Docsity
Docsity
Prepare for your exams
Prepare for your exams

Study with the several resources on Docsity

Earn points to download
Earn points to download

Earn points by helping other students or get them with a premium plan

Guidelines and tips
Guidelines and tips
Sell on Docsity
Sell on Docsity
Docsity AI
Docsity AI
Log inSign up

Prepare for your exams

Study with the several resources on Docsity

Find documents

Prepare for your exams with the study notes shared by other students like you on Docsity

Search for your university

Find the specific documents for your university's exams

Docsity AINEW

Summarize your documents, ask them questions, convert them into quizzes and concept maps

Explore questions

Clear up your doubts by reading the answers to questions asked by your fellow students

Earn points to download

Earn points by helping other students or get them with a premium plan

Share documents
download point icon20 Points

For each uploaded document

Answer questions
download point icon5 Points

For each given answer (max 1 per day)

All the ways to get free points
Get points immediately

Choose a premium plan with all the points you need

Study Opportunities

Choose your next study program

Get in touch with the best universities in the world. Search through thousands of universities and official partners

Community

Ask the community

Ask the community for help and clear up your study doubts

Free resources

Our save-the-student-ebooks!

Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors

MCB 2050 Final exam questions updated version, Exams of Advanced Education

Cheyney University of PennsylvaniaAdvanced Education

MCB 2050 Final exam questions updated version

Typology: Exams

2025/2026

Available from 07/02/2026

tizian-mwangi
tizian-mwangi 🇺🇸

4.1

(8)

29K documents

1 / 38

Toggle sidebar

This page cannot be seen from the preview

Don't miss anything!

bg1
1 / 38
MCB 2050 FINAL EXAM QUESTIONS UPDATED VERSION
1.
what is the largest organelle in the cell? describe its characteristics: -
nuclear
size varies from cell-to-cell and between organisms
-
usually
determined
by
cell
size
(ex:
cytoplasmic
volume)
-
increases
during
development
and
in
cancer
cells
(used
for
diagnosis/treatment)
-
primary
ditterence
between
prokaryotes
and
eukaryotes
2.
eukaryotes possess a membrane bound nucleus, what is the
prokaryotic
equivalent:
- region (nucleoid) where the chromosome is located
-
less
DNA
-
less DNA
packaging
-
limited/no
RNA
processing
3. what cell has no nucleus: - RBC
4.
what
cell
is
multinucleated?:
- muscle cells
5.
what are the
2 main
functions of
the
nucleus?: 1. compartmentalization of the
cellular
genome
and
its
activities
2.
coordination
of
cellular
activities
6.
explain the compartmentalization function of the nucleus... nucleus
is site of
:
- separates genetic material from the cytoplasm, ensuring highly regulated
control of gene expression
-
nucleus
is
the
site
of
DNA
replication,
transcription
and
RNA
processing
(early
processing
such
as
splicing)
-
site
where
translation
components
(ribosomes,
mRNA,
tRNA)
are
synthesized
7.
explain the coordination function of the nucleus: - store's the cells genetic
material and
regulated gene expression to controls a variety of processes
-
control
of
metabolism,
protein
synthesis,
reproduction
(cell
division)
etc.
8. separation of the genome (genetic information) from the cytoplasm
allows
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

Partial preview of the text

Download MCB 2050 Final exam questions updated version and more Exams Advanced Education in PDF only on Docsity!

1 / 38

MCB 2050 FINAL EXAM QUESTIONS UPDATED VERSION

  1. what is the largest organelle in the cell? describe its characteristics: - nuclear size varies from cell-to-cell and between organisms
  • usually determined by cell size (ex: cytoplasmic volume)
  • increases during development and in cancer cells (used for diagnosis/treatment)
  • primary ditterence between prokaryotes and eukaryotes
  1. eukaryotes possess a membrane bound nucleus, what is the prokaryotic equivalent: - region (nucleoid) where the chromosome is located
  • less DNA
  • less DNA packaging
  • limited/no RNA processing
  1. what cell has no nucleus: - RBC
  2. what cell is multinucleated?: - muscle cells
  3. what are the 2 main functions of the nucleus?: 1. compartmentalization of the cellular genome and its activities
  4. coordination of cellular activities
  5. explain the compartmentalization function of the nucleus... nucleus is site of : - separates genetic material from the cytoplasm, ensuring highly regulated control of gene expression
  • nucleus is the site of DNA replication, transcription and RNA processing (early processing such as splicing)
  • site where translation components (ribosomes, mRNA, tRNA) are synthesized
  1. explain the coordination function of the nucleus: - store's the cells genetic material and regulated gene expression to controls a variety of processes
  • control of metabolism, protein synthesis, reproduction (cell division) etc.
  1. separation of the genome (genetic information) from the cytoplasm allows

