MCB 2050 Final (2/2) Exam Questions with Correct Answers Latest Update 2025/2026
Golgi complex - Answers A organelle with unique morphology and polarity consisting of a
'complex' or 'stack' of flattened, membrane-bound cisternae (sacs) with dilated edges and many
associated tubules and vesicles. Possesses several sub-compartments/subdomains.
Mammalian Golgi - Answers typically contains one large Golgi complex located near the centre
of the cell
Plant and yeast Golgi - Answers typically contains several Glogi complexes located throughout
the cell
cis-Golgi network (CGN) - Answers - located at the cis face of the Golgi complex, consisting of a
complex, interconnected network of tubules and vesicles adjacent to the ERES.
- serves as a sorting station
- It is the initial destination of COPII transport vesicles from the ERES
- is the site of COPI vesicle assembly for the transport 'backwar' (retrograde transport) from
CGN to ER
- 'forward' (anterograde) transport as CGN matures to next subcompartment of Golgi
Golgi cisternae - Answers A series of 3, flattened cisternae that comprise the majority of the
Golgi structure. These are the sites of Golgi metabolism, the synthesis of complex
polysaccharides used for cell wall and modification of proteins/lipids. Acts as an 'assembly line'
3 main sections of Golgi cisternae - Answers 1. Cis
2. Medial
3. Trans
trans-Golgi Network (TGN) - Answers - located on the trans face of Golgi complex
- is an interconnected network of tubules and vesicles and serves as a sorting station (like CGN)
- 'forward' (anterograde) transport as previous sub-compartment matures throughout cisternae
- is the site of clathrin coated vesicle assembly for the forward transport of vesicles from TGN
to endosomes.
- Where COPI vesicles assemble for the transport backward (retrograde) to Golgi trans cisternae.
Golgi matrix - Answers Mediates the organization of the Golgi complex and consists of various
Golgi peripheral and integral membrane proteins. Its cytoplasmic-facing domains interact to
form a scaffold to link CGN, cisternae, TGN together (e.g., GRASPs). It also links the Golgi to the
,cytoskeleton, required for positioning and movement of Golgi.
GRASPs - Answers Golgi ReAssembly and Stacking Proteins. These are 'tethering proteins' that
link Golgi sub-compartments together.
If these are deleted or disassembled, organization of the Golgi complex is completely lost,
therefore they are required for Golgi complex structure.
Golgi complex function - Answers Glycosylation.
Most glycoproteins (already synthesized and N-linked glycosylated in ER moving through Golgi)
are subjected to additional glycosylation reactions.
Glycosylation in Golgi complex - Answers N-linked glycosylation is completed in the Golgi
complex as cis, medial and trans cisternae possess unique glycosyltransferase and glycosidase
enzymes.
Additional modification of glycoprotein's N-linked core oligosaccharide(s) is required for proper
protein function and/or targeting.
Core oligosaccharides on proteins moving through Golgi are modified by different enzymes in
each sub-compartment (CGN, cisternae, TGN)
alpha mannosidase 1 modifications - Answers In cis cisternae, 3 mannose sugars are removed
from the core oligosaccharide of the glycoprotein. The glycoprotein then moved to medial
cisternae, then trans cisternae for additional processes reactions. The final processed
glycoprotein resides in Golgi (TGN) or targets to PM or extracellular space.
Sorting signal for lysosome - Answers Other modifications to core oligosaccharides of proteins
in Golgi complex serve as a sorting signal for lysosomes, a unique carbohydrate residue called
M6P.
In cis cisternae, mannose units in core oligosaccharide(s) of soluble proteins destined for
lysosomes get phosphorylated.
N-acetylglucosamine phosphotransferase recognizes unique sequences in lysosome-destined
proteins. This is called a signal patch.
Mannose-6-Phosphate (M6P) groups - Answers Are soluble lysosomal protein targeting signals,
consisting of specific 3D arrangements of molecules on the folded-proteins surface. This is
destinct from NLS/NES signals.
Proteins without M6P - Answers These get packaged at TGN into secretory transport
vesicles/granules destined for PM, extracellular space or residence in Golgi.
