Cell Bio exam questions
Which of the following statements about smooth and non-muscle contraction is false? Actin filaments lack troponins resulting in control of contraction is on the thick filament. Contraction may be initiated by a signal binding to a seven-helix membrane receptor. Myosin light chain kinase phosphorylates the myosin motor domain activating its actin-binding cycle. Ca2+-calmodulin activates myosin light chain kinase
***NOT Actin filaments lack troponins resulting in control of contraction is on the thick filament.
Structurally, the catalytic core of kinesins is similar to that of dynein. myosin and Ras family members. dynein and myosin. myosin only
***NOT myosin only
Adenylyl cyclase can be activated by trimeric G protein-linked receptors. protein kinases. Ca++-calmodulin. All of the above.
***NOT trimeric G protein-linked receptors - not sure abt this one, thinking its all of the above
Approximately when did the first eukaryotes appear? 3 billion years ago 300 million years ago 800 million years ago 1 to 2 billion years ago
1 to 2 billion years ago
Proteins destined for the mitochondrion usually bind within the cytoplasm to which of the following? Mitochondrial import stimulating factor (MSF). A protein of the HSP70 family. A chaperonin. TOM22.
A protein of the HSP70 family.
Proteins destined for the mitochondrion usually bind within the cytoplasm to which of the following? Mitochondrial import stimulating factor (MSF). A protein of the HSP70 family. A peptidase. TOM22.
A protein of the HSP70 family.
By which of the following mechanisms do seven-helix receptors act? Changing the membrane permeability. Activating a G protein. Activating a serine/threonine kinase. Activating a protein tyrosine kinase.
Activating a G protein
Which of the following proteins are actin cross-linking proteins? A. ADF/Cofilin B. Filamin C. Alpha-actinin D. Gelsolin A and B A, B, and C B and C B, C and D
B and C
The lipid and protein composition of the endoplasmic reticulum is maintained by: Constant synthesis of both lipid and proteins Transport of vesicles with lipids and proteins from the plasma membrane Exclusive retrograde transport of vesicles with lipids and proteins from the Golgi apparatus Both synthesis of lipids and proteins in the ER and retrograde transport of vesicles with lipids and proteins from the Golgi apparatus
Both synthesis of lipids and proteins in the ER and retrograde transport of vesicles with lipids and proteins from the Golgi apparatus
How is the intracellular pathogenic bacteria Listeriamoved around the cytoplasm of the host animal cell? On microtubules via kinesin and dynein By polymerizing actin filaments driven by activation of Arp2/3 complex By recruiting myosin I By swimming using its bacterial flagellae
By polymerizing actin filaments driven by activation of Arp2/3 complex
Which protein works together with actin microfilaments to contract the contractile ring? Cortactin Profilin Myosin I Myosin II
Myosin II
Which of the following statements about molecular switches is false? Phosphatases remove the phosphate from GTP on GTP-binding proteins, turning them off. Protein kinases transfer the terminal phosphate from ATP onto a protein. Serine/threonine kinases are the most common types of protein kinase. A GTP-binding protein exchanges its bound GDP for GTP to become activated
Phosphatases remove the phosphate from GTP on GTP-binding proteins, turning them off.
Which of the following is true concerning the effect of phosphorylation of intermediate filaments proteins during mitosis? Phosphorylation of lamin by Cdk1/cyclin destabilizes the filaments. Phosphorylation of vimentin by Cdk1/cyclin stabilizes the filaments. Phosphorylation of keratin by Cdk1/cyclin has no effect on the stability of the filaments. Phosphorylation always occurs outside the rod domain.
Phosphorylation of lamin by Cdk1/cyclin destabilizes the filaments.
Which of the following is correct concerning proteolysis? Both cellular compartments for proteolysis, the lysosome and the proteosome, are membrane bound organelles. Proteases and proteosomes function at low pH to protect the cell against unregulated proteolytic activity. Proteases degrade mainly long-lived proteins, proteosomes degrade mainly short-lived proteins. All of the above.
Proteases and proteosomes function at low pH to protect the cell against unregulated proteolytic activity.
Which of the following statements about the endoplasmic reticulum (ER) is false? The ER is the major site for new membrane synthesis in the cell. Proteins to be delivered to the ER lumen are synthesized on smooth ER. Steroid hormones are synthesized on the smooth ER. The ER membrane is contiguous with the outer nuclear membrane
Proteins to be delivered to the ER lumen are synthesized on smooth ER.
Which of the following may explain why the first forms of life are thought to have evolved in an "RNA world"? RNA molecules can grow very long. RNA molecules have charged and hydrophobic regions. RNA molecules can adopt many different structures. RNA molecules can store information and catalyze biochemical reactions. RNA molecules can contain modified purine bases.
RNA molecules can store information and catalyze biochemical reactions.
Which of the small GTPases in eukaryotes are involved in transducing extracellular signals? Rab and Arf. Rab and Ran. Ras and Rho. Sar and Ran
Ras and Rho
A cell passes the restriction point in the cell cycle in response to phosphorylation of which of the following? Rb protein the transcription factor E2F cyclin dependent kinase E2F/DP1/pRb
Rb protein
What is NOT a common strategy for the regulation of protein kinases? Binding with regulatory peptides. Interaction with growth factors. Phosphorylation. Targeting to particular cell compartments
Targeting to particular cell compartments.
The MAP that accumulates in the neurofibrillary tangles of Alzheimer's disease is MAP2 MAP9 Tau Stathmin
Tau
Which of the following regarding the ER is FALSE? Oil droplets are formed on the ER. The ER is a reservoir for calcium ions. The ER is the site of ATP production through the citric acid cycle. The ER of a typical cell has 30 times the area of the plasma membrane.
The ER is the site of ATP production through the citric acid cycle.
