Content from 9/3 to 9/5

Question 1

T/F - The phosphorylation of proteins is a critical component of signal transduction that modifies cell function?

Answer 1

TRUE

Question 2

T/F - The use of second messengers allows for signal transduction events to be amplified inside of the cell?

Answer 2

TRUE

Question 3

T/F - Signal transduction is a mechanism for altering various functions of cells?

Answer 3

TRUE

Question 4

T/F - Signal transduction relies on chemical messengers such as ions, metabolites, and hormones?

Answer 4

TRUE

Question 5

T/F - Signal transduction relies exclusively on cell surface receptors in order to change cellular behavior?

Answer 5

FALSE

Question 6

In the beta cells of the pancreas the process of glucose-stimulated insulin secretion involves the movement of K+ across the membrane. Which receptor type would this movement require?

Answer 6

Ligand-gated ion channel receptor

Question 7

The “transduction” step of signaling by plasma membrane receptors involves?

Answer 7

The activation of the plasma membrane receptor which then produces an initial second messenger

Question 8

What are three events that the termination step of the signal transduction process can involve?

Answer 8

• Dissociation of the ligand from the hormone.
• Internalization of the hormone-receptor complex.
• Dephosphorylation of the activated receptor, if phosphorylation of the receptor was part of the transduction process.

Question 9

T/F - Phosphorylation events remain constant throughout the subsequent stages of cellular signal transduction?

Answer 9

FALSE

Question 10

Which of the following statements regarding protein phosphorylation is/are true?

• It occurs only on serine, threonine, and tyrosine amino acid residues.
• It requires the addition of water.
• Phosphorylation can increase the catalytic activity of enzymes.
• Phosphorylation can decrease the catalytic activity of enzymes.
• Kinases and phosphatases alter the functions of cellular proteins via the same mechanism.

Answer 10

It occurs only on serine, threonine, and tyrosine residues.
Phosphorylation can increase the catalytic activity of enzymes.
Phosphorylation can decrease the catalytic activity of enzymes.

Question 11

T/F - A chemical messenger secreted by one cell acting on an adjacent cell in the same tissues is an example of autocrine communication?

Answer 11

FALSE - that is paracrine. Autocrine is the same cell and endocrine is distant cells.

Question 12

T/F - The magnitude of the ultimate response initiated by ligand binding to plasma membrane receptors is linearly related to the number of these receptors bound by the ligand?

Answer 12

FALSE

Question 13

T/F - Binding of plasma membrane receptor tyrosine kinases by ligand results in immediate maximal activation of the receptor tyrosine kinase activity?

Answer 13

FALSE

Question 14

Put the following steps in order associated with GPCR activation from first to last:

• Ligand binding results in receptor activation.
• The alpha-subunit modulates the effector protein to change second messenger production in the cell.
• The G-protien dissociates from the receptor.
• The alpha and beta-gamma subunits of the G-protein reassemble with each other.
• GDP is exchanged for GTP within the associated G-protein.
• GTP is hydrolyzed to GDP on the alpha subunit.

Answer 14

1. Ligand bind results in receptor activation.
2. GDP is exchanged for GTP within the associated G-protein.
3. The G-protein dissociates from the receptor.
4. The alpha-subunit of the G-protein dissociates from the beta-gemma subunit.
5. The alpha-subunit modulates the effector protein to change second messenger production in the cell.
6. GTP is hydrolyzed to GDP on the alpha subunit.
7. The alpha and beta-gamme subunits of the G-protein reassemble with each other.

Question 15

T/F - The alteration in cell response brought about by a ligand binding to a GPCR is dependent on the specific receptor type and the G-protein expressed in a cell?

Answer 15

TRUE

Question 16

Which of the following statements about ligand-gated ion channel receptors is/are TRUE?

• They are the only plasma membrane receptor category that modifies ion flux in cells.
• They can function by either opening or closing ion channels.
• The can themselves be ion channels or associate with physically distinct ion channels.
• They act by allowing ions to move down their concentration gradient across membranes.

Answer 16

They can function by either opening or closing ion channels.
They can themselves be ion channels or can associate with physically distinct ion channels.
They act by allowing ions to move down their concentration gradients across membranes.

Question 17

T/F - Adenylate cyclase (AC) is activated by Gs?

Answer 17

TRUE

Question 18

T/F - PKA activity is increased when cAMP binds to the catalytic subunits of the enzyme and allosterically activates them?

Answer 18

FALSE

Question 19

T/F - The insulin receptor is a catalytic receptor?

Answer 19

TRUE

Question 20

T/F - The insulin receptor dimerizes upon insulin binding?

Answer 20

FALSE

Question 21

T/F - The insulin receptor undergoes autophosphorylation on threonine residues when insulin binds to the receptor?

Answer 21

FALSE (it is tyrosine residues)

Question 22

T/F - The insulin receptor can activate adenylate cyclase upon insulin binding?

Answer 22

FALSE

Question 23

T/F - The insulin receptor phophorylates tyrosine residues on cytosolic effector proteins?

Answer 23

TRUE

Question 24

Which of the following statements about GPCRs are FALSE?

• The alpha subunit of the G-protein functions by synthesizing GTP from GDP and Pi?
• Gs can either activate or inhibit adenylate cyclase, depending on which hormone binds to the receptor that associates with Gs?
• The GPCR must be activated by a ligand before it can associate with the G-protein.
• The alpha subunit is deactivated by the hydrolysis of GTP to GDP.
• Only the activated alpha subunit can modulate effector proteins.

Answer 24

• The alpha subunit of the G-protein functions by synthesizing GTP from GDP and Pi.
• Gs can either activate or inhibit adenylate cyclase depending on which hormone binds to the receptor that associates with Gs.
• Only the activated alpha subunit can modulate effector proteins.