Lecture 12-21 Flashcards
Which of the following proteins are made in the rough endoplasmic reticulum?
a. cytosolic proteins
b. proteins destined for chloroplasts
c. proteins sent to the nucleus
d. proteins sent to lysosomes
e. c and d
d
- Once an ER-derived vacuole or -cisterna has surrounded an organelle to be destroyed with a double membrane, it fuses with a lysosome. What is the resultant structure called?
a. autophagolysosome
b. phagolysosome
c. bacteriophage
d. phagosome
e. autophagosome
a
- How are integral membrane proteins distinguished from secretory proteins as they are being synthesized on ribosomes bound to the RER?
a. Integral membrane proteins possess one or more hydrophilic transmembrane segments of amino acids that block further movement of protein into the ER lumen.
b. Integral membrane proteins possess stop-transfer sequences.
c. Integral membrane proteins possess one or more hydrophobic transmembrane segments of amino acids that block further movement of protein into the ER lumen.
d. a and b
e. b and c
e
- Stop-transfer sequences typically include ___________.
a. at least 15 continuous hydrophobic or uncharged amino acids
b. at least 15 continuous hydrophilic or charged amino acids
c. at least 15 continuous hydrophobic or charged amino acids
d. at least 15 continuous hydrophilic or uncharged amino acids
e. more than one of the above
a
- Phospholipids are made by integral ER membrane enzymes whose active sites face the cytosol and they are inserted into the outer (cytoplasmic) side of the ER membrane. How then do lipids destined for the luminal side of the ER membrane get there?
a. They diffuse freely into the luminal side.
b. There are enzymes that actively translocate them across the bilayer.
c. They are disassembled on the cytoplasmic side and reassembled on the luminal side.
d. They move to the cytoplasmic side by osmosis.
e. They move to the cytoplasmic side by diffusion.
b
- Which of the following strategies do bacteria use to avoid being destroyed by a lysosome’s fusion with the phagosome in which it was ingested?
a. The bacterium uses a H+-ATPase to neutralize the acidic environment in the phagolysosome.
b. The bacterium inhibits fusion of the phagosome with a lysosome.
c. The bacterium allows fusion with the lysosome, but neither the acidic pH nor the lysosomal enzymes can destroy it.
d. a and b
e. b and c
e
- What GTP-binding protein plays a regulatory role in the formation and disassembly of the COPII coat?
a. Sar1
b. Rab
c. ARF1
d. clathrin
e. SNARE
a
- What is the function of the protein coat on budding vesicles?
a. It acts as a mechanical device that helps to form the vesicle.
b. It provides a mechanism for selecting components and cargo to be carried by each vesicle.
c. It restricts certain molecules from being included in the vesicle.
d. a and b
e. a, b, and c
d Note that coat proteins don’t actually control what is packaged into the vesicles; that level of control is mediated by the receptors
- Mad cow disease is caused by mutant, misfolded _______________ proteins. These mutant proteins cause damage to neural cells because the protein-degrading machinery, known as the ________________________, is unable to deal with them.
prion; proteasome
- Which model suggests that the Golgi cisternae are transient structures that form at the cis face and travel through the Golgi complex, moving physically and exiting the organelle at the trans face, while changing during the journey?
the cisternal maturation model
What is the relevance of mannose-6-phosphate to lysosomes?
a. It is the sugar that lines the interior of a lysosome’s membrane.
b. It is a sugar added to proteins destined to be digested by the lysosomes.
c. It is a receptor for lysosomal lipids.
d. It is a sugar added to proteins that enables them to be transported into lysosomes.
e. It creates an acidic pH environment within the lysosomes.
d
A mouse fibroblast cell line will grow and divide normally in in vitro cultures at 37ºC. Some of the cells from this culture were subsequently removed and genetically altered such that they now constitutively expressed an antibody that bound to the protein HSP70. This genetically altered cell line, when grown at 37ºC, showed a 40 % reduction in the cell division rate when compared to the unmodified cells. When both the control cells and genetically altered cells were transferred to 42ºC for a period of 3 hours, and then returned to 37ºC, the genetically-altered cells failed to divide any more, while the control cells resumed their cell divisions at the previously observed rate.
The control cells continued to divide after the 43ºC exposure while the genetically engineered cells did not divide because:
a) the genetically-altered cells could not recover from the high temperature while the control cells did recover.
b) the control cells could refold their heat-denatured proteins while the genetically-altered cells could not.
c) the control cells synthesized sufficient chaperone proteins to refold the heat denatured proteins, while the genetically-altered cells did not synthesize enough chaperone proteins.
d) a and b
e) a, b, and c
d Note that E is incorrect because the altered cells could still produce normal levels of HSP70, but the antibody that is also produced will interfere with HSP70’s function.
