Cell Membrane

What The Cell Membrane Made Up Of?

Wednesday 09th Mar 2022 |

Cell membranes are known for protecting and organizing the cells, and every cell in existence has an outer membrane which regulates it, this includes what enters it and how much of any substance can enter it too. 

But, what exactly makes these cell membranes so powerful and useful to living things? 

The biological makeup of every living thing from plant to whale is so important, and cell membranes are present in anything with a cell.  What we all want to know is what they are made of that makes them so capable of being so incredibly well organized.  Eukaryotic cells will not only have this outer membrane, but they will also have an inner membrane too which will help to control the transfer and exchange of the components of the cell. Whichever membrane you refer to will have a specific structure that helps to keep this function as a gatekeeper intact. 

To learn more, keep reading, however, if you want even more information, look here; https://microscopeclarity.com/cell-membrane-explained-heres-everything-you-need-to-know/.

Now, let’s keep learning!

What Is The Cell Membrane?

Cell membranes are also known as plasma membranes. They are a fine membrane which surrounds every cell that is alive. They keep them safe and secure from the environment that surrounds them. 

Inside the membrane will be the makeup of the cell which will often contain proteins, acids, carbohydrates, and so on. Outside the cell will be ions, acids, and also alkalis, many of which are toxic to the cell itself. 

However, on the outside there will also be nutrition that the cell requires to live and grow better, this is why the membrane is there, to distinguish between these good nutrients, and the bad ions, acids, and alkalis. 

It protects the cell from harmful substances, but lets in the nutrients in the correct amounts to keep the cell functional.

 

What Are They Made Out Of?

 

Pretty cool right?  So, what are these membranes made from? For the most part, these membranes are made up of glycerophospholipids. These are molecules that are made up of glycerol which is a group of phosphates as well as a duo of fatty acid chains. This molecule is a three-carbon make up, and it acts as the fortification of lipid membranes. Within each individual glycerophospholipid there will be fatty acids that attach to the carbons 1 and 2, and a phosphate group will attach to the third carbon. Let’s look at the makeup individually, acknowledging that there are two primary things that make up a cell membrane, lipids and proteins.

Lipids

Lipids include phospholipids which we have already mentioned, as well as cholesterol and glycolipids. Phospholipids will make up the bi-layer- or the basic structure of the membrane. It has a lot of power over what enters and exits the cell. Think of these are the bouncers standing at the entrance, checking ID’s. Cholesterol is like the backup for phospholipids, it also controls the incoming and outgoing of substances. It also has hydrophilic heads and tails. This can also stabilize the membrane and assists in the fluidity of the cell’s membrane. Finally, there are glycolipids. These are receptors, antigens and assist in cell-adhesion.

Proteins

Then there are the proteins, proteins are absolutely essential in any living thing. We often think of protein as a food group, but it is necessary in everything. In cell membranes there are also three primary proteins you will find. These include glycoproteins, which do the same sort of thing as glycolipids, standing guard and checking the ID of anything that wants to enter the cell.  There are also Enzymes and transport proteins too. 

What Do Membranes Do?

Cell membranes are just barriers. They are like immigration control at country borders, however their function is much more dire. They control what gets in and out of a cell, stopping harmful substances from entering and allowing in positive substances. 

Cell membranes are semi-permeable; this means that there are some molecules which are able to diffuse the lipid layer, but there are many that cannot.  Molecules and gasses such as oxygen and C02 can cross membranes quickly, but others such as water and ethanol will pass at a slower rate.  They will also protect the cell from ions, sugars, and amino acids, should these molecules need to get into the cell they will have to rely on the transport proteins we mentioned earlier in order to enter. These membranes are very selective in what they allow in and out and are in many ways vital to the health of the cell. 

Plant Vs Animal Cell Membranes

Since everything has a cell membrane, you would naturally think that a plant cell and an animal cell would be the same. However, this is not the case. Many of us will remember from High School Biology that plant cells and animal cells are very different. 

