Final answer:
Myristylation and farnesylation are post-translational modifications that help target proteins to the cell membrane by attaching lipid groups, ensuring proper protein function and membrane association.
Step-by-step explanation:
Myristylation and farnesylation are types of post-translational modifications that affect the distribution and function of proteins within the cell. Farnesylation involves the addition of a 15-carbon farnesyl group to a protein, typically to a cysteine residue within a CaaX motif at the carboxyl terminus, which facilitates the attachment of the protein to cell membranes. This modification can lead to a shift of protein distribution from the cytosol to the membranes, which is crucial for the function of certain proteins, such as Ras, which require membrane association to be activated. Similarly, myristylation refers to the covalent attachment of a 14-carbon myristoyl group to the amino-terminal glycine of a protein, again promoting membrane association.
Both of these lipid modifications are critical as they enable proteins to interact with the membrane's hydrophobic environment, which allows them to properly function in signaling or as membrane-bound enzymes. Therefore, the correct answer to the question would be B) Target proteins to the cell membrane.