If the DNA damage checkpoint in G2 prevents a cell from going into mitosis, what other fate may well ensue? The cell reverts to G0 stage The cell enters the apoptotic pathway Necrotic cell death
The cell enters the apoptotic pathway
Which of the following best describes the "restriction point" in G1? The point at which cells commit to mitosis or die The point at which cells express restriction endonucleases The point at which cells develop a restriction in the middle as the contractile ring begins to contract The point after which the cell cycle will proceed even if mitogenic factor are withdrawn
The point after which the cell cycle will proceed even if mitogenic factor are withdrawn
Which of the following is true concerning phagosomes? They are phagocytic vacuoles where foreign particles are completely engulfed. The actin cytoskeleton is involved in their movement towards lysosomes and their subsequent fusion. They are lysosomes that have engulfed a foreign particle. Fusion of lysosomes and phagosomes uses a fusion machinery distinct from that of the endosome-specific targeting and fusion machinery used in the biosynthetic pathway.
They are phagocytic vacuoles where foreign particles are completely engulfed.
Which is the most likely reason that cells have evolved a mechanism to break down the Golgi apparatus at mitosis? To prevent unwanted protein secretion during mitosis. To allow an equitable passive distribution of Golgi apparatus between daughter cells. To conserve cellular energy resources for the demanding events of mitosis. To prevent the Golgi apparatus from interfering with spindle dynamics during chromosome segregation.
To allow an equitable passive distribution of Golgi apparatus between daughter cells.
Which of the following proteins caps the pointed end of the thin filaments of muscle? Cap-Z DNAse I Tropomyosin Tropomodulin
Tropomodulin
By definition, prokaryotic cells do not possess __________. a nucleus. replication machinery. ribosomes. membrane bilayers.
a nucleus.
Proteins destined for insertion into the endoplasmic reticulum are targeted to that site by a polyadenylated mRNA . a hydrophylic amino acid sequence at the N- terminus of the protein. a short, largely hydrophobic, N-terminal amino acid sequence. a short sequence of double-stranded RNA.
a short, largely hydrophobic, N-terminal amino acid sequence.
FRAP (fluorescence activated photobleaching) is a useful technique because it can demonstrate diffusability (mobility) of membrane proteins. chemical reactivity of membrane proteins. presence of a signaling molecule. light-sensitive receptors in the membrane.
diffusability (mobility) of membrane proteins.
When a signal needs to be sent to most cells throughout a multicellular organism, the signal most suited for this is a ___________. neurotransmitter. hormone. dissolved gas. scaffold
hormone
Although all protein structures are unique, there are common structural building blocks that are referred to as regular secondary structures. Some proteins have α helices, some have β sheets, and still others have a combination of both. What makes it possible for proteins to have these common structural elements? specific amino acid sequences side-chain interactions the hydrophobic-core interactions hydrogen bonds along the protein backbone
hydrogen bonds along the protein backbone
The stimulation of auditory nerves depends on the opening and closing of channels in the auditory hair cells. Which type of gating mechanism do these cells use? voltage-gated extracellular ligand-gated intracellular ligand-gated mechanically-gated
mechanically-gated
A rich source of F 0 F 1 ATPase is the nucleus. Golgi apparatus. vacuolar membrane of archebacteria. mitochondrial membranes of eukaryotes.
mitochondrial membranes of eukaryotes.
Lysosomal degradation of plasma membrane proteins involves which of the following? smooth endoplasmic reticulum rough endoplasmic reticulum Golgi cisternae multivesicular bodies
multivesicular bodies
The sarcoplasmic reticulum Ca 2+ ATPase is particularly abundant in connective tissue. brain. the lymphatic system. muscle.
muscle
What type of macromolecule helps package DNA in eukaryotic chromosomes? lipids carbohydrates proteins RNA
proteins
How are actin and tubulin polymerization similar? Treadmilling is common in both Both use nucleotide hydrolysis as a mechanism in remodeling of the cytoskeleton. Both are nucleated at many sites throughout the cytoplasm Both are oriented randomly with respect to the cell nucleus.
***NOT Both are nucleated at many sites throughout the cytoplasm, also NOT treadmilling is common in both - I think it is "Both use nucleotide hydrolysis as a mechanism in remodeling of the cytoskeleton." but not sure
For mitosis to occur which one of the following is true: CDK1 must bind cyclin B2. CDK1 must be phosphorylated at positions T14 and Y15. CDK1 must be dephosphorylated at position T161. CDK1 must accumulate in the nucleus.
***NOT CDK1 must be dephosphorylated at position T161. NOT CDK1 must bind cyclin B2.
Which of the following does not inhibit contraction of the contractile ring? blebbistatin cytochalasin B colchicine ML-7
***NOT blebbistatin
A sperm tail is very active in its movement because it the sliding of actinomyosin filaments past one another generates a whip-like motion of the flagellum it has a rotary motor that spins the flagellum its tail is thrown into S-shape movements by a sliding of microtubules that causes bending its head contains a very powerful motor that thrashes the tail up and down
***NOT it has a rotary motor that spins the flagellum - I believe it is "its tail is thrown into S-shape movements by a sliding of microtubules that causes bending"
Cytokinesis in animal cells ________________. is induced by either equatorial asters or spindle midzone MTs leaves a small circular "scar" of actin filaments on the inner surface of the plasma membrane. requires the activation of cdc42 is assisted by motor proteins that pull on microtubules attached to the cell cortex.
***NOT leaves a small circular "scar" of actin filaments on the inner surface of the plasma membrane
If nerve axons are constricted at one particular site to locally inhibit vesicle transport , vesicles accumulate at both sides of the constriction. there is no particular vesicle accumulation at the constriction site. vesicles accumulate at the proximal side. vesicles accumulate at the distal side.
***NOT vesicles accumulate at the proximal side. - I believe it is "vesicles accumulate at both sides of the constriction."
