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MCB 2050 Final Exam questions latest upload, Exams of Advanced Education

Cheyney University of PennsylvaniaAdvanced Education

MCB 2050 Final Exam questions latest upload

Typology: Exams

2025/2026

Available from 07/02/2026

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MCB 2050 FINAL EXAM QUESTIONS LATEST UPLOAD
1. What are the main differences between prokaryotes and eukaryotes?:
Prokary-
otes have:
-
nucleoid
-
free
ribosomes
-
no
endomembrane
system
-
no
mitochondria
-
typically
small
-
they
are
very
simple
Eukaryotes
have:
-
enclosed
nucleus
-
free
ribosomes
and
rough
ER
-
vast,
interconnected
endomembrane
system
-
mitochondria/chloroplasts
-
larger
(typically)
2.
What are the characteristics of the nucleus?: - irregular shape, typically one per
cell
-
largest
organelle
3.
What are the two main functions of the nucleus?: - compartmentalization of the
cellular
genome and its activities
-
coordination
of
cellular
activities
4.
What
is
the
nuclear
membrane?:
phospholipid bilayer (hydrophilic heads and
hydrophobic tails)
5.
What
is
the
nuclear
lamina?:
A
scattolding
of
protein
to
prevent
the
membrane
from
collapsing
on
itself
pf3
pf4
pf5
pf8
pf9
pfa
pfd
pfe
pff
pf12
pf13
pf14
pf15
pf16
pf17
pf18
pf19
pf1a
pf1b
pf1c
pf1d
pf1e
pf1f
pf20
pf21
pf22
pf23
pf24
pf25
pf26
pf27
pf28

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MCB 2050 FINAL EXAM QUESTIONS LATEST UPLOAD

  1. What are the main differences between prokaryotes and eukaryotes?: Prokary-otes have:
  • nucleoid
  • free ribosomes
  • no endomembrane system
  • no mitochondria
  • typically small
  • they are very simple Eukaryotes have:
  • enclosed nucleus
  • free ribosomes and rough ER
  • vast, interconnected endomembrane system
  • mitochondria/chloroplasts
  • larger (typically)
  1. What are the characteristics of the nucleus?: - irregular shape, typically one per cell
  • largest organelle
  1. What are the two main functions of the nucleus?: - compartmentalization of the cellular genome and its activities
  • coordination of cellular activities
  1. What is the nuclear membrane?: phospholipid bilayer (hydrophilic heads and hydrophobic tails)
  2. What is the nuclear lamina?: A scattolding of protein to prevent the membrane from collapsing on itself

2 / 40

  1. What are the nuclear pores?: Protein-lined channels in the nuclear envelope that regulates the transportation of molecules between the nucleus and cytoplasm
  2. What are the components of the nuclear envelope?: - nuclear membrane
  • nuclear lamina
  • nuclear pores
  1. What is chromatin?: A complex of DNA and proteins that carry the cell's genetic instructions
  2. What is the nucleoplasm?: The nuclear content of the nucleus (similar to cytoplasm)
  3. What is the nucleolus?: A specialized sub-organelle or region the components of ribosomes are synthesized
  4. What is the nuclear content?: - chromatin
  • nucleoplasm
  • nucleolus
  1. What does the outer membrane of the nuclear envelope bind to?: Ribosomes and is continuous with the RER
  2. What is the structure of the inner nuclear envelope membrane?:
  • contains unique protein composition distinct from outer membrane
  • integral membrane proteins that connect to nuclear lamina
  1. What is the nuclear envelope intermembrane space continuous with?: ER lumen
  2. What do the nuclear pores join?: The inner and outer membranes of the nuclear envelope
  3. What are the functions of the nuclear envelope?: - separates nuclear content from cytoplasm
  • selective barrier
  • binds nuclear lamina
  1. What is the structure and location of the nuclear lamina?: Thin meshwork of long filament-like proteins that is bound to the inner surface of the nuclear envelope
  2. What are the functions of the nuclear lamina?: - support structure for nuclear envelope

