Biology Chapter 9

Consider this pathway: epinephrine → G protein-coupled receptor → G protein → adenylyl cyclase → cAMP. The second messenger in this pathway is _____. adenylyl cyclase G protein-coupled receptor G protein cAMP

cAMP

Put the steps of the process of signal transduction in the order they occur: 1. A conformational change in the signal-receptor complex activates an enzyme. 2. Protein kinases are activated. 3. A signal molecule binds to a receptor. 4. Target proteins are phosphorylated. 5. Second messenger molecules are released. 3, 1, 5, 2, 4 3, 1, 2, 4, 5 1, 2, 5, 3, 4 1, 2, 3, 4, 5

3. A signal molecule binds to a receptor. 1. A conformational change in the signal-receptor complex activates an enzyme. 5. Second messenger molecules are released. 2. Protein kinases are activated. 4. Target proteins are phosphorylated.

Which of the following is true during a typical cAMP-type signal transduction event? The second messenger amplifies the hormonal response by attracting more hormones to the cell being affected. Adenylyl cyclase is activated after the hormone binds to the cell and before phosphorylation of proteins occurs. The hormone activates the second messenger by directly binding to it. The second messenger is the last part of the system to be activated.

Adenylyl cyclase is activated after the hormone binds to the cell and before phosphorylation of proteins occurs.

Which of these is NOT correct? Tyrosine-kinase receptors consist of two polypeptides that join when activated by a signal molecule. Ion channels are found on both the plasma membrane and the endoplasmic reticulum. Kinases are enzymes that phosphorylate other molecules. Phospholipase C catalyzes the formation of IP3. Cyclic AMP binds to calmodulin.

Cyclic AMP binds to calmodulin. Hint:Calcium binds to calmodulin.

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. ion-channel intracellular receptor tyrosine kinase steroid G-protein-linked

G-protein-linked

Epinephrine acts as a signal molecule that attaches to _____ proteins. receptor tyrosine kinase ion-channel receptor nuclear receptor intracellular receptor G-protein-linked receptor

G-protein-linked receptor

In the nematode C. elegans, ced-9 prevents apoptosis in a normal cell in which of the following ways? Ced-9 prevents blebbing by its action on the cell membrane. Ced-9 cleaves to produce ced-3 and ced-4. It prevents the caspase activity of ced-3 and ced-4. Ced-9 remains inactive until it is signaled by ced-3 and other caspases.

It prevents the caspase activity of ced-3 and ced-4.

If an animal cell suddenly lost the ability to produce GTP, what might happen to its signaling system? It would be able to carry out reception and transduction but would not be able to respond to a signal. It would use ATP instead of GTP to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane. It would employ a transduction pathway directly from an external messenger. It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.

It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.

Which of the following provides molecular evidence that signal transduction pathways evolved early in the history of life? Cell signaling is observed in organisms that do not utilize sexual reproduction. The pathways in primitive organisms, such as bacteria, are short, whereas those in advanced forms, such as mammals, are long. Receptor molecules have been identified in preparations of fossilized organisms billions of years old. The molecular details of cell signaling are quite similar in organisms whose last common ancestor was a billion years ago. Simple forms of life, such as prokaryotic cells, utilize cell signaling.

The molecular details of cell signaling are quite similar in organisms whose last common ancestor was a billion years ago.

Why can a signaling molecule cause different responses in different cells? Different cells have membrane receptors that bind to different sides of the signaling molecule. The transduction process is unique to each cell type; to respond to a signal, different cells require only a similar membrane receptor. Different cells possess different enzymes, which modify the signaling molecule into different molecules after it has arrived. The transduction pathway in cells has a variable length. All of the above are correct.

The transduction process is unique to each cell type; to respond to a signal, different cells require only a similar membrane receptor.

If an adult person has a faulty version of the human analog to ced-4 of the nematode, which of the following is most likely to result? formation of molecular pores in the mitochondrial outer membrane activation of a developmental pathway found in the worm but not in humans excess skin loss a form of cancer in which there is insufficient apoptosis

a form of cancer in which there is insufficient apoptosis

Not all intercellular signals require transduction. Which one of the following signals would be processed without transduction? a signal that binds to a receptor in the cell membrane a lipid-soluble signal a signal that binds to the ECM a signal that is weakly bound to a nucleotide

a lipid-soluble signal

Protein kinase is an enzyme that _____. serves as a receptor for various signal molecules produces second messenger molecules activates or inactivates other proteins by adding a phosphate group to them functions as a second messenger molecule

activates or inactivates other proteins by adding a phosphate group to them

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because they _____. are species specific counter the harmful effects of phosphatases amplify the original signal many times always lead to the same cellular response

amplify the original signal many times

To what does the term "ligand" refer in cell biology? the change in shape that occurs when a signaling molecule binds to its receptor the bond that forms between a signaling molecule and its receptor the target cell of a signal molecule any small molecule that can bind in a specific manner to a larger one a molecule that can occupy a receptor site while not activating the receptor

any small molecule that can bind in a specific manner to a larger one

Which of the following are among the most common second messengers? kinase and phosphatase G proteins and GTP kinase and phosphate groups calcium ion and cAMP GTP and GDP

calcium ion and cAMP

Which of these is activated by calcium ions? calmodulin IP3 G protein adenylyl cyclase PIP2

calmodulin

Transcription factors _____. regulate the synthesis of DNA in response to a signal control gene expression transcribe ATP into cAMP regulate the synthesis of lipids in the cytoplasm

control gene expression

What is apoptosis? a way to stimulate transcription a type of membrane receptor controlled cell suicide a metabolic step in blood clotting a type of second messenger

controlled cell suicide

The cleavage of glycogen by glycogen phosphorylase releases _____. fructose-1-phosphate cellulose galactose-1-phosphate nothing: glycogen phosphorylase cannot cleave glycogen glucose-1-phosphate

glucose-1-phosphate

Which of the following is a substance that acts at a long distance from the site at which it is secreted? paracrine signal neurotransmitter hormone local regulator synaptic signal

hormone

A G-protein receptor with GTP bound to it _____. is in its active state signals a protein to maintain its shape and conformation will use cGMP as a second messenger directly affects gene expression

is in its active state

Scaffolding proteins are _____. microtubular protein arrays that allow lipid-soluble hormones to get from the cell membrane to the nuclear pores proteins that can reach into the nucleus of a cell to affect transcription large molecules to which several relay proteins attach to facilitate cascade effects relay proteins that orient receptors and their ligands in appropriate directions to facilitate their complexing

large molecules to which several relay proteins attach to facilitate cascade effects

A signal molecule is also known as a(n) _____. ligand initiator protein key receptor

ligand

An inhibitor of which of the following could be used to block the release of calcium from the endoplasmic reticulum? phospholipase C adenylyl cyclase serine/threonine kinases phosphodiesterase

phospholipase C

In general, a signal transmitted via phosphorylation of a series of proteins _____. results in a conformational change to each protein activates a transcription event generates ATP in the process of signal transduction requires binding of a hormone to an intracellular receptor

results in a conformational change to each protein

A signal transduction pathway is initiated when a _____ binds to a receptor. cyclic AMP tyrosine kinase G protein signal molecule calmodulin

signal molecule

Which of these is the second of the three stages of cell signaling? gene activation reception binding of a neurotransmitter to a plasma membrane receptor transduction cell response

transduction