Dominic Corsini has an extensive educational background with a B.S. in Secondary Biology and General Science with a Minor in Environmental Education, an M.Ed. in Educational Leadership, an M.S. in Biology, and a K-12 Principal Certification Program. Corsini has experience as a high school Life, Earth, Biology, Ecology, and Physical Science teacher.
What Are Cell Membranes?
Let's begin this lesson with a question: what do all cells have in common? Truth be told, there are several characteristics cells all share, things like basic metabolism or having genetic material. But for the purposes of this lesson, we'll focus on the fact that all cells contain a cell membrane.
The cell membrane is the outer covering of a cell, and it's responsible for controlling entry and exit of material from the cell. Cell membranes, regardless of whether they exist in plants, animals, fungi or bacteria, are all made of the same basic components. These components are phospholipids, proteins, carbohydrates and cholesterol or sterols.
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The first major component of the cell membrane is the phospholipid. Phospholipids are amphipathic fats that form the majority of the membrane. In the cell membrane below, the red pieces with the two yellow tails are phospholipids.
They are arranged in a double layer so that the tails face inward. This arrangement works because the head of the phospholipid is hydrophilic and immerses itself inside the watery environment inside and outside the cell. The fatty acid tails are hydrophobic and are repelled by water. By sandwiching the fatty acid tails within the membrane, it keeps them away from water while simultaneously immersing the heads in water.
Proteins form another integral part of the cell membrane. Proteins are large molecules formed from long chains of amino acids. You'll notice that there are many different types of proteins. These proteins perform functions such as moving materials across the membrane. For example, have you ever heard that eating bananas will help protect you from getting cramps? That's because bananas contain potassium. This potassium is moved into your cells by proteins embedded in the cell membrane.
The third major component of cell membranes is carbohydrates. Carbohydrates are other large molecules that are made from simple sugars. These molecules generally allow cells to communicating, such as through acting as sites where chemical signaling molecules, such as hormones, can attach to the cell. Carbohydrates also act like a name tag for cells and allow cells to identify each other as part of a larger multicellular organism.
Finally, we come to the sterols and cholesterol. Plant, fungi cells and bacteria have different types of sterols, waxy fats that play a role in the cell membrane. These molecules serve a structural role in the membrane, reinforcing it and also participating in lipid signaling pathways.
Animal cells contain cholesterol. Cholesterol is a waxy, fat-like material found in all cell membranes. While cholesterol may sometimes be portrayed negatively in the media, it's actually vital to our cells. Cholesterol's function is to regulate the fluidity of the cell membrane. If cells lacked cholesterol, the membrane would be too fluid and not firm enough to maintain its functionality.
All living things are made of cells, and all those cells are contained in cell membranes. Membranes are responsible for controlling entry to and exit from cells. Cell membranes are made of four major components. Phospholipids are fats that create the vast majority of the surface of membranes. Interwoven into this surface are also proteins. Proteins are made of amino acid chains and function as transport devices within cells. Sometimes these proteins have carbohydrates extending from them. Carbohydrates are large molecules made from simple sugars. Their function is to link cells together or act as binding sites. Finally, the cell membrane has a slightly rigid nature that is created due to sterols and cholesterol. Cholesterol is a waxy material found embedded within the membrane. Sterols are waxy fats that are important in cell membrane structure in plants, fungi and bacteria.
Your understanding of the major structural components of the cell membrane could enable you to accomplish these objectives:
- Discuss the function and structure of cell membranes
- Enumerate the four main components of cell membranes
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Major Structural Components of the Cell Membrane
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