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

Receptor tyrosine kinases (RTKs) are found at high levels on various cancer cells. A protein, Herceptin, has been found to bind to an RTK known as HER2. This information can now be utilized in breast cancer treatment if which of the following is true?

Receptor tyrosine kinases (RTKs) are found at high levels on various cancer cells. A protein, Herceptin, has been found to bind to an RTK known as HER2. This information can now be utilized in breast cancer treatment if which of the following is true? 

A) If Herceptin is found in the breast lymph nodes of the patient.
B) If HER2, administered by injection, is in sufficient concentration.
C) If the patient's cancer cells have detectable HER2.
D) If the patient's genome codes for the HER2 receptor.
E) If the patient's genome codes for the manufacture of Herceptin.






Answer: C

Since steroid receptors are located intracellularly, which of the following is true?

Since steroid receptors are located intracellularly, which of the following is true? 

A) The receptor molecules are themselves lipids or glycolipids.
B) The steroid/receptor complex can cross the nuclear membrane.
C) The unbound steroid receptors are quickly recycled by lysosomes.
D) The concentration of steroid receptors must be relatively high in most cells.
E) The receptor molecules are free to move in and out of most organelles.






Answer: B