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70 Terms
In order for a target cell to receive a signal, it must possess a ____ specific to the signaling molecule.
| a. | glycolipid |
| b. | glycoprotein |
| c. | receptor |
| d. | transfer protein |
| e. | hormone |
c
Adjacent animal cells utilize ____ to rapidly communicate with each other.
| a. | gap junctions |
| b. | plasmodesmata |
| c. | hormones |
| d. | desmosomes |
| e. | neurotransmitters |
a
Adjacent plant cells utilize ____ to rapidly communicate with each other.
| a. | gap junctions |
| b. | plasmodesmata |
| c. | transport proteins |
| d. | desmosomes |
| e. | neurotransmitters |
b
How do cells in the body of a multicellular organism communicate with each other?
| a. | by way of signaling molecules that interact with specific receptors |
| b. | through long projections that directly connect cells to each other |
| c. | through electrical signals passed between a cell and its external environment |
| d. | by the transport of ions between cells in different parts of the organism |
| e. | by the transport of ions in water |
a
Substance B is synthesized in neurons, travels through gap junctions, and triggers the transduction of an electrochemical signal. This is an example of ____.
| a. | autocrine signaling |
| b. | paracrine signaling |
| c. | long-distance signaling |
| d. | local signaling |
| e. | communication by direct contact |
e
Substance A is synthesized in the liver, travels through the circulatory system bound to a carrier protein, and causes a change in gene expression in a target cell. This is an example of ____.
| a. | autocrine signaling |
| b. | paracrine signaling |
| c. | long-distance signaling |
| d. | local signaling |
| e. | communication by direct contact |
c
In order for a cell to respond to the signaling molecule epinephrine, it must have ____.
| a. | ion channels |
| b. | a lipid bilayer through which epinephrine can pass |
| c. | receptors with an epinephrine binding site on the cytoplasmic side of the plasma membrane |
| d. | receptors with an epinephrine binding site on the plasma membrane surface |
| e. | nuclear membrane receptors |
d
Receptors for polar molecules are found ____, while receptors for nonpolar molecules are located ____.
| a. | on the cell surface; within the cell |
| b. | within the cell; on the cell surface |
| c. | on the cell surface; on the nuclear membrane |
| d. | on the nuclear membrane; on the cell surface |
| e. | on the cell surface; within the lipid bilayer |
a
Nonpolar signaling molecules enter the cell by ____.
| a. | facilitated diffusion |
| b. | simple diffusion |
| c. | osmosis |
| d. | active transport |
| e. | receptor-mediated endocytosis |
b
An example of a nonpolar signaling molecule is ____.
| a. | epinephrine |
| b. | insulin |
| c. | testosterone |
| d. | growth factors |
| e. | neurotransmitters |
c
How does a cell surface receptor respond to the binding of a signaling molecule?
| a. | The cell surface receptor denatures. |
| b. | The signal is transduced through the plasma membrane and into the cell. |
| c. | The receptor relays a signal to another location on the cell surface. |
| d. | The cell surface receptor flips through the membrane to the inside of the cell. |
| e. | Polarization of the cell surface changes. |
b
The overall process by which information carried by a signaling molecule is translated into changes that occur inside the cell is called signal ____.
| a. | digestion |
| b. | digression |
| c. | induction |
| d. | interaction |
| e. | transduction |
e
You have recently identified a molecule you believe to be a signaling molecule associated with signal transduction. All you know about this molecule is that it is hydrophilic; therefore, you expect it to interact with a receptor ____.
| a. | on the cell surface |
| b. | within the cytoplasm of the cell |
| c. | in the nucleus of the cell |
| d. | on the cytoplasmic surface of the plasma membrane |
| e. | associated with the endoplasmic reticulum |
a
In the 1950s, Earl Sutherland and colleagues discovered that epinephrine ____.