2 / 38 : spatial and temporal regulation of gene expression in eukaryotes

  1. compare prokaryotes and eukaryotes in their timing of transcription and translation: prokaryotes:
  • mRNA translated while transcription in process eukaryotes:
  • mRNAs undergo post-transcriptional processing (eg splicing) before transport out of the nucleus and then translated IN the cytoplasm or AT the ER *additional control of gene expression *nucleus limits access of transcription factors from cytoplasm to genome
  1. describe the nucleoplasm and its role/function in the nucleus: - fluid filled interior of nucleus (highly organized)
  • similar to cells' cytoplasm
  • consists of >30 specialized regions (subdomains) that participate in specific functions
  1. are subdomains in the nucleus membrane bound?: NO
  • chromosomes are, subdomains are not
  1. describe the nucleolus and its role/function in the nucleus: - most conspicuous nuclear subdomain (irregularly shaped, sense, and granular in appearance)
  • size and number (1-5) depend on metabolic activity of cell (‘cellular activity = ‘protein synthesis = ‘size/number to produce more ribosomes for protein synthesis)
  • function in producing ribosomes
  • site of ribosomal DNA (rDNA) gene transcription, rRNA processing and initial stages of ribosomal subunit assembly (rRNA + protein)
  1. explain the assembly of the ribosomal subunit: - rRNA transcribed in the nucleolus from DNA
  • ribosomal proteins gets transcribed in nucleus, mRNA gets exported out of the nucleus where the translation machinery is located in the cytoplasm
  • protein gets exported back to nucleus (nucleolus) and can participate in initial ribosomal assembly (subunit assembly = rRNA + protein)
  • subunit gets exits out the nuclear pore into the cytoplasm for function

4 / 38

  • membranes serve as barriers to passage of ions, solutes and macromolecules between N/C
  1. eve rywhere in nuclear membrane that there is a pore, there is no .: het-erochromatin
  • want to keep the bas stutt away from the cytoplasm
  • don't need to be translated, so don't need to be in cyto
  • if pore is "clogged" with heterochromatin other things can't get in/out
  1. outer nuclear membrane is continuous with : RER
  • ribosomes attached to cytoplasmic surface of outer membrane (functionally similar to RER)
  • nuclear envelope lumen is continuous with RER lumen
  1. outer and inner nuclear membranes are joined where?: - highly curved
  • jointed at NPC
  1. describe the nuclear lamina and its role/function: - located on the inner surface (nucleoplasmic side) of nuclear inner membrane
  • network (mesh) of long filament like proteins
  • ABC nuclear lamins are the related proteins that form intermediate filaments in the cytoskeletal network
  • lamina provides mechanical support to envelope (binds to inner membrane integral proteins)
  • serves as a scattold for attachment of chromatin (HC) and other components of the nucleus
  1. explain the mutations in the nuclear lamin genes?: - responsible for several human diseases
  • EG: hutchinson-Gilford progeria syndrome
  • rare, characterized by premature aging in children, death by early adolesence
  • due to a point mutation in LAMIN A gene leading to untruncated lamin protein
  • results in breakdown of nuclear lamina and causes changes in envelope morphology/function
  1. what is the nuclear pore complex and its function: - channels / doorways in the nuclear envelope
  • responsible for regulated traflcking between N/C -> small polar molecules -> RNAs

