Describe the structure of Golgi apparatus.

Structure:

(i) Basic Organization:

• Composed of flattened, membrane-bound cisternae (sac-like structures)
• Stacked arrangement: Usually 4–8 cisternae per stack (may vary: 3–20)
• Resembles smooth ER in membrane structure

(ii) Spatial Arrangement:

• Forms concentric network near nucleus
• Dictyosomes: Individual Golgi stacks (in plant cells, scattered; in animal cells, centralized)

(iii) Size and Variation:

• Cisternae diameter: 5–1.0 µm
• Shape, size, number vary with cell type and functional state
• More prominent in secretory cells (pancreatic acinar cells, goblet cells)

(iv) Polarity – Two Distinct Faces:

Cis Face (Convex)	Trans Face (Concave)
Forming/Entry face	Maturing/Exit face
Receives vesicles from ER	Releases vesicles to destinations
Initial glycosylation	Final modification, sorting

Intermediate cisternae (medial Golgi): Between cis and trans; sequential enzymatic modifications

(v) Associated Structures:

• Vesicles: Transport carriers budding from/fusing with cisternae
• COPI/COPII proteins: Coat proteins for vesicle formation
• SNAREs: Membrane fusion machinery