The simplest way in which a transmembrane protein can pass through a lipid bilayer is by having a single alpha-helix of: 20 hydrophilic amino acids 20 polar amino acids 20 hydrophobic amino acids 20 amphipathic amino acids
20 hydrophobic amino acids
Which of the following is involved in the removal of acetylcholine from aneuromuscular synapse? A. destruction by specific esterase enzymes B. endocytosis at the post synaptic terminal C. endocytosis back into the presynaptic terminal A only A and B B and C A and C
A and C
What is a protein kinase? A protein that moves. A protein that hydrolyses other proteins by proteolysis. A protein that lyses bacteria by digesting the bacterial cell wall. A protein that adds a phosphate to proteins or other molecules
A protein that adds a phosphate to proteins or other molecules.
Peripheral membrane proteins are attached to membranes by: a. ionic bonds b. covalent bonds c. lipid tails d. a and c
*** I put covalent bonds and i was wrong (i think its d)
Calveolae Are very large structures that make up more than 10% of the endothelial cell surface Are specific to endothelial cells and are propose to mediate transport from the blood to the tissue The coat of calveolae is made of a 22kd protein called Calveolin that, unlike clathrin, cannot self assemble. Are enriched in cholesterol and glycosphingolipids
***NOT Are enriched in cholesterol and glycosphingolipids - might be first answer
Tagged glucose is added to a medium containing intestinal epithelial cell apical membranevesicles, and a slow uptake of glucose occurs into the vesicles. Na + is then added. Whatresponse would you expect? Glucose uptake halts immediately. Glucose is rapidly lost from the vesicles. Glucose continues to be taken up but very much faster than before. The rate of glucose uptake is unchanged but Na + uptake increases?
Glucose continues to be taken up but very much faster than before
Unconventional myosins do not play a role in: Actin to membrane linkage Pigment granule movements Golgi centration
Golgi centration
Which of the following is correct concerning proteolysis? Both cellular compartments for proteolysis, the lysosome and the proteosome, are membrane bound organelles. Proteases and proteosomes function at low pH to protect the cell against unregulated proteolytic activity. Proteases degrade mainly long-lived proteins, proteosomes degrade mainly short-lived proteins. All of the above.
Here it was "Proteases degrade mainly long-lived proteins, proteosomes degrade mainly short-lived proteins." but before it was "Proteases and proteosomes function at low pH to protect the cell against unregulated proteolytic activity."
Phospholipase C breaks down PIP2 (phosphatidyl inositol 4,5 biphosphate) into diacylglycerol (DAG) and IP3 (inositol 1,4,5 triphosphate). PIP (phosphatidylinositol-4 phosphate). ceramide. phosphatidic acid.
IP3 (inositol 1,4,5 triphosphate)
Calcium is released into the cytoplasm from the ER in response to the action of ______________ in the ER membrane. Ca++ -ATPases DAG-gated channels IP3-gated CA++ channels All of the above
IP3-gated CA++ channels
Which of the following statements about membrane-enclosed organelles is true? In a typical cell, the area of the endoplasmic reticulum membrane far exceeds the area of plasma membrane. The nucleus is the only organelle that is surrounded by a double membrane. Other than the nucleus, most organelles are small and thus, in a typical cell, only about 10% of a cell's volume is occupied by membrane-enclosed organelles; the other 90% of the cell volume is the cytosol. The nucleus is the only organelle that contains DNA.
In a typical cell, the area of the endoplasmic reticulum membrane far exceeds the area of plasma membrane.
Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell. Which of the following ions is the most abundant inside a typical mammalian cell? Na + K + Ca 2+ Cl -
K+
Which of the following is NOT correct? All of the spindle microtubules have their minus ends at or near the spindle poles. Most interpolar microtubules are attached to neither kinetochores nor to spindle poles. Astral microtubules radiate from the spindle poles to interact with the cell cortex Kinetochore microtubules emanate from kinetochores and grow towards the spindle poles.
Kinetochore microtubules emanate from kinetochores and grow towards the spindle poles.
Which of the following is NOT correct? All of the spindle microtubules have their minus ends at or near the spindle poles. Most interpolar microtubules are attached to neither kinetochores nor to spindle poles. Astral microtubules radiate from the spindle poles to interact with the cell cortex. Kinetochore microtubules emanate from kinetochores and grow towards the spindle poles.
Kinetochore microtubules emanate from kinetochores and grow towards the spindle poles.
Which of the following statements about kinetochores is true? Kinetochores assemble onto chromosomes during late prophase. Kinetochores contain DNA-binding proteins that recognize sequences at the telomere of the chromosome. Kinetochore proteins bind to the tubulin molecules at the minus end of microtubules. Kinetochores assemble on chromosomes that lack centromeres.
Kinetochore proteins bind to the tubulin molecules at the minus end of microtubules.
Which ABC transporter protects cells from xenotoxins (foreign potentially damagingchemicals)? TAP2 CFTR MDR HlyB
MDR
What happens to the microtubule (MT) cytoskeleton at prophase? MTs depolymerize and repolymerize to form a ring around the center of the cell. MTs retain their position and organization throughout prophase. MTs depolymerize and repolymerize at the centrosomes, which have divided so the two asters of MTs now exist. MTs depolymerize and the tubulin subunits are destroyed.
MTs depolymerize and repolymerize at the centrosomes, which have divided so the two asters of MTs now exist.
Which of the following factors inhibits the Anaphase-Promoting Complex and thereby prevents progression through the spindle assembly checkpoint until all the kinetochores are attached to spindle microtubules? Cohesins Mad2 Separin Securin
Mad2
Which statement best describes microtubule behavior in a test tube containing only a buffered solution of tubulin and GTP? Microtubules grow until the free tubulin dimer concentration decreases to a critical concentration, after which individual microtubules are relatively stable. Microtubules grow until the tubulin dimer concentration decreases to a critical concentration, after which the amount of polymer stabilizes, but individual microtubules fluctuate in length dramatically. Individual microtubules grow steadily until the concentration of tubulin becomes too low to support additional growth. Microtubules will not polymerize in this solution because they require ATP for polymerization.
Microtubules grow until the tubulin dimer concentration decreases to a critical concentration, after which the amount of polymer stabilizes, but individual microtubules fluctuate in length dramatically.
