Mastering Biology Chapter 11

Which of these acts as a second messenger? cyclic AMP protein kinase G-protein-linked receptor G protein adenylyl kinase

cyclic AMP

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

cAMP

What role does a transcription factor play in a signal transduction pathway?

By binding to DNA it triggers the transcription of a specific gene.

Why are there often so many steps between the original signal event and the cell's response?

Each step in a cascade produces a large number of activated products, causing signal amplification as the cascade progresses.

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.

Cell signaling involves converting extracellular signals to specific responses inside the target cell. Different molecules are involved at each stage of the process. In this activity, you will sort items based on which stage they are involved in: reception, transduction, or response.

Reception: G protein-coupled receptor Receptor Tyrosine Kinase Signaling Molecule Transduction: Phosphorylation Cascade Second Messenger Adenylyl Cyclase IP3, Ca2+, cAMP Response: Protein Synthesis

What are the functions of signal transduction pathways?

Signal transduction pathways allow different types of cells to respond differently to the same signal molecule. Signal transduction pathways convert a signal on a cell's surface to a specific cellular response. Signal transduction pathways amplify the effect of a signal molecule.

Cyclic GMP, or cGMP, acts as a signaling molecule whose effects include relaxation of smooth muscle cells in artery walls. In the penis, this signaling pathway and the resulting dilation of blood vessels leads to an erection. Select the correct statement about the effect of Viagra on this signaling pathway.

Viagra inhibits the hydrolysis of cGMP to GMP.

Protein phosphorylation is commonly involved with all of the following except

activation of G protein-coupled receptors.

A protein kinase activating many other protein kinases is an example of _____.

amplification

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

calcium ion and cAMP

The activation of receptor tyrosine kinases is characterized by

dimerization and phosphorylation

Calcium ions that act as second messengers are stored in _____.

endoplasmic reticula

What is the function of tyrosine-kinase receptors?

enzymatic phosphorylation of tyrosine in the receptor protein

Lipid-soluble signal molecules, such as testosterone, cross the membranes of all cells but affect only target cells because

intracellular receptors are present only in target cells.

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

ligand

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

ligand-gated ion channel

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

Apoptosis involves all but which of the following? fragmentation of the DNA cell-signaling pathways lysis of the cell activation of cellular enzymes digestion of cellular contents by scavenger cells

lysis of the cell

A signal transduction pathway is initiated when a _____ binds to a receptor.

signal molecule

which of the following, when activated by a signal transduction pathway, moved from the cytoplasm to the nucleus of a cell?

transcription factor

Histamine is a chemical substance released in inflammatory and allergic responses. The histamine H1 receptor is a G protein-coupled receptor that activates phospholipase C in response to the binding of histamine. Complete the flowchart showing the process of histamine signal transduction from the H1 receptor.

1) Enzyme cleaves PIP2, forming DAG and IP3 2)IP3 binds to a ligand-gated ion channel in the ER membrane 3) Calcium ions flow through the ligan-gated ion channel 4) Calcium ion concentration increases in the cytosol 5) Calcium ions activate a protein, leading to a cellular response

Which statement correctly distinguishes the roles of protein kinases and protein phosphatases in signal transduction pathways?

Protein kinases activate enzymes by phosphorylating or adding phosphate groups to them. Protein phosphatases dephosphorylate or remove phosphate groups from enzymes, including protein kinases.

Select the statement that correctly distinguishes between relay proteins and second messengers in signal transduction pathways.

Signal transduction pathways are multistep pathways that include relay proteins and small, nonprotein, water-soluble molecules or ions called second messengers.

The cholera bacterium Vibrio cholerae produces an enzyme toxin that chemically modifies a G protein involved in regulating salt and water secretion in intestinal cells. Stuck in its active form, the modified G protein stimulates the production of a high concentration of cAMP, which causes the intestinal cells to secrete large amounts of salts into the intestines, with water following by osmosis. An infected person quickly develops profuse diarrhea and if left untreated can soon die from the loss of water and salts. What is the basic effect of the cholera toxin?

The basic effect of the cholera toxin is signal amplification.

Which of the following provides molecular evidence that signal transduction pathways evolved early in the history of life?

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? Why can a signaling molecule cause different responses in different cells?

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

Protein phosphorylation is commonly involved with all of the following except Protein phosphorylation is commonly involved with all of the following except: activation of G protein-coupled receptors. enzyme activation. regulation of transcription by extracellular signaling molecules. activation of receptor tyrosine kinases. activation of protein kinase molecules.

activation of G protein-coupled receptors

Which of the following sequences is correct? Which of the following sequences is correct? binding of a growth factor to its receptor → phosphorylation cascade → activation of transcription factor → transcription diffusion of a signaling molecule across the plasma membrane → binding of the signaling molecule to its receptor → movement of the signaling molecule-receptor complex into the nucleus → transcription binding of a signaling molecule to its receptor → G protein activation → phospholipase C activation → IP3 production → increase in cytoplasmic calcium concentration binding of a signaling molecule to its receptor → G protein activation → adenylyl cyclase activation → cAMP production → protein phosphorylation

all of the choices are correct

To what does the term "ligand" refer in cell biology?

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

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

hormone

The histamine H1 receptor is one of several existing histamine G protein-coupled receptors. Depending on many factors, including the type of receptor, histamine can trigger a variety of responses, including vasodilation, smooth muscle contraction, stimulation of gastric secretion, cardiac stimulation, and increased vascular permeability (causing runny nose and watery eyes). Which of the following could account for the different cellular responses to histamine?

the cell type in which the histamine receptor is located the type of second messengers involved in the signal transduction pathway the types of relay molecules within the cell the enzyme that is activated by the G protein associated with the receptor

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

they amplify the original signal manyfold.

Dioxin, produced as a by-product of various industrial chemical processes, is suspected of contributing to the development of cancer and birth defects in animals and humans. It apparently acts by entering cells by simple diffusion and binding to proteins in the cytoplasm, then altering the pattern of gene expression. Which of the following are likely to be the cytoplasmic proteins to which dioxin binds?

transcription factors

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