Bio HW ch. 11

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

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

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

cAMP

What are the functions of signal transduction pathways?

=Signal transduction pathways amplify the effect of a signal molecule. =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.

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.

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.

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?

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

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.

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

cAMP

Which of the following are among the most common second messengers?

calcium ion and cAMP

What is apoptosis?

controlled cell suicide

The activation of receptor tyrosine kinases is characterized by

dimerization and phosphorylation

What is the function of tyrosine-kinase receptors?

enzymatic phosphorylation of tyrosine in the receptor protein

Which of the following is a substance that acts at a long distance from the site at which it is secreted?

hormone

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.

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.

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?

lysis of the cell

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

they amplify the original signal manyfold

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?

transduction