Which of the following is a consequence of the 2 nm diameter of the TOM40 pore? Most proteins must be unfolded to enter the mitochondrion. Only small proteins can enter the mitochondrion. The pore diameter is increased during protein translocation. TOM40 also functions as an ion channel.
Most proteins must be unfolded to enter the mitochondrion.
Which families of cytoskeletal motor proteins are related by evolution? Myosin and kinesin Dynein and kinesin Myosin and dynein Actin and myosin
Myosin and kinesin
Catterall showed that scorpion toxin inhibits the: K+ channel Na+ channel Cl- channel glucose transporter
Na+ channel
Nodes of Ranvier are periodic points along a nerve axon which are not covered by myelin sheaths. These nodes are locations where: K+ channels are concentrated to dampen the nerve impulse Na+ channels are concentrated to dampen the nerve impulse Na+ channels are concentrated to make the nerve impulse move faster K+ channels are concentrated to make the nerve impulse move faster
Na+ channels are concentrated to make the nerve impulse move faster
Which of the following is not a cell cycle checkpoint? Restriction DNA damage Spindle assembly Nuclear
Nuclear
Your friend works in a biotechnology company and has discovered a drug that blocks the ability of Ran to exchange GDP for GTP. What is the most likely effect of this drug on nuclear transport? Nuclear transport receptors would be unable to bind cargo. Nuclear transport receptors would be unable to enter the nucleus. Nuclear transport receptors would be unable to release their cargo in the nucleus. Nuclear transport receptors would interact irreversibly with the nuclear pore fibrils.
Nuclear transport receptors would be unable to release their cargo in the nucleus
Which of the following statements is correct concerning facilitated diffusion? It requires an input of energy. It allows diffusion to proceed against a gradient. Occurs via a uniporter. All of the above.
Occurs via a uniporter.
What is the name given to genes that occur in the same cell that have resulted fromduplication and mutation? Homologs Paralogs Captinslogs Ortholog
Paralogs
SGLT1 transports glucose into the epithelial cells of the small intestine. Where does the energy come from? SGLT1 is an ATPase and uses ATP hydrolysis as a source of energy to bring glucose into epithelial cells against a concentration gradient. SGLT1 is an antiporter. SGLT1 only works when there is more glucose in the gut than in the enterocytes. SGLT1 is a symporter that uses transport of sodium ions down their concentration gradient to bring glucose into the cell up its concentration gradient.
SGLT1 is a symporter that uses transport of sodium ions down their concentration gradient to bring glucose into the cell up its concentration gradient.
Which of the following regarding caveolae is FALSE? Uses the GTPase dynamin to pinch off the vesicle The caveolin coat dissociated from the vesicle after it separates from the plasma membrane Caveolin binds to cholesterol Caveolin is immobile within the plasma membrane
The caveolin coat dissociated from the vesicle after it separates from the plasma membrane
Which of the following best describes the events that result in the breakdown of the nuclear envelope? The nuclear envelope breaks down to form vesicles that disperse in the cytoplasm. The nuclear envelope breaks down to form vesicles that associate with the spindle. The nuclear envelope breaks to form two vesicles, which then associate with the plasma membrane-facing side of the spindle poles. The nuclear envelope breaks and the remnants fuse with the plasma membrane.
The nuclear envelope breaks down to form vesicles that disperse in the cytoplasm.
To study how proteins fold, scientists must be able to purify the protein of interest, use solvents to denature the folded protein, and observe the process of refolding at successive time points. What is the effect of the solvents used in the denaturation process? The solvents break all covalent interactions. The solvents break all noncovalent interactions. The solvents break some of the noncovalent interactions, resulting in a misfolded protein. The solvents create a new protein conformation.
The solvents break all noncovalent interactions.
Which of the following statements is correct? Lipid membranes throughout the cell have the same chemical composition, but those in the two halves of any bilipid membrane are different. The two layers of a bilipid membrane do not have the same chemical identity, nor do membranes from different sites in the cell have the same composition. The membranes throughout the cell do not have the same composition, but the two halves of a bilipid layer do. Bilipid layers throughout a cell have the same composition, as do membranes from any part of the cells.
The two layers of a bilipid membrane do not have the same chemical identity, nor do membranes from different sites in the cell have the same composition.
Which of the following is NOT correct concerning cells in the G0 phase of the cell cycle? They are metabolically inactive. They can remain in this state indefinitely, They can be recruited back into the cell cycle again They are often terminally differentiated
They are metabolically inactive.
Which one of the following statements about Green Fluorescent Protein (GFP) is NOT true? GFP can still fluoresce when fused to other proteins. GFP can be modified to make it fluoresce red, blue or yellow. To fluoresce, GFP needs chemical energy to be supplied by the host cell. Once expressed, GFP can be visualized in any living cell.
To fluoresce, GFP needs chemical energy to be supplied by the host cell.
Pumps are transporters that are able to harness energy provided by other componentsin the cells to drive the movement of solutes across membranes, against theirconcentration gradient. This type of transport is called _____________. active transport free diffusion facilitated diffusion passive transport
active transport
The restriction point is defined best as the point in the cell cycle at which G1 ends and S-phase begins. after which mitogens can promote cell cycle progression. before which mitogens can not influence cell cycle progression. after which withdrawal of mitogens will not prevent cell cycle progression.
after which withdrawal of mitogens will not prevent cell cycle progression.
Biologists cannot possibly study all living species. Instead, they try to understand cell behavior by studying a select subset of them. Which of the following characteristics are useful in an organism chosen for use as a model in laboratory studies? amenability to genetic manipulation ability to grow under controlled conditions rapid rate of reproduction all of the above
all of the above
Tethering proteins ensure vesicle binding of the vesicle membrane to the target membrane by forming homodimers that link the two. are linked to membranes by the GDP-bound form of the membrane GTPase. are associated with the target membrane only. are associated with both the vesicle and target membranes.
are associated with both the vesicle and target membranes.
