Integral membrane proteins, basic

Figure 41-7. The fluid mosaic model of membrane structure. The membrane consists of a bimolecu-lar lipid layer with proteins inserted in it or bound to either surface. Integral membrane proteins are firmly embedded in the lipid layers. Some of these proteins completely span the bilayer and are called transmembrane proteins, while others are embedded in either the outer or inner leaflet of the lipid bilayer. Loosely bound to the outer or inner surface of the membrane are the peripheral proteins. Many of the proteins and lipids have externally exposed oligosaccharide chains. (Reproduced, with permission, from Junqueira LC, Carneiro J Basic Histology. Text Atlas, 10th ed. McGraw-Hill, 2003.)...

The enzyme NaTK+-ATPase is a highly conserved integral membrane protein that is expressed in virtually all cells of higher organisms. NaTK -ATPase has been estimated to hydrolyze nearly 25% of all cytoplasmic ATP in resting humans. In nerve cells, approximately 70% of the ATP is consumed to fuel this enzyme. More basic information about NaTK -ATPase can be found at the website http //arbl.cvmbs.colostate.edu/hbooks/molecules/sodium pump. 

The basic conclusions for transmembrane helices in integral membrane proteins are as follows ... 

Many important proteins (e.g., ion channels, neurotransmitter receptors, transporters, and ion pumps) are integral membrane proteins. You need membranes to examine the binding sites of these proteins. If appropriate to the question being researched, you can obtain the basic material (e.g., muscle, liver, brain) from the slaughterhouse. Pig brain is much less expensive than rat brain. 

Biological membranes are the supramolecular structures which define the boundary of the cell and its organelles, and which con- trol communication between the exterior and interior. As such they constitute one of the basic organizing principles of biological organisms. In this chapter a review will be given of the overall compositional and structural features of biomembranes, which lead to their dynamic and functional properties. The structure of phospholipids and of integral membrane proteins will be described. Results on the rotational and translational mobility of membrane components will be discussed to indicate the dynamic nature of membrane structure and the possible functional role of membrane fluidity. 

Fig. 7 Diagrammatic representation of the fluid mosaic model of the cell membrane. The basic structure of the membrane is that of a lipid bilayer in which the lipid portion (long tails) points inward and the polar portion (round head ) points outward. The membrane is penenetrated by transmembrane (or integral) proteins. Attached to the surface of the membrane are peripheral proteins (inner surface) and carbohydrates that bind to lipid and protein molecules (outer surface). (Modified from Ref. 14.)...

Biological membranes consist of a bilayer of phospholipids in which membrane proteins are either embedded (integral proteins) or simply adsorbed (boundary proteins) (1) (Figure 1.). These systems fulfill a variety of functions oT basic importance. One of the most significant is the compartimentation via the formation of cells and cell subunits based on the self organization of membranes (hydrophobic effect (2j). 

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