Summary
The plasma membrane, also known as the cell membrane, separates the cytoplasm inside the cell and from the outside of the cell. The cell membrane contains phospholipids, which form two layers. These two layers of phospholipids are called the phospholipid bilayer. A phospholipid has a hydrophilic head and two hydrophobic tails. The hydrophilic head and hydrophobic tails of a phospholipid explain the arrangement of the phospholipid bilayer. Since cytoplasm and the environment outside of the cell are both primarily made of water, the water-loving heads face outward, toward the outside or inside of the cell. The tails face each other on the inside of the membrane because they are water-hating. Also, cell membranes are selectively permeable, meaning that they only let certain molecules pass through the membrane.
Relevance to Class
Recently, we learned about cellular transport involving the cell membrane. In class, we defined the cell membrane as a matrix of relatively fluid proteins and phospholipids. This article talks more about how molecules can pass through the phospholipid bilayer than we talked about in class. This article is relevant to class mainly because it explains more about the structure of the phospholipid bilayer and how it is used for cellular transportation. For example, it explains why certain molecules can pass through the phospholipid bilayer and why others cannot.
Author of Article: Zannie Dallara
Date of Publication: September 14, 2012
How does the plasma membrane control what passes through it and what doesn't?
ReplyDeleteHydrophobic molecules (that are small enough) can pass through the membrane easily because the tails of a phospholipid are also hydrophobic. Hydrophilic molecules cannot pass through the membrane (without a protein's help) because the heads of the phospholipid are hydrophilic, too. Therefore, the membrane is selectively permeable and does not let everything pass through.
DeleteWhat would a plasma membrane be more likely to let pass through
ReplyDeleteIt easily lets hydrophobic molecules pass through the membrane (if the molecules are small enough). If large or hydrophilic molecules need to pass, the assistance of a protein is needed.
ReplyDeleteI am really enjoying reading your well written articles. It looks like you spend a lot of effort and time on your blog. I have bookmarked it and I am looking forward to reading new articles. Keep up the good work. canopy membrane
ReplyDelete