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 metabolism 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 a (alpha) factor. The purpose of this molecule is to ...
stimulate an (alpha) yeast cell to grow toward the (alpha) 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 moleculed can enter all cells, why do only specific cells respond to their presence?
Non-target cells lack the intracellular receptors that, when activated by the signal molecule, can interact with genes in the cell's nucleus.
Different types of cells can respond differently to the same signaling molecule. What explains this apparent paradox?
Different types of cells possess different proteomes.
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 ...
ligand
Receptors for signal molecules...
may be found embedded in the plasma membrane, or found within the cytoplasm or nucleus.
Testosterone does not affect all cells of the body because...
not all cells have cytoplasmic receptors for testosterone.
G-protein linked receptors _____, where as receptor tyrosine kinases _______.
are not enzymes.... have enzymatic function
What is activated when the binding of single molecules causes it to form a dimer?
receptor tyrosine kinases
The binding of a signal molecule to a ligand-gated ion channel ...
affects the membrane potential.
Nitric oxide is unusual among animal signal molecules in that it ...
is a gas.
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 loced in the "on" position, transmitting signal even in the absence of a signaling molecule.
What event would activate a G protein?
replacement of GDP with GTP
The cellular response of a signal pathway that terminates at a trascription 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
Phosphorylation...
can either activate or inactivate a protein
The source of phosphate for a phosphorylation cascade is ...
ATP
Second messengers tend to be water-soluble and small. This accounts for their ability to ...
rapidly move throughout the cell by diffusion
cAMP usually directly activates...
protein kinase A
A mutation in the active site of adenylyl cyclase that inactivates it would most likely lead to ...
lower activity of protein kinase A
In a typical cell, calcium ions...
are often concentrated within the ER
A difference between the mechanisms of cAMP and Ca2+ in signal transduction is that cAMP _____ and Ca2+ ______.
is synthesized by an enzyme in response to a signal ... 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 acts by ...
opening Ca2+ channels
What is NOT a potential source of Ca2+ that can be released into the cytoplasm?
lysosomes
In eukaryotic cells, what is a 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 a signal-transduction pathway progresses, ...
the signal is amplified
Cells of the 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
Apoptosis ...
is essential for normal development of the nervous system
