During nervous system development in Drosophilia, the membrane-bound protein delta acts as an inhibitory signal to prevent neighboring cells from developing into neuronal cells. Delta is involved in ______ signaling.
a)endocrine
b)neuronal
c)contact-depen
c)contact-dependent
You have been assigned to identify a novel purified protein in your lab. You immediately notice this protein contains a polypeptide chain that traverses the membrane seven times and the transmembrane portion of the protein consist of alpha helices. What c
a)it belongs to the family of G-protein coupled receptors
Which of the following statements is TRUE?
a)Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor so as to signal a target cell to change behavior
b)to function, all extracellular signal molecules must be transported by
a)Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor so as to signal a target cell to change behavior
T/F: Tubulin dimmers carrying ATP bind more tightly to one another than do tubulin dimmers carrying ADP. Therefore, rapidly growing plus ends of microtubules,which have freshly added tubulin dimmers with ATP bound, tend to keep growing.
False
The local mediator nitric oxide stimulates the intracellular enzyme guanylyl cyclase by_____.
a)Diffusing into cells and stimulating the cyclase directly
b)activating a G protein
c)activating a receptor tyrosine kinase
d)activating an intracellular protei
a)Diffusing into cells and stimulating the cyclase directly
Consider the mechanism by which actin and tubulin polymerize. Which of the following does not describe something similar about the polymerization mechanisms of actin and microtubules?
a)although both filaments can grow from both ends, the growth rate is f
b)Depolymerization initiates at the plus ends of filaments
Which of the following statements about the cell cycle is FALSE?
a)an unfavorable environment can cause cells to arrest in G1
b)A cell has more DNA during G2 than it did in G1
c)the cleavage divisions that occur in an early embryo have short G1 and G2 pha
d) once a cell decides to enter the cell cycle, the time from start to finish is the same in all eukaryotic cells
The abrupt degradation of M and S cyclins part way through M phase depends on a large enzyme complex called:
a)G1/S CDK
b)G1/S promoting complex
c)anaphase promoting complex
d)the ORC complex properly bound to the replication of origin
c)anaphase promoting complex
Which of the following statements about molecular switches is FALSE?
a)phosphatases remove the phosphate from GTP on GTP-binding proteins, turning them off
b)protein kinases transfer the terminal phosphate from ATP onto a protein.
c)serine/threonine kinas
a)phosphatases remove the phosphate from GTP on GTP-binding proteins, turning them off
Mitogens are____.
a)extracellular signals that stimulate cell division
b)transcription factors important for cyclin production
c)kinases that cause cells to grow in size
d)produced by mitotic cells to keep nearby neighboring cells from dividing
a)extracellular signals that stimulate cell division
Working in a lab you are given an unknown sample to analyze. After numerous biochemical steps you recognize a cross section of a microtubule with a distinctive 9+2 arrangement. Due to this you can conclude that the microtubule is from"
a)the cytoplasm
b)c
b)cilium
Which one of the following statements is TRUE?
a) MAP kinase is important for phosphorylating MAP kinase kinase
b)Ras becomes activated when an RTK phosphorylates its bound GDP to create GTP
c)STAT proteins phosphorylate JAK proteins, which enter the nucl
d)PI-3 kinase phosphorylates a lipid in the plasma membrane
Intermediate filaments help protect animal cells from mechanical stress because_____?
a)filaments directly extend from the interior of the cell to the extracellular space and into the next cell, linking one cell to the next helping to distribute locally a
b) filaments in each cell are indirectly connected to the filaments of a neighboring cell through desmosome, creating a continuous mechanical link between cells.
Keratins, neurofilaments and vimentins are all categories of intermediate filaments. Which of the following properties is not true of these types of intermediate filaments?
a)they strengthen cells against mechanical stress
b)dimers associate by noncovalen
d)phosphorylation causes disassembly during every mitotic cycle
Which situation described below will lead to an increase in Brainy transcription?
a)a mutation in the Nerd gene that produces a protein that cannot be phosphorylated by PKA
b)a mutation in the nuclear import sequence of PKA from PPKKKRKV to PPAAAAV
c)a mu
c)a mutation in the gene that encodes cAMP phosphodiesterase that makes the enzyme inactive
Which of the following statements about the structure of microtubules is FALSE?
a)microtubules are built form protofilaments that come together to make a hollow structure
b)alpha-tubulin and beta tubulin are covalently bound to make the tubulin dimer that
b)alpha-tubulin and beta tubulin are covalently bound to make the tubulin dimer that then assembles into protofilaments
The activation of serine/threonine protein kinase Akt requires phosphoinositide 3-kinase (PI 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 A
b)create phosphorylated lipids that serve as docking sites that localize Akt to the plasma membrane
Which of the following statements about the function of the centrosome is FALSE?