| a. | triggers the release of a second messenger which leads to the hydrolysis of glycogen to glucose |
| b. | triggers the release of a second messenger which lowers blood glucose by causing it to bind to liver cells |
| c. | interacts directly with the enzyme glycogen phosphorylase |
| d. | interacts directly with the cell membrane to help transport glucose into the cell |
| e. | is a signaling molecule that does not require a cell surface receptor |
a
In general, a cell receiving a message undergoes three stages of cell signaling. What are these stages?
| a. | paracrine, autocrine, and local |
| b. | signal reception, signal transduction, and cellular response |
| c. | signal reception, nucleus disintegration, and apoptosis |
| d. | signal reception, cellular response, and cell division |
| e. | the alpha, beta, and gamma |
b
A pathway for cell growth control is conserved between Drosophila and humans, indicating that the pathway is ____.
| a. | also found in prokaryotes |
| b. | also found in all animals |
| c. | at least 800 million years old |
| d. | at least 3.8 billion years old |
| e. | at least 8 million years old |
c
In the process of quorum sensing, bacteria release signaling molecules in ____ concentrations as cell density ____.
| a. | increasing; decreases |
| b. | increasing; increases |
| c. | decreasing; increases |
| d. | decreasing; decreases |
| e. | constant; increases |
b
Quorum sensing ____.
| a. | allows receptors from different parts of the cell to work together to elicit a response |
| b. | allows receptors from different parts of the body to work together to elicit a response |
| c. | uses multiple cellular pathways to elicit a specific response |
| d. | is a type of communication between unicellular organisms |
| e. | is a type of cell communication between multicellular organisms |
d
The evolution of which class of molecules played an important role in the development of multicellular organisms?
| a. | G proteins |
| b. | protein kinases |
| c. | second messengers |
| d. | ligand-gated ion channels |
| e. | steroid hormones |
b
The two major categories of extracellular signaling molecules that bind to cell surface receptors are ____.
| a. | peptide hormones and steroid hormones |
| b. | steroid hormones and neurotransmitters |
| c. | neurotransmitters and vitamins |
| d. | growth hormones and vitamins |
| e. | peptide hormones and neurotransmitters |
e
Neurotransmitters are molecules released by ____.
| a. | gonads |
| b. | polar hormones |
| c. | peptide hormones |
| d. | cells in the blood |
| e. | neurons |
e
The surface receptors that recognize and bind signaling molecules are ____.
| a. | glycoproteins |
| b. | glycolipids |
| c. | phospholipids |
| d. | promoters |
| e. | ligands |
a
The recognition of a chemical signal by a receptor protein in the membrane is most similar to ____.
| a. | mRNA specifying the sequence of amino acids in a polypeptide |
| b. | binding of a specific substrate to the active site of an enzyme |
| c. | turning on gene transcription |
| d. | allosteric regulation of proteins |
| e. | an enzyme requiring a specific optimum pH and temperature for activity |
b
The last protein in a signaling pathway is called the ____.
| a. | target protein |
| b. | final acceptor |
| c. | electron acceptor |
| d. | second messenger |
| e. | effector protein |
a
Amplification of a signal increases as the ____.
| a. | number of enzyme-catalyzed steps increases |
| b. | number of enzyme-catalyzed steps decreases |
| c. | volume of the cell increases |
| d. | volume of the cell decreases |
| e. | rate of reaction of the rate-limiting reaction increases |
a
In the first step of signal transduction, what is the trigger for the cellular response?
| a. | target protein |
| b. | kinase |
| c. | ligand |
| d. | second messenger |
| e. | effector |
c
What is the second step of signal transduction?
| a. | reception |
| b. | transduction |
| c. | differentiation |
| d. | division |
| e. | response |
b
Protein kinases ____.
| a. | add phosphate groups to proteins |
| b. | bind cGMP |
| c. | stimulate adenylyl cyclase |
| d. | polymerize amino acids |
| e. | hydrolyze proteins |
a
The effects of protein kinases are reversed by another group of enzymes called ____.
| a. | hydrolases |
| b. | catalases |
| c. | isomerases |
| d. | phosphatases |
| e. | proteases |
d
Once transduction of a signal is complete, the receptor and its bound signaling molecule are removed from the cell surface by ____.
