Biology. Essay Sample

How does the process of diffusion work? Diffusion is a lifelong process for the cells life functions when molecules move from one area of concentration to another. All cells have permeable membranes that doesnt allow any solution to pass through. When gaseous or dissolved stuff are allowed to pass through the membrane, this process is called diffusion. This process can go only when nothing keeps particles from moving, so we can observe diffusion only in gases or solutions, but cannot find it in solids. When molecules move, they go from an area with a high concentration to the area with a low concentration. A good example of it is when smell of fresh soup goes around the flat from the kitchen, or smell of bonfire goes through the forest. So, diffusion can happen only when there is a concentration gradient. Diffusion is a vital process for living organisms, there are a lot of examples how the diffusion works in human body. Digestion products that are dissolved in water, can pass through the small intestine thanks to diffusion. In the small intestine they have a higher concentration compared to the blood, so the concentration gradient will cause the process of diffusion. Carbon dioxide and oxygen are exchanged in our lungs according the same process. Osmosis is a special type of diffusion process of water molecules. This process goes through the partially selectively (permeable) membrane. The result of this process goes differently in animal and plant cells. Active transport is a process of moving of dissolves ions into or out a membrane of cell. In opposite to the diffusion, molecules move from the area with small concentration to the area with big concentration. This process doesnt go without energy, and sometimes it happens that the concentration of dissolved molecules is less outside that inside, but if the human body needs more molecules, the process wont stop. In this case, the specific molecules can be taken by carrier proteins and moving through the cell membranes. Here are some illustrations of active transport inside the human body and plants: glucose absorption in the human small intestine (the process goes in the epithelial cells share); absorption of ions by plants from ground water (the process goes in root hair cells).