The role of a metabolite that controls a repressible operon is to

The role of a metabolite that controls a repressible operon is to 

A) bind to the promoter region and decrease the affinity of RNA polymerase for the promoter.
B) bind to the operator region and block the attachment of RNA polymerase to the promoter.
C) increase the production of inactive repressor proteins.
D) bind to the repressor protein and inactivate it.
E) bind to the repressor protein and activate it.






Answer: E

Sutherland discovered that epinephrine signals

Sutherland discovered that epinephrine signals 

A) a decrease in levels of cAMP as a result of bypassing the plasma membrane.
B) lower blood glucose by binding to liver cells.
C) interactions with insulin inside muscle cells.
D) interactions directly with glycogen phosphorylase.
E) elevation of cytosolic concentrations of cyclic AMP.





Answer: E

In general, a signal transmitted via phosphorylation of a series of proteins

In general, a signal transmitted via phosphorylation of a series of proteins 

A) brings a conformational change to each protein.
B) requires binding of a hormone to a cytosol receptor.
C) cannot occur in yeasts because they lack protein phosphatases.
D) requires phosphorylase activity.
E) allows target cells to change their shape and therefore their activity.








Answer: A

The receptors for a group of signaling molecules known as growth factors are often

The receptors for a group of signaling molecules known as growth factors are often 

A) ligand-gated ion channels.
B) G protein-coupled receptors.
C) cyclic AMP.
D) receptor tyrosine kinases.
E) neurotransmitters.







Answer: D