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Cell > Cell communication > Flashcards

Cell communication Flashcards

1
Q

What three factors account for the extraordinary sensitivity of signal transducers?

A

High affinity of signal molecules, cooperativity (often but not always) in ligand-receptor interaction, and amplification of signal by enzyme cascades

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2
Q

Membrane-bound signaling can be demonstrated by:

A. paracrine signaling
B. autocrine signaling
C. neurocrine signaling
D. immune interactions

A

D

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3
Q

Which is true about paracrine and autocrine signaling?

A. Both are forms of contact-dependent signaling
B. In paracrine signaling, the chemical signal diffuses into
the blood stream and acts on nearby tissues
C. in autocrine signaling, the signaling cell secretes signals that may affect neighboring cells of the same type and itself
D. the chemical signal typically enters the bloodstream in order to be inactivated or metabolized

A

C

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4
Q

The following are true about acetylcholine nicotinic receptor (neuromuscular junctions) EXCEPT:

A. It is an ion-channel linked receptor
B. It is a ligand-gated channel
C. It is directly gated by Gsa protein
D. It allows traffic of lions like Na+, K+, Ca++ into the cell

A

C

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5
Q

What are the components of a G-protein coupled receptor signal transduction system?

A

A heptahelical transmembrane receptor, an effector enzyme that generates a second messenger, and G-protein that activates the effector enzyme

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6
Q

What kind of receptor is a B-adrenergic receptor?

A

A heptahelical transmembrane receptor

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7
Q

What are agonists?

A

Structural analogs that binds to a receptor and mimic the effect of its natural ligand

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8
Q

What are antagonists?

A

Analogs that bind the receptor without triggering the normal effect and thereby blocks the effects of agonists, including the biological ligand

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9
Q

What is the biological ligand of a B-adrenergic receptor?

A

Epinephrine

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10
Q

Largest category of plasma membrane receptors

A

GPCRs

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11
Q

An extracellular signal such as epinephrine can have quite different effects on different tissues or cell types, depending on three factors, which are?

A

The receptor type in the tissue, the G-protein coupled to this receptor and the PKA target enzymes

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12
Q

G proteins may be involved in the coupling of receptors and their respective effector systems through activation of which of the following?

A. Ion channel
B. Adenylate cyclase
C. Phospholipase C
D. All of the above

A

D

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13
Q

Which of the following determines the specificity of communication in the endocrine system?

A. The chemical nature of the hormone
B. The distance between the endocrine cell and its target cell
C. The presence of specific receptors on target cells
D. Anatomic connections between the endocrine and target cells

A

C

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14
Q

Growth hormone (GH)

A. Phospholipase C 
B. Tyrosine kinase 
C. JAK kinase 
D. Adenylyl cyclase 
 E. Nota
A

C

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15
Q

Prolactin

A. Adenylate Cyclase 
B. Phospholipase C 
C. Jak Stat Pathway 
D. Guanylyl Cyclase 
E. Tyrosine Kinase
A

C

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16
Q

Which of the following BEST describes the biological effect of inositol triphosphate (IP3)?

A. Activating calmodulin
B. Stimulating protein kinase C
C. Promoting release of calcium from intracellular stores

A

C

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17
Q

Which are hormones that participate in enzyme-linked receptors?

a) AMP -> guanylyl cyclase receptor
b) insulin-like type 1 GF -> tyrosine kinase receptor
c) GH -> JANUS-STAT pathway
d) A and B only
e) all of the above

A

E

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18
Q

G-protein linked receptors

A. typically initiate a cascade of signals involving second
messengers
B. directly regulate the activity of membrane proteins (eg
protein messengers)
C. are single-pass transmembrane receptors
D. are linked to monomeric G protein complexes

A

A

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19
Q

Which of the ff is true about G proteins?

A. They preferentially bind GDP in the active state
B. They associate as complexes of 4 subunits
C. In its active form, the alpha and beta subunits for a tightly bound complex
D. The active alpha subunit can inactivate a transmembrane enzyme

A

D

20
Q

Which of the following statements best describes the cellular response to signals?

A. The cell response to a signal depends on the cell receptor and intracellular machinery
B. Polar ligands typically enter the cell and bind to intracellular receptors
C. Only ligands that bind to intracellular receptors can active gene transcription
D. A chemical signal will elicit an identical response in different target cells if it binds to identical receptors

A

A

21
Q

Norepinephrine

A. Phospholipase C 
B. Tyrosine kinase 
C. JAK kinase 
D. Adenylyl cyclase 
 E. Nota
A

D

22
Q

Oxytocin

A. Phospholipase C 
B. Tyrosine kinase 
C. JAK kinase 
D. Adenylyl cyclase 
 E. Nota
A

A

23
Q

Insulin

A. Phospholipase C 
B. Tyrosine kinase 
C. JAK kinase 
D. Adenylyl cyclase 
 E. Nota
A

B

24
Q

ANP

A. Adenylate Cyclase 
B. Phospholipase C 
C. Jak Stat Pathway 
D. Guanylyl Cyclase 
E. Tyrosine Kinase
A

D

25
Q

TSH

A. Adenylate Cyclase 
B. Phospholipase C 
C. Jak Stat Pathway 
D. Guanylyl Cyclase 
E. Tyrosine Kinase
A

A

26
Q

Vasopressin

A. Adenylate Cyclase 
B. Phospholipase C 
C. Jak Stat Pathway 
D. Guanylyl Cyclase 
E. Tyrosine Kinase
A

B

27
Q

Insulin

A. Adenylate Cyclase 
B. Phospholipase C 
C. Jak Stat Pathway 
D. Guanylyl Cyclase 
E. Tyrosine Kinase
A

E

28
Q

How is DAG thought to produce its biological effect?

