cell bio in class practice questions exam 3

what about molecular switches is false

A phosphates remove the phosphate from GTP on GTP binding proteins turning them off

You recently identified a molecule that you believe is a primary messenger for a signal transduction mechanism. All you know about this ligand is that it is hydrophilic. Where would you expect to find initial interaction of the molecule with its receptor? A) On the outer surface of the plasma membrane B)Within the cytoplasm of the cell C)Within the nucleus of the cell D)On the cytoplasmic side of the plasma membrane E)In endosome vesicles

A) On the outer surface of the plasma membrane

Which of the following mechanisms is NOT directly Involved in inactivating an activated RTK? A) dephosphonyfation by serine/thereonine phosphates B) idlephosphorylation by tyrosine prosphatases C)removal of the RTK from the plasma membrane by endocylosis D) digestion of the RTK in lysosomes

A) dephosphorylation by serine/thereonine phosphates

Which of the following statements is true? A).MAP kinase is important for phosphorylating MAP kinase kinase. B) PI 3-kinase phosphorylates a lipid in the plasma membrane. C) Ras becomes activated when an RTK phosphorylates is bound GDP to create GTP D). Dimerization of GPCRs leads to Ga activation.

B) PI 3-kinase phosphorylates a lipid in the plasma membrane

What happens when a G-protein-coupled receptor (GPCR) activates a G protein? A)The 3 subunit exchanges its bound GDP for GTP. B) The GDP bound to the a subunit is phosphorylated to form bound GTP. C The a subunit exchanges its bound GDP for GTP. D) It activates the a subunit and inactivates the By complex.

B) The GDP bound to the a subunit is phosphorylated to form bound GTP.

CAMP affects cell activities by interacting directly with A) adenylyl cyclase. B) protein kinase A regulatory subunits. C)protein kinase A catalytic subunits. D)cAMP phosphodiesterase. E)calmodulin.

B) protein kinase A regulatory subunits.

The activation of the serine/threonine protein kinase Akt requires phosphoinositide 3-kinase (PI 3-kinase) to A) activate the RTK. B)create phosphorylated lipids that serve as docking sites that localize Akt to the plasma membrane. C)directly phosphorylate Akt. D) create DAG.

B)create phosphorylated lipids that serve as docking sites that localize Akt to the plasma membrane

A protein kinase can act as an integrating device in signaling if it A) phosphorylates more than one substrate. B) catalyzes its own phosphorylation. C) is activated by two or more proteins in different signaling pathways. D) initiates a phosphorylation cascade involving two or more protein kinases.

C) is activated by two or more proteins in different signaling pathways.

The low level of cytosolic calcium ions in inactivated cells is established by which of the following? Calmodulin Calcium ATPases Kinases Phosphatases Phospholipase C

Calcium ATPases

What role does GAP play in the RTK pathway? A) GAP promotes the dephosphorylation of the intracellular domains of the RTK receptor. B) GAP promotes the cross phosphorylation of tyrosine residues in the intracellular domains of the RTK receptors. C) GAP promotes the activation of the Ras protein, which then leads to the phosphorylation of MAP kinase pathway. D) GAP stimulates the hydrolysis of GTP to GDP in the Ras protein, and thus helps to inactivate the RTK

D) GAP stimulates the hydrolysis of GTP to GDP in the Ras protein, and thus helps to inactivate the RTK

All members of the nuclear receptor family A)are cell-surface receptors. B)do not undergo conformational changes. C) are found only in the cvtoplasm. D) interact with signaling molecules that diffuse through the plasma membrane.

D) interact with signaling molecules that diffuse through the plasma membrane.

The length of time that a G protein will signal is determined by the A) activity of phosphatases that turn off G proteins by dephosphorylating Ga B)activity of phosphatases that turn GTP into GDP. C)degradation of the G protein after Ga separates from GBy. D)GTPase activity of Ga.

D)GTPase activity of Ga.