4 / 40 processing

  • initial stages of ribosomal subunit assembly
  1. What are key components of the NPC structure?: - highly conserved
  • octagonal symmetry
  • structural nucleoporins/membrane nucleoporins
  1. What is the function of the structural nucleoporins of the NPC?: - anchors the complex to the nuclear envelope
  • forms an aqueous central channel
  1. What lines the inner channel of the NPC?: FG nucleoporins
  2. What makes FG nucleoporins different from nucleoporins?: They contain a large number of phenylalanine-glycine (FG) repeat sequences
  3. What is the structure and function of FG domains?: Highly disordered 2° structure that extends into the central channel and forms a hydrophobic mesh that limits the dittusion of macromolecules larger than 40 kDa
  4. What are cytoplasmic filaments?: Long protein filaments that extend into the cytosol and are involved in nuclear receptor-cargo protein recognition and import
  5. What is the nuclear basket?: 'basket-like' structure located on the nuclear side of the NPC that is involved in nuclear receptor-cargo protein import and export
  6. What are the functions of the NPC?: - passive dittusion of small molecules (e.g. nucleotide, histones)
  • regulation of large molecule movement (e.g. RNAs)
  1. How many small and large molecules per min can the NPC diffuse?: - small: 100 molecules/min/pore
  • large: 6 molecules/min/pore
  1. What do most nuclear-imported proteins contain?: A NLS
  2. What is the role of the NLS?: Serves as a 'zipcode' to mediate targeting of the protein from the cytosol to the nucleus

5 / 40

  1. What are the two types of NLS?: - 'classic': short stretch of positively-charged amino acid residues e.g. KKQRKK
  • 'bipartite': two short stretches of basic amino acids and a -10 amino acid long 'spacer' sequence e.g. KR(PAATK-AGQA)KKKK
  1. What makes a NLS 'necessary'?: If the sequence is mutated, the modified protein fails to target to the nucleus
  2. What makes a NLS 'sufficient'?: If the sequence linked to a non-nuclear 'passenger' protein is capable of redirecting the resulting fusion protein to the nucleus
  3. What are transport receptors?: karyopherins or importins/exportins
  4. What is the functions of importins/exportins?: They are mobile proteins that are respon- sible for 'ferrying' protein cargo across the nuclear envelope
  5. What is Ran?: small G-protein
  6. What would mutation of an NPC cause?: cell death
  7. What is Swyer syndrome associated with?: A mutation of the NLS on the SRY gene
  8. What is step 1 of nuclear import?: Nascent NLS-containing 'cargo' protein is recognized by importin a, which changes importin a conformational structure and allows to bind importin b
  9. What is step 2 of nuclear import?: 'cargo' protein-importin receptor complex moves towards the nucleus and importin b binds to a cytoplasmic filament at the NPC
  10. What is step 3 of nuclear import?: 'cargo' protein-importin receptor complex is translocated through the NPC central channel
  11. What is step 4 of nuclear import?: 'cargo'-receptor complex associates with the nuclear baskets and importin b binds to Ran-GTP resulting in its dissociation from the NPC and disassembly into the nucleoplasm
  12. Ran-GTP gradient determines:: the directionality of nucleocytoplasmic transport

7 / 40

  1. What is the biosynthesis pathway?: Materials are transported from the ER to the Golgi, to endosomes, and then to either lysosomes or in some instances the plasma membrane
  2. What is constitutive secretion?: ER-derived materials are continually transported from the Golgi to the PM and released in the extracellular space
  3. What is regulated secretion?: ER-derived materials from the Golgi are stored in secretory granules which fuse with PM in response to cellular signals, and release their lumenal 'cargo' into extracellular space
  4. What is the endocytic pathway?: Opposite of secretion, materials from the PM and/or extracellular space are incorporated into the cell and then transported to endosomes and lysosomes
  5. What comprises of the endomembrane system?: - ER
  • Golgi
  • lysosomes/vesicles
  • secretory granules
  • plasma membrane
  1. What is the ER the site of?: Protein synthesis, protein folding, and processing
  2. Why are the organelles of the endomembrane system structurally and functionally distinct?: - contain a particular set of proteins
  • perform a unique set of activities
  • provides compartmentalization and functional diversity
  • conserved in eukaryotes
  • dynamic structures
  1. What is the lumen?: Aqueous space inside of ER tubules and cisternae
  2. What mediates tubules and cisternae shapes?: reticulons
  3. What are reticulons?: Unique ER membrane proteins that possess a 'hairpin' secondary structure and regulate ER membrane curvature
  4. Which organelle has the most surface area?: ER
  5. What are two examples of ER subdomains?: rough ER and smooth ER
  6. What's the rough ER associated with?: ribosomes, which synthesize many proteins, including

