Every living cell acquires the raw materials needed for biosynthesis and energy production from its surrounding. There are many methods a molecule can enter and leave the cells. These are Diffusion, Osmosis, Active Transport., etc. In this essay, I will be looking into different types of transport across a cell membrane and their importance to the human body.
While drawing a cell, we all used to draw the plasma membrane with a straight line separating the inner contents of the cell from its exterior environment. What we don't know is that there is a lot going on in that straight line. Plasma membrane is a selectively permeable membrane made up of phospholipids, proteins and carbohydrates. This membrane consists of not one, but two layers of phospholipid layers adjacent to each other. These phospholipid molecules contains two parts known as a head and a tail. The tails faces each other as the head of one layer faces the interior of the cell and the head of the second layer faces the surrounding environment. The head is is negatively charged making it hydrophilic - or water loving. However, the lipid tails are uncharged making it hydrophobic - or water fearing. Due to this, when a cell is placed in a water environment the head will face towards the water and the tails move away. This gives the cell membrane its fluid like nature.
The phospholipid bilayer is scattered with various proteins. The proteins span across the entire phospholipid layer. There are two different types of proteins in the cell membrane, and they are carrier proteins and ion channels. The carrier proteins help the large molecules such as, amino acids and glucose that can't pass through the phospholipid bilayer to transport itself inside the cell by changing its shape. The ion channels located in the cell membrane gives it the characteristic of "selective permeability." These channels allow only ions that are of a certain size, charge to pass through.