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Chapter 11 Cell Communication Chapter 12 Cell Cycle

adenylyl cyclase

an enzyme that converts ATP to cyclic AMP in response to a signal

amplification

the strengthening of stimulus energy during transduction

apoptosis

a program of controlled cell suicide, which is brought about by signals that trigger the activation of a cascade of suicide proteins in the cell destined to die

biofilm

a surface-coating colony of one or more species of prokaryotes that engage in metabolic cooperation

cyclic AMP (cAMP)

a ring-shaped molecule made from ATP that is a common intracellular signaling molecule (second messenger) in eukaryotic cells

cytoplasm

the contents of the cell, exclusive of the nucleus and bounded by the plasma membrane

diacylglycerol (DAG)

a second messenger produced by the cleavage of a certain kind of phospholipid in the plasma membrane

epinephrine

a catecholamine that, when secreted as a hormone by the adrenal medulla, mediates "fight-or-flight" responses to short-term stresses

G protein

a GTP-binding protein that relays signals from a plasma membrane signal receptor to other signal transduction proteins inside the cell

gap junction

a type of intercellular junction in animals that allows the passage of materials between cells

glycogen

an extensively branched glucose storage polysaccharide found in the liver and muscle of animals

inositol trisphosphate (IP3)

a second messenger that functions as an intermediate between certain nonsteroid hormones and a third messenger, a rise in cytoplasmic Ca2+ concentration

ligand

a molecule that binds specifically to another molecule, usually a larger one

ligand-gated ion channel

a protein pore in cellular membranes that opens or closes in response to a signaling chemical (its ligand), allowing or blocking the flow of specific ions

local regulator

a secreted molecule that influences cells near where it is secreted

nitric oxide (NO)

a gas produced by many types of cells that functions as a local regulator and as a neurotransmitter

protein kinase

an enzyme that transfers phosphate groups from ATP to a protein, thus phosphorylating the protein

protein phosphatase

an enzyme that removes phosphate groups from (dephosphorylates) proteins, often functioning to reverse the effect of a protein kinase

receptor tyrosine kinase

a receptor protein in the plasma membrane, the cytoplasmic part of which can catalyze the transfer of a phosphate group from ATP to a tyrosine on another protein

scaffolding protein

a type of large relay protein to which several other relay proteins are simultaneously attached, increasing the efficiency of signal transduction

second messenger

a small, nonprotein, water-soluble molecule or ion that relays a signal to a cell's interior in response to a signaling molecule bound by a signal receptor protein

signal transduction

the linkage of a mechanical, chemical, or electromagnetic stimulus to a specific cellular response

signal transduction pathway

a series of steps linking a mechanical or chemical stimulus to a specific cellular response

testosterone

a steroid hormone required for development of the male reproductive system, spermatogenesis, and male secondary sex characteristics

transcription factor

a regulatory protein that binds to DNA and affects transcription of specific genes

transduction

the conversion of a signal from outside the cell to a form that can bring about a specific cellular response

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because (?)

they amplify the original signal manyfold

Binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane?

ligand-gated ion channel

The activation of receptor tyrosine kinases is characterized by (?)

dimerization and phosphorylation

Which observation suggested to Sutherland the involvement of a second messenger in epinephrine's effect on liver cells?

Glycogen breakdown was observed only when epinephrine was administered to intact cells.

Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because (?)

intracellular receptors are present only in target cells

Consider this pathway: epinephrine → G protein-coupled receptor → G protein → adenylyl cyclase → cAMP. Identify the second messenger.

cAMP

Which of these is a receptor molecule? (A-E)

B

A signal transduction pathway is initiated when a (?) binds to a receptor.

signal molecule

Which of these is a signal molecule? (A-E)

A

A signal molecule is also known as a(n) (?).

ligand

Which of these receptors is NOT a membrane receptor? (A-E)

E

Which of these is a G-protein-linked receptor? (A-E)

A

Which of these is a receptor tyrosine kinase? (A-E)

C

Which of these is an ion-channel receptor? (A-E)

D

The binding of signal molecules to (A-E) results in the phosphorylation of tyrosines.

C

Which of these receptor molecules would allow Na+ to flow into the cell? (A-E)

D

Which extracellular signal molecule could diffuse through a plasma membrane and bind to an intracellular receptor?

estrogen

A(n) (?) is an example of a signal molecule that can bind to an intracellular receptor and thereby cause a gene to be turned on or off.

steroid

(?) is a signal molecule that binds to an intracellular receptor.

D

Thyroid hormones bind to (?) receptors.

intracellular

Which of these acts as a second messenger? (A-E)

D

Calcium ions that act as second messengers are stored in (?).

endoplasmic reticula

(1) catalyzes the production of (2), which then opens an ion channel that releases (3) into the cell's cytoplasm.

1) Phospholipase C
2) IP3
3) Ca2+

A protein kinase activating many other protein kinases is an example of (?).

amplification

The cleavage of glycogen by glycogen phosphorylase releases (?).

glucose-1-phosphate

Epinephrine acts as a signal molecule that attaches to (?) proteins.

G-protein-linked receptor

A toxin that inhibits the production of GTP would interfere with the function of a signal transduction pathway that is initiated by the binding of a signal molecule to (?) receptors.

