Final answer:
Cotranslational import occurs when translation and protein import into the cell occur simultaneously, while posttranslational import occurs after translation is complete.
Step-by-step explanation:
There are two main ways in which proteins can be imported into cells - cotranslational import and posttranslational import. Cotranslational import occurs when translation and protein import into the cell occur simultaneously.
This process takes place in prokaryotes and some organelles, such as mitochondria. Translation happens on the ribosomes bound to the endoplasmic reticulum (ER), and as the protein is synthesized, it enters the ER lumen.
On the other hand, posttranslational import occurs after translation is complete and the protein is free in the cytoplasm. This process takes place in eukaryotes and involves the protein being recognized by a receptor and transported into the target organelle, such as the nucleus or mitochondria.