Proteins with M6P - Answers These get packaged at TGN into clathrin-coated transport vesicles
to endosomes and then lysosomes (via M6P receptor & biosynthetic pathway.
, How do proteins move through the Golgi complex and onto other compartments of
endomembrane system? - Answers Heavily debated, however, most favoured model today is the
Cisternal progression/maturation model.
Cisternal progression/maturation model - Answers States:
- Golgi sub-compartments are dynamic structures
- each sub-compartment continually moved forward from cis to trans side of Golgi complex
(mediated by Golgi matrix proteins and cytoskeleton motors)
- composition of each sub-compartment will change while moving from cis to trans
- COPII-coated transported vesicles from ERES carrying newly-synthesized cargo proteins to cis
face of Golgi, fuses with CGN (wherew forward/anterograde transport causes progressive
maturation into cis cisternae)
- COPI-coated vesicles transport resident Golgi proteins backward (retrograde) through Golgi
complex, but those destined for compartment in endomembrane system or PM, are excluded
from COPI vesicles.
- TGN eventually disperses into various types of transport vesicles to deliver certain cargo to
other endomembrane compartments
How does the Golgi complex persist structurally and functionally? - Answers COPI transport
vesicles continuously transport vesicles with resident Golgi proteins backward (retrograde) to
its proper, original sub-compartment. This allows the continuous trange and forward movement
throughout the Golgi complex.
What is the order of Golgi complex maturation? - Answers CGN -> cis cisternae -> medial
cisternae -> trans cisternae -> TGN
While moving through, composition of each component constantly changes.
What does TGN disperse into? - Answers Different types of transport vesicles:
1. Clathrin-coated vesicles: M6P bearing protein targets to endosomes
2. Secretory vesicles: targets PM/extracellular space
3. Secretory granules: eventually targets PM/extracellular space
4. COPI-coated vesicles: target back to trans cisternae through retrograde transport
Lysosome - Answers A digestive organells that degrades all types of macromolecules and plays
role in degradation of larger cellular components/organelles (autophagy). Analogous to
vacuoles in plants and possess wide variety of shapes and sizes.
Golgi complex - Answers A organelle with unique morphology and polarity consisting of a
'complex' or 'stack' of flattened, membrane-bound cisternae (sacs) with dilated edges and many
associated tubules and vesicles. Possesses several sub-compartments/subdomains.
Mammalian Golgi - Answers typically contains one large Golgi complex located near the centre
of the cell
Plant and yeast Golgi - Answers typically contains several Glogi complexes located throughout
the cell
cis-Golgi network (CGN) - Answers - located at the cis face of the Golgi complex, consisting of a
complex, interconnected network of tubules and vesicles adjacent to the ERES.
- serves as a sorting station
- It is the initial destination of COPII transport vesicles from the ERES
- is the site of COPI vesicle assembly for the transport 'backwar' (retrograde transport) from
CGN to ER
- 'forward' (anterograde) transport as CGN matures to next subcompartment of Golgi
Golgi cisternae - Answers A series of 3, flattened cisternae that comprise the majority of the
Golgi structure. These are the sites of Golgi metabolism, the synthesis of complex
polysaccharides used for cell wall and modification of proteins/lipids. Acts as an 'assembly line'
3 main sections of Golgi cisternae - Answers 1. Cis
2. Medial
3. Trans
trans-Golgi Network (TGN) - Answers - located on the trans face of Golgi complex
- is an interconnected network of tubules and vesicles and serves as a sorting station (like CGN)
- 'forward' (anterograde) transport as previous sub-compartment matures throughout cisternae
- is the site of clathrin coated vesicle assembly for the forward transport of vesicles from TGN
to endosomes.
- Where COPI vesicles assemble for the transport backward (retrograde) to Golgi trans cisternae.
Golgi matrix - Answers Mediates the organization of the Golgi complex and consists of various
Golgi peripheral and integral membrane proteins. Its cytoplasmic-facing domains interact to
form a scaffold to link CGN, cisternae, TGN together (e.g., GRASPs). It also links the Golgi to the
,cytoskeleton, required for positioning and movement of Golgi.