G-protein-linked

Evidence that cell signaling evolved early in the history of life comes from (?).

the similarity of the mechanisms in organisms that have a very distant common ancestor

When a platelet contacts a damaged blood vessel, it is stimulated to release thromboxane A2. Thromboxane A2 in turn stimulates vascular spasm and attracts additional platelets to the injured site. In this example thromboxane A2 is acting as a (?).

local regulator

Early work on signal transduction and glycogen depolymerization by Sutherland indicated that (?).

the signal molecule did not interact directly with the cytosolic enzyme, but required an intact plasma membrane before the enzyme could be activated

Certain yeast cells secrete a molecule called the α factor. The purpose of this molecule is to (?).

stimulate an a yeast cell to grow toward the α cell

Cells use different signaling strategies to achieve different goals. In hormonal signaling, (?).

specialized cells release hormone molecules into the circulatory system, permitting distant cells to be affected

Testosterone and estrogen are lipid-soluble signal molecules that cross the plasma membrane by simple diffusion. If these molecules can enter all cells, why do only specific cells respond to their presence?

Nontarget cells lack the intracellular receptors that, when activated by the signal molecule, can interact with genes in the cell's nucleus.

Steroid hormones can enter a cell by simple diffusion. Therefore steroids (?).

do not initiate cell signaling by interacting with a receptor in the plasma membrane

A small molecule that specifically binds to a larger molecule is called a(n) (?).

ligand

Receptors for signal molecules (?).

can be found as part of the plasma membrane or found within the cytoplasm

Testosterone does not affect all cells of the body because (?).

not all cells have cytoplasmic receptors for testosterone

G-protein-linked receptors (1), whereas receptor tyrosine kinases (2).

1) are not enzymes
2) have enzymatic function

The binding of a signal molecule to a ligand-gated ion channel (?).

affects the membrane potential

A G protein is active when (?).

GTP is bound to it

If a modified form of GTP that cannot be enzymatically converted to GDP were added to a culture of cells, the likely result would be (?).

that the activated G proteins would remain locked in the "on" position, transmitting signal even in the absence of a signaling molecule

The cellular response of a signal pathway that terminates at a transcription factor would be (?).

the synthesis of mRNA

Cholera develops when the bacterial toxin (?).

prevents G-protein inactivation, which leads to the continuous production of cAMP

What did Sutherland discover about glycogen metabolism in liver cells?

The hormone epinephrine binds to a specific receptor on the plasma membrane of the liver cell.

The general name for an enzyme that transfers phosphate groups from ATP to a protein is (?).

protein kinase

Second messengers tend to be water-soluble and small. This accounts for their ability to (?).

rapidly move throughout the cell by diffusion

In a typical cell, calcium ions are often concentrated within the (?).

endoplasmic reticulum

A difference between the mechanisms of cAMP and Ca2+ in signal transduction is that cAMP (1) and Ca2+ (2).

1) is synthesized by an enzyme in response to a signal
2) is released from intracellular stores

IP3 (inositol trisphosphate) is produced as a result of (?).

the cleavage of a certain kind of phospholipid in the plasma membrane

IP3 (inositol trisphosphate) acts by (?).

opening Ca2+ channels

In eukaryotic cells, what is the second messenger that is produced as a response to an external signal such as a hormone?

cyclic AMP

In the inherited disorder Wiskott-Aldrich syndrome, (?).

a multifunctional relay protein involved with the proliferation of immune cells is defective

In liver cells, epinephrine stimulates the breakdown of glycogen. As the signal-transduction pathway progresses, (?).

the signal is amplified

Cells of the gastrointestinal (GI) tract and cells of the heart respond differently to epinephrine because (?).

there are differences in the proteins found in the two types of cells

dimer

a chemical entity consisting of two structurally similar subunits called monomers joined by bonds that can be either strong or weak.

signal-transduction pathway

the process by which a signal on a cell's surface is converted into a specific cellular response

hormone

the secretion of an endocrine gland that is transmitted by the blood to the tissue on which it has a specific effect

kinase

an enzyme that catalyzes the conversion of a proenzyme to an active enzyme

tyrosine-kinase receptor

a receptor protein in the plasma membrane that responds to the binding of a signal molecule by catalyzing the transfer of phosphate groups from ATP to tyrosines on the cytoplasmic side of the receptor

tyrosine

an amino acid found in most proteins

scaffolding protein

a type of large relay protein to which several other relay proteins are simultaneously attached, increasing the efficiency of signal transduction.

actin

a globular protein that links into chains, two of which twist helically about each other, forming microfilaments in muscle and other kinds of cells

anaphase

the fourth stage of mitosis, in which the chromatids of each chromosome have separated and the daughter chromosomes are moving to the poles of the cell

anchorage dependence

the requirement that a cell must be attached to a substratum in order to divide

aster

a radial array of short microtubules that extends from each centrosome toward the plasma membrane in an animal cell undergoing mitosis

benign tumor

a mass of abnormal cells that remains at the site of its origin

binary fission

a form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size

checkpoint

a control point in the cell cycle where stop and go-ahead signals can regulate the cycle

cell cycle

an ordered sequence of events in the life of a cell, from its origin in the division of a parent cell until its own division into two

cell cycle control system

a cyclically operating set of molecules in the eukaryotic cell that both triggers and coordinates key events in the cell cycle

cell plate

a double membrane across the midline of a dividing plant cell, between which the new cell wall forms during cytokinesis

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