The smooth endoplasmic reticulum is involved in what process(es)?
a. synthesis of cytoplasmic proteins
b. synthesis of proteins destined for the lysosomes
c. synthesis of steroids
d. synthesis of endosomal proteins
e. more than one of the above
c
The lifespan of a protein within a cell can depend upon _______.
a. the identity of its N-terminal amino acid
b. whether it is bound to polyubiquitin
c. whether it is properly folded
d. a and b
e. a, b, and c
e
The primary site for protein modifications is within the _______ whereas the site for receptor protein recycling is primarily within the __________.
a. endoplasmic reticulum; Golgi
b. Golgi; phagosomes
c. endosomes; lysosomes
d. Golgi; late endosomes
e. lysosomes; primary endosomes
d
The lifespan of a protein within a cell can depend upon _______.
a. the identity of its N-terminal amino acid
b. whether it is bound to polyubiquitin
c. whether it is properly folded
d. a and b
e. a, b, and c
e recall that answer A refers to the N-end rule
Which protein is responsible for helping the COP-I protein bind to a budding vesicle?
a. ARF1
b. Sar1
c. SNARE
d. Rab
e. Clathrin
a
In which of the following processes is a lysosome least likely to be involved?
a. Removal of unneeded cells in a developing embryo
b. Digestion of an extracellular parasite
c. Digestion of polyubiquitinated proteins
d. Egg fertilization
e. Digestion of glycolipids
c
In which of the following processes is a lysosome least likely to be involved?
a. Removal of unneeded cells in a developing embryo
b. Digestion of an extracellular parasite
c. Digestion of polyubiquitinated proteins
d. Egg fertilization
e. Digestion of glycolipids
c recall that polyubiquitin typically guides proteins to the proteasome, not the lysosome
A transport system that moves 2 substances into the cell per cycle could be called a(n) _____.
a. uniport
b. antiport
c. symport
d. transmembrane channel
e. biport
c
- The sodium-potassium pump helps to make the cell interior _________ charged by __________.
a. negatively; pumping negative ions into the cell.
b. negatively; pumping 3 sodium ions out of the cell for every 2 potassium ions pumped in.
c. negatively; pumping 3 potassium ions out of the cell for every 2 sodium ions pumped in.
d. positively; pumping 3 sodium ions into the cell for every 2 potassium ions pumped out.
e. positively; pumping 3 potassium ions into the cell for every 2 sodium ions pumped out.
b
- What is largely responsible for establishing the resting potential of neurons and other cells?
a. H+/K+ pump
b. Na+/K+pump
c. Ca2+ ATPase
d. Na+/Ca2+ pump
e. Na+ ATPase
b
- The tendency of an electrolyte to diffuse between two compartments depends upon ________.
a. a chemical or concentration gradient
b. an electric potential gradient
c. an osmotic gradient
d. a and b
e. a, b, and c
d
- Which of the following statements about lipid rafts is/are correct?
a. Lipid rafts are often enriched with sphingosine.
b. Lipid rafts are often enriched with glycerol.
c. Lipid rafts help cluster integral proteins that work together.
d. a and b.
e. a, b, and c.
e
- Which of the following statements about cholesterol is NOT true?
a. At low temperatures, cholesterol increases the fluidity of membranes.
b. Cholesterol is often found concentrated in lipid rafts.
c. At high temperatures, cholesterol decreases fluidity of the membranes.
d. Cholesterol is not found in plant cell membranes.
e. Cholesterol is a lipid common to all animal cells.
d
The outward pressure exerted by a plant cell’s membrane on the surrounding cell wall is specifically known as _______.
a. osmotic pressure
b. cytoplasmic pressure
c. turgor pressure
d. plasmolytic pressure
e. cellular pressure
c
An amoeba living in freshwater must expel water from its cell using a contractile vacuole. The water enters the vacuole by the process of _______, passing through ________, and is then dumped into the extracellular environment by a process of _______.
a. diffusion; aquaporin channels; endocytosis
b. osmosis; aquaporin channels; exocytosis
c. diffusion; the lipid bilayer; exocytosis
d. active transport; aquaporin channels; exocytosis
e. osmosis; aquaporin channels; endocytosis
b
Which of the following compounds cannot cross the cell’s membrane without the aid of carrier or transporter proteins?
a. oxygen
b. glucose
c. water
d. testosterone
e. carbon dioxide
b
Which of the following would not occur within a cell’s membrane in an animal preparing for winter hibernation?
a. The cholesterol content of the membranes will increase.
b. There will be increased desaturation of the membrane’s lipids.
c. There will be increased activity of acyltransferases.
