Ch 11 Bio

Thyroid hormones bind to _____ receptors.

intracellular

Which of these acts as a second messenger?

cyclic AMP

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

cAMP

Which of these extracellular signal molecules could diffuse through a plasma membrane and bind to an intracellular receptor?

estrogen

Which of the following sequences is correct?

1. 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 2. binding of a growth factor to its receptor → phosphorylation cascade → activation of transcription factor → transcription 3. binding of a signaling molecule to its receptor → G protein activation → adenylyl cyclase activation → cAMP production → protein kinase activation → cellular response 4. binding of a signaling molecule to its receptor → G protein activation → phospholipase C activation → IP3 production → increase in cytoplasmic calcium concentration

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

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

Which of the following statements describes why there are 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.

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.

G-protein linked receptor

Epinephrine acts as a signal molecule that attaches to _____ proteins.

G-protien linked receptors

Which of the following occurs during apoptosis?

fragmentations of DNA

_____ catalyzes the production of _____, which then opens an ion channel that releases _____ into the cell's cytoplasm.

Phospholipase C ... IP3 .... Ca2+

Which of the following statements describes why a signaling molecule can 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 which of the following?

activation of protein kinase molecules

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

amplification

To what does the term ligand refer in cell biology?

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

Given that caffeine blocks the activity of cAMPcAMP phosphodiesterase, propose a mechanism by which caffeine ingestion leads to heightened alertness and sleeplessness.

cAMP phosphodiesterase breaks a phosphodiester bond in a cAMP molecule. Caffeine can prolong or enhance the effects of epinephrine by inhibition of cAMP degradation by cAMP phosphodiesterase.

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

calcium ions and cAMP

Which of these is activated by calcium ions?

calmodulin

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 receptor tyrosine kinases?

enzymatic phosphorylation of tyrosine in the receptor protein

The cleavage of glycogen by glycogen phosphorylase releases

glucose-1 phosphate

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

hormone

Lipid-soluble signaling molecules, such as aldosterone, 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 the distribution of substances on opposite sides of the membrane?

ligand-gated ion channel

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

signal molecule

signal transduction pathway is initiated when a ____ binds to a receptor.

signal molecule

A(n) _____ is an example of a signal molecule that can bind to an intracellular receptor and thereby cause a gene to be turned on or off.

steroid

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

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