In which of the following organelles would you expect to first find a protein destined to be secreted from a cell? Endosome Golgi apparatus Lysosome Secretory vesicle Endoplasmic reticulum

ER

Which of the following choices reflects the appropriate order of locations through which a newly synthesized protein destined for the plasma membrane travels? lysosome - endosome - plasma membrane ER - lysosome - plasma membrane Golgi - lysosome - plasma membrane ER - Golgi - plasma membrane

ER - Golgi - plasma membrane

You add a large amount of XFF to cultured alien liver cells. Which of the following would confirm that XFF is the alien equivalent of human epinephrine? Increased cell division Decreased cell division Glycogen breakdown Increased glucose uptake Insensitivity to insulin

Glycogen breakdown

Which of the following statements about membrane-enclosed organelles is true? a. In a typical cell, the area of the endoplasmic reticulum membrane far exceeds the area of plasma membrane. b. The nucleus is the only organelle that is surrounded by a double membrane. c. 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. d. 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.

Each of the following is correct about cholera and its effect on G-protein-adenylyl cyclase activity except Vibrio cholera bacteria colonize the gut. Cholera toxin is secreted by Vibrio cholera bacteria. Intestinal cells infected with cholera toxin import abnormally high levels of salts and fluids into the bloodstream. Cholera toxin alters Gsa so that it no longer hydrolyzes GTP. Intestinal cells infected with cholera toxin maintain abnormally high cAMP levels

Intestinal cells infected with cholera toxin import abnormally high levels of salts and fluids into the bloodstream.

Which of the following is the correct order of steps in the Epinephri GPCR signaling pathway? A)Ligand binding cAMP production-G-protein activation- adenyly cyclase activation -protein kinase A activation B)Ligand binding--protein kinase A activation- G-protein activation-adenylyl cyclase activation -CAMP production C)G-protein activation--ligand binding- -adenylyi cyclase activation production- protein kinase A activation D)Ligand binding-G-protein activation -adenylyi cyclase activation production-protein kinase A activation E) Ligand binding-adenylyl cyclase activation -G-protein activation production- protein kinase A activation

Ligand binding-G-protein activation -adenylyi cyclase activation production-protein kinase A activation

Each of the following is an intracellular messenger except calcium ions. IP3. DAG. CAMP. PDGF.

PDGF

Which of the following proteins exerts direct control over the glycogen synthesis and breakdown pathways when epinephrine stimulates glycogen conversion to glucose in liver cells? Glycogen phosphorylase Phosphorylase kinase Protein kinase A CAMP phosphodiesterase Glycogen synthase

Protein kinase A

Which of the following statements about the protein quality control system in the ER is FALSE? Chaperone proteins help misfolded proteins foldproperly. Proteins that are misfolded are degraded in the ER lumen. Protein complexes are checked for proper assembly before they can exit the ER. A chaperone protein will bind to a misfolded protein to retain it in the ER.

Proteins that are misfolded are degraded in the ER lumen

Which of the following statements about the endoplasmic reticulum (ER) is FALSE? The ER is the major site for new membrane synthesis in thecell Proteins to be delivered to the ER lumen are synthesized on the 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 the smooth ER.

Each of the following is true about Ras except Ras is monomeric. Ras activity is inhibited by GTPase activating proteins (GAPs). Ras binds steroid hormones. Ras is activated by Sos, a guanine nucleotide exchange factor. Ras activates a cascade of phosphorylation events within the cell.

Ras binds steroid hormones.

A protein that is normally localized in the cytoplasm has been engineered so that it will be secreted from the cell instead. Which of the following represents the most likely pathway for the protein after it has been completely synthesized? Rough ER - Golgi - secretory vesicle - environment Rough ER - Golgi - smooth ER -> cytoplasm - environment cytoplasm - rough ER - Golgi - secretory vesicle - environment Smooth ER - Golgi - secretory vesicle - environment Rough ER - secretory vesicle - Golgi - environment

Rough ER - Golgi - secretory vesicle - environment

Kinase enzymes add phosphate groups. always inhibit target molecule activity. bind tightly by wrapping around a target molecule to regulate its activity. remove phosphate groups. metabolize glucose.

add phosphate groups

Each of the following is an endoplasmic reticulum function except addition of carbohydrate to proteins to make glycoproteins. peptide folding. the assembly of multimeric proteins. the export of protein that cannot be folded into the cytoplasm for destruction. All are endoplasmic reticulum functions.

all

Ribosomes that do not anchor on the surface of the rough endoplasmic reticulum during translation most probably are synthesizing cytoplasmic proteins. have a defect in ribosomal proteins that allow attachment to the surface. have a signal peptidase error. do not make the appropriate anchor protein. All of the above are probable reasons.

are synthesizing cytoplasmic proteins.