d. The fatty acid chains will be lengthened.
e. More double bonds on the lipids’ hydrocarbon tails will occur.
d
Which type of membrane pump has been associated with some cancer cells becoming resistant to chemotherapy drugs?
a. P-type ATPase
b. V-type ATP
c. ABC-type ATPase
d. Symport pump
e. Antiport pump
c
Sound waves cause cilia on cells within the ear to bend. The bending of the cilia opens ion channels, thereby initiating a change in the electric potential across the cell’s membrane. The initial movement of the ions across the cell’s membrane in response to the cilia’s movement is an example of ___.
a. voltage-gated diffusion
b. voltage-gated active transport
c. facilitated active transport
d. mechanically-gated diffusion
e. ligand-gated transport
d
How do cells in the body of a multicellular organism usually communicate with each other?
a. intracellular messenger molecules b. direct connection by cells through long projections c. extracellular messenger molecules d. electrical signals between cells e. ion transport between cells
c
What allows cells to respond to an extracellular messenger molecule?
a. They must have ion channels. b. They must have a lipid bilayer that allows a response. c. They must have receptor proteins exposed on the inner plasma membrane surface. d. They must express transmembrane receptors that specifically recognize and bind that particular messenger molecule. e. They must have nuclear membranes.
d
Where may second messengers be found?
a. diffusing through the cytoplasm b. in the nuclear membrane c. embedded in the membrane lipid bilayer d. a and b e. a and c
e
Where may second messengers be found?
a. diffusing through the cytoplasm b. in the nuclear membrane c. embedded in the membrane lipid bilayer d. a and b e. a and c
e recall that DAG is embedded in the cell’s plasma membrane
What strategies can be used to turn off the cell signaling response when it is necessary to do so?
a. elimination of the extracellular messenger molecule b. internalization of activated receptors and degradation of the receptor and its ligand c. internalization of activated receptors and their ligand, degradation of the ligand and return of the receptor to the cell surface d. degradation of activated signaling proteins e. all of the above
e
If the receptor is degraded along with its ligand after internalization, what is the effect on the cells ability to respond to a hormone?
a. The response is enhanced. b. The cell has increased sensitivity to subsequent stimuli. c. The cell has decreased sensitivity to subsequent stimuli. d. The cell exhibits no change in responsiveness to subsequent stimuli. e. a and b
c
What is the major effect of activated steroid receptor proteins?
a. activation of cell division b. initiates membrane transport of ions c. an increase in the rate of gene transcription d. c and e e. a decrease in the rate of gene transcription
d
What is the major effect of activated steroid receptor proteins?
a. activation of cell division b. initiates membrane transport of ions c. an increase in the rate of gene transcription d. c and e e. a decrease in the rate of gene transcription
d steroids can bind specific transcription factors – these factors can either increase or decrease gene expression, depending on which response element they bind on the proximal promoter
Place the following events in the proper order.
1 – Activation of one or more cellular signaling proteins.
2 – Dissociation of G-alpha from the G protein complex.
3 - Production of a second messenger, like cAMP.
4 – Replacement of GDP by GTP on the G-alpha after interaction with an activated GPCR.
5 – Conformational change in the G-alpha subunit causing a decreased affinity for the G-beta and gamma subunit.
6 - G-alpha subunit with its attached GTP activates an effector like adenylyl cyclase.
a. 4 – 5 – 2 – 6 – 3 – 1 b. 5 – 4 – 2 – 6 – 3 – 1 c. 4 – 6 – 2 – 5 – 3 – 1 d. 4 – 5 – 2 – 3 – 1 – 6 e. 1 – 5 – 2 – 4 – 3 – 6
a
How does IP3 get from the plasma membrane where it is made to the receptor on the SER?
a. It is carried there by a transport molecule. b. It diffuses. c. It crawls. d. It osmoses. e. It is moved enzymatically.
b
Both the glucagon and epinephrine receptor ___________.
a. directly activate adenylyl cyclase b. indirectly activate adenylyl cyclase c. directly activate the same type of heterotrimeric G protein d. a and c e. b and c
e
Insulin __________.
a. functions as an extracellular messenger molecule b. informs the cells of the body that blood-glucose levels are high c. directly transports glucose into the cell d. a and b e. a and c
d
The concentration of calcium ions in the ER lumen, the plant cell vacuole and the extracellular space are on average more than _______ times higher than in the cytosol.
a. 10 b. 100 c. 1,000 d. 10,000 e. 1,000,000
d
The enzyme that terminates the response to cAMP through the destruction of cAMP molecules present in the cell is called
phosphodiesterase
The generic term for an extracellular messenger molecule that binds to transmembrane receptors is a _________________.
ligand
In the absence of insulin, where is the GLUT4 glucose transporter generally located?
