UBC BIOL 200 - UNIT 4:
ENDOMEMBRANES EXAM QUESTIONS
AND ANSWERS GRADED A+ 2026
What are the three major subdivisions of the Endomembrane system? - ANS -Secretory
pathway
-Lysosomal pathway
-Endocytic pathway
How do proteins travel through the endomembrane system? - ANS -Proteins only enter
through the start of each pathway, (never from the middle) and never leave pathway until they
have reached their destination
What are 3 types of protein that enter the endomembrane system upon translation? - ANS 1.
Proteins destined for secretion
2. Plasma membrane proteins
3. Proteins that are destined to be endomembrane resident proteins
What type of proteins does the rough endoplasmic reticulum synthesize? - ANS Proteins
destined for secretion, lysosomes, or membranes
True or false: the cytosolic surface of the ER have ribosomes - ANS True: these ribosomes are
responsible for synthesizing proteins for import into the ER
@COPYRIGHT 2026/2027 ALL RIGHTS RESERVED
1
, What does the smooth endoplasmic reticulum synthesize? - ANS Lipids and steroids
Where do newly synthesized proteins exit the ER? - ANS The transitional ER (where two types
of ER meet)
How do proteins stay in the ER? - ANS Proteins that stay in the ER have a ER retention signal
(KDEL or HDEL sequence based on amino acids) at carboxyl ends
-Even if they get out of the ER into the cis cisternae of the Golgi their ER targeting signal gets
them sorted into vesicles and brings them back into the ER
What is retrograde movement? - ANS Backward movement (from trans to cis) of vesicles
What is the unfolded protein response? - ANS Production of chaperone proteins and the
expansion of the ER to promote proper folding and processing triggered by misfolded proteins
in the ER lumen
What proteins are part of membranes? - ANS Proteins inserted into membranes (only
partially translocated) are destined for the ER, membranes of another organelle, or the plasma
membrane
These proteins stay within the membrane once they are inserted into the ER membrane
What proteins are not part of membranes? - ANS Proteins that are soluble and completely
translocated into membrane
Destined for secretion or transfer to lysosomes
Never part of membrane
Where does translation of proteins occur? - ANS On free ribosomes
@COPYRIGHT 2026/2027 ALL RIGHTS RESERVED
2
ENDOMEMBRANES EXAM QUESTIONS
AND ANSWERS GRADED A+ 2026
What are the three major subdivisions of the Endomembrane system? - ANS -Secretory
pathway
-Lysosomal pathway
-Endocytic pathway
How do proteins travel through the endomembrane system? - ANS -Proteins only enter
through the start of each pathway, (never from the middle) and never leave pathway until they
have reached their destination
What are 3 types of protein that enter the endomembrane system upon translation? - ANS 1.
Proteins destined for secretion
2. Plasma membrane proteins
3. Proteins that are destined to be endomembrane resident proteins
What type of proteins does the rough endoplasmic reticulum synthesize? - ANS Proteins
destined for secretion, lysosomes, or membranes
True or false: the cytosolic surface of the ER have ribosomes - ANS True: these ribosomes are
responsible for synthesizing proteins for import into the ER
@COPYRIGHT 2026/2027 ALL RIGHTS RESERVED
1
, What does the smooth endoplasmic reticulum synthesize? - ANS Lipids and steroids
Where do newly synthesized proteins exit the ER? - ANS The transitional ER (where two types
of ER meet)
How do proteins stay in the ER? - ANS Proteins that stay in the ER have a ER retention signal
(KDEL or HDEL sequence based on amino acids) at carboxyl ends
-Even if they get out of the ER into the cis cisternae of the Golgi their ER targeting signal gets
them sorted into vesicles and brings them back into the ER
What is retrograde movement? - ANS Backward movement (from trans to cis) of vesicles
What is the unfolded protein response? - ANS Production of chaperone proteins and the
expansion of the ER to promote proper folding and processing triggered by misfolded proteins
in the ER lumen
What proteins are part of membranes? - ANS Proteins inserted into membranes (only
partially translocated) are destined for the ER, membranes of another organelle, or the plasma
membrane
These proteins stay within the membrane once they are inserted into the ER membrane
What proteins are not part of membranes? - ANS Proteins that are soluble and completely
translocated into membrane
Destined for secretion or transfer to lysosomes
Never part of membrane
Where does translation of proteins occur? - ANS On free ribosomes
@COPYRIGHT 2026/2027 ALL RIGHTS RESERVED
2
