Question

which structure is required for proteins to enter the endomembrane system?
transport vesicle
kinesin
signal sequence
microtubules

Explanation:

Proteins destined for the endomembrane system (such as the endoplasmic reticulum, Golgi apparatus, lysosomes, etc.) have a signal sequence. The signal sequence is recognized by the signal recognition particle (SRP), which then directs the ribosome - nascent protein complex to the endoplasmic reticulum membrane. Transport vesicles are involved in the movement of proteins within the endomembrane system (e.g., from the ER to the Golgi), but not in the initial entry. Kinesin is a motor protein that moves along microtubules (another option) for intracellular transport, but not for protein entry into the endomembrane system. The signal sequence is the key for the co - translational targeting of proteins to enter the endomembrane system.

Answer:

signal sequence