Chapter 7, Problem 1IQ

Label the components in the following diagram of a small portion of a plasma membrane. Indicate whether regions are hydrophobic or hydrophilic.

Summary Introduction

To label: The components in the given diagram of a small portion of a plasma membrane and indicate whether the regions are hydrophobic or hydrophilic.

Introduction: All living organisms are made up of one or many cells. The organisms are classified as prokaryotes and eukaryotes. The prokaryotes are usually unicellular including the bacteria and archaea, while the eukaryotes are usually multicellular including the plants and animals. The prokaryotic cells are simpler and smaller than the eukaryotic cells.

Answer to Problem 1IQ

Pictorial representation: Fig.1 illustrates the diagram of a small portion of plasma membrane.

Fig.1: Plasma membrane

Explanation of Solution

Plasma membrane is a selectively permeable membrane with lipid bilayer and protein. The lipid bilayer structure is a barrier structure. Lipid molecule consists of the polar head region called hydrophilic head, and a non-polar fatty acid chain tail called hydrophobic tail. The hydrophilic region is attracted toward aqueous condition, and the hydrophobic end is repelled away from the aqueous condition.

Membrane proteins are a part of biological membrane that primarily interacts with it to perform various functions in the cell. There are various membrane proteins that help in the transportation of molecules in and out of the cell. Based on the extend of attachment to the membrane, the membrane proteins are classified as integral proteins, peripheral proteins, and transmembrane proteins.

1. Integral membrane proteins: Integral membrane proteins are a type of membrane proteins that are firmly bound to the membrane. These types of proteins are amphipathic in nature. Here, the hydrophilic head region is extended out of the cell, and its hydrophobic tail region interacts with the fatty acids present on the membrane phospholipids.
2. Transmembrane proteins: Transmembrane proteins extend completely through the membrane. These types of proteins majorly function on both sides of the layer (intracellular and extracellular) and help to transport molecules across it.
3. Peripheral membrane proteins: Peripheral membrane proteins are located on the inner and outer surfaces of the plasma membrane, and are not embedded in the lipid bilayer as the other membrane proteins. They bound to the exposed regions of the integral proteins through non-covalent interactions.