Functions Of A Cell Membrane

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The cell is a basic unit of life. All living organisms are made up of cells. Cells are vital to maintain life and to allow reproduction. Each cell is separated from its surrounding environment by a cell membrane and acts as a barrier. The cell membrane is a cell’s most essential organelle. Cell membranes are composed of four different types of molecules; phospholipids, cholesterol, proteins and carbohydrates. The main function of a cell membrane is to control which substances can move in and out of the cell. Different organisms have different cell membranes.
The phospholipids create the basic structure of a cell membrane. A phospholipid has two separate ends; a head and a tail end. The head of the phospholipid is known as hydrophilic,
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Diffusion only occurs when there is a concentration gradient. This means when a particular type of molecule is not spread out at an even concentration, but either exists in a higher concentration. The concentration gradient in regards to the movement of molecules (except water) always moves from high concentration to low concentration. Diffusion across cell membranes can occur in three main ways. The way in which it diffuses is depended on whether the molecules are small or large, and whether the molecules have already been concentrated. When really small molecules appear they are able to fit into a protein channel that is in the plasma membrane. This process of crossing the membrane can occur either by passive transport of active transport. When molecules are too big to fit through any channels, then they enter the cells by moving in a vesicle or by pumping, and this process is called active transport. When a molecule is crossing the membrane through passive transport, it is doing this because no extra energy needs to be used to get the molecule across the membrane. However when active transport is occurring this is because extra energy needs to be applied. Active transport can be done in two different ways, either by using pumps or using vesicles. Active transport using pumps moves small molecules against the concentration gradient. This is why there is extra energy needed. The pumps push molecules from areas of low concentration to high
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