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Unformatted text preview: Cell Biology (BIOL 4374 and BCHS 4313)
Name_______KEY______________ 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. (4) Describe the differences between endocrine and paracrine signaling.
Endocrine signaling is conveyed to distant target cells through the blood stream, whereas
Paracrine signaling occurs over short distances to neighboring cells.
2. (4) Match the following hormones to the appropriate time course of action.
____d____ Catecholamines a) Days ____a____ Thyroxine b) Hours to days ____b____ Steroids c) Minutes to hours ____c____ Peptides and proteins d) Seconds or less 3. (5) Draw a ß-adrenergic receptor in the membrane of a cell. Be sure to note the
transmembrane domains, the N and C termini, the portion of the receptor that interacts
with the ligand and the portion of the receptor that interacts with the G-protein.
Ligand binding region
C G-protein binding region 1 4. (2) Adrenalin is what type of hormone?
c) Catecholamine answer: c
e) protein 5. (4) Adrenalin activates __beta__ adrenergic receptors in the liver to liberate __glucose___,
and activates _alpha_ adrenergic receptors in smooth muscles lining blood vessels
of the intestine to __restrict____ blood flow.
6. (2) Adenylyl cyclase is directly activated by __Galpha protein______ to produce the second
7. (4) The adapter protein ___GRB2_____ has two domains: an SH2 domain that binds to
phosphotyrosines on the ___RTK________ (receptor type), and an ___SH3_______
domain that is used to activate SOS. Once SOS is activated, it then activates
____Ras_________ by exchanging GDP for GTP.
8. (2) Which of the following steps is part of the kinase cascade that transmits signals from
a) MEK kinase phosphorylates effector proteins
b) Raf phosphorylates MEK
c) MAP kinase phosphorylates MEK kinase
d) Ras phosphorylates Raf
9. (3) PIP2 is cleaved by ___phospholipase c______to produce IP3 and DAG. IP3 then
releases ___Ca+2________ from the ER. DAG and Ca+2 then combine to activate
10. (4) Match the enzyme regulatory event with its affect on glycogen metabolism.
____c_____ IP phosphorylation a) Stimulate glycogen breakdown ____d_____ GP dephosphorylation b) Stimulate glycogen synthesis ____a_____ GPK phosphorylation c) Inhibit glycogen synthesis ____b_____ GS dephosphorylation d) Inhibit glycogen breakdown 2 11. (4) Describe two ways to downregulate cell surface receptors.
1) Endocytosis to reduce the number of cell surface receptors
2) Phosphorylation to inactivate cell surface receptors
12. (6) Describe how insulin and glucagon control blood glucose levels. Be sure to indicate
where these hormones come from, the type of receptors they bind and how they affect the
levels of blood glucose.
Insulin is released from beta islet cells in the pancreas and binds to RTK receptors on
target cells (ex. Muscle cells) to increase absorption of glucose and lower blood glucose
Glucagon is released from alpha islet cells in the pancreas and binds to GPCRs on target
cells (ex. Liver) to liberate glucose from glycogen and increase the levels of blood
13. (2) Phosphorylation of CREB by cAMP kinase leads to:
a) Activation of transcription
b) Activation of adenylyl cyclase
c) Inhibition of Ras
d) Activation of phospholipase C
e) Inhibition of MAP kinase
14. (3) Label the motor neuron. answer: a ___dendrites______ __cell body_______
____axon_________ 15. (2) Motor neurons release the neurotransmitter ___acetylcholine__________________. 3 16. (6) During the propagation of an action potential, the opening of ___voltage____ gated
Na+ channels leads to ___depolarization____ of the membrane due to Na+ ions
flowing ___into______ the cell, and the opening of __voltage_____ gated K+
channels leads to __reploarization_________ of the membrane due to K+ ions flowing
__out ___ of the cell.
17. (3) When an action potential reaches the ___axon terminus_________, Ca+2 enters the cell
through voltage gated Ca+2 channels and binds to __synaptotagmin______, which
triggers the fusion of secretory vesicles to the plasma membrane and the release of
18. (4) Explain why fast synapses are so much faster than slow synapses.
Fast synapses have receptors that are neurotransmitter gated ion channels, and the ion
influx immediately leads to an alteration in membrane potential in the post-synaptic cell.
Slow synapses have GPCRs on the post-synaptic cell which are relatively slow to
produce a change in membrane potential because they must first activate signal
19. (6) Briefly describe the functions of the following parts of voltage gated Ca+2 channels.
a) S4 domain
The S4 domain has positively charged amino acids that act as voltage sensors
The P-segment lines the channel and determines ion specificity
c) N-terminal ball
The N-terminal ball is a plug for the channel that is required for inactivation.
20. (2) Which inhibitory neurotransmitter leads to the opening of Cl- channels? answer: d
b) glutamate c) adrenalin d) glycine
21. (2) An increase in response to an adverse stimulus is called __sensitization_______.
22. (6) State whether the following phenomena occur in the light or the dark in photoreceptors.
a) Opsin bound to 11-cis retinal
b) Active transducin
c) Active cGMP gated Na /Ca channels
d) Neurotransmitter release
e) Membrane depolarization
f) Low cGMP levels
__light___ 4 23. (2) During long term memory formation, additional time between training sessions is
required for the induction of __gene transcription____________, which leads to the
restructuring of ____neuronal connections________________.
24. (4) During classical conditioning in Aplysia, the unconditioned stimulus is a
___blow to the tail______________________ and the conditioned stimulus is a
___light touch of the siphon_____________.
25. (4) Name two types of cell adhesion molecules that make heterophilic interactions.
Integrins and selectins
26. (2) During leukocyte extravasation, aLb2 integrin is activated by:
a) Exocytosis of P-selectin by endothelial cells
b) Binding of P-selectin to its ligand on the leukocyte plasma membrane
c) PAF receptor activation on the leukocyte plasma membrane
d) Binding of aLb2 integrin to ICAM-1
27. (2) Integrins, adapter proteins, keratin intermediate filaments and laminin are part of what
a) tight junctions
c) adherens junction
e) focal adhesion
28. (2) Which amino acid modification in collagen requires vitamin C as a cofactor?
a) lysine hydroxylation b) proline hydroxylation c)Aldol crosslinks
d) disulfide bond formation e) hydroxyglycine
29. (2) Which cell-cell adhesion molecule is dependent on Ca+2?
c) Fibronectin d) Selectin answer: d
e) hyaluronin 30. (2) Laminin is a major structural element of the ___basal lamina________. 5 ...
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