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Cell Biology (BIOL 4374 and BCHS 4313)
Third Exam
4/24/01
Name_________________________
SS#______________________________
This exam is worth a total of 100 points. The number of points each question is worth is shown
in parentheses. For multiple choice questions, circle the correct answer. Good luck!
1. (6) Put the stages of extracellular signaling in order of occurrence from first to last.
a)
b)
c)
d)
e)
f)
Detection of signal by a receptor
Termination of signaling
Release of signaling molecule
Transport of signaling molecule to target
Synthesis of signaling molecule
Response of cell to signal
first ___e___
second ___c___
third ___d___
fourth ___a___
fifth ___f___
sixth ___b___
2. (2) G-protein linked receptors have _______7_______ (number) transmembrane domains.
3. (2) Upon adrenalin binding, the ß-adrenergic receptor causes cAMP production by activating
what two factors?
Gs protein and adenylyl cyclase
4. (2) cAMP kinase leads to the phosphorylation of __glycogen synthetase_____ (enzyme)
to block glycogen synthesis and _glycogen phosphorylase or GP kinase_ (enzyme) to
increase glycogen breakdown.
5. (2) Upon binding to ligand, the RTK class of receptors ___dimerize_______, then
phosphorylate each other at ___tyrosine_______ residues.
6. (2) GRB2 is an adapter protein having and SH2 domain that binds to _phosphotyrosines on
RTK_ and an SH3 domain that binds to ______SOS_______.
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7. (2) During RTK signaling, the GTPase switch protein Ras is activated by the guaninenucleotide exchange factor (GEF) _________SOS__________.
8. (2) The following steps are part of the kinase cascade that transmits signals from
activated Ras protein except:
a)
b)
c)
d)
MEK phosphorylates MAP kinase
Raf phosphorylates MEK
MAP kinase phosphorylates target proteins
Ras phosphorylates Raf
answer: d
9. (4) Phospholipase C cleaves PIP2 into _____IP3______ and ______DAG_______.
10. (2) IP3 releases Ca+2 from what cellular compartment?
Endoplasmic reticulum or sarcoplasmic reticulum
11. (2) When acetylcholine binds to muscarininc acetylcholine receptors, activation of
__________________ leads to a decrease in the level of cAMP.
answer: d
a) GS
b) Golf
c) Gt
d) Gi
e) Gq
12. (4) Insulin binds to ______RTK________ (type of receptor) on the surface of liver cells to
_____decrease_______ (increase or decrease) glucose in the blood stream, whereas
glucagon binds to ______GPCR________ (type of receptor) on the surface of liver
cells to ____increase______ (increase or decrease) glucose in the blood stream.
13. (2) Phosphorylation and endocytosis are two common mechanisms by which__________
can be downregulated.
a)
b)
c)
d)
e)
Cell surface receptors
Adenylyl cyclase
Ras
Phospholipase C
cAMP kinase
answer: a
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14. (2) What second messenger pathway activates CREB transcription?
answer: d
a) Ca+2
b) IP3
c) DAG
d) cAMP
e) PIP2
15. (3) List thee three types of neurons.
Sensory neuron, interneuron, motor neuron.
16. (2) The resting potential of an average neuron is _-60mV (-50 to –70mV is OK)
and units).
(number
17. (8) During the propagation of an action potential, __Na+_ ions move __into_ (direction)
the cell due to the opening of _voltage___ gated ___ Na+__ (ion) channels,
thereby depolarizing the membrane. To repolarize the membrane, __voltage__ gated
___K+___ (ion) channels open and __ K+__ ions flow __out of___ (direction)
the cell.
