Question

2d. The translocon of the mitochondrial outer membrane is functionally equivalent to ER translocon.  However, why is Hsc70 needed for mitochondrial import but not for import into the ER

Answer 1

Translocon of mitochondiral outer membrane as a complex structure of proteins which allows the proteins to enter into the mitochondira through inter membranal space. Hsc70 is type of cystolic chaperon having precursors and interact with this specific complex and promotes the import of the proteins into the mitochondria.

Whereas ER translocon complex though functions in similar fashion, it contains membrane protein itself which were cotranslationally integrated to the membrane and the foloding would happen inside the cell. any protein may enter into ER but incase of mitochondiral import, correctly folded proteins would enter which were beneficial to the cell.