1)How does a mutation in the G-alpha subunit of the G-protein that decreases its
ID: 208396 • Letter: 1
Question
1)How does a mutation in the G-alpha subunit of the G-protein that decreases its GTPase activity affect liver cell responses to epinephrine?
It would increase secretion of epinephrine.
It would increase glycogen breakdown.
It would decrease protein kinase A activity.
It would decrease proliferation.
2)What happens to GTP in response to epinephrine binding to its receptor on liver cells?
It binds to G-alpha
It falls off of G-alpha
It is hydrolyzed
It gets phosphorylated
3)Which of the following correctly describes a second messenger?
Kinase activity
cAMP Phosphodiesterase activity (remember cAMP PDE breaks down cAMP)
Phosphatase activity
GTPase activity
5)Which of the following is true for all enzymes?
They provide energy for endergonic reactions.
They decrease G.
They alter the transition state.
They harness energy from ATP.
6)Which of the following statements is TRUE?
X + Y + ATP <=> X-P + Y + ADP <=> Z + ADP + Pi
Is ATP an enzyme for this reaction?
Yes, because it alters the transition state
Yes, because it increases the rate of the reaction
Yes, because it provides energy to get over the activation energy barrier
No, because it is irreversibly altered by the reaction
No, because it does not alter the transition state
The entropy of a closed system never increases.
The sign (+ or -) of the change in enthalpy tells you whether a reaction is exergonic or endergonic.
For any process to be energetically favorable, G must be < 0.
If the free energy of the products (Gproducts) is greater than that of the reactants (Greactants) the reaction is favorable.
Both the 2nd and 3rd answers above
7)ATP hydrolysis provides the energy for the endergonic reaction: X + Y <=> Z . The mechanism by which this occurs is that compound X is phosphorylated using the phosphate group from ATP. dephosphorylation of X, which itself is exergonic, makes it possible for X and Y to combine to form Z. In this scheme X-P can be considered the transition state. The entire reaction, including ATP is as follows:
A protein, such as a G-protein, that is activated upon ligand binding to receptor.
An enzyme such as Adenylate Cyclase that is activated upon ligand binding to receptor.
An enzyme responsible for the cellular effects of a signal transduction pathway, like Protein Kinase A or Glycogen Phosphorylase.
A soluble cytoplasmic molecule produced in response to ligand binding that activates a cellular response.
4)Imagine you are a drug developer aiming to inhibit G-protein coupled receptor signal transduction specifically in liver cells. An inhibitor of which of the following would accomplish this?
It would increase secretion of epinephrine.
It would increase glycogen breakdown.
It would decrease protein kinase A activity.
It would decrease proliferation.
2)What happens to GTP in response to epinephrine binding to its receptor on liver cells?
It binds to G-alpha
It falls off of G-alpha
It is hydrolyzed
It gets phosphorylated
3)Which of the following correctly describes a second messenger?
Kinase activity
cAMP Phosphodiesterase activity (remember cAMP PDE breaks down cAMP)
Phosphatase activity
GTPase activity
5)Which of the following is true for all enzymes?
They provide energy for endergonic reactions.
They decrease G.
They alter the transition state.
They harness energy from ATP.
6)Which of the following statements is TRUE?
X + Y + ATP <=> X-P + Y + ADP <=> Z + ADP + Pi
Is ATP an enzyme for this reaction?
Yes, because it alters the transition state
Yes, because it increases the rate of the reaction
Yes, because it provides energy to get over the activation energy barrier
No, because it is irreversibly altered by the reaction
No, because it does not alter the transition state
The entropy of a closed system never increases.
The sign (+ or -) of the change in enthalpy tells you whether a reaction is exergonic or endergonic.
For any process to be energetically favorable, G must be < 0.
If the free energy of the products (Gproducts) is greater than that of the reactants (Greactants) the reaction is favorable.
Both the 2nd and 3rd answers above
7)ATP hydrolysis provides the energy for the endergonic reaction: X + Y <=> Z . The mechanism by which this occurs is that compound X is phosphorylated using the phosphate group from ATP. dephosphorylation of X, which itself is exergonic, makes it possible for X and Y to combine to form Z. In this scheme X-P can be considered the transition state. The entire reaction, including ATP is as follows:
A protein, such as a G-protein, that is activated upon ligand binding to receptor.
An enzyme such as Adenylate Cyclase that is activated upon ligand binding to receptor.
An enzyme responsible for the cellular effects of a signal transduction pathway, like Protein Kinase A or Glycogen Phosphorylase.
A soluble cytoplasmic molecule produced in response to ligand binding that activates a cellular response.
4)Imagine you are a drug developer aiming to inhibit G-protein coupled receptor signal transduction specifically in liver cells. An inhibitor of which of the following would accomplish this?
Explanation / Answer
Answer:
1. (b) it would increase glycogen breakdown
Explanation:
i. The first step in epinephrine signaling occurs when the hormone binds to an epinephrine receptor on the cell surface. The hormone triggers the receptor to change shape, converting the receptor to its active form.
ii. The activated receptor triggers a cascade of events within the cell, beginning with the activation of a G protein. The G protein binds to the activated receptor, releases GDP, and takes up a molecule of GTP.
iii. After taking up GTP, the G protein is released from the receptor and splits into two parts. One of the parts is activated and continues the signaling cascade. Soon, the hormone also leaves the receptor, and the receptor reverts to its inactive form.
iv. The G protein activates an enzyme called adenylyl cyclase. When activated, adenylyl cyclase converts a large number of ATP molecules into signaling molecules, called cyclic AMP (cAMP). Because cAMP carries the message of the first messenger (epinephrine) into the cell, cAMP is referred to as a second messenger.
v. In response to an internal timer, the G protein soon inactivates itself by cleaving GTP, and the subunits reassociate. With the G protein no longer attached, the adenylyl cyclase turns off and can no longer convert ATP into cAMP.
The successive signaling events results in conversion of glycogen to glucose.
If the G protein loses its GTPase activity, the subunits do not dissociate, resulting in continued signaling.
2. (a) It binds to G-alpha
Explanation:
Similar to step ii above (question 1)
3. (d) A soluble cytoplasmic molecule produced in response to ligand binding that activates a cellular response.
Explanation:
Second messengers are molecules that relay signals received at receptors on the cell surface, such as the arrival of protein hormones, growth factors, etc. to target molecules in the cytosol and/or nucleus.
4. (b) cAMP Phosphodiesterase activity (remember cAMP PDE breaks down cAMP)
Explanation:
Since cAMP PDE breaks down cAMP, the downstream signaling mediated by cAMP would no longer take place.
(Since there are multiple questions, the first 4 questions have been answered according to the rules of Chegg)
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