8 / 40 those destined for secretion

  1. What is the smooth ER the primary site of?: lipid synthesis
  2. The filament like proteins which extend into the central channel of the nuclear pore complex are called:: FG nucleoporins
  3. You are creating a tagged protein fragment for use in a pull down assay as depicted in the tutorial reading in order to isolate Exportin. What sequence should your protein fragment contain? A) a tag which will bind importin - α B) an NLS sequence C)an NES sequence D) an importin - α fragment: C) an NES sequence
  4. What is the outer nuclear membrane continuous with?: the rough ER, it contains NUPs and attached ribosomes
  5. What are MAM and PAM?: mitochondria and plasma membrane-associated membranes of the ER that make direct contact with mitochondria or the PM and are involved in lipid exchange
  6. What are ER exit sites?: regions where transport vesicles bud ott from the ER en route to the Golgi
  7. What are the two main sites for protein synthesis in the cell?: - 'free' ribosomes in the cytosol
  • ER 'membrane-bound' ribosomes
  1. What is steps 1 and 2 of co-translocation of a soluble protein into the rough ER?: - translation of an mRNA begins in a 'free' ribosome
  • the N-terminus has an ER targeting signal that is recognized by the SRP
  • the SRP binds to the ribosome and stops protein translation
  1. What is a SRP?: signal recognition particle - protein dimer
  2. What is step 3 of co-translation of a soluble protein into the rough ER?: - the SRP targets the entire translocon complex to the surface of the ER
  • the SRP binds to the SRP receptor which serves as a 'docking site' for the incoming SRP

10 / 40

  1. What are two mechanisms that ensure the right materials go to the right compartment?: - lipid composition
  • modification and orientation of integral membrane proteins
  1. What are Type I membrane anchored proteins?: The signal sequence is at the N-terminus which is located in the lumen and the C-terminus is in the cytosol
  • LDL receptor
  • influenza
  • HA protein
  • insulin receptor
  • growth hormone receptors
  1. What are Type II membrane anchored proteins?: The N-terminus is located in the cytosol and the C-terminus is in the lumen
  • asialoglycoprotein receptor
  • transferrin receptor
  • golgi galactosyl-transferase
  • golgi sialyltransferase
  1. What are Type III membrane anchored proteins?: No signal sequence, but the N-ter-minus is located in the lumen and the C-terminus is in the cytosol
  • cytochrome P
  1. What are Type IV membrane anchored proteins?: Multi-transmembrane proteins, where the N-terminus is located in the lumen and the C-terminus is located in the cytosol
  • G-protein coupled receptors
  • glucose transporters
  • voltage-gated Ca2+ channels
  • ABC small molecule pumps
  • CFTR channel
  • Sec
  1. What are tail-anchored proteins?: The C-terminus is embedded in the membrane
  • v-SNAREs
  • t-SNAREs

11 / 40

  1. What does the TMD serve as in Type I co-translational insertion?: A stop-transfer sequence
  2. What are the steps of co-translational insertion of a Type I integral mem-brane protein?: - N-terminus of the nascent polypeptide enters the translocon and signal sequence is cleaved
  • TMD enters the translocon and interaction of its hydrophobic pore ring stops and further translocation of the nascent protein and signals the translocon to 'open' laterally
  • TMD segment is 'released' laterally into the membrane lipid bilayer
  • the ribosome is released from the mRNA and translocon
  1. What's step 1 of co-translational insertion of a Type 2 integral membrane protein?: - they begin translation on a free ribosome until the SAS emerges (they have no signal sequence)
  • the SAS is bound by the SRP in an analogous manner as the signal sequence; translation is paused and nascent protein is transferred to the translocon
  • upstream of the SAS is a series of positively-charged residues that are repelled by the positively- charged residues on the luminal side of the translocon
  • the SAS inverts, sending the N-terminus into the cytoplasm
  1. What's step 2 and 3 of co-translational insertion of a Type 2 integral mem-brane protein?: - translation continues until the C-terminus emerges from the ribosome and is deposited into the lumen of the ER
  • ribosome is disassembled and moves ott the translocon
  1. What are the steps of co-translational insertion of a Type III integral mem-brane protein?: - they possess a SAS, but they have positively-charged residues downstream of the SAS (towards the C-terminus)
  • these residues are attracted to the negatively-charged residues on the cytoplasmic side of the translocon so inversion doesn't occur
  • translation continues until the C-terminus emerges from the ribosome
  1. How are tail-anchored proteins inserted into the membrane?: - they are entirely translated on free ribosomes
  • their hydrophobic a-helix is always on the C-terminus of the protein, which is bound by Get3-ATP upon emergence from the ribosome
  • the Get3-ATP binds with the Get1/Get2 heterodimer on the ER membrane; Get1/Get2 hydrolyze the ATP of Get3, which facilitates the transfer of the a-helix to a membrane spanning channel of the dimer
  • Get1/Get2 exchanges the ADP for ATP causing the release of Get

