Documento

Membranas Biológicas
Composição das membranas biológicas •Características dos lipídeos de membrana (composição, associação, movimentação e distribuição) •Características do colesterol •Características das proteínas de membrana (disposição na bicamada lipídica e funções) Transporte através de membrana •Comparação da concentração de íons no interior e exterior de uma célula típica de mamífero •Proteínas carreadoras x proteínas canal •Transporte ativo x transporte passivo

Molécula hidrofílica

Molécula hidrofóbica

Membranas biológicas

Figure 10-1. Three views of a cell membrane. (A) An electron micrograph of a plasma membrane (of a human red blood cell) seen in cross section. (B and C) These drawings show two-dimensional and three-dimensional views of a cell membrane. (A, courtesy of Daniel S. Friend.)

Lipídeos de membrana

Fosfolipídeos

Figure 10-12. Four major phospholipids in mammalian plasma membranes. Note that different head groups are represented by different colors. All the lipid molecules shown are derived from glycerol except for sphingomyelin, which is derived from serine.

Glicolipídeos

Figure 10-16. Glycolipid molecules. (A) Galactocerebroside is called a neutral glycolipid because the sugar that forms its head group is uncharged. (B) A ganglioside 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 serine, as is the case for the phospholipid sphingomyelin (see Figure 10-12). Gal = galactose; Glc = glucose, GalNAc = N-acetylgalactosamine; these three sugars are uncharged.

Comportamento dos lipídeos em ambiente aquoso

Comportamento dos lipídeos de membrana em ambiente aquoso

Figure 10-4. Packing arrangements of lipid molecules in an aqueous environment. (A)