What are the three types of signaling mechanisms

Recitation 9: covers lectures March 12 - 14

1. What are the three types of signaling mechanisms?

2. Which of the following can not act as hormones
a. peptides
b. amino acids (or their derivatives)
c. steroids
d. sugars
e. all of the above can act as hormones

3. What are second messengers? how do they act ?

4. The G-protein
a. is activated by cAMP
b. is deactivated by cAMP
c. activates (in an enzyme cascade) protein kinase A.
d. is activated by glucagon and epinephrine signaling
e. two answers are correct

5. Which statement about ras is false
a. ras is activated by a Receptor Tyrosine Kinase
b. ras-GTP activates certain proteins which leads to the activation of MAP kinase
c. the signaling response is terminated by the conversion of ras-GTP is to ras-GDP
d. mutated ras can turn a normal cell into a cancer cell
e. all are true

6. What is a disease related to a faulty Receptor Tyrosine Kinase (RTK)
a. diarrhea
b. hypoglycemia
c. diabetes type I
d. diabetes type II
e. cancer
f. all of the above

7. What is not a function of activated protein kinase A and protein kinase C
a. activate (through phosphorylation) enzymes that catalyze reaction in the glucose metabolism
b activate (through phosphorylation) enzymes that catalyze reactions during cellular division
c. activate enzymes that are instrumental in muscle contraction
d. activate transcription factors
e. all of the above

8. Which statement about motor nerve signaling is correct?
a. the neurotransmitter is released form the terminal branches of the axon, travels through the blood and attaches to its receptor on a muscle cell
b. the neurotransmitter is released form the terminal branches of the axon, travels through the synaptic cleft to the muscle cell. Because of the ionic (charged ) nature of the neurotransmitter it polarizes the muscle cell membrane , which causes muscle contraction.
c. the signaling between a neve cell and a muscle cell is based on direct contact, via an electrical impulse
d. the neurotransmitter is released form the terminal branches of the axon travels through the synaptic cleft to the muscle cell, where it attaches to (activates) a Na+ channel.
e. all statements are false

9. Termination of a neurotransmitter activated signaling pathway is caused by
a. release of a "stop response" neurotransmitter
b. absorption of the neurotransmitter into the target cell (= the cell being acted upon by the neurotransmitter)
c. re-uptake of the neurotransmitter by the nerve cell
d. hydrolysis of the neurotransmitter

10. Explain excitatory and inhibitory response of brain neurons

11. Which statement is false
a. GABA activates a CL-channel on a neuron, which leads to an inhibitory response
b. Glu and Asp cause an excitatory
c. Valium and Librium mimic the GABA response
d. Antagonists bind to the receptor but do not activate it.
e. Agonists prolong the neurotransmitter activity
f. all statements are correct

Answers: 2e, 3: cAMP, Ca++, IP3, 4:c and d, 5e, 6d, 7c, 8d, 9 c and d, 10 excit.resp.: activ. of Na+ channel, inhib.resp. act. of e.g. CL channel, 11f