5 / 38 -> proteins/txn factors

  • typically 3-4k per nucleus but related to nuclear activity
  1. describe the structure of the NPC *: - large, highly complex structure
  • composed of 40 ditterent proteins (nucleoporins / nups)
  • proteins are highly conserved among all eukaryotes
  • include both integral and peripheral inner and outer membrane proteins
  • several nups are related to COPII proteins involved in vesicle formation
  • nups + COPII proteins function to curve membranes
  • overall: 8-fold symmetrical structure organized around a large central aqueous channel
  1. what is the central scaffold of the NPC: - composed of integral and trans- membrane bound nucleoporing
  • anchors NPC to nuclear envelope membranes (at junction)
  • forms aqueous central channel
  1. the inner surface of central NPC channel is lined by what proteins?: - FG nucleoporins (possess unusual AA composition; hydrophilic polypeptides with repeats of hydrophobic domains enriched in F/G)
  • FG Nups possess a unique highly disorganized secondary structure
  • extended organization fills central channel
  1. what is the function of FG nucleoporins in the central channel?: - form mesh like sieve that limits dittusion of macromolecules > 40kDa (selective import/export by active process)
  • small molecules move freely through the central channel
  1. what are the Y-complexes in the NPC: - formed from Nups (structural)
  • includes cytoplasmic ring and nuclear ring
  • located on cytoplasmic and nucleoplasmic side of NPC
  • linked to central scattold and to cytoplasmic filaments / nuclear basket
  1. what are the cytoplasmic filaments in the NPC: - long, filament-shaped (structural) Nups that extend into the cytoplasm
  • invovled in nuclear cargo receptor protein recognition and import from the cytoplasm

7 / 38

  1. suflcient: if the sequence is linked to a non-nuclear protein, that protein becomes localized to the nucleus
  2. the characterization of different NLSs led to the identification of ?: - factors necessary for the nuclear import of proteins from cytoplasm -> ex: transport receptors, karyopherins, importins/exportins
  3. transport receptors are mobile proteins responsible for ?: - moving / ferrying protein 'cargo' across the nuclear envelope
  4. importin/exportin are part of a large family of receptor proteins responsible for ?: - moving macromolecules (proteins/RNA) into/out of nucleus
  5. what is importin's structure like?: - importin is a heterodimeric protein that consists of two distinct subunits (A/B)
  6. what is step 1 of C -> N transport: - nascent NLS containing cargo protein is recognized in the cytoplasm by importin
  • importin a (contains binding domain) for NLS and binds to basic residues in cargo protein's NLS -importin b binds to cytoskeleton
  1. what is step 2 of C-> N transport: - cargo protein-importin receptor complex moves through cytoplasm towards nucleus (via importin B's ability to bind cytoskeleton)
  • cytoskeleton elements serve as highways for almost all types of intracellular transport (RNA, protein, organelles)
  • at the surface of the nucleus, importin B binds to cytoplasmic filaments of NPC
  1. what is step 3 of C -> N transport: - cargo protein-importin receptor complex is translocated through central channel of NPC
  • not well understood, thought that cargo-receptor complex interacts with hydrophilic and FG domains of FG Nups in central channel (interactions untangle the FG domain network allowing translocation)
  1. what is step 4 of C -> N transport: - cargo receptor complex associates with nuclear basket on inner surface of NPC
  • cargo-receptor complex binds to RAN-GTP (via importin B) resulting in its release from NPC (basket) and disassembly into nucleoplasm
  • import of the NLS containing cargo protein into nucleus is accomplished

8 / 38

  1. is the NLS signal cleaved?: NO!
  • not proteolytically cleaved from cargo protein unlike most other targeting signals
  1. RAN is what kind of protein?: - small GTPase whose conformation and activity is regulated by GTP binding & hydrolysis
  • exists in GTP or GDP bound states (active/inactive)
  • steep concentration gradient between N/C
  1. what is the RAN GTP gradient?: - nucleus > cytoplasm
  2. what is Ran GDP gradient?: - cytoplasm > nucleus
  3. how is the RAN GTP gradient mediated?: 1. RCC1: nuclear (no NES) GEF that promotes the conversion GDP -> GTP
  4. RanGAP1: cytoplasmic GAP that promotes hydrolysis of GTP -> GDP in cytoplasm
  5. Ran GTP gradient determines what?: - directionality of nucleocytoplasmic transport
  • GTP hydrolysis provides energy requires for nucleocytoplasmic transport (active process)
  1. what is step 5 of C -> N transport: - RAN GTP bound importin B subunit moves back to cytoplasm due to gradient N>C
  • in the cytoplasm GTP is hydrolyzed via RanGAP1 and RanGDP is released from importin B
  • importin B can now be used for another round of import
  • Ran GDP moved back into nucleus via gradient (converted to GTP by RCC1)
  1. you don't want importin a accumulating in the nucleus, so it binds to what protein?: - exportin 2
  • when importin a dissociates from importin B, NES is exposed *importin B does NOT need an NES
  1. what is an NES?: - specific stretch of amino acids recognized by exportin that serves as a postal code to mediate the movement of proteins N -> C
  • there are several types of NESs
  • all are both necessary and suflcient for N->C targeting
  1. what is the most common type of NES?: - leucine rich motif

