Biology: The Dynamic Science

Peter J. Russell, Paul E. Hertz, Beverly McMillan

Chapter 9

Cell Communication - all with Video Answers

Educators

Chapter Questions

Problem 1

In signal transduction, which of the following is not a target protein?
a. proteins that regulate gene activity
b. hormones that activate the receptor
c. enzymes of pathways
d. transport proteins
e. enzymes of cell reactions

Joanna Quigley

Joanna Quigley

Numerade Educator

Problem 2

Which of the following could not elicit a signal transduction response?
a. a protein kinase
b. a virus mimicking a normal signal molecule
c. a peptide hormone
d. a steroid hormone
e. a neurotransmitter

Josee Pacheco

Numerade Educator

Problem 3

A cell that responds to a signaling molecule is distinguished from a cell that does not respond by the fact that it has:
a. a cell adhesion molecule.
b. cAMP.
c. a first messenger molecule.
d. a receptor.
e. a protein kinase.

Emily Himsel

Numerade Educator

Problem 4

The mechanism to activate an immune cell to make an antibody involves signal transduction using tyrosine kinases. Place in order the following series of steps to activate this function.
(1) The activated receptor phosphorylates cytoplasmic proteins.
(2) Conformational change occurs in the receptor tyrosine kinase.
(3) Cytoplasmic protein crosses the nuclear membrane to activate genes.
(4) An immune hormone signals the immune cell.
(5) Activation of protein kinase site(s) adds phosphates to the receptor to activate it.

Emily Himsel

Numerade Educator

Problem 5

Which of the following describes the ability of enzymes, involving few surface receptors, to activate thousands of molecules in a stepwise pathway?
a. autophosphorylation
b. second-messenger enhancement
c. amplification
d. ion channel regulation
e. G protein activation

Emily Himsel

Numerade Educator

Problem 6

Which of the following is incorrect about pathways activated by G-protein-coupled receptors?
a. The extracellular signaling molecule is the first messenger.
b. When activated, plasma membrane-bound G protein can switch on an effector.
c. Second messengers enter the nucleus.
d. ATP converts to cAMP to activate protein kinases.
e. Protein kinases phosphorylate molecules to change cellular activity.

Josee Pacheco

Numerade Educator

Problem 7

Which of the following would not inhibit signal transduction?
a. Phosphate groups are removed from proteins.
b. Endocytosis acts on receptors and their bound signals.
c. Receptors and signaling molecules separate.
d. Receptors and bound signaling molecules enter lysosomes.
e. Autophosphorylation targets the cytoplasmic portion of the receptor.

Josee Pacheco

Numerade Educator

Problem 8

An internal receptor binds both a signaling molecule and controlling region of a gene. What type of receptor is it?
a. protein
b. steroid
$\mathrm{c} . \mathrm{IP}_{3} / \mathrm{DAG}$
d. receptor tyrosine kinase
e. switch protein

Emily Himsel

Numerade Educator

Problem 9

Place in order the following steps for the normal activity of a Ras protein.
(1) Ras turns on the MAP kinase cascade.
(2) Adaptor proteins connect phosphorylated tyrosine on a receptor to Ras.
(3) GTP activates Ras by binding to it, displacing GDP.
(4) The last MAP kinase in the cascade phosphorylates proteins in the nucleus that activate genes.
(5) Receptor tyrosine kinase binds a signaling molecule and is activated.
a. 1,2,3,4,5
b. 2,3,5,1,4
c. 5,2,3,1,4
d. 2,3,1,5,4
e. 4,1,5,3,2

Emily Himsel

Numerade Educator

Problem 10

Which of the following does not exemplify cross-talk?
a. a protein kinase in one pathway that phosphorylates a site on a target protein in another signal transduction pathway
b. modifications of cellular responses controlled by pathways
c. two second-messenger pathways interacting
d. olfactory sensory perception
e. signal transduction pathways controlled by G-proteincoupled receptors

Emily Himsel

Numerade Educator

Problem 11

Describe the possible ways in which a G-protein–coupled receptor pathway could become defective
and not trigger any cellular responses.

Josee Pacheco

Numerade Educator

Problem 12

Is providing extra insulin an effective cure for an individual who has diabetes that is caused by a hereditary defect in the insulin receptor? Why or why not?

Emily Himsel

Numerade Educator

Problem 13

There are molecules called GTP analogs that resemble GTP so closely that they can be bound by G proteins. However, they cannot be hydrolyzed by cellular GTPases. What differences in effect would you expect if you inject GTP or a nonhydrolyzable GTP analog into a liver cell that responds to glucagon?

Josee Pacheco

Numerade Educator

Problem 14

Why do you suppose cells evolved internal response mechanisms using molecules that bind GTP instead of ATP?

Josee Pacheco

Numerade Educator

Problem 15

How would you set up an experiment to determine whether a hormone receptor is located on the cell surface or inside the cell?

Josee Pacheco

Numerade Educator

Problem 16

Based on their distributions among different groups of organisms, which signaling pathway is the oldest?

Emily Himsel

Numerade Educator