Select the statement that is true of transmembrane domains.
The Correct Answer and Explanation is :
The correct statement about transmembrane domains is:
“They contain hydrophobic amino acids that allow them to embed within the lipid bilayer of the cell membrane.”
Explanation:
Transmembrane domains are specific segments of proteins that span across the lipid bilayer of cell membranes. These domains are essential components of integral membrane proteins, which play crucial roles in various cellular processes, including signal transduction, transport, and cellular communication.
The lipid bilayer of the cell membrane is composed mainly of phospholipids, which have hydrophobic (water-fearing) tails and hydrophilic (water-loving) heads. The hydrophobic tails face inward, creating a non-polar environment within the membrane. To be embedded in this hydrophobic core, transmembrane domains of proteins must have amino acids with non-polar side chains, making them hydrophobic.
Typically, transmembrane domains are composed of stretches of 20-25 hydrophobic amino acids that form alpha helices. These helices can span the membrane once (single-pass) or multiple times (multi-pass). The hydrophobic amino acids in these helices interact favorably with the lipid bilayer, allowing the protein to remain stably embedded in the membrane.
Hydrophobic interactions between the transmembrane domain and the lipid bilayer are crucial because they provide stability to the protein’s structure within the membrane. In contrast, regions of the protein that face the aqueous environment outside the membrane (such as cytoplasmic or extracellular domains) usually contain hydrophilic (water-attracting) amino acids, which interact with the surrounding water molecules.
Transmembrane domains also play an essential role in maintaining the orientation of membrane proteins and facilitating their functional activities, such as transporting ions or molecules across the membrane, receiving signals, or serving as channels or receptors.