Final answer:
Proteins are sorted at the trans face of the Golgi apparatus after undergoing further modifications.
Step-by-step explanation:
The Golgi apparatus plays a crucial role in sorting and modifying proteins as they move through it. After proteins enter the cis face of the Golgi, they undergo further modifications such as the addition of short chains of sugar molecules. These modified proteins are then tagged with phosphate groups or other small molecules to determine their proper destinations. Therefore, proteins are sorted at the trans face of the Golgi apparatus.