The bacterium Listeria uses actin to move around in cells by ... binding actin on its surface and using this to move along cellular myosin networks. assembling actin behind itself and being pushed forward by the force of actin polymerization. assembling an actin comet on its leading end and using this to move along cellular myosin networks. expressing a surface protein that resembles myosin, and using this to run along cellular actin filaments. causing local cycles of actin and myosin assembly which result in a streaming of the cytoplasm.
assembling actin behind itself and being pushed forward by the force of actin polymerization.
In which phase of the cell cycle do cells check to determine whether the DNA is fully and correctly replicated? at the transition between G1 and S when cells enter G0 during M at the end of G2
at the end of G2
The COPII complex that packages cargo into transport vesicles is assembled when the Sar 1 protein binds GTP. hydrolyzes GTP. binds ATP. hydrolyzes ATP
binds GTP.
Arrestin inhibits a seven helic receptor by phosphorylating the C-terminal domain. phosphorylating the G protein. blocking G protein binding. stabilizing the resting state conformation.
blocking G protein binding.
Misfolded proteins in the ER membrane and lumen are degraded by the lysosome. in the cis-Golgi. by proteolysin. by the proteosome.
by the proteosome
Which of the following is not involved in cytokinesis? cdc42 Rho ESCRT MLCK
cdc42
The principal microtubule-organizing center in animal cells is the ____________. centrosome. centromere. kinetochore. cell cortex.
centrosome
Which of the following membrane lipids does not contain a fatty acid tail? phosphatidylcholine a glycolipid phosphatidylserine cholesterol
cholesterol
At the end of DNA replication, the sister chromatids are held together by the ___________. kinetochores. securins. cohesins. histones.
cohesins
Levels of Cdk activity change during the cell cycle, in part because ________________. the Cdks phosphorylate each other. the Cdks activate the cyclins. Cdk degradation precedes entry into the next phase of the cell cycle. cyclin levels change during the cycle.
cyclin levels change during the cycle.
Defects in the ABC transporter that clears excess chloride from the surface of the lung epithelium results in Asthma Emphysema Pneumonia cystic fibrosis
cystic fibrosis
Changes in DNA sequence from one generation to the next may result in offspring that are altered in fitness compared with their parents. The process of change and selection over the course of many generations is the basis of __________. mutation. evolution. heredity. reproduction.
evolution
Mitochondria use these two direct precursors as fuel: pyruvate and NADH fatty acids and pyruvate acetyl groups and CO2 CO2 and fatty acids
fatty acids and pyruvate
Which type of microscopy requires the use of two sets of filters. The first filter narrows the wavelength range that reaches the specimen and the second blocks out all wavelengths that pass back up to the eyepiece except for those emitted by the dye in the sample. confocal bright field fluorescence phase contrast
fluorescence
The ER enzyme protein disulfide isomerase plays an important role in the ______________ of newly synthesized proteins. glycosylation folding release from the signal sequence Phosphorylation
folding
Which of the following methods would be the most suitable to assess the relative purityof a protein in a sample you have prepared? gel-filtration chromatography gel electrophoresis western blot analysis ion-exchange chromatography
gel electrophoresis
Dolichol lipid in the ER membrane is a glycosylphosphtidylinositol (GPI) anchor which attaches proteins to the cytoplasmic side of the membrane. is a 14-sugar oligosaccharide precursor to the N-linked oligosaccharides added to protein in the ER. is the site for assembly of the N-linked oligosaccharide precursor added to proteins in the ER. forms a membrane channel through which glycolipids are moved across the membrane.
is the site for assembly of the N-linked oligosaccharide precursor added to proteins in the ER.
Your friend works in a biotech company that has just discovered a drug that seems to promote lamellipodia formation in cells. Which of the following molecules is unlikely to be involved in the pathway that this drug affects? Rac ARP actin myosin
myosin
Unlike soluble, cytosolic proteins, membrane proteins are more difficult to purify.Which of the following substances is most commonly used to help purify anintegral membrane protein? high salt solution sucrose non-ionic detergent ethanol ionic detergent
non-ionic detergent
Steroid hormones act to regulate gene expression by binding to plasma membrane receptor tyrosine kinases. receptors which activate cytoplasmic serine/threonine kinases. nuclear receptors which act as transcription factors. receptors which activate cytoplasmic tyrosine kinases.
nuclear receptors which act as transcription factors.
Large molecules are moved into cells in most cases using the energy of thermal motion. glycolysis. a proton gradient. ATP hydrolysis.
ATP hydrolysis.
Which of the following is false? the mitochondrial genome is found in the matrix citric acid cycle enzymes are found in the matrix__________ proteins of the electron-transport chain is found in the inner mitochondrial membrane ATP synthase is found in the outer mitochondrial membrane
ATP synthase is found in the outer mitochondrial membrane
Adenylyl cyclase generates cAMP from adenosine. 3'5'AMP. 5' AMP. ATP.
ATP.
The contractile ring is composed of which of the following two proteins? Actin and dynein. Actin and myosin Tubulin and kinesin Tubulin and dynein
Actin and myosin
How does the leading lamellae of a moving cell expand? Microtubule growth presses the membrane forward. Brownian motion of the membrane pulls the cell forward. Actin polymerization presses the membrane forward. Hydrostatic pressure pushes the membrane forward.
Actin polymerization presses the membrane forward.
If the plasma membrane depolarizes beyond the threshold potential what happens to ensurethat the action potential is an all-or-none event? K + efflux is speeded up by voltage-gated pumps. N + channels suddenly close. K + rectifying channels activity increases. Additional Na + channels are activated.
Additional Na + channels are activated.
Which of the following statements about proteins is true? Disulfide bonds are formed by the cross-linking of methionine residues. Disulfide bonds are formed mainly in proteins that are retained within the cytosol. Disulfide bonds stabilize but do not change a protein's final conformation. Agents such as mercaptoethanol can break disulfide bonds through oxidation.
