BSC2010 Chapter 11 (HOMEWORK)

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1
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Which of these is a receptor molecule?

B

2

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

single molecule

3
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Which of these is a signal molecule?

A

4

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

ligand

5

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

transduction

6

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.

7

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

hormone

8
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Which of the following types of signaling is represented in the figure?

synaptic

9

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

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

10

A G-protein receptor with GTP bound to it _____.

is in its active state

11

If an animal cell suddenly lost the ability to produce GTP, what might happen to its signaling system?

It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.

12

Not all intercellular signals require transduction. Which one of the following signals would be processed without transduction?

a lipid-soluble signal

13

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

calcium ion and cAMP

14

In general, a signal transmitted via phosphorylation of a series of proteins _____.

results in a conformational change to each protein

15

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

phospholipase C

16

Protein kinase is an enzyme that _____.

activates or inactivates other proteins by adding a phosphate group to them

17

Consider this pathway: epinephrine → G protein-coupled receptor → G protein → adenylyl cyclase → cAMP. The second messenger in this pathway is _____.

cAMP

18

Which of the following is true during a typical cAMP-type signal transduction event?

Adenylyl cyclase is activated after the hormone binds to the cell and before phosphorylation of proteins occurs.

19

Put the steps of the process of signal transduction in the order they occur:

1. A conformational change in the signal-receptor complex activates an enzyme.

2. Protein kinases are activated.

3. A signal molecule binds to a receptor.

4. Target proteins are phosphorylated.

5. Second messenger molecules are released.

3, 1, 5, 2, 4

20

The cleavage of glycogen by glycogen phosphorylase releases _____.

glucose-1-phosphate

21

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

G-protein-linked receptor

22

Which of these is activated by calcium ions?

calmodulin

23

Which of these is NOT correct?

  • Ion channels are found on both the plasma membrane and the endoplasmic reticulum.
  • Cyclic AMP binds to calmodulin.
  • Tyrosine-kinase receptors consist of two polypeptides that join when activated by a signal molecule.
  • Kinases are enzymes that phosphorylate other molecules.
  • Phospholipase C catalyzes the formation of IP3.

Cyclic AMP binds to calmodulin.

(Calcium binds to calmodulin)

24

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

25

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.

26

Transcription factors _____.

control gene expression

27

Scaffolding proteins are _____.

large molecules to which several relay proteins attach to facilitate cascade effects

28

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

amplify the original signal many times

29

What is apoptosis?

controlled cell suicide

30

If an adult person has a faulty version of the human analog to ced-4 of the nematode, which of the following is most likely to result?

a form of cancer in which there is insufficient apoptosis

31

In the nematode C. elegans, ced-9 prevents apoptosis in a normal cell in which of the following ways?

It prevents the caspase activity of ced-3 and ced-4.