Diffusion, Osmosis, and Active Transport
One of the most important functions of cells is to maintain a stable internal environment, despite changing external conditions. This is accomplished in part by selectively regulating the molecules that are able to cross the cell membrane. Diffusion is one of the most common ways of transporting molecules across the cell membrane and plays an important role in many cellular processes.
2. What is Diffusion?
Diffusion is the movement of particles from an area of high concentration to an area of low concentration. This process occurs until the concentration of particles is equalized throughout the space. Diffusion can be explained using the following analogy:
Imagine a room that is filled with smoke. The smoke will spread out evenly throughout the room until there is an equal concentration of smoke in all areas of the room. This occurs because the smoke particles are constantly moving and bumping into each other. Over time, the smoke particles will become evenly distributed throughout the room.
The same process occurs with molecules in a solution. The molecules are constantly moving and bumping into each other. Over time, the molecules will become evenly distributed throughout the space.
3. The Cell Membrane
The cell membrane is a thin layer that surrounds the cells and regulates what enters and leaves the cell. The cell membrane is made up of a double layer of lipid molecules (phospholipids). Lipid molecules are non-polar, meaning they do not interact with water molecules. This makes the cell membrane impermeable to water molecules (hydrophobic).
However, the cell membrane is permeable to some small, non-polar molecules, such as oxygen and carbon dioxide. These molecules are able to diffuse through the cell membrane because they are small enough to fit between the lipid molecules.
Osmosis is a special type of diffusion that occurs when water diffuses across a semi-permeable membrane. A semi-permeable membrane is a barrier that allows small molecules, such as water, to pass through, but does not allow larger molecules, such as proteins, to pass through.
Osmosis occurs when there is a difference in solute concentration on either side of the semi-permeable membrane. For example, if there is a higher concentration of salt (solute) on one side of the semi-permeable membrane than on the other side, then water will diffuse from the side with less salt to the side with more salt in order to equalize the concentrations on both sides of the semi-permeable membrane.
5. Active Transport
Active transport is a type of transport that requires energy in order to move molecules across a cell membrane. Active transport typically moves molecules against their concentration gradient (from an area of low concentration to an area of high concentration).
One example of active transport is called “primary active transport.” Primary active transport uses ATP (adenosine triphosphate) to fuel transporter proteins that move ions or other small molecules across cell membranes against their concentration gradient (from an area of low concentration to an area of high concentration).
6 Conclusion In conclusion, diffusion is one of several ways that cells use to regulate what enters and leaves their cells membranes in order