| a. | hydrolysis |
| b. | diffusion |
| c. | endocytosis |
| d. | pinocytosis |
| e. | exocytosis |
c
The protein kinase activity of the receptor tyrosine kinase (RTK) is located ____ region of the protein.
| a. | on the extracellular |
| b. | on the cytoplasmic |
| c. | within the hydrophobic |
| d. | in the nuclear |
| e. | in the inactive |
b
During autophosphorylation, RTKs add phosphate groups to which amino acids?
| a. | serine |
| b. | glycine |
| c. | threonine |
| d. | tryptophan |
| e. | tyrosine |
e
What happens immediately after a signaling molecule binds to an RTK?
| a. | receptor dimerization |
| b. | receptor trimerization |
| c. | receptor denaturation |
| d. | receptor polymerization |
| e. | receptor hydrolysis |
a
Structurally similar RTKs have been found in all multicellular animals, suggesting that ____.
| a. | RTK genes are resistant to mutation |
| b. | RTKs evolved relatively early in the history of animals |
| c. | RTKs evolved from G proteins |
| d. | RTKs are not involved in vital processes in animals |
| e. | RTKs have evolved independently of each other in animals |
b
The insulin receptor is an example of a(n) ____.
| a. | G-protein-coupled receptor |
| b. | hydrophobic receptor |
| c. | hormone receptor |
| d. | receptor tyrosine kinase |
| e. | ion channel receptor |
d
Substance E is made in the pancreas, travels through the blood, and binds to a surface receptor on a target cell. After dimerization and autophosphorylation, the receptor activates a signaling protein. Substance E is therefore the ligand for ____.
| a. | a receptor tyrosine kinase |
| b. | a G-protein-coupled receptor |
| c. | a hormone receptor |
| d. | a ligand-gated ion channel |
| e. | guanylyl cyclase |
a
Arrange the events in the pathway activated by G-protein-coupled receptors (GPCRs) in the correct order.
1. Activation of effector
2. Activation of protein kinases
3. Receptor binds first messenger
4. Production of second messenger
5. Activation of G protein
| a. | 1→3→5→2→4 |
| b. | 2→3→5→4→1 |
| c. | 3→1→5→4→2 |
| d. | 3→5→1→4→2 |
| e. | 3→5→2→4→1 |
d
Inactive G proteins are ____.
| a. | bound to GMP |
| b. | bound to GDP |
| c. | bound to GTP |
| d. | phosphorylated |
| e. | unphosphorylated |
b
Activated G proteins ____.
| a. | trigger endocytosis of the G-protein-coupled receptor |
| b. | bind to second messengers |
| c. | separate into two parts |
| d. | activate a kinase |
| e. | inhibit guanylyl cyclase |
c
How many transmembrane domains are present in a G-protein-coupled receptor?
| a. | one |
| b. | three |
| c. | five |
| d. | seven |
| e. | nine |
d
Many of the different types of GPCRs in humans function to ____.
| a. | distinguish different volatile molecules for odor recognition |
| b. | regulate metabolism by sensing and responding to changes in glucose levels |
| c. | regulate liver function by responding to different macromolecules |
| d. | aid in memory by binding to neurotransmitters in the amygdala |
| e. | trigger the fight of flight response by binding to hormones in the hypothalamus |
a
More than 60% of all prescribed drugs target ____, due to their wide physiological impact.
| a. | receptor tyrosine kinases |
| b. | hormone receptors |
| c. | guanylyl cyclase |
| d. | ligand-gated ion channels |
| e. | G-protein-coupled receptors |
e
G proteins are inactivated when ____.
| a. | GDP is converted to GTP |
| b. | GTP is converted to GDP |
| c. | the G protein rebinds the receptor |
| d. | the G protein is released from the receptor |
| e. | the receptor is broken down |
b
Many signal transduction pathways utilize second messengers to ____.