A. Activating calmodulin
B. Stimulating protein kinase C
C. Promoting release of calcium from intracellular stores
D. Activating the alpha subunit of G protein

A

B

29
Q

Which of the following hormones does NOT mediate their effects by activating the phosphatidyl inositol second messenger system?

a. ADH on the v1 receptor
b. Angiotensin II acting on the adrenocortical cell
c. TRH on the thyrotrope
d. ACTH on the corticotrope

A

D

30
Q

Which of the following is true regarding G proteins

A. May by mutated in tumor cells
B. Mediate the action of androgens
C. Act as transcription factors
D. None of the above

A

A

31
Q

Which of the following hormones bind to receptors with inherent tyrosine kinase activity or those associated with intracellular molecules with tyrosine kinase activity?

A. Growth hormone
B. Oxytocin
C. FSH
D. All of the above

A

A

32
Q

Which of the following is true regarding steroid hormones

A. Stimulate production of IP3
B. Suppress the transcription of genes
C. Have half lives of less than 15 minutes in the circulation
D. Are stored w/in secretory granules of steroid secreting cells

A

A

33
Q

Which of the following is not included in the signal transduction pathways of peptide hormones

A. Activation of nuclear factor kB transcription factor
B. Activation of monomeric G-protein, Ras
C. Activation of cytosolic enzyme, cyclic AMP response element binding globulin (CREB-P)
D. Activation of the serine/threonine kinase (MAPK)

A

C

34
Q

Which of the ff hormones bind/s to G-protein linked cell surface receptor/s

A. Insulin
B. Glucagon
C. Epidermal growth factor
D. Cortisol

A

B

35
Q

Which of the following about hormone receptors is true?

A. Receptor function can be reduced by phosphorylation of receptors
B. Approximately 50% of the receptors is occupied by a hormone circulating in concentrations within the normal range
C. Maximum biological responses can only be achieved when 75% of the receptors is occupied
D. When the number of receptors is reduced, a smaller concentration of hormones is needed to occupy it

A

A

36
Q

Which ligands bind to nuclear or cytosolic receptors?

a) cortisol
b) cathecolamines
c) thyroxine
d) b and c only
e) a and c only

A

E

37
Q

Characteristics of 2nd messengers?

a) non proteins
b) intercellular chmical signaling
c) cAMP, PIC, PKA
d) all of the above

A

A

38
Q

Which statement is true regarding G-protein linked receptors?

a) They are ideal for rapid signaling between excitable cells.
b) The insulin receptor is a good example.
c) The receptor directly regulates the ability of an ion channel.
d) This constitutes the largest category of plasma membrane proteins.
e) none of the above.

A

D

39
Q

All of the following molecules/ ligands upon binding to G-proteins would activate adenylyl cyclase except:

a) glucagon
b) vasopressin
c) parathyroid hormone
d) none of the above

A

B

40
Q

Which of the following regarding steroid hormones is TRUE?

A. Stimulate the production of diacylglycerol
B. Stimulate the transcription of genes
C. Have half-lives of less than 15 minutes in the circulation
D. Are stored within secretory granules of steroid secreting cells

A

B

41
Q

Which channel proteins are NOT mediated through GPCR?

A. IP3-Ca2+ Release Channel
B. Na+ Activated K+ Channel
C. CAMP gated Na+ Channel
D. cGMP-activated Na+ Channel

A

B

42
Q

Which of the following is true regarding G protein activation?

A. Directly activates calcium channel through IP3
B. Indirectly activates sodium channel through DAG
C. Directly activates potassium channel, i.e. muscarinic Ach
D. Indirectly activates sodium channel, i.e. olfactory receptors

A

D

43
Q

Which is/are involved in receptor inactivation?

A. First messenger is metabolized by enzymes in the vicinity
B. GTPase breakdown of GTP to GDP in alpha subunit
C. Dephosphorylation of previously phosphorylated proteins by protein phosphatases
D. All of the above

A

D

44
Q

Heterotrimeric G-proteins can activate the following transmembrane protein except

A. Ion Channels
B. Guanylyl Cyclase
C. Adenylyl Cyclase
D. Phosphokinase C

A

D

45
Q

Example of receptor that has intrinsic enzyme activity includes the receptors of the hormones:

A. Fibroblast growth factor
B. ANP
C. Erythropoietin
D. Prolactin
E. AOTA
A

E

46
Q

Which of the following statements is/are incorrect?

A. Km has the same unit of measurement as substrate concentration
B. When affinity of the substrate to the enzyme is increased, Km is also increased
C. When Km is increased, substrate concentration required to occupy all binding sites is also increased
D. A & B

A

B

Cell (7 decks)

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