3 polar head groups cholesterol. stiffened region more fluid regton 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
CH CH3 CH3 CH NH3 NH3 CH2 H--C-COO O CH CH2 H2 2 O=P-O O=p-O CH2-CH--CH2 CH2-CH--CH2 CH2-cH一CH2 cH一CH-CH2 a c⊙ 产 phosphatidylethanolamine phosphatidylserine phosphatidylcholine 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 Q00000000会会0Q009009Q99 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
NAN H CH-CH-CH CH一CH-CH2 COO CH NH CH NH CH z>su CHOH CH2OH (C) sialic acid (NANAN 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 CYTOSOL 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