10 / 38

  1. what are the main components of standard brightfield microscopy (6)? what is the purpose?: - components: light source, condenser lens, stage (holding specimen), objective and ocular lens, detector (eye/camera)
  • light dittracted by specimen and undittracted light (field of view) focused by objective lens
  1. what is deconvolution?: - computer based program software that is designed to remove background and out of focus light to yield a better contrast and clarity image
  2. what is the primary purpose of magnification?: - generate a magnified, high quality view of specimen
  • magnification = objective lens x ocular lens
  • empty magnification means that continuing to enlarge the image provides no new detail
  1. what is the primary purpose of resolution?: - minimum distance that can separate two points that still remain identifiable as separate points
  • ability to distinguish two close objects as separate entities
  1. resolution depends on what 2 factors?: 1. wavelength of illumination light
  2. numerical aperture (NA): light gathering qualities of objective lens and specimen mounting medium
  • ability to gather light and resolve fine detail R (nm) = 0.61 x wavelength / NA
  • lower nm distance is higher resolution
  1. what two ways is resolution maximized?: 1. shorter wavelength of light
  • blue light increases resolution compared to red
  1. increase NA
  • use oil instead of water to increase NA (decrease resolution)
  1. what is a major limitation of brightfield microscopy?: - specimens poor contrast (lack of structural/ cellular details)

11 / 38

  • specimens are usually 'fixed' (eg formaldehyde fixes cross-linked groups on adjacent proteins), embedded in wax for support them sectioned with microtome and stained with specific molecule dyes
  • fixation results in cell death, embedding and sectioning can lead to structural artifacts
  1. what is the general description of the endomembrane system?: - dynamic coordinated and interconnected network of organelles (except mito/chloroplasts) and related structures
  • ER, ER derived organelles (nucleus, peroxisomes, lipid bodies), golgi, endosomes, lysosomes, secretory granules, PM

13 / 38

  1. what is a general description of the biosynthetic pathway?: - materials (lysosomal membrane and soluble proteins) transported from ER to golgi, endosomes and then lysosomes/vacuoles
  • occasionally material (HIV particles) can be transported via exosomes from endosome to PM and extracellular space (interact with neighboring cells)
  1. what are the two types of secretions in the secretory pathway?: 1. constitutive
  2. regulatory
  3. explain the constitutive secretory pathway: - materials continuously transported from golgi to PM and are released via exocytosis to the extracellular space via secretory vesicles
  • secretory vesicle membrane components are incorporated into the PM and luminal cargo is released into extracel-lular space
  • exocytosis = traflcking to PM, fusion and release of contents
  1. explain the regulatory secretory pathway: - occurs only in specialized cells (ex: neurotrans-mitter regulation in nerve cells)
  • ER-derived materials from golgi is stored in secretory granules
  • in response to a cellular target, secretory granules fuse with PM and release via exocytosis luminal cargo into extracellular space
  • secretory granule membrane components are incorporated into PM
  1. what is the endocytic pathway? in what direction do vesicles traffic?: - operates in the opposite direction of secretory pathways (into cell)
  • materials from PM (receptor proteins destined for degradation or bound to ligand) and/or from extracellular space are incorporated into the cell (endocytosis) and transported to endosomes and lysosomes/vacuoles
  • endocytosis = uptake of materials from PM and extracellular space into transport vesicles
  1. what are sec yeast mutants?: - deficient in secretory pathways
  • proteins that would normally be secreted (to PM) accumulate in ditterent cellular compartments within the EM system
  • proper movement through the EM system is blocked by either mutations in various components of the system or defects in organelle morphology, distribution and location

