Test 4 Cram study guide Flashcards
Which happens when a cell surface receptor activates a G protein?
the alpha subunit exchanges GDP for GTP
When cells respond to an extracellular signaling molecule they most often convert the information carried from one form to another, this is a process called?
signal transduction
What shortens during muscle contraction?
sarcomeres
When the hormone insulin is secreted into the bloodstram, what form of cell to cell signalling is being used?
endocrine
Many of the extracellular signalling molecules that regulate inflammation are released locally at the site of the infection. What form of extracellular signalling is this?
paracrine
Monomer that binds to ATP
Actin
What includes keratin and neurofilaments?
intermediate filaments
What can be connected by desmosomes?
intermediate filaments
What is used in eukaryotic cilia?
microtubules
True/False
Each type of extracellular signaling molecules elicits similar responses in different target cells
False
Where are lamins found?
nucleus
Where are neurofilaments found?
nerve cells
Where are vimentins found?
nucleus
Where are keratins found?
connective tissue
Most extracellular signal molecules act on cell-surface receptors rather than intracellular receptors because?
too hydrophobic/too large
The Ras protein is a GTPase that functions in many growth factors signaling pathways with GTP bound it transmits downstream signal for cell proliferation inactive with GDP bound and no signal is transmitted.
Mutations for Ras are frequently found in cancers. What would contribute to uncontrollable growth in cancers?
A change that decreases the rate of hydrolysis of GTP by Ras
True or False:
When studying signal transduction pathways in lab, mutant transmemberane protein receptors can be synthesized to determine exactly where intracellular signaling molecules bind
true
Figure 3 shows normal signalling with Ras downstream of RTK and and you examine a cell line with a constituively active Ras. Which of these will turn of signalling?
Addition of any drug that blocks protein y from interacting with its target
Which is important for flagellar movement?
microtubules, Dynein, ATP
Figure 4, shows intracellular signal pathways are highly connected. Which of these is false about the pathway
cyclic AMP is activated only when RTK is active and not when GPCR is active
Which would enhance microtubule polymerization?
addition of anything that inhibits hydrolysis of GTP carried by tubulin dimers
True/False:
In the Notch signalling pathway the tail of the surface receptor travels to the nucleus where is regulates the transcription of specific genes
true
Certain mutant RAS proteins found in cancers can’t hydrolyze GTP to GDP and therefor?
Can’t turn themselves off
What is the main function of intermediate filaments?
enable cells to withstand significant mechanical stress when stretched
GTP binding proteins that act as molecular switches inside the cell?
activate when GTP is bound
T/F
Subunits of microtubules and actin filaments are globular proteins, wheras those of intermediate filaments are themselves filamentous
true
T/F
enzyme coupled receptors are transmembrane proteins that display their ligand binding domains on the outer surface of the plasma membrane
true
What grows out from a centrosome towards the cell membrane preiphery
microtubules
Which component of a G proetin can activate target proteins in an intracellular signalling pathway
alpha subunit and beta gamma subunit
T/F
Serine/theronine kinases remove phosphate groups from phosphoroylated serines and theronines
false
Hydrolysis of GTP to GDP carried out in microtubules?
allows for behavior of microtubules called dynamic stability
Following binding of an extracellular signal molecule, RTKs are activated by dimerization of respective ligands which allows?
Each polypeptide chain to cross phosphoylate the other chain in the dimer specific tryosines in its cytoplasmic tail
Kinesin and dynein motor proteins each use the energy of _______ to power movements, _______ along microtubules.
ATP hydrolysis; in a single direction
T/F
The concentration on actin monomers is high in the cytosol but monomer sequestering proteins that bond to actin monomers can prevent them from polymerizing into fully mature actin
true
GPCRs are referred to as 7 pass membrane receptors because:
Polypeptide chain crosses the lipid bilayer 7 times
Phosphorylates tyrosines on activated RTKs?
Serve as binding sites for a variety of intracellular signalling proteins
T/F some intracellular signalling proteins serve to integrate incoming signals in these pathways cellular response is achieved only when both/all activating signals are presents
true
T/F
The cytoskeleton gives a cell its shape and allows the cell to organize its internal components
true
What is included in the cytoskeleton?
Intermediate filaments
microtubules
actin filaments
All of the above
How are the intermediate filaments in each cell connected?
through desmosomes
What does a target cell require to respond to an extracellular signal molecule?
(A) Access to the signal molecule
(B) Appropriate intracellular signaling pathways
(C) The presence of an appropriate receptor for the signal molecule
(D) All of the above
D) All of the above
T/F
Each type of extracellular signal molecule induces a similar response in different target cells.
false
Most extracellular signal molecules act on cell-surface receptors, rather than intracellular receptors, because they are:
(A) too hydrophilic to pass directly across the plasma membrane.
(B) too hydrophobic to pass directly across the plasma membrane.
(C) too large to pass directly across the plasma membrane.
(D) A and C
(E) B and C
A and C
too hydrophilic to pass directly across the plasma membrane.
too large to pass directly across the plasma
The GTP-binding proteins that act as molecular switches inside cells:
(A) are active only in their trimeric forms.
(B) are active when GDP is bound.
(C) are active when GTP is bound.
(D) turn themselves on by hydrolyzing GTP to form GDP.
are active when GTP is bound.
Which component or components of a G protein can, on its own, activate target proteins in an intracellular signaling pathway? (A) α Subunit (B) βγ Complex (C) β Subunit (D) All of the above (E) A and B
A and B
(A) α Subunit
(B) βγ Complex
Small intracellular signaling molecules are often called: (A) extracellular signals. (B) primary messengers. (C) secondary messengers. (D) none of the above
secondary messengers.
Ras is activated by a Ras-activating protein that:
(A) causes Ras to exchange GDP for GTP.
(B) causes Ras to hydrolyze its bound GTP.
(C) phosphorylates Ras.
(D) dephosphorylates Ras.
causes Ras to exchange GDP for GTP.
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 kinases are the most common types of protein kinase.
(d) 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
Acetylcholine binds to a GPCR on heart muscle, making the heart beat more
slowly. The activated receptor stimulates a G protein, which opens a K+
channel
in the plasma membrane, as shown in Figure Q16-32. Which of the following
would enhance this effect of the acetylcholine?
Figure Q16-32
(a) addition of a high concentration of a nonhydrolyzable analog of GTP
(b) addition of a drug that prevents the α subunit from exchanging GDP for
GTP
(c) mutations in the acetylcholine receptor that weaken the interaction
between the receptor and acetylcholine
(d) mutations in the acetylcholine receptor that weaken the interaction
between the receptor and the G protein
addition of a high concentration of nonhydrolyzable analog of GTP
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 its bound GDP to
create GTP.
(d) STAT proteins phosphorylate JAK proteins, which then enter the nucleus
and activate gene transcription.
PI 3-Kinase phosphorylates a lipid in the plasma membrane
