Final answer:
Folded cargo proteins targeted to mitochondria or other organelles are commonly unfolded during transport, a process assisted by chaperone proteins like HSP70 which also help in refolding upon entry. Not all proteins require folding assistance, but chaperones are crucial for preventing misfolding under abnormal conditions.
Step-by-step explanation:
When it comes to the transportation of folded cargo proteins across membranes, not all of them need to be unfolded beforehand. Typically, proteins that are targeted to mitochondria or other organelles are transported across membranes in an unfolded state. The process is facilitated by helper molecules known as chaperone proteins. In the case of mitochondrial proteins, the chaperone protein HSP70 is responsible for unfolding the protein as it enters the matrix and then refolding it once it's inside. Protein folding is a critical process that determines the functionality of a protein, and some proteins may require the help of chaperones to fold correctly and avoid dysfunctional shapes that could arise from abnormal conditions such as improper temperature or pH.