13 / 40

  1. What does nascent glycoprotein bind to?: calnexin
  2. What is the role of calnexin?: membrane-bound reticuloplasmin that mediates the glycoprotein's final folding step
  3. What initiates the glycoprotein's release from the calnexin?: removal of the last glucose unit by glucosidase II
  4. What recognizes misfolded proteins?: GT monitoring enzyme or UGGT
  5. What is GT monitoring enzyme?: ER lumenal glucosyltransferase that recognizes hydrophobic residues that are usually 'masked' by attached sugars in a correctly folded protein
  6. How does GT monitoring enzyme fix misfolding?: by adding back a glucose to the terminal end of the 'trimmed' core so it can rebind to calnexin
  7. What destroys abnormal proteins in the ER lumen?: ER-associated degradation (ERAD)
  8. What is mono-Ub?: serves as a 'signal' for membrane protein import into endosomal vesicles
  9. What is poly-Ub?: serves as a 'signal' for ER protein degradation and most other cellular proteins destined for normal turnover via degradation by the proteasome
  10. What is the proteasome?: complex 'barrel-shaped', multi-subunit protein- degrading machine located in the cytosol (& nucleus)
  11. How does ERAD occur?: Ub-protein binds to the 'lid' of the proteasome, Ub chain is removed (and recycled), the protein is 'threaded' into the proteasome, where it is degraded (via proteolysis), and amino products are reused for new protein synthesis
  12. What is the adaptor molecule of the Clathrin coated vesicles that mediate TGN to endosome transport?: GGA
  13. What are the steps of the PERK-mediated UPR pathway?: - BiP is released from PERK in order to aid in the folding of accumulated misfolded proteins
  • PERK sensors dimerize and become 'active'
  • cytosolic-facing kinase domains of PERK dimer phosphorylate and inhibit eIF2a

14 / 40

  • protein synthesis in the cell decreases
  • available chaperones can focus on pre-existing misfolded proteins in the ER
  • ER stress is alleviated or cell death occurs
  1. What are the steps in ATF6-mediated UPR pathway?: - BiP is released from ATF
  • 'active' ATF6 moves from the ER to the Golgi, where the cytosolic-facing transcription factor domain of ATF is cleaved ott and targets to the nucleus
  • ATF6 TFD up-regulates a number of genes encoding: ER molecular chaperones, ER export components, ERAD components
  • ER stress is alleviated or cell death occurs
  1. The transcription of ribosomal RNA, rRNA processing and the initial assem-bly the ribosomal subunits occurs in the: A) Nucleolus B) rRNA processing factories C)Nuclear speckles D) Cytoplasm: A) Nucleolus
  2. The NPC is a complex structure composed of ~ 40 different highly con-served protein components called:: Nucleoporins
  3. The consists of two phospholipid membrane bilayers, the outer of which is continuous with the endoplasmic reticulum membrane.: Nuclear envelope
  4. Long filamentous proteins that extend from the cytoplasmic ring of the NPC into the cytoplasm are called:: Cytoplasmic filaments
  5. Once the karyopherins importin - α and importin- β release their cargo into the nucleoplasm they are shuttled back to the cytosol. What provides the energy for this transport?: GTP hydrolysis
  6. In the cytosol i)[ ] > [ ], and the reverse is true in the nucleus. This concentration gradient is maintained in the cytosol by an accessory ii) protein which promotes the hydrolysis of Ran-GTP to Ran-GDP.: - i)[Ran-GDP] > [Ran-GTP]; ii) GAP
  7. The process in which mis-folded proteins move from the ER lumen to the cytosol is called:: Retro-translocation

16 / 40

  1. What class of vesicle coat proteins mediates the vesicular transport of cargo through the Golgi?: COP I
  2. COP II vesicles mediate i) transport of cargo ii) .: i) antero- grade; ii) from the ER to the Golgi
  3. In the early stages of COPII vesicle assembly, Sar1 a small i) protein is recruited to the ER membrane in its GDP-bound form. Here GDP is exchanged for GTP by a membrane bound ii) protein.: i) G-protein; ii) GEF
  4. Which component of a COP II vesicle coat is responsible for recruiting and concentrating cargo proteins?: Sec23/
  5. Which of the following nuclear import/export proteins contains a nuclear export signal? A) Ran-GDP B) Ran-GTP C)Importin-β D) Importin-α E)Exportin: D) Importin-α
  6. Which of the following is a characteristic of a 'classic; nuclear localization signal? A) possession of a short stretch of positively-charged amino acids B) possession of a short stretch of negatively-charged amino acids C)possession of a stretch of positively-charged amino acids that form an amphipathic α-helix D) possession of two short stretches of positively-charged amino acids E)possession of large numbers of phenylalanines and glycines: A) possession of a short stretch of positively-charged amino acids
  7. After import into the nucleus, what binds to the importin-'cargo' complex and what effect does it have on the complex?: Ran-GTP, causes the importin-'cargo' complex to disassemble
  8. What is the function of FG nucleoporins in the Nuclear Pore Complex?: They prevent the dittusion of larger molecules through the NPC

