Difficulty: Easy
Correct Answer: Target and transport proteins to specific cellular locations (e.g., ER, mitochondria)
Explanation:
Introduction / Context:
Most eukaryotic and prokaryotic proteins must be delivered to the correct cellular compartment to function. Short amino-terminal or internal signal sequences act as postal codes that direct trafficking during or after translation.
Given Data / Assumptions:
Concept / Approach:
Signal sequences are recognized by receptors (e.g., SRP for ER targeting) or import machineries (TOM/TIM in mitochondria, importins for nucleus). They ensure proteins reach membranes, organelles, or are secreted, enabling proper function and preventing mislocalization.
Step-by-Step Solution:
Verification / Alternative check:
Loss-of-function experiments (mutated signals) cause mislocalization; fusing signals to reporters retargets proteins, confirming the function.
Why Other Options Are Wrong:
Common Pitfalls:
Equating “signal” with “stop” or confusing various targeting signals; note that signal peptides are often cleaved after translocation.
Final Answer:
Target and transport proteins to specific cellular locations (e.g., ER, mitochondria)
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