“Compare and contrast the different methods molecules can either enter or exit cells”
In this essay I am going to discuss and compare the methods that molecules enter and exit cells.
There are various ways in which molecules enter and exit cells, and I am going to talk about the three main transport mechanisms: active transport, bulk transport and diffusion.
Firstly I will briefly summarize each method with a short explanation to what it does and then I will go on to compare and contrast the three methods, to show a greater understanding of what I have learnt.
The first method I am going to talk about is active transport. Active transport is the process where dissolved molecules move across the cell membrane from a lower to a higher concentration. The particles involved in active transport move against the concentration gradient, this means there needs be an input of energy from the cell. It may occur that the dissolved molecules are sometimes at a higher concentration inside the cell than outside, but as the organism needs the molecules they must still be absorbed. Active transport is highly selective, proteins are pumps ( carrier proteins) that use energy (ATP) and pick up specific molecules that are then taken through the cell membrane against the concentration gradient (one direction only). It is also know as 'uphill transport.'
Diffusion is an important mode of molecular transportation too. Basically how it works is, substances diffuse from a region of high concentration to a region of low concentration and this is called a concentration gradient- simply, diffusion tries to make the concentration equal on both sides. I am now going to talk about the differences of Active and passive transport, Passive Transport is the movement of solutes towards the concentration gradient. The solutes pass from a high solute concentration to a low solute concentration, therefore it is also known as "downhill transport". As you can see this contrasts with active...