Chapter 11- Cell Signaling

Question 1

The stage of cell signaling in which a chemical signal is “detected” when the signaling molecule bind to a receptor protein located at the cell’s surface is called ___________.

Answer 1

Reception

Question 2

What effect does ligand binding have on receptor tyrosine kinase proteins?

Answer 2

Ligand binding causes them to phosphorylate and form dimers

Question 3

When a platelet contacts a damaged blood vessel, it is stimulated to release thromboxane A2. Thromboxane A2 in turn stimulates vascular spasm and attracts additional platelets to the injured site. In this example thromboxane A2 is acting as a __________. Explain.

Answer 3

Local regulator.

Because of the damaged blood vessel, thromboxane A2 became responsible to heal the injured site.

Question 4

Second-messengers tend to be water-soluble and small. This accounts for their ability to _______.

Answer 4

rapidly move throughout the cell by diffusion

Question 5

In liver cells, epinephrine stimulates the breakdown of glycogen. As the signal-transduction pathway progresses, __________.

Answer 5

the signal is amplified

Question 6

What happens during the process of paracrine signaling?

Answer 6

Numerous cells simultaneously receive and respond to the molecules of growth factor produced by a single cell in their vicinity.

Question 7

A small molecule that specifically bind to a larger molecule is called a(n) _________.

Answer 7

Ligand

Question 8

In which part of the cell are calcium ions usually found?

Answer 8

Endoplasmic reticulum

Question 9

The stage of cell signaling in which the signal is converted to a form that can bring about a response in the cell is called _________.

Answer 9

Trandsduction

Question 10

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

Answer 10

they amplify the original signal manyfold

Question 11

Evidence that cell signaling evolved early in the history of life comes from _________.

Answer 11

the similarity of the mechanisms in organisms that have a very distant common ancestor

Question 12

A difference between the mechanisms of cAMP and Ca2+ in signal transduction is that cAMP ________ and Ca2+ _________.

Answer 12

is synthesized by an enzyme in response to a signal; is released from intercellular stores

Question 13

G-protein-linked receptors _________, whereas receptor tyrosine kinases ________.

Answer 13

are not enzymes; have enzymatic functions

Question 14

What is the general name for an enzyme that transfers phosphate groups from ATP to other molecules?

Answer 14

Protein kinase

Question 15

After signaling molecule binds to a G-protein-coupled receptor, what activates the associated G-protein?

Answer 15

GTP displaces GDP on the G-protein

Question 16

Describe the function of inositol trisphosphate (IP3) as a second messenger?

Answer 16

Inositol trisphosphate bind to an IP3-gated calcium channel, causes the release of calcium ions from the endoplasmic reticulum

Question 17

In phosphorylation cascade, __________ phosphorylate proteins, and __________ dephosphorylate them.

Answer 17

Protein kinases; protein phosphatases

Question 18

How is nitric oxide different from other signal molecules?

Answer 18

It is a gas

Question 19

cAMP usually directly activates _________.

Answer 19

Protein kinase A

Question 20

A G-protein is active when ….

Answer 20

GTP is bound to it

Question 21

What did Sutherland discover about glycogen metabolism in liver cells?

Answer 21

The hormone epinephrine binds to a specific receptor on the plasma membrane of the liver cell

Question 22

What happens to cells undergoing apoptosis?

Answer 22

Cells shrink and form lobes, which are eventually shred as membrane fragments

Question 23

Describe the process of hormonal signaling

Answer 23

Specialized cells release hormone molecules, which travel via the circulatory system to other parts of the body, where they reach target cells that can recognize and respond to the hormones.

Question 24

How does adenylyl cyclase help transmit signal within a cell?

Answer 24

It converts ATP to cAMP, which then broadcasts the signal to the rest of the cell.

Question 25

Ras, a small G-protein located at the plasma membrane, is often mutated in different types of cancer. Ras normally signals to a cell that it should divide. Cancer cells divide uncontrollably.

Answer 25

A mutation that means Ras cannot hydrolyze GTP to GDP

Question 26

The process of phosphorylation is very important as a cellular mechanism for regulating protein activity. Phosphorylation does this by __________.

Answer 26

activating or inactivating proteins

Question 27

IP3 (inositol trisphosphate) is produced as a result of __________.

Answer 27

The cleavage of a certain kind of phospholipid in the plasma membrane

Question 28

Testosterone and estrogen are lipid-soluble signal molecules that cross the plasma membrane by simple diffusion. If these molecules can enter all cells, why do only specific cells respond to their presence?

Answer 28

Nontarget cells lack the intracellular receptors that, can interact with genes in the cell’s nucleus

Question 29

Why does testosterone not affect all cell in the body?

Answer 29

Only certain cells have cytoplasmic receptors for testosterone

Question 30

Certain yeast cells secrete a molecule called the -factor. The purpose of this molecule is to _____________.

Answer 30

stimulate an a yeast cell to grow toward the cell

Question 31

An inhibitor of which of the following could be used to block the release of calcium from the endoplasmic reticulum?

A.) phosphodiesterase 
B.) serine/threonine kinases
C.) phospholipase C
D.) adenylyl cyclase
E.) tyrosine kinases

Answer 31

C.) phospholipase C

Question 32

What are the three stages of the process by which a signal is converted to a specific cellular response?

Answer 32

1. ) reception if signaling molecule
2. ) transduction of the signal
3. ) response to the signal

Question 33

What molecules are involved in Reception?

Answer 33

1. ) G protein-coupled receptor
2. ) receptor tyrosine kinase
3. ) signaling molecule

Question 34

What molecules are involved in Transduction?

Answer 34

1. ) Phosphorylation cascade
2. ) second messenger
3. ) adenylyl cyclase
4. ) Ca2+
5. ) cAMP
6. ) IP3

Question 35

What molecules are involved in Response?

Answer 35

1.) protein synthesis