Test 4 Cram study guide

Question 1

Which happens when a cell surface receptor activates a G protein?

Answer 1

the alpha subunit exchanges GDP for GTP

Question 2

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?

Answer 2

signal transduction

Question 3

What shortens during muscle contraction?

Answer 3

sarcomeres

Question 4

When the hormone insulin is secreted into the bloodstram, what form of cell to cell signalling is being used?

Answer 4

endocrine

Question 5

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?

Answer 5

paracrine

Question 6

Monomer that binds to ATP

Answer 6

Actin

Question 7

What includes keratin and neurofilaments?

Answer 7

intermediate filaments

Question 8

What can be connected by desmosomes?

Answer 8

intermediate filaments

Question 9

What is used in eukaryotic cilia?

Answer 9

microtubules

Question 10

True/False

Each type of extracellular signaling molecules elicits similar responses in different target cells

Answer 10

False

Question 11

Where are lamins found?

Answer 11

nucleus

Question 12

Where are neurofilaments found?

Answer 12

nerve cells

Question 13

Where are vimentins found?

Answer 13

nucleus

Question 14

Where are keratins found?

Answer 14

connective tissue

Question 15

Most extracellular signal molecules act on cell-surface receptors rather than intracellular receptors because?

Answer 15

too hydrophobic/too large

Question 16

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?

Answer 16

A change that decreases the rate of hydrolysis of GTP by Ras

Question 17

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

Answer 17

true

Question 18

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?

Answer 18

Addition of any drug that blocks protein y from interacting with its target

Question 19

Which is important for flagellar movement?

Answer 19

microtubules, Dynein, ATP

Question 20

Figure 4, shows intracellular signal pathways are highly connected. Which of these is false about the pathway

Answer 20

cyclic AMP is activated only when RTK is active and not when GPCR is active

Question 21

Which would enhance microtubule polymerization?

Answer 21

addition of anything that inhibits hydrolysis of GTP carried by tubulin dimers

Question 22

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

Answer 22

true

Question 23

Certain mutant RAS proteins found in cancers can’t hydrolyze GTP to GDP and therefor?

Answer 23

Can’t turn themselves off

Question 24

What is the main function of intermediate filaments?

Answer 24

enable cells to withstand significant mechanical stress when stretched

Question 25

GTP binding proteins that act as molecular switches inside the cell?

Answer 25

activate when GTP is bound

Question 26

T/F
Subunits of microtubules and actin filaments are globular proteins, wheras those of intermediate filaments are themselves filamentous

Answer 26

true

Question 27

T/F
enzyme coupled receptors are transmembrane proteins that display their ligand binding domains on the outer surface of the plasma membrane

Answer 27

true

Question 28

What grows out from a centrosome towards the cell membrane preiphery

Answer 28

microtubules

Question 29

Which component of a G proetin can activate target proteins in an intracellular signalling pathway

Answer 29

alpha subunit and beta gamma subunit

Question 30

T/F

Serine/theronine kinases remove phosphate groups from phosphoroylated serines and theronines

Answer 30

false

Question 31

Hydrolysis of GTP to GDP carried out in microtubules?

Answer 31

allows for behavior of microtubules called dynamic stability

Question 32

Following binding of an extracellular signal molecule, RTKs are activated by dimerization of respective ligands which allows?

Answer 32

Each polypeptide chain to cross phosphoylate the other chain in the dimer specific tryosines in its cytoplasmic tail

Question 33

Kinesin and dynein motor proteins each use the energy of _______ to power movements, _______ along microtubules.

Answer 33

ATP hydrolysis; in a single direction

Question 34

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

Answer 34

true

Question 35

GPCRs are referred to as 7 pass membrane receptors because:

Answer 35

Polypeptide chain crosses the lipid bilayer 7 times

Question 36

Phosphorylates tyrosines on activated RTKs?

Answer 36

Serve as binding sites for a variety of intracellular signalling proteins

Question 37

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

Answer 37

true

Question 38

T/F

The cytoskeleton gives a cell its shape and allows the cell to organize its internal components

Answer 38

true

Question 39

What is included in the cytoskeleton?
Intermediate filaments
microtubules
actin filaments

Answer 39

All of the above

Question 40

How are the intermediate filaments in each cell connected?

Answer 40

through desmosomes

Question 41

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

Answer 41

D) All of the above

Question 42

T/F

Each type of extracellular signal molecule induces a similar response in different target cells.

Answer 42

false

Question 43

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

Answer 43

A and C
too hydrophilic to pass directly across the plasma membrane.
too large to pass directly across the plasma

Question 44

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.

Answer 44

are active when GTP is bound.

Question 45

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

Answer 45

A and B

(A) α Subunit
(B) βγ Complex

Question 46

Small intracellular signaling molecules are often called:
(A) extracellular signals.
(B) primary messengers.
(C) secondary messengers.
(D) none of the above

Answer 46

secondary messengers.

Question 47

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.

Answer 47

causes Ras to exchange GDP for GTP.

Question 48

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.

Answer 48

phosphatases remove the phosphate from GTP on GTP-binding proteins, turning them off

Question 49

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

Answer 49

addition of a high concentration of nonhydrolyzable analog of GTP

Question 50

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.

Answer 50

PI 3-Kinase phosphorylates a lipid in the plasma membrane