with two phospholipid molecules in one leaflet of a lipid bilayer
⊙NH3 CH3∠CH3 CH CH NH? N CH2 H-C-COO O CH CH2 Hz CH2 Clz o=p-0⊙ O=p-0⊙ o=p-0⊙ CH2-CH--CH2 CH2-CH--CH2 CH2CH--CH2 CH-CH--CHz CH NH ● -O C=O Hoo>L phosphatidylethanolamine phosphatidylserine phosphatidyl sphingomyelin Figure 10-10. Four major phospholipids in mammalian plasma membranes. note that different head groups are represented by different symbols in this figure and the next. All of the lipid molecules shown are derived from glycerol except for sphingomyelin, which is derived from serine
Figure 10-10. Four major phospholipids in mammalian plasma membranes. Note that different head groups are represented by different symbols in this figure and the next. All of the lipid molecules shown are derived from glycerol except for sphingomyelin, which is derived from serine
EXTRACELLULAR SPACE 909000 CYTOSOL Figure 10-11. The asymmetrical distribution of phospholipids and glycolipids in the lipid bilayer of human red blood cells. The symbols used for the phospholipids are those introduced in Figure 10-10. In addition, glycolipids are drawn with hexagonal polar head groups(blue) Cholesterol(not shown) is thought to be distributed about equally in both monolayers
Figure 10-11. The asymmetrical distribution of phospholipids and glycolipids in the lipid bilayer of human red blood cells. The symbols used for the phospholipids are those introduced in Figure 10-10. In addition, glycolipids are drawn with hexagonal polar head groups (blue). Cholesterol (not shown) is thought to be distributed about equally in both monolayers
NANAH Gal CH OH CH-CH-CH CH-CH--CH2 HN H NH CH NH CH C=O CHOH HOH CH,OH (A) galactocerebroside B) GMI ganglionic tC) sialic acid (NANA Figure 10-12. Glycolipid molecules. Galactocerebroside(A)is called a neutral glycolipid because the sugar that forms its head group is uncharged. a ganglioside(b )always contains one or more negatively charged sialic acid residues(also called N-acety neuraminic acid or NANA), whose structure is shown in( C). Whereas in bacteria and plants almost all glycolipids are derived from glycerol, as are most phospholipids, in animal cells they are almost always produced from sphingosine, an amino alcohol derived from serine, as is the case for the phospholipid sphingomyelin. Gal=galactose; Glc=glucose, GaINAC =N-acetylgalactos-amine these three sugars are uncharged
Figure 10-12. Glycolipid molecules. Galactocerebroside (A) is called a neutral glycolipid because the sugar that forms its head group is uncharged. A ganglioside (B) always contains one or more negatively charged sialic acid residues (also called N-acetylneuraminic acid, or NANA), whose structure is shown in (C). Whereas in bacteria and plants almost all glycolipids are derived from glycerol, as are most phospholipids, in animal cells they are almost always produced from sphingosine, an amino alcohol derived from serine, as is the case for the phospholipid sphingomyelin. Gal = galactose; Glc = glucose, GalNAc = N-acetylgalactos-amine; these three sugars are uncharged
Membrane proteins ⊙●● lipid bilayer 6E 2s 0R COOH Figure 10-13. Six ways in which membrane proteins associate with the lipid bilayer. Most trans-membrane proteins are thought to extend across the bilayer as a single a helix (1)or as multiple a helices (2); some of these"single-pass and"multipass" proteins have a covalently attached fatty acid chain inserted in the cytoplasmic monolayer(1). Other membrane proteins are attached to the bilayer solely by a covalently attached lipid-either a fatty acid chain or prenyl group -in the cytoplasmic monolayer (3)or, less often, via an oligosaccharide, to a minor phospholipid, phosphatidylinositol, in the noncytoplasmic monolayer (4 ) Finally, many proteins are attached to the membrane only by noncovalent interactions with other membrane proteins (5)and (6). How the structure in( 3)is formed is illustrated in Figure10-14
Figure 10-13. Six ways in which membrane proteins associate with the lipid bilayer. Most trans-membrane proteins are thought to extend across the bilayer as a single a helix (1) or as multiple a helices (2); some of these "single-pass" and "multipass" proteins have a covalently attached fatty acid chain inserted in the cytoplasmic monolayer (1). Other membrane proteins are attached to the bilayer solely by a covalently attached lipid - either a fatty acid chain or prenyl group - in the cytoplasmic monolayer (3) or, less often, via an oligosaccharide, to a minor phospholipid, phosphatidylinositol, in the noncytoplasmic monolayer (4). Finally, many proteins are attached to the membrane only by noncovalent interactions with other membrane proteins (5) and (6). How the structure in (3) is formed is illustrated in Figure10-14. Membrane proteins