| a. | transport a signal through the lipid bilayer of the plasma membrane |
| b. | relay a signal from the outside of the cell to the inside |
| c. | relay a signal from the inside of the cell to the outside |
| d. | decrease the message once the signaling molecules have left the receptor |
| e. | relay the message from the inner surface of the plasma membrane throughout the cytoplasm |
e
The amino acid targets of protein kinases in all GPCR pathways are ____.
| a. | serine and glycine |
| b. | serine and tyrosine |
| c. | serine and threonine |
| d. | glycine and tyrosine |
| e. | glycine and threonine |
c
Which molecule is a common second messenger?
| a. | cGTP |
| b. | cATP |
| c. | PIP2 |
| d. | diacylglycerol |
| e. | Ras |
d
In the cAMP pathway, the G protein activates ____.
| a. | adenylyl cyclase |
| b. | diacylglycerol |
| c. | phospholipase C |
| d. | inositol triphosphate |
| e. | phosphodiesterase |
a
Once activated, cAMP is quickly degraded to AMP by ____, switching off the signal pathway.
| a. | adenylyl cyclase |
| b. | diacylglycerol |
| c. | phospholipase C |
| d. | acetylcholinesterase |
| e. | phosphodiesterase |
e
In the IP3/DAG pathway, what is the effector molecule?
| a. | IP3 |
| b. | DAG |
| c. | PIP2 |
| d. | phospholipase C |
| e. | calcium |
d
Substance C is secreted from a neuron, and binds to its receptor on a nearby cell, triggering an increase in intracellular cAMP. Substance C is therefore a ligand for a ____.
| a. | a receptor tyrosine kinase |
| b. | a G-protein-coupled receptor |
| c. | a hormone receptor |
| d. | a ligand-gated ion channel |
| e. | guanylyl cyclase |
b
Ras proteins are of interest to researchers because of their role in ____.
| a. | reproduction |
| b. | linking plant hormones to germination |
| c. | the development of many types of cancer |
| d. | relieving cluster headaches |
| e. | eliciting the fight-or-flight response |
c
Inactive Ras is bound to receptor tyrosine kinases by ____.
| a. | G proteins |
| b. | adapter proteins |
| c. | phosphate bonds |
| d. | peptide tethers |
| e. | GDP |
b
Activated Ras ____.
| a. | activates MAP kinase (MAP K) |
| b. | opens a calcium channel |
| c. | triggers gene transcription |
| d. | binds DNA |
| e. | triggers the secretion of growth factors |
a
Acetylcholine, a neurotransmitter, binds to ____.
| a. | receptor tyrosine kinases |
| b. | ligand-gated ion channels |
| c. | adenylyl cyclase |
| d. | MAPK |
| e. | G-coupled protein receptors |
b
Which cellular response follows activation of a ligand-gated ion channel?
| a. | direct regulation of gene expression |
| b. | generation of an electrical signal |
| c. | activation of a phosphorylation cascade |
| d. | activation of a second messenger pathway |
| e. | direct activation of a kinase |
b
A neuron synthesizes and secretes substance D, which binds to a receptor on the neuron cell membrane, triggering an influx of calcium. Substance D therefore is a ligand for a ____.
| a. | a receptor tyrosine kinase |
| b. | a G-protein-coupled receptor |
| c. | a hormone receptor |
| d. | a ligand-gated ion channel |
| e. | guanylyl cyclase |
d
Steroid and thyroid hormones do not bind to membrane surface receptors because they ____.
| a. | are small enough to pass directly through the membrane |
| b. | are soluble in the lipid bilayer |
| c. | pass through special membrane channels |
| d. | are water-soluble |
| e. | dissolve in the cholesterol present in cell membranes |
b
Steroid hormones ____.
| a. | are proteins |
| b. | include testosterone, estrogens, and cortisol |
| c. | never activate second messengers |
| d. | never alter membrane transport of ions |
| e. | are large nonpolar molecules |
b
Why are steroid hormones bound to carrier proteins in the blood?