GRASPs - Answers Golgi ReAssembly and Stacking Proteins. These are 'tethering proteins' that
link Golgi sub-compartments together.
If these are deleted or disassembled, organization of the Golgi complex is completely lost,
therefore they are required for Golgi complex structure.
Golgi complex function - Answers Glycosylation.
Most glycoproteins (already synthesized and N-linked glycosylated in ER moving through Golgi)
are subjected to additional glycosylation reactions.
Glycosylation in Golgi complex - Answers N-linked glycosylation is completed in the Golgi
complex as cis, medial and trans cisternae possess unique glycosyltransferase and glycosidase
enzymes.
Additional modification of glycoprotein's N-linked core oligosaccharide(s) is required for proper
protein function and/or targeting.
Core oligosaccharides on proteins moving through Golgi are modified by different enzymes in
each sub-compartment (CGN, cisternae, TGN)
alpha mannosidase 1 modifications - Answers In cis cisternae, 3 mannose sugars are removed
from the core oligosaccharide of the glycoprotein. The glycoprotein then moved to medial
cisternae, then trans cisternae for additional processes reactions. The final processed
glycoprotein resides in Golgi (TGN) or targets to PM or extracellular space.
Sorting signal for lysosome - Answers Other modifications to core oligosaccharides of proteins
in Golgi complex serve as a sorting signal for lysosomes, a unique carbohydrate residue called
M6P.
In cis cisternae, mannose units in core oligosaccharide(s) of soluble proteins destined for
lysosomes get phosphorylated.
N-acetylglucosamine phosphotransferase recognizes unique sequences in lysosome-destined
proteins. This is called a signal patch.
Mannose-6-Phosphate (M6P) groups - Answers Are soluble lysosomal protein targeting signals,
consisting of specific 3D arrangements of molecules on the folded-proteins surface. This is
destinct from NLS/NES signals.
Proteins without M6P - Answers These get packaged at TGN into secretory transport
vesicles/granules destined for PM, extracellular space or residence in Golgi.
Proteins with M6P - Answers These get packaged at TGN into clathrin-coated transport vesicles
to endosomes and then lysosomes (via M6P receptor & biosynthetic pathway.
, How do proteins move through the Golgi complex and onto other compartments of
endomembrane system? - Answers Heavily debated, however, most favoured model today is the
Cisternal progression/maturation model.
Cisternal progression/maturation model - Answers States:
- Golgi sub-compartments are dynamic structures
- each sub-compartment continually moved forward from cis to trans side of Golgi complex
(mediated by Golgi matrix proteins and cytoskeleton motors)
- composition of each sub-compartment will change while moving from cis to trans
- COPII-coated transported vesicles from ERES carrying newly-synthesized cargo proteins to cis
face of Golgi, fuses with CGN (wherew forward/anterograde transport causes progressive
maturation into cis cisternae)
- COPI-coated vesicles transport resident Golgi proteins backward (retrograde) through Golgi
complex, but those destined for compartment in endomembrane system or PM, are excluded
from COPI vesicles.
- TGN eventually disperses into various types of transport vesicles to deliver certain cargo to
other endomembrane compartments
How does the Golgi complex persist structurally and functionally? - Answers COPI transport
vesicles continuously transport vesicles with resident Golgi proteins backward (retrograde) to
its proper, original sub-compartment. This allows the continuous trange and forward movement
throughout the Golgi complex.
What is the order of Golgi complex maturation? - Answers CGN -> cis cisternae -> medial
cisternae -> trans cisternae -> TGN
While moving through, composition of each component constantly changes.
What does TGN disperse into? - Answers Different types of transport vesicles:
1. Clathrin-coated vesicles: M6P bearing protein targets to endosomes
2. Secretory vesicles: targets PM/extracellular space
3. Secretory granules: eventually targets PM/extracellular space
4. COPI-coated vesicles: target back to trans cisternae through retrograde transport
Lysosome - Answers A digestive organells that degrades all types of macromolecules and plays
role in degradation of larger cellular components/organelles (autophagy). Analogous to
vacuoles in plants and possess wide variety of shapes and sizes.
