Question 1

The phosphorylation of proteins by ATP

Accepted Answer

A)   is catalyzed by enzymes known as "protein kinases."
B)   always stimulates the activity of an enzyme.
C)   is catalyzed by adenyl cyclase.
D)   always takes place in the cytoplasm.
E)   is catalyzed by G proteins. A

Question 2

In general, all cell signaling causes

Accepted Answer

A)   increased expression of genes.
B)   an influx of ions.
C)   protein kinase activity.
D)   G protein activation.
E)   a change in receptor conformation. E

Question 3

Signal binding to a receptor differs from enzyme-substrate binding in that

Accepted Answer

A)   in signal binding the signal is not altered during the process.
B)   the single-binding process is reversible.
C)   in signal binding, cell receptors can become saturated by signal molecules.
D)   signal binding can be inhibited by an antagonist.
E)   None of the above A

Question 4

What is the correct order for the following events in the interaction of a cell with a signal? (1) Alteration of cell function; (2) signal binds to receptor; (3) signal released from source; (4) signal transduction.

Accepted Answer

A)   1234
B)   2314
C)   3214
D)   3241
E)   3421

Question 5

The transmembrane protein EnvZ in a signal transduction pathway found in E. coli is an example of a(n)

Accepted Answer

A)   autocrine molecule.
B)   transductor.
C)   responder.
D)   hormone.
E)   None of the above

Question 6

Caffeine restores wakefulness because it binds to receptors for _______, thus preventing this chemical from causing drowsiness.

Accepted Answer

The answer of Caffeine restores wakefulness because it binds to...

Question 7

A universal feature of receptors is that they

Accepted Answer

A)   are present in the plasma membrane.
B)   are protein kinases.
C)   undergo structural (shape)  changes when the signal molecule is bound.
D)   are ion channel proteins.
E)   are effector proteins.

Question 8

The entry of a sperm into an egg causes a massive opening of _______ channels.

Accepted Answer

The answer of The entry of a sperm into an...

Question 9

Why do some signals ("first messengers") trigger "second messengers" to activate target cells?

Accepted Answer

A)   The first messenger requires activation by ATP.
B)   The first messenger is not water soluble.
C)   The first messenger binds to many types of cells.
D)   The first messenger cannot cross the plasma membrane.
E)   There are no receptors for the first messenger.

Question 10

Which of the following statements is false?

Accepted Answer

A)   Diacylglycerol can act as a second messenger.
B)   Inositol triphosphate can act as a second messenger.
C)   Protein kinase C can phosphorylate a wide variety of proteins.
D)   Inositol triphosphate remains bound to the membrane after phospholipase C catalyzes its formation.
E)   Inositol triphosphate can open an ion channel, releasing calcium into the cytoplasm.

Question 11

Which of the following is true?

Accepted Answer

A)   For most ligand-receptor complexes, binding is favored.
B)   Ligand-receptor interactions are reversible.
C)   Many drugs that alter human behavior prevent binding of receptors' specific ligands.
D)   Both a and b
E)   All of the above

Question 12

_______ is a second messenger found in the pathway by which epinephrine activates the liver enzyme that breaks down glycogen.

Accepted Answer

The answer of _______ is a second messenger found in...

Question 13

In order, from start to finish, the basic steps of a signal transduction pathway are

Accepted Answer

A)   signal, responder, receptor, effects.
B)   receptor, signal, responder, effects.
C)   signal, receptor, responder, effects.
D)   signal, receiver, responder, effects.
E)   None of the above

Question 14

Steroid hormones such as estrogen act on target cells by

Accepted Answer

A)   initiating second messenger activity.
B)   binding to membrane proteins.
C)   initiating gene expression.
D)   activating enzymes.
E)   binding to membrane lipids.

Question 15

Located inside the cell, _______ receptors bind to signals that can diffuse across the plasma membrane.

Accepted Answer

The answer of Located inside the cell, _______ receptors bind...

Question 16

The active responder in the EnvZ signal transduction system is _______ and it _______ the protein _______.

Accepted Answer

A)   OmpR; increases the synthesis of; OmpC
B)   phosphorylated OmpR; increases the synthesis of; OmpC
C)   OmpR; phosphorylates; OmpC
D)   phosphorylated OmpR; phosphorylates; OmpC
E)   OmpC; increases the synthesis of; OmpR

Question 17

Which of the following is not involved in the signal transduction pathway for the detection of odorants?

Accepted Answer

A)   A G protein
B)   Adenylyl cyclase
C)   A specific odorant molecule receptor
D)   A gated ion channel in the endoplasmic reticulum
E)   A cAMP gated ion channel

Question 18

Which of the following would likely not be observed in a person injected with epinephrine?

Accepted Answer

A)   Contraction of muscles surrounding the blood vessels that line the digestive tract
B)   Increased activity of heart muscle
C)   Increased glucose mobilization
D)   Activation of G proteins
E)   All of the above would occur.

Question 19

If a G protein were able to release its bound nucleotide but not to hydrolyze it, signal transduction would

Accepted Answer

A)   cease.
B)   be continuous.
C)   be unaffected.
D)   be constantly switching on and off.
E)   be unpredictable.

Question 20

Discuss the role of secondary messengers in a signaling pathway. How are they different from signals and receptors? What roles do secondary messenger and signals have in common?

Accepted Answer

The answer of Discuss the role of secondary messengers in...

Exam 7: Cell Signaling and Communication