Secretory proteins are synthesized in -

Ans. is 'b' i.e., Endoplasmic reticulum Remember that all the proteins are synthesized on ribosomes.Ribosomes are of two types * Free ribosomes (in cytoplasm) * Ribosomes attached to endoplasmic reticulumProtein synthesis takes place both in free ribosomes located in cytoplasm and ribosomes attached to endoplasmic reticulum.The point which must be emphasized is that proteins which are meant to be transported or secreted are synthesized in ribosomes attached to the endoplasmic reticulum. Whereas proteins which have to be delivered in the cytosol are synthesized in free polyribosomes.The secretory proteins and transport proteins contain signal peptides, which helps them to be transported into Golgi apparatus via endoplasmic reticulum.Golgi body is the organelle where sorting of proteins for their respective destination occurs. The proteins which enter the galli apparatus are segregated into two types when they reach the exit side of Golgi apparatus. These two types are -Transport proteinsThese proteins are destined for plasma membrane they are stored in transport vesicles and are secreted in constitutive mannerSecretory proteinsProteins which are destined for secretion are stored in secretory vesicles.