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Molec Cell > Cell signaling > Flashcards

Cell signaling Flashcards

1
Q
  1. G protein-coupled receptors are important molecules involved in signal transduction. Which of the following statements best describes G protein-coupled receptors?
    a. G protein-coupled receptors are only activated by steroid hormones
    b. G protein-coupled receptors generally contain seven membrane-spanning  helices
    c. G protein-coupled receptors bind only guanine nucleotides
    d. G protein-coupled receptors bind both adenine and guanine nucleotides
A

b. G protein-coupled receptors generally contain seven membrane-spanning a helices

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2
Q
  1. Signaling by the steroid hormone estrogen is an example of ____ signaling
    a. Autocrine
    b. Endocrine
    c. Paracrine
    d. Direct cell-to-cell
A

b. Endocrine

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3
Q
  1. An example of signaling by direct cell-cell interactions is
    a. The pathway leading to vulval development in C elegans
    b. The notch pathway
    c. The wingless (Wnt) signaling pathway
    d. The JAK/STAT pathway
A

b. The notch pathway

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4
Q
  1. Which of the following steroid hormones is (are) not secreted by the gonads?
    a. Testosterone
    b. Progesterone
    c. Corticosteroids
    d. Estrogen
A

c. Corticosteroids

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5
Q
  1. The term “paracrine signaling” refers to
    a. Signaling between cells located far from each other
    b. Stimulation of a cell by substances produced by the cell itself
    c. Signaling between cells located close to each other
    d. Signaling between parenchyma cells
A

c. Signaling between cells located close to each other

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6
Q
  1. Which of the following is not a commonly observed consequence of the binding of a signaling molecule to its cell surface receptor?
    a. Increased synthesis of the receptor
    b. Receptor phosphorylation
    c. Receptor dimerization
    d. Conformational changes in the receptor
A

a. Increased synthesis of the receptor

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7
Q
  1. Which of the following hormones is (are) not synthesized from cholesterol?
    a. Testosterone
    b. Progesterone
    c. Corticosteroids
    d. None of the above
A

d. None of the above

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8
Q
  1. Which of the following is true in reference to G protein signaling?
    a. Hormone binding induces an interaction of the receptor with the G protein, stimulating the release of GDP and the exchange of GTP on the  subunit
    b. Once activated, the GTP-bound  subunit dissociates from  and interacts with its target
    c. Activity of the  subunit is terminated by the hydrolysis of GTP to GDP
    d. All of the above
A

d. All of the above

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9
Q
  1. Which of the following is not a therapeutic effect of aspirin?
    a. Reducing the chance of acquiring colon cancer
    b. Stimulation of the growth of fibroblasts at the site of a wound, thus aiding the healing process
    c. Reduction of inflammation and pain
    d. Reduction of blood clotting
A

b. Stimulation of the growth of fibroblasts at the site of a wound, thus aiding the healing process

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10
Q
  1. The signaing molecule nitric oxide (NO) functions
    a. By binding its cell surface receptor and triggering an intracellular signaling cascade
    b. By diffusing across the membrane and binding its intracellular receptor, which then activates transcription
    c. By diffusing across the cell membrane and changing the activities of intracellular enzymes
    d. On cells located far from the cells where it was synthesized
A

c. By diffusing across the cell membrane and changing the activities of intracellular enzymes

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11
Q
  1. The MEK kinase (MAP kinase/ERK kinase) is unusual in that it
    a. Activates a kinase
    b. Is activated by a kinase
    c. Lies downstream of G protein-coupled receptors
    d. Is a dual-specificity kinase, having the ability to phosphyorylate both threonines d tyrosines
A

d. Is a dual-specificity kinase, having the ability to phosphyorylate both threonines d tyrosines

