Lecture 8 - Signaling Mechanisms

Question 1

list the major examples of signaling mechanisms

Answer 1

• Endocrine
• Paracrine

Autocrine

Neurotransmitters

Neuroendocrine

Question 2

• Signaling molecules released by one cell act on neighboring
target cells.

A. Endocrine

B. Paracrine

C. Autocrine

D. Neurotransmitters

E. Neuroendocrine

Answer 2

B. Paracrine

Question 3

• Cells respond to signaling molecules that they themselves
produce.

A. Endocrine

B. Paracrine

C. Autocrine

D. Neurotransmitters

E. Neuroendocrine

Answer 3

C. Autocrine

Question 4

• Signaling molecules (hormones) are secreted by specialized
endocrine cells and transported through the circulation to target
cells at distant body sites.

A. Endocrine

B. Paracrine

C. Autocrine

D. Neurotransmitters

E. Neuroendocrine

Answer 4

A. Endocrine

Question 5

The G protein consists of several subunits. Which of the following subunits exchanges its GDP for GTP when activated?

A. Alpha subunit

B. Beta subunit

C. Gamme subunit

D. Delta subunit

Answer 5

A. Alpha subunit

Question 6

In the ERK-MAP kinase pathway, activation of the GTP binding protein Ras interacts with Raf kinase. Raf phosphorylates and activates which of the following?

A. cAMP

B. MEK

C. ERK

D. Elk-1

Answer 6

B. MEK

Question 7

In the JAK-STAT pathway, a ligand binds to a membrane receptor. Associated with this receptor is molecule “A”. Molecule “B” binds to molecule “A”, resulting in the phosphorylation and dimerization of molecule “B”. What is the identification of molecule “B”

A. JAK

B. MEK

C. STAT

D. Elk-1

Answer 7

C. STAT

Question 8

In the cyclic AMP second messenger pathway, which of the following degrades cAMP?

A. Phosphodiesterase

B. Diacyl-glycerol

C. Arrestins

D. Protein kinase A

Answer 8

A. Phosphodiesterase

Question 9

Estrogen is synthesized from:

Answer 9

Cholesterol

Question 10

What are the names of the non-steroid receptors that bind to intracellular receptors?

Answer 10

• Thyroid hormone: Synthesized from tyrosine
• Vitamin D3
• Retinoids

Question 11

Review Figure 3-1

Question 12

Review figure 3-2

What are the negative and positive feedback loops?

Question 13

Which of the following is not a messenger that binds to the cell surface receptors?

A. Glutamate

B. Aspartate

C. Glycine

D. GABA

E. Arginine

Answer 13

E. Arginine

Question 14

Note that neurotransmitters are (hydrophilic or hydrophobic) and can only bind to
membrane ________.

Answer 14

hydrophilic, receptors

Question 15

Which of the following is a Indoleamine?

A. Serotonin

B. Dopamine

C. Noepinephrine

D. Epinephrine

Answer 15

A. Serotonin

Question 16

Many neurotransmitter receptors are ______-gated ion
channels.

Answer 16

ligand

Question 17

Binding of growth factors to extracellular domains results in….

Answer 17

phosphorylation of both the receptors and the intracellular
target proteins that propagate the signal.

• First step is ligand-induced receptor dimerization.
• Leads to receptor autophosphorylation.

Question 18

• All receptors for G proteins are ___-membrane-spanning α helices:

Answer 18

7

What is special about 7? One end sticking out

Question 19

Which subunit of the G protein is the most variable (more than 20 types) and is specific
for a particular G protein.

Answer 19

α subunit

• α subunit binds GDP when inactivated.
• Activation results in the exchange of GDP to GTP.
• The β and γ subunits form a dimer.

Question 20

Effectors associated with G proteins include:

Answer 20

• Adenyl cyclase
• Phospholipases
• Ion channels

Question 21

Categories of G proteins\

• GS
• Gi
• Gt/g
• Go
• Gq

Answer 21

• GS
• Stimulates activity of adenyl cyclase
• Gi
• Inhibits activity of adenyl cyclase
• Gt/g
• Stimulates breakdown of GMP in photoreceptors and taste
receptors.
• Go
• Opens calcium channels in neurons.
• Gq
• Activates phospholipases which increases activity of IP3.