Concept explainers
Test Your Understanding
1. Transmembrane proteins (a) are peripheral proteins (b) receptor proteins (c) extend completely through the membrane (d) extend along the surface of the membrane (e) are secreted from the cell
Introduction: 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 extend of attachment to the membrane, the membrane proteins are classified as integral proteins, peripheral proteins, and transmembrane proteins.
Answer to Problem 1TYU
Correct answer: Transmembrane proteins are the proteins that extend completely through the membrane. Hence, the correct answer is option (c).
Explanation of Solution
Reason for the correct answer:
Transmembrane proteins are much larger than the lipids molecule, therefore it extends 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. Transmembrane proteins have nonpolar residues where they are embedded in the protein membrane. For maintaining stability within the bilayer, residues of transmembrane proteins form hydrophobic coils and helix such as α-helix and β-pleated sheets.
Option (c) is given as “extends completely through the membrane”.
Transmembrane proteins are much larger than the lipids molecule, therefore it extends completely through the membrane.
Hence, the correct answer is option (c).
Reasons for incorrect answers:
Option (a) is given as “are peripheral proteins”.
This is incorrect because peripheral membrane proteins are located on the inner and outer surface of the plasma membrane and are not embedded in the lipid bilayer as the other membrane proteins.
Hence, option (a) is incorrect.
Option (b) is given as “are receptor proteins”.
This is incorrect because receptor proteins either occur as intracellular receptors (located on the cytoplasm) or cell-surface receptors (located on cell surface) and do not extend completely through the membrane as the transmembrane proteins.
Hence, option (b) is incorrect.
Option (d) is given as “extended along the surface of the membrane”.
This is incorrect because transmembrane protein does not extend along the surface of the membrane like integral proteins.
Hence, option (d) is incorrect.
Option (e) is given as “are secreted from the cell”.
Transmembrane proteins are not secretary proteins that are secreted from cells. They are synthesized and modified in the ER and then transported into the cell membrane.
Hence, option (e) is incorrect.
Hence, the options (a), (b), (d), and (e) are incorrect.
Transmembrane proteins consist of nonpolar residues where they are embedded in the protein membrane and extend completely through the membrane.
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Chapter 5 Solutions
Biology (MindTap Course List)
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- Biology (MindTap Course List)BiologyISBN:9781337392938Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. BergPublisher:Cengage Learning