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12
Q
  1. Integrins are transmembrane proteins that connect
    a. Microtubules to actin filaments
    b. The nuclear laminae to cytoplasmic kinases
    c. Focal adhesions to hemidesmosomes
    d. The extracellular matrix to the cytoskeleton
A

d. The extracellular matrix to the cytoskeleton

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13
Q
  1. Heterotrimeric G proteins are not the only guanine nucleotide-binding proteins. Which of the following represents a family of more than 50 small GTP-binding proteins?
    a. Ras
    b. Smad
    c. ERK
    d. Raf
A

a. Ras

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14
Q
  1. Most of the effects of cyclic AMP (cAMP) in the cell are mediated by
    a. Ion channels
    b. cAMP phosphodiesterase
    c. protein kinase C
    d. protein kinase A
A

d. protein kinase A

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15
Q
  1. Cyclic AMP (cAMP) is synthesized from ATP by the action of
    a. Phosphodiesterase
    b. Phosphorylase kinase
    c. Adenylyl cyclase
    d. Protein kinase A (PKA)
A

c. Adenylyl cyclase

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16
Q
  1. Cell adhesion molecules can be divided into four major groups. Which of the following is not one of those
    a. Selectins
    b. Integrins
    c. Collagens
    d. Immunoglobulin superfamily
A

c. Collagens

17
Q
  1. Which of the following is an example of endocrine signaling?
    a. Epinephrine release by motor neurons at the neuromuscular junction and binding to receptors on adjacent skeletal muscle cells
    b. Antigen stimulation of T lymphocytes leading to the stimulation and synthesis of a growth factor that drives their own proliferation
    c. Insulin release by  cells in the pancreas mediating an effect of glucose uptake by muscle cells
    d. None of the above
A

c. Insulin release by  cells in the pancreas mediating an effect of glucose uptake by muscle cells

18
Q
  1. What is the difference between neurotransmitters and neuropeptides?
    a. Some neuropeptides can act on distant cells, whereas neurotransmitters cannot
    b. Neurotransmitters are small protein molecules and neuropeptides are large ones
    c. Neurotransmitters are small hydrophilic molecules and neuropeptides are small proteins
    d. Neuropeptides are generated by neuronal cells but do not transmit signals
A

c. Neurotransmitters are small hydrophilic molecules and neuropeptides are small proteins

19
Q
  1. Neurotransmitters act by binding to receptors that are
    a. Ligand-gated ion channels
    b. Located in the cytoplasm
    c. Tyrosine-kinase receptors
    d. Not coupled to G proteins
A

a. Ligand-gated ion channels

20
Q
  1. Which of the following statements about G protein signaling is false?
    a. Hormone binding reduces an interaction of the receptor with the G protein, stimulating the release of GDP and the exchange of GTP on the  subunit
    b. Once activated, the GTP-bound subunit dissociates from  and interacts with its target
    c. Activity of the  subunit is terminated by the hydrolysis of GTP to GDP
    d. The  subunit becomes deactivated when the hormone dissociates from the receptor
A

d. The a subunit becomes deactivated when the hormone dissociates from the receptor

21
Q
  1. Receptor protein-tyrosine kinases represent critical molecules involved in growth and differentiation through phosphorylation of target substrates on tyrosine residues. Which of the following is not a common structural feature of all receptor protein-tyrosine kinases?
    a. A single transmembrane  helix
    b. An N-terminal extracellular ligand-binding domain
    c. A single polypeptide
    d. A cystosolic C-terminal domain with protein-tyrosine kinase activity
A

c. A single polypeptide

22
Q
  1. SH2 domains are
    a. The domains on receptor protein-tyrosine kinases that contain the phosphorylated tyrosine
    b. The domains on receptor protein-tyrosine kinases that possess the kinase activity
    c. Protein domains that bind phosphotyrosine-containing peptides
    d. Domains that mediate the dimerization of receptor protein-tyrosine kinases
A

c. Protein domains that bind phosphotyrosine-containing peptides

23
Q
  1. Which of the following statements about protein kinase A (PKA) is false
    a. PKA binds a total of four molecules of cAMP, one on each of the four subunits
    b. In the inactive state, PKA exists as a tetramer of two regulatory (R) and two catalytic (C) subunits
    c. PKA binds a total of four molecules, two molecules on each of the two regulatory (R) subunits
    d. Once activated, the catalytic (C) subunits dissociate and active target molecules
A

a. PKA binds a total of four molecules of cAMP, one on each of the four subunits

24
Q
  1. Which of the following is true regarding heterotrimeric G proteins in a resting state?
    a. GTP is bound to the  subunit in complex with both the  and  subunits
    b. The  subunit is bound to GDP in complex with both the  and  subunits
    c. G proteins are in complex with G protein-coupled receptors
    d. GDP is bound to the  subunit in complex with both the  and  subunits
A

d. GDP is bound to the alpha subunit in complex with both the Beta and gamma subunits

Molec Cell (13 decks)

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