cell diffusionDiffusion is a process that occurs when a substance such as water, molecules, and ions, which are usually needed for various cellular processes, enter and leave cells. The way that cell diffusion happens is by molecules moving from an area of high concentration to an area of low concentration. This usually occurs until both molecules have the same amount of the substance and it is distributed evenly.

Cell diffusion can have different rates, and it is a process that is studied heavily in biology. If you want to learn more about cell diffusion and how it works, then you should check out the Udemy course, An Introduction to Basic Biology.

Understanding the Concept of Diffusion 

Diffusion occurs through molecules spreading out into an available space. Imagine someone spraying a very powerful perfume in a large room. Initially, the perfume’s smell will be overpowering, but over time the smell dissipates to the point where it becomes unnoticeable. The reason for this happening is because of diffusion.

When the perfume is initially released it is let out in a concentrated burst, but due to diffusion, the substances spread out evenly in the air. This process occurs until the perfume is practically unnoticeable.

There are various types of diffusion that takes place in biology. The two most common types are passive transport and active transport. The key differences between these two types of diffusion is that in one case the substances naturally move from an area of higher concentration to lower concentration and in the other case the substances are pushed towards moving to an area of lower concentration to higher concentration.

If you’re interested in learning more about cell diffusion or biology on a cellular level in general, then you should check out the two Udemy courses, GCSE Biology: OCR B1 and the standard GCSE Biology.

Passive Transport 

In passive transport, substances move across the cell membrane without the use of cellular energy. This process just happens naturally. It is important to remember, as mentioned before, that substances move naturally from a higher concentration to a lower one. Think of a crowded room. In these cases, the moment that the door opens and people are allowed to leave the crowded room for more space, they do so. Passive transport acts in the same way.

This process is spontaneous, but how the substances are transported is directly related to the permeability of the cells membrane. Permeability simply means that the cell membrane does not allow for anything to pass through it. All cell membranes have a permeability rate, in which some substances can pass through and other substances cannot.  The permeability rate also means that there are some substances that can move across a cell membrane more easily than others.

An interesting thing to note is that a lot of plant cells have a cell wall, which is much thicker and sits right outside of the cell membrane. This means that the permeability rate of plant cells is much lower than most molecules.

Another important thing to note is water. Water can easily move through most cell membranes. This is incredibly important since a lot of cellular processes require water to happen.

Facilitated Diffusion

Facilitated diffusion is a particular part of passive transport. This type of transport involves the help of special transport proteins. Facilitated diffusion, which is also referred to as carrier-mediated diffusion, is the process much larger molecules being helped to move along the cell membrane because they cannot do so on their own.

There are several molecules, such as glucose, that are not able to go through the pores of the membrane and diffuse properly. In order to remedy this situation, facilitated diffusion is done where the molecule will bind to a carrier protein. The protein will do as it name suggests and carry the molecule through the cell membrane and out of the cell. Although facilitated cell diffusion does require more help through the use of proteins, it is still considered a passive form of transport because of the fact that it does not require any cellular energy to happen.

Active Transport 

Active transport is the direct opposite of passive transport. The process of active transport involves substances moving across the cell membrane, but instead of going to where there are less substances the molecules move to an area where there are more substances or an area of higher concentration. Essentially this is like having a crowded room full of people and then having more people push themselves inside.

There are two types of active transport. The first type is primary active transport. This form of transport uses metabolic energy in order to transport molecules across a cell membrane. The other type of transport is called secondary active transport. This form of transport also uses energy to move molecules across a cell membrane, but it doesn’t do it with ATP. Instead, secondary active transport operates by creating entropy and pumping ions of the cell, which directly has an effect on the electrochemical potential difference.

The main reason that active transport exists is to provide the cell with a large amount of molecules that it may need for processes, molecules such as ions, amino acids, and glucose are common reasons for active transport.

Variables that Determine how Diffusion Works 

In order to determine how diffusion will happen, there are a lot of different variables that come into play. Some variables include the number of molecules that are inside the cell, the time it takes for the molecules to diffuse, the permeability of the molecule and cell membrane, and the size of the cell.

Some of these terms can seem highly scientific and complicated, but these are basic biology vocabulary terms that you will have to learn if you want to understand the different types of cellular activity, such as diffusion.

Doing More Research 

If you want to learn more about cellular diffusion and other forms of biology, then you can always do more research. If you’re trying to learn more for a paper, then check out the Udemy course A+ Research Paper in Biology, which will help you get the high grades you want for your class.

Page Last Updated: February 2020

Featured course

Animalist - zoology of animal 2

Last Updated April 2021

  • 2 total hours
  • 52 lectures
  • All Levels
5 (1)

English | By Gove Lee

Explore Course

Biology students also learn

Empower your team. Lead the industry.

Get a subscription to a library of online courses and digital learning tools for your organization with Udemy for Business.

Request a demo