18. (2) The entire timecourse of an action potential is _______________. answer: c
a) 2 seconds b) 0.1 milliseconds c) 2 milliseconds d) 20 seconds e) 20 milliseconds
19. (2) Myelin is derived from Schwann cells and functions to __insulate___ axons and
__increase___ impulse rate.
20. (2) The threshold potential (~-40mV) is measured at the ____________________?
answer: c
a) dendrites b) cell body c) axon hillock
d) axon
e) axon terminal
21. (2) What type of amino acids allow the S4 domain to detect changes in membrane voltage?
answer: a
a) basic amino acids b) acidic amino acids c) hydrophobic amino acids
22. (2) The N-terminal ball and chain is responsible for V-gated channel inactivation. What is
the effect of lengthening the chain on inactivation?
answer: b or c
a) decreases inactivation time
b) increases inactivation time
c) no effect
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23. (2) Which type of synapse is faster?
a) electrical
b) chemical
answer: a
24. (2) When an action potential reaches the axon terminal it triggers the opening of voltage
gated ____Ca+2__________ channels.
25. (4) The nicotinic acetylcholine receptor is found on ___muscle____ cells and is a
ligand gated _____Na+/K+ channel___________ (type of molecule).
26. (2) GABA and Glycine act as inhibitory neurotransmitters because they activate
_____Cl-_____ channels that hyperpolarize the post-synaptic cell.
27. (2) Glutamate will only open __NMDA__ receptors after partial depolarization releases
blockage by a ___Mg+2___ ion.
28. (6) Under dark conditions, photoreceptors are __depolarized_ (polarized or depolarized).
When light activates _rhodopsin__ (protein) by causing isomerization of _11-cis_
retinal to _all trans__ retinal, the G-protein transducin is activated. Transducin then
activates cGMP __phosphodiesterase___ (protein), which destroys cGMP and
inactivates cGMP-gated ____Na+/Ca+2___ channels, thereby causing hyperpolarization
and blockage of neurotransmission.
29. (2) The ability to tune out a non-threatening stimulus that you experience frequently is
called __habituation__.
30. (2) During classical conditioning in Aplysia, a weak touch to the siphon is the
____conditioned_____ stimulus , and a blow to the head is the
____unconditioned___ stimulus.
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31. (4) Name two types of cell adhesion molecules that make homophilic interactions.
Cadherins and Ig like CAMs.
32. (2) During leukocyte extravasation, what is the order of cell adhesion molecule binding from
the earliest event to the latest event:
answer: a
a)
b)
c)
d)
e)
P selectin to carbohydrate, PAF to PAF receptor, αLβ2 integrin to I-CAM
PAF to PAF receptor, αLβ2 integrin to I-CAM, P selectin to carbohydrate
P selectin to carbohydrate, αLβ2 integrin to I-CAM, PAF to PAF receptor
αLβ2 integrin to I-CAM, PAF to PAF receptor, P selectin to carbohydrate
PAF to PAF receptor, P selectin to carbohydrate, αLβ2 integrin to I-CAM
33. (2) Collagen triple helices are held into fibers through ______________ crosslinks of lysine
residues at their N and C termini.
answer: c
a) hydroxylysine b) hydroxyproline c) aldol d) ascorbic acid e) glycosaminoglycan
34. (2) Cadherins, adapter proteins and keratin intermediate filaments are part of what cell-cell
junction?
answer: b
a) tight junctions
b) desmosomes
c) adherens junction
d) hemi-desmosome
e) gap junction
35. (2) Glycosaminoglycan polysaccharides are found on serine and threonine residues in:
answer: a
a) proteoglycans b) hyaluronin c)laminin d) fibronectin e) integrin
36. (2) The two ECM components that comprise the major structural elements of the basal
lamina are __laminin____ and ___collagen IV___.
37. (3) Which Cell-Cell adhesion molecule is dependent on Ca+2?
answer: b
a) Integrin b) Cadherin c) N-CAM d) Fibronectin e) Hyaluronin
38. (2) Growth factors must be bound by which glycosamino glycan before they can bind to
growth factor receptors?
answer: b
a) hyaluronin
b) heparan sulfate
c) chondroitin sulfate
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d) keratan sufate