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Multiple Choice
Which of the following statements correctly describes the function of a signal peptide?
A
A signal peptide acts as an enzyme that catalyzes the phosphorylation of proteins.
B
A signal peptide binds to DNA to regulate gene transcription.
C
A signal peptide is responsible for the degradation of misfolded proteins in the cytosol.
D
A signal peptide directs a newly synthesized protein to the endoplasmic reticulum for secretion or membrane insertion.
Verified step by step guidance
1
Step 1: Understand the concept of a signal peptide. A signal peptide is a short sequence of amino acids located at the beginning of a newly synthesized protein. It plays a crucial role in directing the protein to specific locations within the cell, such as the endoplasmic reticulum (ER).
Step 2: Eliminate incorrect options by analyzing their descriptions. For example, a signal peptide does not act as an enzyme for phosphorylation, nor does it bind to DNA to regulate gene transcription. These functions are unrelated to the role of a signal peptide.
Step 3: Consider the role of the signal peptide in protein targeting. Newly synthesized proteins destined for secretion or membrane insertion are directed to the ER by the signal peptide. This ensures proper folding and processing of the protein.
Step 4: Evaluate the remaining options and identify the correct one. The correct description aligns with the function of a signal peptide, which is to direct proteins to the ER for secretion or membrane insertion.
Step 5: Conclude that the correct answer is: 'A signal peptide directs a newly synthesized protein to the endoplasmic reticulum for secretion or membrane insertion.' This matches the biological function of signal peptides in cellular processes.