Agents such as mercaptoethanol can break disulfide bonds through oxidation
What is the likely role of the dynactin complex in dynein motor function? To target the dynein motor to particular cargo vesicles. To link dynein to the vesicle surface. To interact with spectrin associated with the vesicle membrane. All the above.
All of the above
Which of the following can open a channel gate? Ligand binding to an extracellular domain of the protein Ligand binding to an intracellular domain of the protein Membrane potential All the above
All the above
The coat complex I (COPI) activity has been shown to be critical for The movement of vesicles from the ER to the Golgi. the movement of vesicles between Golgi stacks. the recycling of membrane proteins from the Golgi to the ER. formation of lysosomes from the cis Golgi.
Answer was "the recycling of membrane proteins from the Golgi to the ER." but got point back for "the movement of vesicles between Golgi stacks."
The assembly of the COPI coat is dependent upon the activity of what GTPase? Sar1 Rab Arf1 Ras
Arf1
Which of the following is true about flagella and cilia? Axonemes grow by adding new protein subunits at the tip furthest from the cell using kinesin Dynactin motors move flagellar proteins along the microtubules during intraflagellar transport. Most cells in the body produce a primary cilium, mutations in which cause colonic polyps Although they look similar, key functional differences mean that basal bodies and centrioles have completely distinct roles. Flagellar movement is powered by dynein subunits radiating outward from the central pair microtubules.
Axonemes grow by adding new protein subunits at the tip furthest from the cell using kinesin
Select the statement about tubulin assembly that is most correct. Catastrophic disassembly of microtubules is likely caused by loss of the GTP cap. Dynamic instability is observed only in vitro. The dissociation rate constant of GDP tubulin is similar to that of GTP tubulin. Dynamic instability refers to the tendency of polymerizing microtubules to break.
Catastrophic disassembly of microtubules is likely caused by loss of the GTP cap.
Which of the following statements is true? The signal sequences on mitochondrial proteins are usually C-terminal. Most mitochondrial proteins are not imported from the cytosol but are synthesized inside the mitochondria. Chaperone proteins in the mitochondria facilitate the movement of proteins across the outer and inner mitochondrial membranes. Mitochondrial proteins cross the membrane in their native, folded state.
Chaperone proteins in the mitochondria facilitate the movement of proteins across the outer and inner mitochondrial membranes
Which of the following statements is true? The signal sequences on mitochondrial proteins are usually C- terminal. Most mitochondrial proteins are not imported from the cytosol but are synthesized inside the mitochondria. Chaperone proteins in the mitochondria facilitate the movement of proteins across the outer and inner mitochondrial membranes. Mitochondrial proteins cross the membrane in their native, folded state.
Chaperone proteins in the mitochondria facilitate the movement of proteins across the outer and inner mitochondrial membranes.
Which of the following statements correctly summarizes the nature of the gradient of lipids from the ER through the Golgi to the plasma membrane (PM)? Cholesterol and sphingolipids are intermediate in the ER, low in the Golgi, and high in the PM. Cholesterol and sphingolipids are high in the ER, intermediate in the Golgi, and low in the PM. Cholesterol and sphingolipids are low in the ER, high in the Golgi, and low in the PM. Cholesterol and sphingolipids are low in the ER, intermediate in the Golgi, and high in the PM.
Cholesterol and sphingolipids are low in the ER, intermediate in the Golgi, and high in the PM.
Which of the following statements about vesicle budding from the Golgi is false? Clathrin molecules are important for binding to and selecting cargoes for transport. Adaptins interact with clathrin. Once vesicle budding occurs, clathrin molecules are released from the vesicle. Clathrin molecules act at the cytosolic surface of the Golgi membrane.
Clathrin molecules are important for binding to and selecting cargoes for transport.
Telophase is best characterized by which of the following events? Chromosomes separate. Nuclear envelope breaks down. Centrosomes separate. Cleavage furrow constricts.
Cleavage furrow constricts.
Which of the following does not describe the centrosome: Contains y-TURC Contains pericentrin Contains centrioles Contains dynactin
Contains dynactin
Which statement is NOT true of the prokaryotic cell? DNA is circular. It is enclosed by plasma membrane. It lacks a cytoskeletal support structure. Contains many organelles.
Contains many organelles.
What are the constituents of maturation promotion factor (MPF)? Wee1 and cyclin B Cyclin A and cyclin B Cyclin-dependent kinase-1 and cyclin B Wee1 and Myt1
Cyclin-dependent kinase-1 and cyclin B
Which of the following is true about membrane lipids? The composition of lipids in the membrane is symmetric from the inner to the outer leaflet of the bilayer. Lipids arrive at their proper membrane destination via a system of targeting signals similar to that used by to direct membrane proteins to their destinations. Different organelles are characterized by distinct lipid compositions. Free diffusion of lipids occurs between adjacent bilayer membranes, facilitating membrane and vesicle fusion
Different organelles are characterized by distinct lipid compositions
Treatment of animal cells with the drug colchicine, leads to vesiculation of the endoplasmic reticulum and Golgi compartments. This is a result of colchicine: Binding to the kinetochore. Inhibiting dynein. Stabilizing microfilaments. Disrupting microtubules.
Disrupting microtubules.
After the clathrin-coated pit forms during receptor-mediated endocytosis, which protein promotes the final scission of the membrane to release the endocytic vesicle? Alpha-actinin Vinculin Annexin Dynamin
Dynamin
Which of the following statements are true concerning the movement of conventional kinesins and cytoplasmic dyneins along microtubules? Both move toward the minus end. Both move toward the plus end. Kinesins move toward the minus end, and dyneins towards the plus end. Dyneins move toward the minus end, and kinesins towards the plus end.
Dyneins move toward the minus end, and kinesins towards the plus end.