While they retain the same function, and have the same purposes, plant cells do more and have more. This means that as well as having a cell membrane, plant cells will also have a cell wall too. 

This gives them a secondary protective layer that will surround the membrane of the cell. It gives them a more rigid structure because plants need to grow up and out. 

Animal cells (like ours) are more flexible, and thanks to the flexibility that the cell and cell membrane has, a cell membrane in an animal or human will be able to come in multiple shapes and sizes. 

For plants there is not so much flexibility, plants usually have rectangular shaped cells. In a diagram of the cell, you would find that a plant cell seems to be outlined, this is because of the plant cell’s cell wall, which animal cells do not have. 

A plants’ cell membrane is made up of the same components, as it is no different from any other living thing. A plants’ cell just needs that little extra protection of its wall.

Transport Through The Cell Membrane

We did speak about the function of the cell membrane, and how some of its makeup act as front door bouncers into the cell, checking IDs of molecules and seeing who can enter and who cannot. 

Well, it is essential that the parts of the cell do take in nutrients through the cell wall. The cell will need these to continue operating. However, a cell is a lot like us, it too needs to take in nutrition and expel waste material too. 

Whether it is nutrition or waste things must enter and exit. Transport proteins will help in getting things in and out of the cell. However, osmosis or diffusion can both be ways in which transport can occur. 

Although it could also occur via exocytosis, or endocytosis. Molecules may also move across a membrane where they are low concentration to high concentration.  In a case of passive diffusion this might be oxygen as an example, where the movement into the cell is effortless and requires no assistance. There may also be diffusion that happens through a channel for something such as sodium. This is less effortless and may require the help of phospholipids, allowing the sodium to come in.

 

Should something like glucose need to enter the cell, it might need assistance from a carrier protein (remember we spoke about those proteins in a cell membrane that transport molecules into the cell). This could be facilitated diffusion. However, because cells let things in and out, while the cell membrane monitors what enters and exits, this means things can leave like they may enter. Sodium might need to exit the cell while potassium may need to enter. This could happen at the same time, and would be active transportation into the cell.  Do not forget that all the while phospholipids and other lipids in the makeup of the cell membrane will be monitoring what comes in and goes out, ensuring that no damaging bacteria or viruses enter the cell. 

The Cell Membrane In Simple Terms – A Conclusion

We use the analogy of the lipids and proteins that make up a cell membrane like being bouncers at a club because in a sense, this is what they are and what they do to protect the cell. 

However, we will explain in simple terms, because for many of us eager to learn about the functioning of the cell membrane and what it is made of, this is exactly what we need to best understand it. 

Whether a cell is an animal cell or a plant cell it will have a cell membrane. These membranes will have two layers. On one side of the cell will be the extracellular environment (the outside of the cell), and the other will have the cytoplasm (the inside of the cell). 

Every layer of the cell will be made up of phospholipids and proteins. Phospholipids will be able to move around inside the layers of the cell and give the cell flexibility. The proteins will be embedded within the phospholipids, hidden amongst them.  Some proteins will be able to respond to signals from other cells, some may be enzymes, and others will be transport proteins helping to move things into or out of the cell if needed. 

This membrane is selectively permeable, it will let some things in, some quickly, some slowly, and other things not at all.  As we discussed when we mentioned transportation through the membrane, there are some things that do not need the permission of the phospholipid bilayer to enter the cell, such as O2 (oxygen), H20 (water), and CO2 (Carbon dioxide).  Glucose, and perhaps sodium will need permission from the phospholipids to enter the cell, so they will need the assistance of a specific protein to transport them across the membrane. 

Eternal proteins will be too big to move through the membrane of the cell, and they cannot get it at all.  The membrane of a cell is made up of lipids and proteins, each of these has a specific job to do, and they work together to ensure that the right things are going into and out of the cell.  They also assist in helping larger molecules into the cell when they are too big to enter on their own. 

This unique set of molecules that help the overall function of the cell help in it’s functioning and safety in every living thing, from plants, to bugs, to dogs and cats, and even us. These lipids and proteins make the world go round.