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exams questionnaire for midterm 2
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BIOL 2P03 Student Name: ______________________Midterm 2Student Number: ___________________
Section 1: Multiple Choice. Answer all questions on the Scantron provided. There are 27
questions. Each question is worth 1 mark for a total of 27 marks.
1. A photon of light activates a photoreceptor within the retina of the eye. This photon of light is
considered
a) An endogenous signaling molecule
b) An exogenous signaling molecule
c) A chemical signaling molecule
d) Both a) and c) are correct
e) Photons of light are not considered to be signaling molecules
2. Which of the following statements regarding receptors is incorrect?
a) Some receptors can be activated by more than one ligand (i.e. the receptor is not specific to a
single ligand)
b) Large, hydrophilic ligands typically activate receptors found on the plasma membrane
c) Small, lipophilic ligands can diffuse through the plasma membrane and activate intracellular
receptors
d) Each ligand can only activate one specific type of receptor within a multicellular
organism
e) When a ligand binds to its receptor, the receptor undergoes a conformational change
3. Which of the following pairs of enzymes, receptors and/or molecules do not counteract the
effects of one another?
a) Adenylyl cyclase and phosphodiesterase
b) Gαs and Gαi ***Removed Question***
c) A protein kinase and a protein phosphatase
d) cAMP and protein kinase A
e) A G-protein coupled receptor and the GTPase of the G-protein α subunit
4. Second messengers possess all of the following characteristics, except
a) They are low molecular weight signaling molecules
b) They must be produced through enzymatic reactions
c) Their concentration in the cytosol can be rapidly increased following receptor activation
d) They can interact with target proteins inside of the cell to regulate their activities
e) They can amplify the signal induced by receptor activation
5. The function of a protein can be altered through
a) Conformational changes
b) Phosphorylation
c) Binding of nucleoside triphosphates, such as GTP
d) Dephosphorylation
e) All of the above
, BIOL 2P03 Student Name: ______________________
Midterm 2Student Number: ___________________
6. Which of the following proteins is not commonly attached to the plasma membrane?
a) Protein kinase A
b) G-protein coupled receptor
c) Adenylyl cyclase
d) Ras
e) Heterotrimeric G-protein
7. Inositol 1,4,5-trisphosphate (IP3)
a) Is produced by phosphodiesterase A
b) Stimulates the release of Ca2+ from the endoplasmic reticulum
c) Can only move laterally within the inner leaflet of the plasma membrane
d) Is synthesized from diacylglycerol (DAG)
e) All of the above
8. Receptor tyrosine kinases
a) Are activated by receptor dimerization
b) Are the most diverse class of plasma membrane receptors
c) Activate heterotrimeric G-proteins by facilitating the exchange of GDP for GTP
d) Have an intrinsic GTPase
e) Can be cleaved to generate transcription factors
9. Heterotrimeric G-proteins
a) Are always bound to G-protein coupled receptors
b) Consist of α, β and γ subunits
c) Can directly interact with cytosolic enzymes to activate them
d) Are activated by phosphorylation via protein kinases
e) All of the above
10. The cAMP response element binding protein (CREB)
a) Can be used by G-protein coupled receptor signaling pathways to regulate gene
expression
b) Is held in an inactive state in the cytosol of the cell at rest through the formation of protein
complexes
c) Is activated by protein phosphatases
d) Is a protein kinase
e) Both a) and b) are correct
11. In a resting cell (no receptor activation), Nuclear Factor-κB (NF- κB)
a) Is bound to I-kappa kinase
b) Is located in the nucleus
c) Is polyubiquitinated and targeted for proteasomal degradation
d) Is phosphorylated
e) Is bound to IκB-α
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