The Cell Membrane
Uploaded by ZannaHanna0624 on Dec 02, 2012
Cell membrane
A cell membrane is the outer surrounding of the cell that controls what goes in and out. Also cells need to have a dynamic equilibrium amongst other molecules. There are two types of cellular diffusion; Simple Diffusion and Facilitated Diffusion. Osmosis is also another type of diffusion that involves the transfer of water in the organism. None of the diffusions require energy because it is a natural process that transfers the areas of high concentration too low. Active Transport on the other hand does require energy because the movement of the molecules in the opposite direction of the diffusion, even when the equilibrium is reached the cell still needs the molecules around it.
Endocytosis and Exocytosis are both very important to the cells. When a cell membrane takes in molecules it is called Endocytosis. Endocytosis is a process by which the particles are taken in by the cell, from the outside to the cytoplasm inside a vessel. Exocytosis is a process by which the particles of waste are taken out of the sell. Then the vesicles travel to the Golgi apparatus. By Endocytosis the energy is transferred through the cytoplasm of the cell. Sometimes the cell has a lower level of proteins than its surroundings. That is called diffusion.
Diffusion occurs when the surrounding of the cell has fewer molecules than the inside of it. Then the cell uses diffusions to transfer the molecules into the cell. When diffusions are complete the outcome is called the dynamic equilibrium. Osmosis occurs often too, only with water particles in the organism. Osmosis is used also to establish equilibrium. Sometimes if a membrane can only pass water particles, so the water will adjust itself to have the same hypertonic solution. There are more types of ways diffusion is used with energy.
Facilitated diffusion and active transport are almost the same things, but then the facilitated diffusion tries to adjust the dynamic equilibrium. For example when the protein carrier takes the same amount of molecules, it requires no energy. The active transport uses energy to take more of the molecules that the cell needs, therefore making the numbers of molecules on the outer side fewer than inside the cell. For example, red blood cells use the facilitated diffusion to move glucose across membranes. Some sugars and amino acids are used in the active transport. The thing called Selective permeability also occurs in...