Contains oligosaccharides with one or more sialic acid moieties which give

Contains oligosaccharides with one or more sialic

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Contains oligosaccharides with one or more sialic acid moieties (which give gangliosides a net negative charge) - Can protect the membrane against the harsh conditions found there (low pH, high concentrations of degradative enzymes) - Function in cell-recognition processes – in which membrane-bound carbohydrate- binding proteins (lectins) bind to the sugar groups on both glycolipids and glycoproteins in cell-cell adhesion - Can provide entry points for certain bacterial toxins and viruses
Figure 10-17 Molecular Biology of the Cell (© Garland Science 2015) 28 Review of BLG 311 Cell Biology Proteins are key component of membranes: integral versus peripheral membrane proteins ______peripheral__ membrane proteins (7-8) are held by weak interactions (ionic and hydrogen bonds): not embedded in membrane _____integral_ membrane proteins (1-6) are embedded in the membrane: include transmembrane proteins, amphiphilic helices and lipoproteins
Review of BLG 311 Cell Biology 29
Review of BLG 311 Cell Biology 30
Review of BLG 311 Cell Biology 31 My notes: - Lipid-linked protein - Entirely exposed at the external cell surface, being attached to the lipid bilayer only by a covalent linkage (via a specific oligosaccharide) to a lipid anchor in the outer monolayer of the plasma membrane - Made as soluble proteins in the cytosol and are subsequently anchored to the membrane by the covalent attachment of the lipid group
Review of BLG 311 Cell Biology 32 My notes – Steps in the folding of a multipass transmembrane protein - When a newly synthesized transmembrane alpha-helix is released into the lipid bilayer it is initially surrounded by lipid molecules - As the protein folds, contacts between the helices displace some of the lipid molecules surrounding the helices
Review of BLG 311 Cell Biology 33 My notes - In single pass transmembrane proteins the polypeptide chain crosses only once - Oligosaccharide chains and disulfide bonds are all on the noncytosilic side - Sulfhydryl groups in the cytosilic domain do not normally form disulfide bonds because the reducing environment in the cytosol maintain these groups in their reduced (-SH) form - Oligosaccharid chains - About 30% of an organisms proteins are transmembrane proteins - Hydropathy plots cannot identify the membrane-spanning segments of a beta barrel

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