The outer surface also has carbohydrates

The outer surface also has carbohydrates - glycolipid s or...

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The outer surface also has carbohydrates. This asymmetrical orientation begins during the synthesis of a new membrane in the endoplasmic reticulum. The proteins in the plasma membrane provide a variety of major cell functions. 4. Membrane carbohydrates are important for cell-cell recognition The membrane plays the key role in cell-cell recognition. Cell-cell recognition is the ability of a cell to distinguish one type of neighboring cell from another. This attribute is important in cell sorting and organization into tissues and organs during development. It is also the basis for rejection of foreign cells by the immune system. Cells recognize other cells by keying on surface molecules, often carbohydrates, on the plasma membrane. Membrane carbohydrates are usually branched oligosaccharides with fewer than 15 sugar units. They may be covalently bonded either to lipids, forming
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Unformatted text preview: glycolipid s, or, more commonly, to proteins, forming glycoproteins . • The oligosaccharides on the external side of the plasma membrane vary from species to species, individual to individual, and even from cell type to cell type within the same individual. • This variation marks each cell type as distinct. • The four human blood groups (A, B, AB, and O) differ in the external carbohydrates on red blood cells. B. Traffic Across Membranes 1. A membrane’s molecular organization results in selective permeability • A steady traffic of small molecules and ions moves across the plasma membrane in both directions. • For example, sugars, amino acids, and other nutrients enter a muscle cell and metabolic waste products leave. • The cell absorbs oxygen and expels carbon dioxide....
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This note was uploaded on 08/08/2009 for the course BIO 1406 taught by Professor Gomez during the Spring '09 term at Collin College.

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The outer surface also has carbohydrates - glycolipid s or...

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