Chapter 4, Problem 1FTB

The plasma membrane is composed of two major types of molecules, ______ and ______. Which type of molecule is responsible for each of the following functions? Isolation from the surroundings: __________; interactions with other cells: ___.

Summary Introduction

To review:

The given blank spaces in the given statement, “the plasma membrane is composed of two major types of molecules, _____________ and _________________. Which type of molecule is responsible for each of the following functions? Isolation from the surroundings: _______________; interactions with other cells: ______________________.”

Introduction:

The cell is the basic structural and functional unit of life. The cell is composed of various cellular organelles present in a jelly-like fluid compartment known as cytoplasm. The cytoplasm containing cellular organelles is known as protoplasm, which is surrounded by a semi-permeable structure known as the cell membrane. In case of plants and some other microorganisms cell membrane is further surrounded by cell wall but in case of animals, the cell membrane is the outermost structure.

Explanation of Solution

Cell membranes are primarily composed of lipids and proteins. There are three major classes of lipids that form the lipid bilayer that surrounds the cell. These are phospholipids, glycolipids, and cholesterol. All in all, lipid bilayer maintains a hydrophobic atmosphere, hence only non-polar molecules can pass through it. Thus, it isolates the cell from its surroundings by conferring a semi-permeable nature to it.

The amount of different lipids varies according to the type of cells. Lipids form the lipid bilayer, which confers fluidity to the cell membrane. Some proteins are embedded within the bilayer. They have their hydrophobic amino acids exposed. These are known as integral membrane proteins.

Other types of proteins present in the membrane are peripheral membrane proteins. They are bound to the lipids through some amino acid R-group and exposed to the surrounding completely; hence, they are called peripheral membrane protein. They are exposed as they have to interact with receptors on other cells, or they themselves are receptors for the molecules used in cell signaling.

Conclusion

The plasma membrane is composed of two major types of molecules, lipids and proteins. Which type of molecule is responsible for each of the following functions? Isolation from the surroundings: Lipids; interactions with other cells; peripheral membrane proteins.