In which stage of the cell cycle would a typical cell be likely to spend the most time? Cytokinesis S phase G2 phase G1 phase
G1 phase
The Arf and Rab families of small GTPases regulate the traffic of membrane along the secretory pathway. Which of the following statements is FALSE? Each GTPase is paired with specific coat proteins or tethering proteins. GTP hydrolysis is required to assemble membrane coats. Guanine nucleotide exchange proteins on particular membranes activate specific Arf and Rab GTPases. Coat disassembly depends on specific GTPase activating proteins that inactivate GTPases
GTP hydrolysis is required to assemble membrane coats
Which one of the following is NOT involved in the spindle checkpoint? Ccd20. GTPase RhoA. MAD2.
GTPase RhoA.
STAT is a transcription factor which is activated by phosphorylation of tyrosines by an activated JAK receptor. phosphorylation by a ser/thr cytoplasmic kinase downstream of JAK activation. phosphorylation by a nuclear ser/thr kinase. MAP kinase.
phosphorylation of tyrosines by an activated JAK receptor
Mitochondria are believed to have originated by invagination and pinching off of the plasma membrane. extension of the nuclear membrane. prokaryotic cell developing a stable endosymbiotic relationship with the early eukaryotic cell. association of Golgi-derived vesicles.
prokaryotic cell developing a stable endosymbiotic relationship with the early eukaryotic cell.
Which word best describes microtubule organization in most animal cell types during interphase? random radial linear concentric
radial
Depolymerization of microtubules in the cell leads to movement of the ER from the perinuclear area to the periphery of the cell. rapid dispersal of Golgi components throughout the cell. disassembly of the ER. loss of compartmentalization of ER and Golgi membranes.
rapid dispersal of Golgi components throughout the cell
Which of the following receptors is NOT a G-protein- coupled, seven helix, transmembrane protein? rhodopsin odorant receptors receptor tyrosine kinases R-adrenergic receptor
receptor tyrosine kinases
The receptors for platelet-derived growth factor are receptor tyrosine kinases. seven-helix receptors. cytokine receptors. receptor serine/threonine kinases.
receptor tyrosine kinases.
Which of the following is not an electron carrier that participates in the electron-transport chain? cytochrome quinone rhodopsin copper ion
rhodopsin
The interaction of ADP-myosin and the actin filament is described as the death grip. rigor complex. slow complex. rapid complex.
rigor complex.
Which of the following structures shorten during muscle contraction? myosin filaments flagella sarcomeres actin filaments
sarcomeres
Which of the following structures shorten during muscle contraction? myosin filaments lagella sarcomeres actin filaments
sarcomeres
The plasma membrane serves many functions, many of which depend on the presence of specialized membrane proteins. Which of the following roles of the plasma membrane could still occur if the bilayer were lacking these proteins? intercellular communication selective permeability cellular movement import/export of molecules
selective permeability
What are the effectors that are activated by receptor serine/threonine kinases? STATs. Smads. Inhibins. Cyclic GMP.
smads
Which of the following TWO molecules are usually more abundant in the patches of lipidmembranes called rafts? sphingolipids and cholesterol glycerol and cholesterol phosphinositol and sphingomyelin cholesterol and phosphoitdyl inositol
sphingolipids and cholesterol
The endoplasmic reticulum is pulled toward the periphery of the cell by kinesin and by dynein motors on antiparallel microtubules. hydrostatic pressure. strands of the ER attached to the growing tips of microtubules that are pushed out as the microtubules plus-end grows. the insertion of new membrane at the cell periphery.
strands of the ER attached to the growing tips of microtubules that are pushed out as the microtubules plus-end grows.
Sphingolipids contain sphingosine, a nitrogen-containing base that replaces the phosphoric acid component found in phosphoglycerides. that replaces only the glycerol component found in phosphoglycerides. that replaces the glycerol and one fatty acid of phosphoglycerides. attached to the phosphoric acid component of a phosphoglyceride.
that replaces only the glycerol component found in phosphoglycerides. (don't know if this is right, got it wrong, but emailed him and he gave me point back for putting this answer)
N-linked oligosaccharides on secreted glycoproteins are attached to ________. nitrogen atoms in the polypeptide backbone. the serine or threonine in the sequence Asn-X-Ser/Thr. the N-terminus of the protein. the asparagine in the sequence Asn-X-Ser/Thr.
the asparagine in the sequence Asn-X-Ser/Thr
Patients with hypercholesterolemia probably have a defect in cholesterol biosynthesis. the pathway that leads to cholesterol degradation. the low-density lipoprotein receptor. the LDL-cholesterol blood transport mechanism.
the low-density lipoprotein receptor.
A neuron and a white blood cell have very different functions. For example, a neuron can receive and respond to electrical signals while a white blood cell defends the body against infection. This is because ______. the proteins found in a neuron are completely different from the proteins found in a white blood cell. the neuron and the white blood cell within an individual have the same genome. the neuron expresses some mRNAs that the white blood cell does not. neurons and white blood cells are differentiated cells and thus no longer need to transcribe and translate genes.
the neuron expresses some mRNAs that the white blood cell does not.
The Figure below illustrates changes in membrane potential during the formation ofan action potential. What membrane characteristic or measurement used to studyaction potentials is indicated by the arrow? effect of a depolarizing stimulus resting membrane potential threshold potential action potential
threshold potential
Photosynthesis is a process that takes place in chloroplasts and uses light energy to generate high-energy electrons, which are passed along an electron-transport chain. Where are the proteins of the electron-transport chain located in chloroplasts? thylakoid space stroma inner membrane thylakoid membrane
thylakoid membrane
Photosynthesis is a process that takes place in chloroplasts and uses light energy togenerate high-energy electrons, which are passed along an electron-transport chain. Where are the proteins of the electron-transport chainlocated in chloroplasts? thylakoid space stroma inner membrane thylakoid membrane
thylakoid membrane
Which of the following forms elastic filaments that account for the passive resistance to stretching seen in relaxed muscle? actin elastin desmin titin myosin
titin
Proteins that are fully translated in the cytosol do not end up in _______. the cytosol. the mitochondria. the interior of the nucleus. transport vesicles.
transport vesicles
MAP kinase influences gene expression by the phosphorylation of cytoplasmic transcription factors which then travel to the nucleus. traveling to the nucleus and phosphorylating transcription factors. activation of phospholipase C and subsequent activation of PKC which phosphorylates cytoplasmic transcription factors which then travel to the nucleus. activation of the nuclear response element CREB.
traveling to the nucleus and phosphorylating transcription factors.