14 / 38

  1. what are the 5 classes of sec mutants: * classed based on where the breakdown is (where protein accumulates)
  2. accumulation in the cytosol (defects in protein co-translational translocation)
  3. accumulation in RER (defects in vesicle formation)
  4. accumulation in ER -> golgi transport (defects in fusion of transport vesicles)
  5. accumulation in golgi (defects in transport from golgi to secretory vesicles)
  6. accumulation in secretory vesicles (defect in transport from secretory vesicle to cell surface)
  7. explain double sec mutants? how did they determine which class came first?: - double mutants indicate the order of steps within the pathway
  • B and D mutant is analagous to a B mutant because B comes before D (ER vesicle budding before golgi budding)
  1. what is the general structure of the ER?: - highly complex network of membrane-enclosed, rod like tubules and sheet-like cisternae (flattened sacs)
  • organelle with largest surface area (not volume)
  1. what is the ER lumen? morphology is mediated by what proteins? what kind are these proteins?: - the lumen is the aqueous space inside ER tubules and cisternae
  • morphology of tubules/cisternae is mediated by proteins called reticulons
  • reticulons are ER integral membrane proteins that possess unique hair-pin (v-shaped) secondary structures (2 beta anti-parallel B sheets) that regulate the ER membrane curvature and the overall shape of the ER
  • the tubules and cisternae are in a constant flux and undergo bending, growth/shrinkage, fusion/fission etc.
  1. what are ER subdomains? what are the two most obvious examples?: - subdomain = distinct region of ER network that possess unique morphologies and/or functions
  • SER and RER are the most obvious examples
  1. what is the function of the RER subdomain?: mostly cisternae with bound ribosomes, involved in protein synthesis and membrane phospholipid synthesis

16 / 38

  1. what is step 3 of co-translational translocation of a soluble protein into RER: - SRP targets the entire complex (ribosome, polypeptide, mRNA) to surface of RER
  • SRP binds to SRP receptor (heterodimeric ER integral membrane protein complex)
  • cytoplasmic facing domain of receptor serves as docking site for incoming SRP
  • interaction between SRP and receptor is strengthened by GTP binding to both complexes
  1. what is step 4 of co-translational translocation of a soluble protein into RER: - GTP hydrolysis results in the release of the SRP and SRP receptor
  • simultaneously the polypeptide and ribosome are transferred to the cytoplasmic side of Sec translocon
  • translocon is a multi-protein complex that consists of several ER integral membrane protein subunits forming an hourglass shaped aqueous channel
  • transfer of the polypeptide and ribosome to translocon results in the N terminus of polypeptide being inserted into the opening of translocon channel (SRP gone so we can resume translation)
  • translation resumes and the elongating polypeptide chain continues to pass thorugh the channel towards ER lumen
  • passage of growing polypeptide through translocon is driven by translation
  1. step 4 co-translational translocation continued... translocon contains : - hourglass translocon channel contains pore ring -> ring of 6 hydrophobic amino acids located at narrowest diameter of channel
  • serves as a gate to seal the channel to ions/small molecules (including during translocation) to maintain compart-mentalization
  • pore ring is also blocked by short a-helix plug (second gate keeping mechanism to maintain compartmentalization until polypeptide forces plus away from channel)
  1. what is step 5/6 of co-translational translocation of a soluble protein into RER: - as the N terminus signal sequence enters the ER lumen, it is cleaved by the signal peptidase and degraded
  • peptidase = ER integral membrane protein (protease) that is associated with translocon - catalytic domain faces ER lumen
  • peptidase recognizes the cleavage sequence: a motif at the c-terminal end (downstream) of signal sequence
  • co-translational translocation continues to ER lumen