a)centrosomes contain hundreds of copies of the gamma-tubulin ring complex important for microtubule nucleation
b)centrosome typically contain a pair of centrioles, which is
c)microtubules emanating from the centrosome have alternating polarity such that some have their plus end attached to the centrosome while others have their minus end attached to the centrosome
Which of the following statements is correct? Kinesins and dyneins_____.
a)often move in opposite directions to each other
b)have tails that bind to the filaments
c)move along both microtubules and actin filaments
d)derive their energy from GTP hydrolysis
a)often move in opposite directions to each other
When a signal molecule needs to be sent to most cells throughout a multicellular organism, the signal most suited for this is_____.
a)neurotransmitter
b)hormone
c)dissolved gas
d)scaffold
b)hormone
Which of the following statements about actin is FALSE?
a)ATP hydrolysis decreases actin filament stability
b)Actin at the cell cortex helps govern the shape of the plasma membrane
c)dynamic instability of actin filaments is important for cell movement
d)
c)dynamic instability of actin filaments is important for cell movement
What would be the most obvious outcome of repeated cell cycles consisting of S and M phase only?
a)nuclear envelope closes down
b)cells grow in size
c)DNA is replicated
d)the centrosomes are duplicated
a)nuclear envelope closes down
In which phase of the cell cycle do cells check to determine whether DNA is fully and correctly replicated?
a)at the transition between G1 and S
b)when cells enter G0
c)during M
d)at the end of G2
d) at the end of G2
Progression through the cell cycle requires a cyclin to bind to a Cdk because_____.
a)the binding of a cyclin to Cdk is required for Cdk enzymatic activity
b)the cyclins are the molecules with the enzymatic activity in the complex
c)cyclin binding inhibit
a)the binding of a cyclin to Cdk is required for Cdk enzymatic activity
Which of the following statements is FALSE?
a) DNA synthesis begins at origins of replication
b)the phosphorylation and degradation of Cdc6 help ensure that DNA is replicated only once in each cell cycle
c)the loading of the origin recognition complexes (
c)the loading of the origin recognition complexes (ORCs) is triggered by S-Cdk
The following happens when a G-protein-coupled receptor activates a G protein:
a)the beta subunit exchanges its bound GDP for GTP
b)the GDP bound to the alpha subunit is phosphorylated to form bound GTP
c)the alpha subunit exchanges its bound GDP for GTP
c)the alpha subunit exchanges its bound GDP for GTP
How does S-Cdk help guarantee that replication occurs only once during each cell cycle?
a)it blocks the rise of Cdc6 concentrations early in G1
b)it phosphorylates and inactivates DNA helicase
c)it phosphorylates the Cdc6 protein marking it for destructio
c)it phosphorylates the Cdc6 protein marking it for destruction
The Retinoblastoma (Rb) protein blacks cells from entering the cell by_____.
a)inhibiting cyclin transcription
b)phosphorylating Cdk
c)marking cyclins for destruction by proteolysis
d)activating apoptosis
a)inhibiting cyclin transcription
Irradiated mammalia cells usually stop dividing and arrest at G1 checkpoint. Place the following events in the order in which they occur:
1. Production of p21
2. DNA damage
3. Inhibition of cyclin-Cdk complexes
4. accumulation and activation of p53
2,4,1,3
The G1 DNA damage checkpoint_______.
a)causes cells to proceed through S phase more quickly
b)involves the degradation of p53
c)is activated by errors caused during DNA replication
d)involves the inhibition of cyclin-Cdk complexes by p21
d)involves the inhibition of cyclin-Cdk complexes by p21
Cells in the G0 state_______.
a)do not divide
b)cannot re-enter the cell cycle
c)have entered this arrest state from either G1 or G2
d)have duplicated their DNA
a)do not divide
Which word or phrase below best describes the phase in mitosis depicted in the figure below:
a)anaphase
b)prometaphase
c)metaphase
d)S-phase checkpoint
c)metaphase
The principal microtubule-organizing center in animal cells is_____.
a)centrosome
b)centromere
c)kinetochore
d)cell cortex
a)centrosome
The hydrolysis of GTP to GDP carried out by tubulin molecules________.
a)provides energy needed for tubulin to polymerize
b)occurs because the pool of free GDP has run out
c)tips the balance in favor of microtubule assembly
d)allows the behavior of the mi
d)allows the behavior of the microtubules called dynamic instability
The microtubules in a cell form a stuctural frame work that can have all the following functions except which one?
a) holding internal organelles such as the golgi apparatus in particular positions in the cell
b)creating long, thin cytoplasmic extensions
c)strengthening the plasma membrane