1. BY- NAKSHATRA PAL SINGH CHAUHAN
FAIZAAN KHAN

2. • Golgi complex functions as factory to receive proteins from ER and further
processed and sorted to different locations within cell.
• Most of the glycolipids and sphingomyelin are synthesised.
• Involved in processing the broad range of cellular constituents that travel
along secretory pathway.

3. • Golgi is composed of flattened
membrane-enclosed sacs called
as cisternae and linked vesicles.
• Proteins from ER enter through the
cis face oriented towards nucleus
and exist from trans face after
several modifications and sorting.
• Golgi have four functionally distinct
regions: cis, medial, trans
compartments and trans-golgi
network.

4. Protein processing within Golgi is an extensive modification involving
around 250 enzymes catalysing different sugars to glycoproteins.
Glycoproteins are modified in different ways depending on structure
of protein and type of enzyme processing it during the passage in
the golgi complex.
Proteins destined for lysosomes are modified by addition of
phosphate groups to number 6 position of mannose residue.
Proteins are also modified in golgi by addition of carbohydrates to
the side chain of serine and threonone residues.

5. • Sphingomyelin(non-glycerol phospholipid in cell membrane) is synthesised on
lumenal surface of Golgi by transfer of phosphorylcholine group from
phophatidylchoine to ceramide.
• Alternatively addition of carbohydrates to ceramide yield variety of glycolipids.
• Oligosaccharide portions of glycoproteins are important surface markers in
cell-cell recognition.

6. Proteins, lipids and polysaccharides are
transported through secretory pathway
by different kind of transport vesicles;
which bud off from trans-Golgi network
and deliver them to appropriate cellular
locations.
Proteins carried from Golgi to plasma
membrane; either directly or via
endosomes intermediate.
Protein within Golgi mostly reside as
transmembrane protein and function in
glycosylation.

7. • Plasma membrane of epithelial is polarized. Plasma
membrane of such cells is divided into two separate
regions which contain specific proteins related to their
particular function.
i) apical domain- lumen of intestine specialized for efficient
absorption
ii) basolateral domain- lies just above the basal lamina
Protein transport to such cells take place by packaging of
proteins into transport vesicle targeted for different domains
leaving through trans-Golgi network or in. recycling
endosomes.
- If receptor is mannose-6-phosphate which is derived from
N-linked oligosaccharide will move protein to late
endosome which mature into lysosomes.
- NPXY-signal carry protein to plasma membrane
- Protein with C-terminal KDEL signal carry protein to ER

8. • Membrane proteins and lumenal secretory
proteins with their receptors are collected
into selected regions of donor membrane
where the formation of a cytosolic coat
result in budding of transport vesicle.
• Vesicle is transported by motor proteins
along cytoskeletal filaments to its target .
• Transport vesicle then settle at its target
membrane, the coat is removed and
vesicle fuses with target.
• Three families of protein coat: Clathrin,
COPI and COPII-coated vesicles.

9. • Transport vesicle must recognize the correct target membrane.
• Example- vesicle having lysosomal enzyme must be delivered to
lysosome
• vesicle and target membrane must fuse.
• Vesicle fusion is two step process:-
i) interaction between vesicle and target membrane is mediated by
tethering factors and small-GTP binding proteins (Rab proteins).
• 60 different types of proteins have been identified.
ii)Tethering is followed by formation of complexes called SNAREs
which provide energy to drive fusion of phospholipid bilayers bringing
two membrane in direct contact of lipid bilayers.