17 / 38

  1. what is step 7/8 of co-translational translocation of a soluble protein into RER: - translation is now completed and the ribosome is released from the translocon + disassembly of ribosome subunits
  • remainder of nascent polypeptide enters ER lumen
  • translocon now closes -> plug moves back and blocks aqueous channel
  • the protein is now glycosylated (addition of sugars) and properly folded by reticuloplasmins (calnexin, calreticulin and bip) that mediate proper protein folding
  1. most membrane proteins are synthesized where?: - membrane-bound ribosomes at ER
  • including resident proteins of the ER and all other post ER organelles (golgi, lysosomes etc.)
  • except membrane proteins destined for mitochondria / chloroplast (not part of EM)
  1. describe the co-translational insertion of integral membrane proteins into RER: - ER membrane protein insertion is initially similar to soluble protein import into the lumen
  • however there are mechanistic ditterences resulting in mature membrane protein being integrated (anchored) into the ER membrane with proper topology (organization)
  1. describe the organization of each class of integral membrane protein (TMD, N term, C term and signal sequence): - topology refers to the number of membrane spanning domains and orientation
  • TMD - a helix of 15-26 hydrophobic amino acids 1: 1 TMD, N in/C out, signal sequence, STA 2: 1 TMD, N out/C in, no signal sequence, SA 3: 1 TMD, N in/C out, no signal sequence, SA
  1. explain the co-translational inserton of a type 1 protein: - most analagous to soluble protein
  • N term SS, associated with translocon, SS cleaved, translation continues

19 / 38

  • covalent addition of unique carbohydrate side chains to specific amino acids of the new protein (required for proper folding)
  1. protein folding and assembly
  • nascent protein is folded into proper 3D conformation and if necessary undergoes oligomeric assembly by molecular chaperones (reticuloplasmins)
  1. protein quality control
  • misfolded/improperly assembled proteins are recognized and degraded
  1. the ER serves as the for newly synthesized proteins. why?: - idea processing and quality control site
  • first compartment in EM system (proteins build on ER membrane)
  1. explain the process of glycosylation: - most proteins synthesized in ER are glycoproteins
  • glycoproteins are proteins that are linked to 1+ sugar chain (oligosaccharide)
  • sugar groups iad in the protein's proper folding and serve as binding sites for other macromolecules that interact with the protein
  1. what is the most common example of glycosylation?: - addition of specific shirt chains of sugar monomers (linked together in a specific order to form an oligosaccharide) to terminal amino group of asparagine (N)
  • two stages: core glycosylation and core modifications
  1. explain the basic process of core glycosylation: - complex process, highly branched oligosaccharide chain consisting of 14 sugar residues, including mannose and 3-glucose long terminal branch (protein quality)
  2. what is the role of dolichol phosphate in core glycosylation ?: - core glycosylation begins with the addition of the first sugar dolichol phosphate

20 / 38

  • dolichol is a membrane lipid serving as an an anchor and carrier for new and growing core oligosaccharides
  • can face either side, and would be flipped by flippase enzyme if required
  • glycotransferases continue to add sugars at specific positions on the growing oligosaccharide (add 2 N-acetylglu-cosamine, 5 mannose then flip to luminal side and add 4 more mannose and 3 glucose)
  1. describe how the core oligosaccharide is transferred from lipid carrier to the nascent polypeptide: - final step
  • core oligosaccharide is transferred from dolichol lipid carrier to nascent soluble/membrane protein while its being synthesized and emerging from translocon
  • empty dolichol phosphate is recycled for another round of core oligo synthesis
  • core oligosaccharides are transferred to luminal-facing portions of ER proteins with the specific amino acid sequence -NxS/T- (oligo attaches to N)
  1. core modification is the second stage of N-linked glycosylation. what hap-pens in this process?: - attached 14 sugar core oligosaccharide is sequentially trimmed/modified
  • 2 terminal glucoses are removed by ER luminal glucosidases
  • subsequent removal (and re-addition) of the last glucose is important for proper protein folding and assembly
  1. during N-linked glycosylation and modification, the nascent proteins is ? This is mediated by ?: - rapidly folded into its proper 3D conformation
  • this is mediated by several ER lumen and membrane proteins:
  1. reticuloplasmins: ER molecular chaperones (bip, calnexin, calreticulin) that bind transiently to nascent ER proteins to prevent misfolding
  2. protein disulfide isomerase (PDI): catalyzes the formation of intra/inter molecular disulfide bonds between cysteine residues on the same or ditterent polypeptides that promote proper folding and assembly by stabilizing their 3D conformations
  1. if the protein is properly folded and assembled.. what is the next immedi-ate process to occur?: - one mannose unit is trimmed by ER luminal mannosidase