17 / 40

  1. Put the following steps of the nuclear export of importin-α in order. Im- portin-α enters the nucleus as part of the importin-'cargo' complex A) Exportin recognizes and binds to the NES on Importin-α B) Ran-GTP binds to Importin-α of the importin-'cargo' complex; the complex dissociates exposing the NES on importin-α C)the export complex travels down the [Ran-GTP] gradient through the NPC to the cytosol D) Ran-GTP binds exportin forming the exportin complex: 1. B
  2. A
  3. D
  4. C
  5. What signal is recognized by the Golgi enzyme GlnNac phosphotrans-ferase?: Signal patch
  6. What feature of the KDEL receptor allows this protein to both bind KDEL containing proteins & release them when necessary?: The KDEL receptor has a higher aflnity for the KDEL sequence in a low pH environment
  7. Which of the following protein targeting signals is/are required for proper targeting to the lysosome? A) more than one of the above B) M6P group C)signal patch D) KDEL sequence E)signal peptidase: B) M6P group
  8. Put the following steps of transport vesicle assembly at the ERES in the correct order: A) Sar1-GTP recruits Sec23/24 to the surface of the ERES. These components form a dimer that promotes further outward bending of the ERES membrane B) After the COPII coat is fully assembled the vesicle pinches off from the ERES and begins transport to the Golgi. The COPII coat is disassembled and the components are released into the cytosol for another round of vesicle formation

19 / 40 A) Coat-protein II B) Sar C)Sec61 translocon D) reticuloplasmins E)reticulons: E) reticulons

  1. Put the following steps of PERK-mediated UPR in order: A) global translation is inhibited thus alleviating ER stress B) the active PERK dimer phosphorylates the translation factor eIF2a, render-ing it inactive C)PERK molecules dimerize and become active protein kinases D)A high concentration of unfolded proteins within the ER lumen triggers the recruitment of chaperone protein BiP releasing PERK: 1. D
  2. C
  3. B
  4. A
  5. Put the following steps of vesicle transport through the endomembrane system in the correct order: A) the transport vesicle buds off the donor membrane compartment encap-sulating luminal 'cargo' proteins in a highly regulated process B) the transport vesicle fuses with the target recipient membrane compart-ment in a process regulated by receptor proteins, and both the vesicle mem-brane and the cargo proteins are incorporated into the recipient compart-ments C)the vesicle transport process is repeated and membrane proteins are recycled back to their original membrane compartment D) the transport vesicle is shuttled through the cytosol along cytoskeleton highways, to the recipient membrane compartment in a process regulated by the receptor vesicle proteins: 1. A
  6. D
  7. B
  8. C

20 / 40

  1. Which of the following has been implicated in preparing a protein for import into a mitochondrion? A) mitochondrial processing peptidase B) more than one of the above C)signal recognition particle D) heat shock protein of 60 kDa E)heat shock protein of 70 kDa: E) heat shock protein of 70 kDa
  2. Which of the following is not involved in mitochondrial fusion? A) phospholipase D B) phosphatidic acid C)PI(4,5)P D) cardiolipin E)prohibitin: C) PI(4,5)P
  3. Put the following steps of protein insertion into the mitochondria matrix in order: A) the mitochondrial matrix sequence binds TOM20/22 and the pre- cursor protein passes through TOM B)the proton gradient between the inter membrane space and the mitochon-drial matrix drives the transfer of the matrix protein through the TIM complex C)a precursor protein is recognized by chaperones and maintained in a unfolded state D) ATP driven process pulls the matrix protein into the mitochondrial matrix where the mitochondrial targeting sequence is cleaved: 1. C
  4. A
  5. B
  6. D
  7. Which of the following techniques could be used to determine the size of a protein of interest from a mixed solution. Select all that apply. A. reporter tagging/GFP fusion protein B) Western blot analysis C)immuno-precipitation