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Cross-sectional view of the structures that can be formed by phospholipids in an aqueous solution. A biological membrane, biomembrane or cell membrane is a selectively permeable membrane that separates the interior of a cell from the external environment or creates intracellular compartments by serving as a boundary between one part of the cell and another.
Integral membrane proteins are a permanent part of a cell membrane and can either penetrate the membrane (transmembrane) or associate with one or the other side of a membrane (integral monotopic). Peripheral membrane proteins are transiently associated with the cell membrane. Membrane proteins are common, and medically important—about a third ...
Illustration of a eukaryotic cell membrane Comparison of a eukaryotic vs. a prokaryotic cell membrane. The cell membrane (also known as the plasma membrane or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of a cell from the outside environment (the extracellular space).
Protein–protein interactions regulate enzymatic activity, control progression through the cell cycle, and allow the assembly of large protein complexes that carry out many closely related reactions with a common biological function. Proteins can bind to, or be integrated into, cell membranes.
Schematic representation of transmembrane proteins: 1) a single-pass membrane protein 2) a multipass membrane protein (α-helix) 3) a multipass membrane protein β-sheet. The membrane is represented in light yellow. A transmembrane protein is a type of integral membrane protein that spans the entirety of the cell membrane.
Comparison of transport proteins. A symporter is an integral membrane protein that is involved in the transport of two (or more) different molecules across the cell membrane in the same direction. The symporter works in the plasma membrane and molecules are transported across the cell membrane at the same time, and is, therefore, a type of ...
Schematic diagram of the 2D structure of aquaporin 1 depicting the six transmembrane alpha-helices and the five interhelical loop regions A-E The 3D structure of aquaporin Z highlighting the 'hourglass'-shaped water channel that cuts through the center of the protein. Aquaporin proteins are composed of a bundle of six transmembrane α-helices ...
Through the work of Charles Overton in the 1890s, the concept that the biological membrane is semipermeable became important to understanding the regulation of substances in and out of the cells. [11] The discovery of facilitated diffusion by Wittenberg and Scholander suggested that proteins in the cell membrane aid in the transport of ...