Cell Signalling

Question 1

What is the most common mechanism used to secreto signaling molecules? What other?

Answer 1

exocytosis, other is diffusion

Question 2

In transmembrane proteins, what terminus faces the cytoplasmic side and extracellular side?

Answer 2

cytoplasmic: C-terminus and extracellular: N-terminus

Question 3

Through what signaling system do cancer cells overcome normal control of cell proliferation?

Answer 3

Autocrine signaling

Question 4

State the Neuron Doctrine

Answer 4

nerve cells are connected by sites of contact and not cytoplasmic continuity

Question 5

Compare and contrast endocrine vs synaptic signaling

Answer 5

synaptic signaling is quicker and more precise

Question 6

Compare the affinity of hormone and neurotransmitter receptors and how it relate to their concentration in extracellular flui

Answer 6

Hormones: high affinity (because at low concentrations) and neurotransmitters: low affinity (high concentrations)

Question 7

Explain how epinephrine or adrenaline behave in muscle vs in brain

Answer 7

muscle: act as hormone for glycogen breakdown and brain: neurotransmitter for fight or flight rxns

Question 8

Explain how acetylcholine behaves in skeletal muscle vs in heart muscle

Answer 8

skeletal: stimulates contraction and heart: decreases contraction

Question 9

What two variables will determine the dual effects of signaling molecules such as adrenaline and acetylcholine?

Answer 9

localization of receptor and internal machinery coupled to receptors

Question 10

nAChR: type of receptor and fucntion

Answer 10

voltage gated sodium channels also known as ionotropic receptors. Diffusion of Na+ and K+ causes depolarization, firing of action potential, and potential muscular
contraction.

Question 11

mAChR: type and function

Answer 11

belong to the family of G-protein coupled receptors also known as metabotropic receptors. Intracellular signals coupled to opening of K+ channels causing hyperpolarization.

Question 12

What enzyme is activated by the release of ACh in endothelial cells lining the blood vessels? What is the function of this enzyme?

Answer 12

NO synthase: produce NO

Question 13

What is the function of NO and what type of signaling is used?

Answer 13

NO: relaxes smooth muscles which causes blood flow increase in blood vessels… Guanylyl cyclase-cGMP

Question 14

How does Viagra work?

Answer 14

inhibits the rapid degradation of cGMP by phosphodiesterase 5, increasing blood flow

Question 15

How many transmembrane domains do tyrosine kinase receptors have?

Answer 15

single transmembrane protein

Question 16

What are the major signal tranduction pathways of tyrosine kinase receptor?

Answer 16

cAMP, PLC-IP3 and PKC

Question 17

What are the major signal tranduction pathways of GPCR?

Answer 17

cAMP, cGMP, and Ca-calmodulin pathways

Question 18

cAMP pathway

Answer 18

adenylyl cyclase-cAMP-PKA (bings regulatory subunits)-CREB (catalytic subunits of PKA translocate into nucleus and phosphorylate CREB)

Question 19

PKC pathway

Answer 19

PLC- DAG and IP3 (PLC catalyzes hydrolysis of PIP2)- IP3 signals Ca-DAG activates PKC

Question 20

Describe the two types of nuclear receptor superfamily

Answer 20

Type 1 NR: located in cytosol and Type 2: located in nucleus

Question 21

Describe how molecules bind and exert their function in Type 1 NR

Answer 21

Hormone binding triggers dissociation of heat-shock proteins (HSP), dimerization, and translocation.
• NR binds to a specific sequence of DNA known as the hormone response element (HRE).
• This complex in turn recruits other proteins that are responsible for transcription of downstream DNA into mRNA.

Question 22

Describe how molecules bind and exert their function in Type 2 NR

Answer 22

Directly targets gene expression without cytoplasmic interactions. In the absence of ligand, R is bound to a co-repressor protein. Ligand binding to R causes a dissociation of co-repressor and recruitment of
co-activator proteins leading to transcription of DNA into mRNA.

Question 23

What is hormone response element?

Answer 23

sequence of DNA where type 1 NR bind to