| a. | to prevent them from entering non-target cells |
| b. | to keep them in an inactivate state |
| c. | to mask hydrophobic groups on the steroids to allow for circulation in the blood |
| d. | to help them bind to surface receptors and trigger a cellular response |
| e. | to help them bind to surface receptors and trigger endocytosis |
c
How do cells distinguish between estrogen and testosterone?
| a. | only male cells respond to testosterone and female cells respond to estrogen |
| b. | estrogen is hydrophilic and binds to surface receptors, while testosterone is hydrophobic and binds to internal receptors |
| c. | estrogen and testosterone have similar functional groups but different basic structures that are easily distinguished by their individual receptors |
| d. | estrogen and testosterone have the same basic structures, but different side chains that are easily distinguished by their individual receptors |
| e. | estrogen and testosterone bind to different carrier proteins, which help receptors distinguish between the two molecules |
d
Estrogen receptor (ER) α typically ____, while ERβ typically ____.
| a. | stimulates DNA binding; inhibits DNA binding |
| b. | stimulates cell proliferation; inhibits cell proliferation |
| c. | stimulates channel opening; inhibits channel opening |
| d. | inhibits DNA binding; stimulates DNA binding |
| e. | inhibits cell proliferation; stimulates cell proliferation |
b
Researchers have determined that the growth of hormone-responsive breast cancer cells depends upon ____.
| a. | the relative concentrations of ERα and ERβ in the tumor cells |
| b. | the ability of ERβ to stimulate cancer cell growth |
| c. | the ability of ERα to inhibit cancer cell growth |
| d. | whether DNA binding sites exists for ERα, but not ERβ |
| e. | the relative concentrations of estrogen and testosterone in breast tissue |
a
Hormone receptors are comprised of two domains, the hormone binding domain and the ____, which triggers the cellular response.
| a. | gene activation domain |
| b. | DNA-binding domain |
| c. | phosphorylation domain |
| d. | kinase domain |
| e. | phosphatase domain |
b
Substance A is secreted by the liver, travels through the circulatory system bound to a carrier protein and causes a change in gene expression in its target cell. Substance A is therefore a ligand for ____.
| a. | a receptor tyrosine kinase |
| b. | a G-protein-coupled receptor |
| c. | a steroid hormone receptor |
| d. | a ligand-gated ion channel |
| e. | guanylyl cyclase |
c
Nitric oxide (NO) binds to an ____.
| a. | internal receptor and activates a second messenger cascade |
| b. | internal receptor and triggers a phosphorylation cascade |
| c. | external receptor and activates a second messenger cascade |
| d. | external receptor and triggers a phosphorylation cascade |
| e. | external receptor and opens a ligand-gated ion channel. |
a
NO can only function as a paracrine regulator because____.
| a. | it is hydrophilic and cannot travel free in the blood |
| b. | it is hydrophobic and cannot travel free in the blood |
| c. | it is rapidly converted into nitrates and nitrites |
| d. | its receptors are rapidly turned over |
| e. | its receptors are immediately internalized when the ligand binds |
c
How is the NO pathway manipulated by Viagra to treat erectile dysfunction?
| a. | NO synthesis is decreased |
| b. | NO synthesis is increased |
| c. | the enzyme catalyzed by NO is stabilized |
| d. | the enzyme catalyzed by NO is inhibited |
| e. | the breakdown of cGMP is inhibited |
e
NO binds to and activates____ to trigger its cellular response.
| a. | receptor tyrosine kinase |
| b. | G-protein coupled receptors |
| c. | MAPK |
| d. | adenylyl cyclase |
| e. | guanylyl cyclase |
e
Communication and integration of responses between simultaneously occurring cell signaling pathways is called ____.
| a. | mutualistic responding |
| b. | effector coordination |
| c. | cross-talk |
| d. | amplification |
| e. | signal transduction |
c
Hormone-independent steroid hormone receptor activation is an example of ____.
| a. | allosteric activation |
| b. | gene regulation |
| c. | receptor integration |
| d. | protein mutation |
| e. | cross-talk |
e