Cell Transport And Permeability Essay
April 17, 2015
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Introduction: Cells “are the basic building blocks for all living organisms”(Medical Dictionary), without them life would cease to exist. The cell is responsible for the genetic makeup that makes each organism special …show more content…
The cell is like a large well-oiled machine in the sense that each individual organelle has its own job to do, and if even one part fails to do its job, the entire body would shut down. The cell is composed of many organelles that are protected by the outer wall of the cell, called the plasma membrane. The plasma membrane is a flexible, but sturdy barrier that surrounds and helps contain the cytoplasm of the cell (Tortora P65). The main purpose of the plasma membrane is to protect all of the intracellular structure from its external environment and to determine what passes through and what is not permitted. The permeability of the plasma membrane is different for each substance. It is impermeable to large uncharged polar molecules and ions, but is easily accessed by nonpolar molecules such as carbon dioxide and oxygen (which explains cellular respiration). The structural framework of the plasma membrane is the lipid bilayer, which is two layers that are …show more content…
Ribosomes are the actual site of protein synthesis (Marieb P44). The packaging of proteins and other substances that are being ready to be exported out of the cell and into the plasma membrane is done by the golgi apparatus. From there, the plasma membrane has two processes of exportation, active and passive processes. Passive transport has two important processes known as diffusion and filtration, diffusion being most important because it is the means of transportation for every cell in the body. When a cell experiences a difference in concentration (also known as concentration gradient), molecules are evenly distributed throughout the environment in which they reside. Diffusion deals with the movement of molecules from areas of higher concentration, to lower concentration. There are two types of diffusion, simple and facilitated. Simple diffusion is simply when a small and nonpolar molecule passes through the bilayer without needing assistance from transport proteins. Facilitated diffusion requires special transport proteins in order to pass through a membrane. This could be for many reasons, the main being the composition of the molecule or ion (too thick, physical