Final answer:
Misfolded proteins cannot cross cellular membranes on their own and face a barrier in the form of a need for chaperone proteins like HSP70 for assistance. Chaperone proteins prevent protein aggregation and ensure proper folding, which is crucial to protein function and avoiding diseases such as Alzheimer's and Creutzfeldt-Jakob disease.
Step-by-step explanation:
Proteins must fold correctly to perform their functions, with the folding process being dependent on the three-dimensional shape formed by amino acids. A barrier that misfolded proteins encounter is the inability to cross cellular membranes without assistance. Within cells, chaperone proteins such as HSP70 play a crucial role in guiding proteins across membranes and assisting with proper folding and unfolding. These chaperones are essential as they prevent protein aggregation and help maintain the correct folding needed for protein function. Failure to fold correctly can lead to proteopathies, diseases characterized by the accumulation and toxicity of misfolded proteins, such as Alzheimer's and Creutzfeldt-Jakob disease.