A small polypeptide targets proteins for degradation is urethane. ubiquitin. urease. ligase.
ubiquitin
Which of the following techniques gives investigators a means of studying changes in ion fluxes during the production of an action potential? voltage clamping membrane polarization osmotic shock ion exchange chromatography
voltage clamping
Which of the following is required for the secretion of neurotransmitters in response toan action potential? neurotransmitter receptors Na + -K + pumps voltage-gated K + channels voltage-gated Ca 2+ channels
voltage-gated Ca 2+ channels
What is the polymerizing subunit that forms microtubules? α-Tubulin α-Tubulin homodimer β-Tubulin homodimer α-Tubulin: β-tubulin heterodimer
α-Tubulin: β-tubulin heterodimer
The presence of peptide bonds restricts the rotation of the polypeptide backbone. Two regular types of secondary structure that result from this restricted rotation include: domain and α-helix α-helix and β-sheet β-barrel and α-helix α-helix and ionic sheets
α-helix and β-sheet
What structure forms between a nerve cell and a muscle cell to couple impulses in the nerve to the muscle? The rings of Brodgar The cistern of lamina terminalis The neuromuscular junction The subarachnoid space
The neuromuscular junction
MPF activity was discovered when cytoplasm from a Xenopus M-phase cell was injected into Xenopusoocytes, inducing the oocytes to form a mitotic spindle. In a control experiment, Xenopus interphase cytoplasm was injected into oocytes and shown not to induce the formation of a mitotic spindle. Which of the following statements is not a legitimate conclusion from the control experiment? The piercing of the oocyte membrane by a needle is insufficient to cause mitotic spindle formation. An increased volume of cytoplasm is insufficient to cause mitotic spindle formation. Injection of extra RNA molecules is insufficient to cause mitotic spindle formation. Components of an interphase nucleus are insufficient to cause mitotic spindle formation.
Injection of extra RNA molecules is insufficient to cause mitotic spindle formation
What is Wee1, and how is it involved in mitosis? It is a phosphatase that acts on cyclin-dependent kinase-1 to stall mitosis. It is a lipid that activates cyclin-dependent kinase-1 to initiate mitosis It is a kinase that keeps cyclin-dependent kinase-1 inactive prior to mitosis. It is a kinase that initiates the formation of the contractile ring during telophase.
It is a kinase that keeps cyclin-dependent kinase-1 inactive prior to mitosis.
What is the role of the nuclear localization sequence in a nuclear protein? It is bound by cytoplasmic proteins that direct the nuclear protein to the nuclear pore. It is a hydrophobic sequence that enables the protein to enter the nuclear membranes. It aids in protein unfolding so that the protein can thread through nuclear pores. It prevents the protein from diffusing out of the nucleus through nuclear pores
It is bound by cytoplasmic proteins that direct the nuclear protein to the nuclear pore.
What is the role of the nuclear localization sequence in a nuclear protein? It is bound by cytoplasmic proteins that direct the nuclear protein to the nuclear pore. It is a hydrophobic sequence that enables the protein to enter the nuclear membranes. It aids in protein unfolding so that the protein can thread through nuclear pores. It prevents the protein from diffusing out of the nucleus through nuclear pores.
It is bound by cytoplasmic proteins that direct the nuclear protein to the nuclear pore.
Which of the following statements is true regarding the level of the protein Cdk 1? It peaks at the onset of G2. It is reduced dramatically at the onset of G2. It peaks at the onset of G1. It is present at a constant level throughout the cell cycle.
It is present at a constant level throughout the cell cycle
Which of the following statements about skeletal muscle contraction is false? When a muscle cell receives a signal from the nervous system, voltage-gated channels open in the T-tubule membrane. The changes in voltage across the plasma membrane that occur when a muscle cell receives a signal from the nervous system cause an influx of Ca2+ into the sarcoplasmic reticulum, triggering a muscle contraction. A change in the conformation of troponin leads to changes in tropomyosin such that it no longer blocks the binding of myosin heads to the actin filament. During muscle contraction, the Z discs move closer together as the myosin heads walk toward the plus ends of the actin filaments.
The changes in voltage across the plasma membrane that occur when a muscle cell receives a signal from the nervous system cause an influx of Ca2+ into the sarcoplasmic reticulum, triggering a muscle contraction.
Where do microtubules originate in interphase fibroblasts in tissue culture? The microtubule organizing center (MTOC) near the nucleus The center of the nucleus The trailing edge of mitochondria Under the plasma membrane
The microtubule organizing center (MTOC) near the nucleus
Which of the following statements is true? The mitotic spindle is largely made of intermediate filaments. The contractile ring is made largely of microtubules and actin filaments. The contractile ring is organized by arp2/3. The mitotic spindle helps segregate the chromosomes to the two daughter cells.
The mitotic spindle helps segregate the chromosomes to the two daughter cells.
Which of the following is TRUE of cytokine receptors? When activated, their cytoplasmic domains phosphorylate transcription factors which then enter the nucleus. When activated, their cytoplasmic domains activate a JAK, which then phosphorylates a transcription factor that enters the nucleus. Their cytoplasmic domains are JAKs, which become active tyrosine kinases when a ligand binds. When activated, they cause the release of a STAT which then enters the nucleus.
When activated, their cytoplasmic domains activate a JAK, which then phosphorylates a transcription factor that enters the nucleus.
A portion of a polypeptide theoretically capable of independent folding is known as a: domain primary structure hydrophobic pocket chaperone
domain