File Name: structure and function of biological membranes .zip
The plasma membrane protects the cell from its external environment, mediates cellular transport, and transmits cellular signals. The plasma membrane also known as the cell membrane or cytoplasmic membrane is a biological membrane that separates the interior of a cell from its outside environment. The primary function of the plasma membrane is to protect the cell from its surroundings. Composed of a phospholipid bilayer with embedded proteins, the plasma membrane is selectively permeable to ions and organic molecules and regulates the movement of substances in and out of cells.
Biological membranes allow life as we know it to exist. They form cells and enable separation between the inside and outside of an organism, controlling by means of their selective permeability which substances enter and leave. By allowing gradients of ions to be created across them, membranes also enable living organisms to generate energy. In addition, they control the flow of messages between cells by sending, receiving and processing information in the form of chemical and electrical signals. This essay summarizes the structure and function of membranes and the proteins within them, and describes their role in trafficking and transport, and their involvement in health and disease. Techniques for studying membranes are also discussed. Biological membranes consist of a double sheet known as a bilayer of lipid molecules.
Cambridge, Mass. The main components of biological membranes are proteins, lipids, and carbohydrates in variable proportions. Myelin has few functions and is made up almost entirely of lipids. In plasma membranes, the weight ratio of lipid to protein is close to 1; in several specialized membranes ie, mitochondrion and bacterial cells this ratio is near 2 or 3. Thus, there appears to be a correlation between the number of activities performed by and the amount of protein in a membrane. The main membrane lipids are phospholipids, cholesterol, and glycolipids.
Biological membranes are the basis for many important properties of the cell, not the least of which is to physically define the cell boundary, and in eukaryotes, the boundaries of each intracellular organelle. However, they are not completely impermeable boundaries, and through embedded proteins, the membrane serves as the gatekeeper for the passage of specific molecules into e. Other embedded proteins can identify the cell to other cells, and participate in numerous interactions with the environment or other cells. Finally, the membrane, or more precisely, the chemical gradients across the membrane, is an important energy source for the cell.
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Structure and Function of Biological Membranes explains the membrane phenomena at the molecular level through the use of biochemical and biophysical approaches. The book is an in-depth study of the structure and function of membranes. It is divided into three main parts.
Membrane proteins are common proteins that are part of, or interact with, biological membranes. Membrane proteins fall into several broad categories depending on their location. 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 of all human proteins are membrane proteins, and these are targets for more than half of all drugs.
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Membrane , in biology, the thin layer that forms the outer boundary of a living cell or of an internal cell compartment.Reply