How do membranes and cell walls that surround cells control the movement of materials in and out of living cells? Relate membrane and wall structure to such processes as diffusion, osmosis, pinocytosis and phagocytosis.
The surrounding cell walls and membranes can control the materials that pass in, out and through living cells. Four processes that can be related to this movement of materials are diffusion, osmosis, pinocytosis and phagocytosis.
To perform their functions, cells must maintain an internal steady state in the midst of an ever-changing environment. This consistency, or homeostasis', is maintained in part by the regulation of the movement of materials in and out of the cell. To achieve this control, a cell is bounded by a delicate membrane, which can distinguish between substances, slowing down or stopping the movement of some while allowing others to pass through freely. Because not all substances penetrate the cell membrane equally well, the membrane is known as being differentially', or selectively permeable'.
Cell walls and membrane.
The main purpose of the cell membrane is to regulate the movement of materials in and out of the cell. By doing so, the cell's internal environment can differ greater to the external environment, since only certain materials can pass through. Scientists believe that the cell membrane is selectively permeable, which means that only certain substances may pass through the membrane.
Cell membranes consist mainly of phospholipids. These phospholipids have two parts; a polar phosphate "head" and two nonpolar fatty acid "tails." These molecules are arranged in a way that is known as a bilayer' (or double layer) so that the polar heads face the external and the internal environments of the cell, while the fatty acids form the inside of the cell membrane. The phospholipids are free to move around, often switching places with their neighbours. This movement allows the membrane to stretch and change shape.