______________________________
membrane vesicles in the cytoplasm of insulin-responsive cells
The enzyme that is, in some cases, activated by a receptor brings about the cellular response by generating a second messenger. Such an enzyme is called a(n) __________.
effector
Which statement about heat shock proteins is not correct?
a. Heat shock proteins help refold unfolded proteins following cold stress.
b. Heat shock proteins recognize exposed hydrophilic amino acids on the surface of unfolded proteins.
c. A mild heat shock can result in enhanced cell survival due to accumulation of extra heat shock proteins.
d. Heat shock proteins are sometimes referred to as molecular chaperones.
e. Extra heat shock protein synthesis has been associated with improved tolerance to anoxia.
b
Which statement about prions or their associated disorders is not correct?
a. Scrapie is a disease of sheep caused by a misfolded protein.
b. The normal prion protein PrPC is comprised mostly of alpha helices while the mutant prion protein PrPSc is comprised mostly of beta sheets.
c. The PrPC protein and the PrPSc protein have the same primary protein structure.
d. When PrPC protein comes in contact with PrPSc protein, it causes the PrPSc protein to refold into a PrPC configuration.
e. People can acquire a prion-associated disease by eating beef from an animal infected with bovine spongiform encephalopathy (BSE).
d
Which statement about proteasomes is not correct?
a. Proteasomes found within the nucleus will degrade old, malfunctioning proteins.
b. Proteasomes degrade proteins that are tagged with a chain of ubiquitin proteins.
c. Proteasomes are found within the lumen of the endoplasmic reticulum.
d. The N-end rule is one factor that determines when a proteasome will target a particular protein.
e. Proteasomes unfold proteins before cutting them into pieces.
c
The position or the type of phospholipids found in a cell’s membrane can be altered by:
a. enzymatic modification of the head groups.
b. flippases.
c. phospholipid transfer proteins.
d. a and b
e. a, b, and c
e
Which protein facilitates the final step of fusion of a vesicle to a target membrane?
a. Rab proteins
b. clathrin
c. SNAREs
d. tethering proteins
e. none of the above
c
Which statement about lysosomes is not correct?
a. The pH inside an activated lysosome is below 7.
b. Lysosomes contain about 50 different hydrolytic enzymes.
c. The membrane of a lysosome has vATPase integral proteins.
d. Proteins destined for the lysosomes are tagged with phosphorylated mannose residues.
e. Proteins destined for the lysosomes leave the Golgi apparatus in COP-II coated vesicles.
e
A lysosomal storage disease ______________.
a. is caused by the absence of one type of hydrolytic enzyme within a lysosome
b. is characterized by the accumulation of an undigested compound within lysosomes
c. is caused by bacteria that inhibit fusion of the primary lysosome with an endocytotic vesicle
d. a and b
e. a, b, and c
d
Receptor-mediated endocytosis first produces ______ just inside the cell’s plasma membrane, which then coalesce (i.e. come together) to then form ______.
a. endosomes; late endosomes
b. endocytotic vesicles; early endosomes
c. endocytotic vesicles; lysosomes
d. clathrin-coated vesicles; lysosomes
e. early endosomes; endocytotic vesicles
b
What would happen to an Amoeba cell if it was treated with a drug that inhibited the salt pumps on the contractile vacuole’s membrane?
a. The contractile vacuole would fill normally and the cell would be able to expel excess water normally.
b. The contractile vacuole would fill too quickly with water and the cell would burst.
c. The contractile vacuole would fail to fill with water and the cell would burst.
d. The contractile vacuole would fill too quickly and the cell would shrink.
e. The contractile vacuole would fail to fill and the cell would shrink.
c
Water resorption by kidney cells can be increased by which process?
a. Opening of aquaporin channels on the cell’s outer plasma membrane.
b. Active transport of water through aquaporin channels on the cell’s outer plasma membrane.
c. Transport of vesicles carrying aquaporin channels to the cell’s outer plasma membrane.
d. Increasing fluidity of the plasma membrane by addition of more cholesterol.
e. Water resorption rates by kidney cells cannot be altered.
c
Acetylcholine binds to a sodium channel on a neural cell, opening the channel to allow sodium ions to flow quickly into the cell from a region of high sodium concentration to a region of low sodium concentration. This process is an example of _____________.
a. Ligand-gated facilitated diffusion
b. Repolarization
c. Mechanically-gated channel transport
d. Direct active transport
e. Voltage-gated active transport
a
A signal that is transmitted from one cell to its immediate neighbour is considered a(n) _____ signal.
a. autocrine
b. endocrine
c. paracrine
d. apocrine
e. exocrine
c
