This lesson is about the glycocalyx, which is an important outer covering of all kinds of cells, from humans to bacteria. In this lesson, you’ll learn what it does in our bodies and for bacteria. We’ll also cover medical applications of the glycocalyx.
What Is the Glycocalyx?
How many times have you tried to scrub your bathtub and you just can’t get that slime off? It takes a lot of manpower and some serious cleaners to get it looking white again. Well, unfortunately, that slime is bacteria, and the reason you can’t get it off is because of the glycocalyx! To get started, let’s talk a little about cell structure. Later, we’ll learn what happens with that stubborn slime.Cells have an outer covering called the plasma membrane. This structure is a thin layer that separates the cell from the environment. Some cells live in more challenging environments with physical stress on the surface.
These cells need some extra padding outside their membrane. This is where the glycocalyx comes in.The glycocalyx is a thick outer covering of the plasma membrane.
It is composed of strands of sugars and proteins bound together. The result is a thick, sticky layer that helps cells stay put in environments with lots of physical stress.Think of it as an ultra-sticky tape. If you had an object and you wanted it to stay put on the wall, you wouldn’t just use regular Scotch tape, like our plasma membrane. We would have to bring in some thick duct tape, which is like the glycocalyx. The following is the glycocalyx, labeled number 6.
Glycocalyx in Humans
Although bacteria are notorious for a great glycocalyx, humans have their own version that is important to both vascular function and the digestive system. Your blood vessels are actually tiny tubes made of cells. The cells on the very inside of the tube are called endothelial cells and have to withstand the stress of blood flowing over them constantly. The following is a diagram of blood flowing through an artery. The innermost layer is the endothelial cells.
In order to do this, these cells make a glycocalyx. The glycocalyx helps important vascular cells adhere to blood vessels, such as leukocytes and thrombocytes, which are involved in blood clotting.The second example of a glycocalyx in humans is found in the digestive system. Our small intestine is responsible for absorbing all the nutrients that come through our digestive system. In order to do this, they have many tiny folds called microvilli. The microvilli help the small intestine absorb nutrients.
The following is a diagram of the surface of the microvilli.
Each of the cells that make up the microvilli are covered with a glycocalyx. The physical stress of liquid food, called chyme, flowing through the digestive tract, means the cells need extra protection. Also, the chyme is acidic since it is coming from the stomach, again indicating these cells need some extra padding on the surface. The glycocalyx also contains important enzymes to keep breaking down food for absorption.
Glycocalyx in Bacteria
Next is the bacterial glycocalyx. This is the reason we just can’t get that slime off the bathtub. Most bacteria make a glycocalyx, but some are experts. These expert bacteria make a very thick glycocalyx that helps them to adhere to each other and surfaces in extreme environments. Think of all the water pounding against your shower each day, and yet somehow, those bacteria stay put. They stay put even with extreme scrubbing and chemicals!Bacteria use the glycocalyx to make thick films of bacteria in nature as well, called a biofilm. Biofilms have important applications in breaking down toxic chemicals in our ecosystems and have been used to clean up petroleum spills, as well as contamination in water supplies.
The bacteria in the biofilm break down the toxic chemicals, allowing the ecosystem to return to normal.Some bacteria can even make an extra-thick glycocalyx, called a capsule. These capsules protect bacteria in very harsh environments and can even be pathogenic to humans. The capsule prevents the bacteria from being engulfed in our immune cells.
Here, the bacteria Staphylococcus aureus is shown in a biofilm, which is potentially dangerous to humans.
However, not all bacteria with a glycocalyx are bad. They also exist in our bodies to help with digestion.
Some grow inside our large and small intestine to help us break down food. Like our own cells in the microvilli, these bacteria need protection from the mechanical stress of food flowing against them all day.
Since the glycocalyx is so important to humans and bacteria, it has a lot of applications in medicine. People who have a disrupted glycocalyx on endothelial cells have a greater chance of blood vessels rupturing, causing edema (swelling of the tissues). Since the glycocalyx is involved in keeping cells moving that are involved in blood clotting, if something is wrong with the glycocalyx, there is an increased risk of thrombosis (blood clots) which can lead to heart attacks and death.
The following is a diagram of thrombosis, which can result from problems with the glycocalyx in endothelial cells.
The glycocalyx is also important for pathogenic bacteria. Biofilms are very hard to get rid of due to the thick coating of the glycocalyx. They can form on hospital equipment and be difficult to clean. Some bacteria that have capsules can be pathogenic, leading to secondary infections in hospitals.
Hospital rooms can be covered in pathogenic bacteria due to biofilms!
Let’s review. The glycocalyx is a thick outer covering on cells, made of sugar and proteins. The glycocalyx is present in the human vascular and digestive system.Endothelial cells lining blood vessels have a glycocalyx to protect them from the sheer stress of blood flow, as well as to aid in cell attachment that helps the immune system and blood clotting. The microvilli in the small intestine are coated with a glycocalyx to help protect against the stress of the digestive system and to help digest and absorb food.Bacteria also have a glycocalyx which can create large colonies of bacteria known as a biofilm.
Some bacteria have an extra thick glycocalyx called a capsule. The capsule can be pathogenic and may be difficult to remove, creating secondary infections in hospitals.
Vocabulary ; Definitions
- Glococalyx: thick outer covering on a cell consisting of sugar and proteins
- Endothelial Cells: lines blood vessels with glycocalyx to protect from blood flow stress and help with cell attachment
- Microvilli: found in the small intestine, it protects against the stress of the digestive system
- Biofilm: creates large colonies of bacteria protected by glycocalyx
- Capsule: extra-thick glycocalyx which may be pathogenic in nature and hard to remove
Determine your preparedness to reach these goals after watching the lesson on glycocalyx:
- Provide a description of glycocalyx and specify its function
- Indicate where glycocalyx can be found and the way in which it protects the human body
- Outline the medical applications of glycocalyx