1) A protein kinase can activate small GTPase by directly phosphorylating the GDP bound in the small GTPase.

1) A protein kinase can activate small GTPase by directly phosphorylating the GDP bound in the small GTPase.
a. True
b. Flase

2)A protein such as Cdk1 will be inhibited by phosphorylation.
a. True
b. False

3)Which of the following molecules function as GEF for a Ga?
a. Potassium channel
b. RGS
c. Adenylyl Cyclase
d. a ligand bound GPCR

4)Acetylcholine activates PLC-β in smooth muscle, which in turn will decrease the level of _____?
a. Clacium
b. PI (4, 5) P2
c. PI
d. IP3

5)Wnt pathway sometimes stimulates cell cycle progression. How so?
a. Including more APC
b. Inducing more β-Catenin
c. Inducing Myc

Solutions

Expert Solution

1. The statement is false.

Explanation: Small GTPase is a G protein (similar to the G alpha subunit) which is activated by exchange of GTP for a GDP. The GEF of guanine nucleotide exchange factor promote this activation and GAP or GTPase activating proteins promote GTP hydrolysis to GDP and inactivate the protein. Therefore, the above statement is false.

2. The statement is true.

Explanation: Phosphorylation of Tyr-15 (a conserved tyrosine residue of Cdk 1 protein among all eukaryotes) leads to the inactivation of Cdk1 kinase activity and control the cell cycle.

3. The correct option is: d. A ligand bound GPCR

Explanation: GEF or guanine nucleotide exchange factor turns on signalling by exchanging GTP for a GDP. Similarly, a ligand bound GPCR leads to the activation of the associated heteromeric G protein by promoting exchange of GTP for GDP.

4. Acetylcholine activates PCL- beta in smooth muscle, which in turn will decrease the level of: b. PI (4,5) P2

Explanation: Activated phospholipase C beta stimulate the hydrolysis of tmembrane bound phosphatidylinositol-4,5- bisphosphate (PIP2) into DAG and IP3. Therefore, the level of PIP2 decreases and that of DAG and IP3 increases.

5. Wnt pathway stimulates cell cycle progression by: c. Inducing Myc.

Explanation: Wnt/beta catenin signalling pathway promote cMyc expression which in turn stimulates cell cycle progression.

gladiator answered 1 year ago

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