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

Because most receptors are membrane proteins, which of the following is usually true?

Because most receptors are membrane proteins, which of the following is usually true? 

A) They lead to changes in intracellular ion concentration.
B) They open and close in response to protein signals.
C) They are only attached to one membrane surface: exterior or interior.
D) They preferentially bind with lipid or glycolipid signal molecules.
E) They change their conformation after binding with signal polypeptides.






Answer: E

One of the major categories of receptors in the plasma membrane reacts by forming dimers, adding phosphate groups, and then activating relay proteins. Which type does this?

One of the major categories of receptors in the plasma membrane reacts by forming dimers, adding phosphate groups, and then activating relay proteins. Which type does this? 

A) G protein-coupled receptors
B) ligand-gated ion channels
C) steroid receptors
D) receptor tyrosine kinases




Answer: D

Which of the following is true of transcription factors?

Which of the following is true of transcription factors? 

A) They regulate the synthesis of DNA in response to a signal.
B) They transcribe ATP into cAMP.
C) They initiate the epinephrine response in animal cells.
D) They control gene expression.
E) They regulate the synthesis of lipids in the cytoplasm.






Answer: D

Testosterone functions inside a cell by

Testosterone functions inside a cell by 

A) acting as a signal receptor that activates tyrosine kinases.
B) binding with a receptor protein that enters the nucleus and activates specific genes.
C) acting as a steroid signal receptor that activates ion channel proteins.
D) becoming a second messenger that inhibits adenylyl cyclase.
E) coordinating a phosphorylation cascade that increases spermatogenesis.








Answer: B

Which of the following is true for the signaling system in an animal cell that lacks the ability to produce GTP?

Which of the following is true for the signaling system in an animal cell that lacks the ability to produce GTP? 

A) It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.
B) It could activate only the epinephrine system.
C) It would be able to carry out reception and transduction but would not be able to respond to a signal.
D) It would use ATP instead of GTP to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.
E) It would employ a transduction pathway directly from an external messenger.





Answer: A

Of the following, a receptor protein in a membrane that recognizes a chemical signal is most similar to

Of the following, a receptor protein in a membrane that recognizes a chemical signal is most similar to 

A) the active site of an allosteric enzyme that binds to a specific substrate.
B) tRNA specifying which amino acids are in a polypeptide.
C) a metabolic pathway operating within a specific organelle.
D) an enzyme having an optimum pH and temperature for activity.
E) an antibody in the immune system.






Answer: A

When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway?

When a neuron responds to a particular neurotransmitter by opening gated ion channels, the neurotransmitter is serving as which part of the signal pathway? 

A) receptor
B) relay molecule
C) transducer
D) signal molecule
E) endocrine molecule






Answer: D

In an experiment to track the movement of growth factor molecules from secretion to the point of receptor binding in a particular species of mammal, a student found a 20-fold reduction in mm traveled when in the presence of an adrenal hormone. This is in part attributable to which of the following?

In an experiment to track the movement of growth factor molecules from secretion to the point of receptor binding in a particular species of mammal, a student found a 20-fold reduction in mm traveled when in the presence of an adrenal hormone. This is in part attributable to which of the following? 

A) The growth factor is a paracrine signal.
B) The growth factor depends on osmosis.
C) The mammal only carries growth factor through the lymph.
D) The growth factor is an exocrine signal.
E) The growth factor is an endocrine signal.




Answer: A

In which of the following ways do plant hormones differ from hormones in animals?

In which of the following ways do plant hormones differ from hormones in animals? 

A) Plant hormones interact primarily with intracellular receptors.
B) Plant hormones may travel in air or through vascular systems.
C) Animal hormones are found in much greater concentration.
D) Plant hormones are synthesized from two or more distinct molecules.
E) Animal hormones are primarily for mating and embryonic development.






Answer: B

In yeast signal transduction, the yeast cells

In yeast signal transduction, the yeast cells 

A) must physically and directly interact.
B) produce signal molecules that change themselves so they can interact with one another.
C) produce response molecules that diffuse to other yeast cells.
D) secrete molecules that result in response by other yeast cells.
E) mate, after which the new cells secrete hybrid signals.





Answer: D

In the formation of biofilms, such as those forming on unbrushed teeth, cell signaling serves which function?

In the formation of biofilms, such as those forming on unbrushed teeth, cell signaling serves which function? 

A) formation of mating complexes
B) secretion of apoptotic signals
C) aggregation of bacteria that can cause cavities
D) secretion of substances that inhibit foreign bacteria
E) digestion of unwanted parasite populations







Answer: C

Which of the following is characterized by a cell releasing a signal molecule into the environment, followed by a number of cells in the immediate vicinity responding?

Which of the following is characterized by a cell releasing a signal molecule into the environment, followed by a number of cells in the immediate vicinity responding? 

A) hormonal signaling
B) autocrine signaling
C) paracrine signaling
D) endocrine signaling
E) synaptic signaling






Answer: C

Which of the following is a likely explanation of why naural selection favored the evolution of signals for sexual reproduction?

Which of the following is a likely explanation of why naural selection favored the evolution of signals for sexual reproduction? 

A) Even in the simplest organisms, sexual reproduction required several coordinated responses by cells.
B) Multicellular eukaryotes required signals that were responded to by multiple organ systems.
C) Cells of several kinds of mating types needed to sort themselves to allow self-recognition.
D) Rooted plants required chemical diffusible signals that could travel throughout the organism.
E) Hormones required a mechanism for introducing changes in their target tissues.





Answer: A

What is most likely to happen to an animal's target cells that lack receptors for local regulators?

What is most likely to happen to an animal's target cells that lack receptors for local regulators? 

A) They might compensate by receiving nutrients via a factor.
B) They could develop normally in response to neurotransmitters instead.
C) They could divide but never reach full size.
D) They might not be able to multiply in response to growth factors from nearby cells.
E) Hormones would not be able to interact with target cells.





Answer: D