Chapter 11: Cell Communication

Question 1

What is a signal transduction pathway?

Answer 1

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Question 2

What is the difference between paracrine , synaptic and endocrine signalling?

Answer 2

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Question 3

What are some types of local regulators?

Answer 3

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Question 4

What are plant cell plasmodesmata and how are they an example of cell communication?

Answer 4

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Question 5

In order for a chemical to have an effect on a target cell, what must the target cell have?

Answer 5

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Question 6

Give an overview of Earl W. Sutherland’s research on epinephrine.

Answer 6

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Question 7

Explain how signalling is involved in ensuring that yeast cells fuse only with cells of the opposite mating type.

Answer 7

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Question 8

Explain how nerve cells provide examples of both local and long-distance signalling.

Answer 8

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Question 9

When epinephrine is mixed with glycogen phosphorylase and glycogen in a test tube, is glucose-1 phosphate generated? Why or why not?

Answer 9

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Question 10

In liver cells, glycogen phosphorylase acts in which of the three stages of the signalling pathway associated with an epinephrine-initiated signal?

Answer 10

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Question 11

What is a ligand? What are the effects of ligand binding

Answer 11

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Question 12

Why do cell surface receptor molecules bind to water-soluble signalling molecules?

Answer 12

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Question 13

What are the three main types of cell surface trans-membrane receptors?

Answer 13

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Question 14

What is a G protein? What is GTP/GDP?

Answer 14

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Question 15

Describe what happens when a G protein-coupled receptor is activated by a ligand.

Answer 15

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Question 16

What is meant by “coupling”?

Answer 16

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Question 17

What are receptor-tyrosine kinases?

Answer 17

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Question 18

Explain the difference between monomers vs dimers with respect to RTKs.

Answer 18

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Question 19

What are ligand-gated ion channels?

Answer 19

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Question 20

In reference to the plasma membrane, why do you think protein gates are necessary for ions to travel in/out of the cell?

Answer 20

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Question 21

What sorts of signal molecules would reach intra-cellular receptors?

Answer 21

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Question 22

Nerve growth factor (NGF) is a water soluble signalling molecule. Would you expect the receptor NGF to be intracellular or in the plasma membrane? Why?

Answer 22

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Question 23

What would be the effect if a cell made defective receptor kinase proteins that were unable to dimerize?

Answer 23

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Question 24

How is ligand binding similar to the process of allosteric regulation of enzymes?

Answer 24

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Question 25

Why is a cell-surface receptor protein not required for a steroid hormone (such as testosterone) to enter a cell?

Answer 25

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Question 26

How does DNA initiate protein synthesis?

Answer 26

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Question 27

What are transcription factors? How do they “turn genes on”?

Answer 27

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Question 28

Signal Transduction Pathway

Answer 28

A series of steps linking a mechanical, chemical, or electrical stimulus to a specific cellular response.

Question 29

Local Regulators

Answer 29

A secreted molecule that influences cells near where it is secreted.

Question 30

Hormone

Answer 30

In multicellular organisms, one of many types of secreted chemicals that are formed in specialized cells, travel in body fluids, and act on specific target cells in other parts of the body, changing the target cells’ functioning. Hormones are thus important in long-distance signaling.

Question 31

Ligand

Answer 31

A molecule that binds specifically to another molecule, usually a larger one.

Question 32

Protein Kinase

Answer 32

An enzyme that transfers phosphate groups from ATP to a protein, thus phosphorylating the protein.

Question 33

Protein Phosphatases

Answer 33

An enzyme that removes phosphate groups from (dephosphorylates) proteins, often functioning to reverse the effect of a protein kinase.

Question 34

Second Messenger

Answer 34

A small, nonprotein, water- soluble molecule or ion, such as a calcium ion (Ca2􏰄) or cyclic AMP, that relays a signal to a cell’s interior in response to a signaling mol- ecule bound by a signal receptor protein.

Question 35

Cyclic AMP

Answer 35

Cyclic adenosine monophos- phate, a ring-shaped molecule made from ATP that is a common intracellular signaling mole- cule (second messenger) in eukaryotic cells. It is also a regulator of some bacterial operons.

Question 36

Adenylyl Cyclase

Answer 36

An enzyme that converts ATP to cyclic AMP in response to an extracellular signal.

Question 37

Scaffolding Proteins

Answer 37

A type of large relay protein to which several other relay proteins are simultaneously attached, increasing the efficiency of signal transduction.

Question 38

Apoptosis

Answer 38

A type of programmed cell death, which is brought about by activa- tion of enzymes that break down many chemi- cal components in the cell.

Question 39

Ligand-Gated Protein Channels

Answer 39

A transmembrane protein containing a pore that opens or closes as it changes shape in response to a signaling
molecule (ligand), allowing or blocking the flow of specific ions; also called an ionotropic receptor.

Question 40

Diacylglycerol (DAG)

Answer 40

A second messenger produced by the cleavage of the phospholipid PIP2 in the plasma membrane.

Question 41

Inositol Trisphosphate (IP3)

Answer 41

A second messenger that functions as an inter- mediate between certain signaling molecules and a subsequent second messenger, Ca2􏰄, by causing a rise in cytoplasmic Ca2􏰄 concentration.