MCB 2050 Topic 2: Endomembrane Questions With
Complete Solutions
Consequences of misfolding Correct Answers Inhibits protein
translation factor eLF2a
Protein synthesis in the cell decreases.
ER stress is alleviated or cell death occurs.
Exception to biosynthesis at the ER Correct Answers
Glycolipids synthesized in the gogli, unique chloroplast and
mitochondrial proteins and lipids.
Function Endocytic pathway Correct Answers Operates in teh
opposite direction of the secretory pathway. Materials from the
PM receptor proteins destined for and/or extracellular space are
incorporated into the cell and then transported to endosome to
lysosome.
Function of Biosynthetic Pathway Correct Answers Materials
are transported from ER to Golgi to endosomes. From
endosomes to lysosome (vacuole and plasma membrane)
Function of Constitutive secretion (Secretory pathway) Correct
Answers ER-derived materials are continually transported from
the Golgi to the PM and/or released outside of the cell. Secretory
transport vesicle membrane components are incorporated into
the PM, and vesicle lumenal cargo is released into the
extracellular space
Function of membrane at the ER Correct Answers Most
membrane proteins and lipids are syntehsized at ER. The
, nascent ER membrane protein & lipids can traffic to other
membranes in cell.
Function of Regulated Secretion (Secretory pathway 2) Correct
Answers ER-derived materials from teh golgi are stored in
secretory granules. In responce to a cellular signal secretory
granules fuse with the PM and release their luumenal cargo into
the extracellular space. Regulated release of neurotransmitter by
nerve cells into the synaptic cleft.
Function of unfolded protein response (UPR) pathways Correct
Answers under certain conditions misfolded proteins
accumulate in the ER to very high levels (too high for ERAD)
Causes UPR to activate and PERK+ ATF6 to activate. BiP is
released from PERK in order to aid in folding and perk sensor
dimerize and become active. In Er-stress conditions BiP is
released. At the Golgi the cytosolic-facing, transcription factor
domain of ATF6 is cleaved off and targets the nucleus. ATF6
transcription factor domain up-regulates a number of genes
encoding: ER molecular chaperones.
Functions of Core Glycosylation Correct Answers Various ER
membrane-bound glycosyltransferases synthesize the core
oligosaccharide. The core branched oligosaccharide chain
consiting of 14 sugar reidues including a 3-glucose-long
terminal branch. Core oligosaccharide only transferred to
luminal-facing N residue of the sequence -N-x-S/T-
Functions of Core Modification Correct Answers After transfer
to the nascent protein, the 14-sugar core oligosaccharide is
gradually trimmed first two terminal glucose units are removed
Complete Solutions
Consequences of misfolding Correct Answers Inhibits protein
translation factor eLF2a
Protein synthesis in the cell decreases.
ER stress is alleviated or cell death occurs.
Exception to biosynthesis at the ER Correct Answers
Glycolipids synthesized in the gogli, unique chloroplast and
mitochondrial proteins and lipids.
Function Endocytic pathway Correct Answers Operates in teh
opposite direction of the secretory pathway. Materials from the
PM receptor proteins destined for and/or extracellular space are
incorporated into the cell and then transported to endosome to
lysosome.
Function of Biosynthetic Pathway Correct Answers Materials
are transported from ER to Golgi to endosomes. From
endosomes to lysosome (vacuole and plasma membrane)
Function of Constitutive secretion (Secretory pathway) Correct
Answers ER-derived materials are continually transported from
the Golgi to the PM and/or released outside of the cell. Secretory
transport vesicle membrane components are incorporated into
the PM, and vesicle lumenal cargo is released into the
extracellular space
Function of membrane at the ER Correct Answers Most
membrane proteins and lipids are syntehsized at ER. The
, nascent ER membrane protein & lipids can traffic to other
membranes in cell.
Function of Regulated Secretion (Secretory pathway 2) Correct
Answers ER-derived materials from teh golgi are stored in
secretory granules. In responce to a cellular signal secretory
granules fuse with the PM and release their luumenal cargo into
the extracellular space. Regulated release of neurotransmitter by
nerve cells into the synaptic cleft.
Function of unfolded protein response (UPR) pathways Correct
Answers under certain conditions misfolded proteins
accumulate in the ER to very high levels (too high for ERAD)
Causes UPR to activate and PERK+ ATF6 to activate. BiP is
released from PERK in order to aid in folding and perk sensor
dimerize and become active. In Er-stress conditions BiP is
released. At the Golgi the cytosolic-facing, transcription factor
domain of ATF6 is cleaved off and targets the nucleus. ATF6
transcription factor domain up-regulates a number of genes
encoding: ER molecular chaperones.
Functions of Core Glycosylation Correct Answers Various ER
membrane-bound glycosyltransferases synthesize the core
oligosaccharide. The core branched oligosaccharide chain
consiting of 14 sugar reidues including a 3-glucose-long
terminal branch. Core oligosaccharide only transferred to
luminal-facing N residue of the sequence -N-x-S/T-
Functions of Core Modification Correct Answers After transfer
to the nascent protein, the 14-sugar core oligosaccharide is
gradually trimmed first two terminal glucose units are removed
