Cell Structure And Function

Describe the importance of cell membrane, its structure and function

Cells are the main components of organization in biology. All cells are surrounded by a cell membrane. The cell membrane is semipermeable; made of smaller molecules that form a porous and flexible composition.

The cell membrane is made up of phospholipids that contain a hydrophilic head and a hydrophobic tail. Cholesterol stiffens the membrane by connecting the phospholipids together. Glycolipids signal other molecules and glycoproteins have an attached chain of sugar. This creates a phospholipid bilayer, which is the basic structure of the cell membrane. The main functions of the cell membrane are to isolate the cytoplasm from the surrounding environment, regulate the exchange

They do this by transporting across the cell membrane. There are three major types of transportation: Passive, Active and Bulk. Passive transport differs from active transport as it does not require chemical energy. Passive transport maintains dynamic equilibrium of water, gases, nutrients and wastes. It allows for small nutrients and gases to enter and exit the cell. Also no NET diffusion or osmosis after the equilibrium is established. The three types of passive transport are simple diffusion, facilitated diffusion and osmosis. Simple diffusion is the movement of molecules from higher concentration to lower concentration. Molecules move directly through the membrane without assistance. Facilitated diffusion is when molecules can only move with the aid of a protein in the cell membrane. In simple diffusion, molecule move down the concentration gradient, whereas in facilitated diffusion molecule move up the concentration gradient. Osmosis is the diffusion of water molecules from a lower solute concentration to a higher solute concentration. Active transport requires chemical energy to transport molecules against their concentration gradient so more of the substance is inside or outside the cell than normal. It disrupts the equilibrium established by diffusion. Two examples of active transport are endocytosis and exocytosis. Endocytosis is the movement of substances into a cell and exocytosis is the movement of substances out of a