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
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
a second messenger produced by the cleavage of a certain kind of phospholipid in the plasma membrane
a catecholamine that, when secreted as a hormone by the adrenal medulla, mediates "fight-or-flight" responses to short-term stresses
a GTP-binding protein that relays signals from a plasma membrane signal receptor to other signal transduction proteins inside the cell
a type of intercellular junction in animals that allows the passage of materials between cells
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-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
nitric oxide (NO)
a gas produced by many types of cells that functions as a local regulator and as a neurotransmitter
an enzyme that transfers phosphate groups from ATP to a protein, thus phosphorylating the protein
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
a type of large relay protein to which several other relay proteins are simultaneously attached, increasing the efficiency of signal transduction
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
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
a steroid hormone required for development of the male reproductive system, spermatogenesis, and male secondary sex characteristics
a regulatory protein that binds to DNA and affects transcription of specific genes
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.
Which extracellular signal molecule could diffuse through a plasma membrane and bind to an intracellular receptor?
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.
(1) catalyzes the production of (2), which then opens an ion channel that releases (3) into the cell's cytoplasm.
1) Phospholipase C
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.
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 (?).
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
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
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 (?).
Second messengers tend to be water-soluble and small. This accounts for their ability to (?).
rapidly move throughout the cell by diffusion
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
In eukaryotic cells, what is the second messenger that is produced as a response to an external signal such as a hormone?
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
a chemical entity consisting of two structurally similar subunits called monomers joined by bonds that can be either strong or weak.
the process by which a signal on a cell's surface is converted into a specific cellular response
the secretion of an endocrine gland that is transmitted by the blood to the tissue on which it has a specific effect
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
a type of large relay protein to which several other relay proteins are simultaneously attached, increasing the efficiency of signal transduction.
a globular protein that links into chains, two of which twist helically about each other, forming microfilaments in muscle and other kinds of cells
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
the requirement that a cell must be attached to a substratum in order to divide
a radial array of short microtubules that extends from each centrosome toward the plasma membrane in an animal cell undergoing mitosis
a form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size
a control point in the cell cycle where stop and go-ahead signals can regulate the 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