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Exam #2

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

signal molecule

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


Cell biologists use the term "ligand" to refer to ____

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

From the perspective of the cell receiving the message, the three stages of cell signaling are

signal reception, signal transduction, and cellular response

Which of these is the second of the three stages of cell signaling?


The process of transduction usually begins

when the signal molecule changes the receptor protein in some way.

A signal molecule can cause different responses in different cells because ____

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

Paracrine Signaling...

involves secreting cells acting on nearby target cells by discharging a local regulator into the extracellular fluid

In the yeast signal transduction pathway, after both types of mating cells have released the mating factors and the factors have bound to specific receptors on the correct cells

binding induces changes in the cell that lead to cell fusion

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.


Thyroid hormones bind to _____ receptors.


Membrane receptors that attach phosphates to specific animo acids in proteins are called ____.

receptor tyrosine-kinases

Tyrosine-kinase receptors are characterized by their ____

enzymatic phosphorylation of tyrosine in the receptor protein

One of the major categories of receptors in the plasma membrane reacts by forming dimers, adding phosphate groups, then activating relay proteins. Which type does this?

receptor tyrosine-kinases

Which of the substances below is a protein that can hold several other relay proteins as it binds to an activated membrane receptor?

scaffolding protein

The general name for an enzyme that transfers phosphate groups from ATP to a protein is

protein kinase

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


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

The main proteases involved in apoptosis are


Human caspases can be activated by

irreparable DNA damage or protein misfolding

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

The activation of receptor tyrosine kinases is characterized by

dimerization and phosphorylation

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

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


Two of the most common second messengers are _____.

calcium ion and cAMP

Apoptosis is ____

controlled cell suicide

Apoptosis involves all but the following:

lysis of the cell

Molecular biologists think that signal transduction pathways evolved early in the history of life because ___

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

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