Which of the following statements is true? a. Proteins destined for the ER are translated by a special pool of ribosomes whose subunits are always associated with the outer ER membrane. b. Proteins destined for the ER translocate their associated mRNAs into the ER lumen where they are translated. c. Proteins destined for the ER are translated by cytosolic ribosomes and are targeted to the ER when their signal sequences emerge from the ribosomes during translation. d. Proteins destined for the ER are translated by a pool of cytosolic ribosomes that contain ER-targeting. sequences that interact with ER-associated protein translocators.

c. Proteins destined for the ER are translated by cytosolic ribosomes and are targeted to the ER when their signal sequences emerge from the ribosomes during translation.

Most proteins destined to enter the endoplasmic reticulum a. are transported across the membrane after their synthesis is complete. b. are completely translated on free nbosomes in the cytosol. c. begin to cross the membrane while still being synthesized. d. remain within the endoplasmic reticulum.

c. begin to cross the membrane while still being synthesized.

Each of the following is a second messenger except cyclic adenosine monophosphate. inositol trisphosphate. diacyiglycerol. epinephrine. calcium ions.

epinephrine

Which of the following is a lipophilic primary message that crosses the plasma membrane and interacts with a cytosolic receptor? Estrogen EGF Pertussis toxin TGFB PDGF

estrogen

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

Using the techniques of genetic engineering, you design a protein you want to accumulate within the ER of yeast cells. To accomplish this goal, you need to do nothing; all proteins go through the ER. incorporate appropriate mannose-6-phosphate groups. incorporate the appropriate DNA sequence(s) to create signal sequences in the mature peptide. incorporate radioactive amino acids into the protein. remove the N-formyl group located at the N-terminus of the polypeptide.

incorporate the appropriate DNA sequence(s) to create signal sequences in the mature peptide

Each of the following is a characteristic of hormones except synthesis by endocrine tissue cells secretion directly into the bloodstream. having a hormone-specific lifespan in the blood ranging from seconds to hours. interacting with specific receptors on cells in target tissues throughout the body. All are characteristics of endocrine hormones.

interacting with specific receptors on cells in target tissues throughout the body.

Which of the following organelles is NOT part of the endomembrane system? Golgi apparatus endosome mitochondria lysosomes

mitochondria

Comparing cells synthesizing secretory proteins and cells secreting steroid hormones, the cells synthesizing the steroid hormones have more rough ER. more smooth ER. equal amounts of smooth and rough ER. equal amounts of smooth and rough ER, but more lysosomes. equal amounts of smooth and rough ER, but fewer lysosomes.

more smooth ER

The unfolded protein response slows the production of ______ and increases the _______ signal recognition particles; activity of proteasomes most proteins; production of lysosomal proteins protein disulfide isomerase; activity of proteasomes most proteins; production of proteins required for protein folding and degradation

most proteins; production of proteins required for protein folding and degradation

To test whether the XFF signal system is similar to that of epinephrine, you microinject a nonhydrolyzable analogue of GTP into an XFF-responsive cell. If the XFF mechanism is similar to that of epinephrine, you would expect the cellular response to be blocked completely. prolonged. delayed. 50 percent of normal. It is not possible to predict without knowing how many receptors are present in the cell.

prolonged.

Phosphatase enzymes add phosphate groups. always inhibit target molecule activity. bind tightly by wrapping around a target molecule to regulate its activity. remove phosphate groups. metabolize glucose.

remove phosphate groups.

Kinases and phosphatases are essential in the cell because they directly turn proteins "on and off" through changes in phosphorylation status. bind hydrophobic hormones in the cytoplasm. bind and release calcium ions. destroy IP3, turning off that signaling pathway.

turn proteins "on and off" through changes in phosphorylation status