Chapter 11- Cell--Cell Interactions

Question 1

What do the cell walls of plants and the extracellular matrix of animal cells have in common?
A) They are largely composed of phospholipids and glycoproteins.
B) Their proteins are made by free cytoplasmic ribosomes.
C) They form rigid structures that provide structural support for cells but limit their expansion.
D) They limit the passage of small molecules.
E) They have functional connections with the cytoskeleton inside the cell.

Answer 1

They have functional connections with the cytoskeleton inside the cell.

Question 2

The cell walls of bacteria, fungi, and plant cells and the extracellular matrix of animal cells are all external to the plasma membrane. Which of the following is a characteristic common to all of these extracellular structures?
A) They must block water and small molecules to regulate the exchange of matter and energy with their environment.
B) They must permit information transfer between the cell’s cytoplasm and the nucleus.
C) They must provide a rigid structure that maintains an appropriate ratio of cell surface area to volume.
D) They are constructed of polymers that are synthesized in the cytoplasm and then transported out of the cell.
E) They are composed of a mixture of lipids and nucleotides.

Answer 2

They are constructed of polymers that are synthesized in the cytoplasm and then transported out of the cell.

Question 3

A mutation that disrupts the ability of an animal cell to add polysaccharide modifications to proteins would most likely cause defects in its ________.
A) nuclear lamina and nuclear matrix
B) nuclear matrix and extracellular matrix
C) mitochondria and Golgi apparatus
D) Golgi apparatus and extracellular matrix
E) nuclear pores and secretory vesicles

Answer 3

Golgi apparatus and extracellular matrix

Question 4

Signals from the extracellular matrix to the cytoskeleton may be transmitted by ________.
A) fibronectin
B) proteoglycans
C) integrins
D) collagen
E) middle lamella

Answer 4

integrins

Question 5

One characteristic of life and living systems is that they are able to adapt. In general,
cells interact with other cells and their environment through the action of their ________.
A) plasma membrane and extracellular matrix
B) microtubular tracks
C) hormones
D) intracellular electrical currents

Answer 5

plasma membrane and extracellular matrix

Question 6

Which of the following would you NOT find in a plant cell?
A) pectin
B) polysaccharides
C) collagen
D) lignin

Answer 6

collagen

Question 7

Which of the following statements is FALSE?
A) When plant cells are growing, they release expansins, which are enzymes that can expand the primary cell wall.
B) The secondary cell wall often contains structural components, like lignin, that form a relatively rigid and complex network within the cell wall.
C) A plant cell continues growing after the secondary cell wall forms but stops growing with the formation of the tertiary cell wall.
D) Pectin is a component of the cell wall that attracts and holds water.

Answer 7

A plant cell continues growing after the secondary cell wall forms but stops growing with the formation of the tertiary cell wall.

Question 8

What is a major difference between the extracellular matrix (ECM) of a plant cell and the ECM of an animal cell?
A) Plant ECM is composed primarily of proteins, whereas animal ECM is mainly carbohydrates.
B) Plant ECM is primarily carbohydrate in nature, whereas animal ECM is mainly proteins.
C) Plant and animal ECMs are quite similar in structure and function.
D) ECM components in plant cells are released extracellularly by the Golgi stacks, whereas lysosomes do this in animal cells.

Answer 8

Plant ECM is primarily carbohydrate in nature, whereas animal ECM is mainly proteins

Question 9

Osteocytes are bone cells. Collagen fibers and calcium salts are found in abundance between and among the osteocytes. The collagen and calcium salts are ________.
A) components of the plasma membrane of osteocytes
B) part of the extracellular matrix
C) extensions of the endoplasmic reticulum
D) deposited by the circulatory system but not associated with the osteocytes

Answer 9

part of the extracellular matrix

Question 10

All of the following proteins may be found in the extracellular matrix of animal cells EXCEPT ________.
A) collagen
B) fibronectin
C) actin
D) All of the listed proteins are found in the extracellular matrix of animal cells.

Answer 10

actin

Question 11

Which component is a protein fiber of the extracellular matrix?
A) A
B) B
C) C
D) D
E) E

Answer 11

A

Question 12

The extracellular matrix is thought to participate in the regulation of animal cell behavior by communicating information from the outside to the inside of the cell via which of the following?
A) gap junctions
B) the nucleus
C) DNA and RNA
D) integrins
E) plasmodesmata

Answer 12

integrins

Question 13

Integrins are integral membrane proteins. They are often attached to ________.
A) the membranes of intracellular organelles
B) cytoskeletal proteins and proteins in the extracellular matrix
C) the outside of the plasma membrane
D) glycogen molecules and other types of cellular inclusions

Answer 13

cytoskeletal proteins and proteins in the extracellular matrix

Question 14

Scientists have found that extracellular matrix components may induce specific gene expression in embryonic tissues such as the liver and testes. For this to happen there must be direct communication between the extracellular matrix and the developing
cells. Which kind of transmembrane protein would most likely be involved in this kind of induction?
A) integrins
B) collagens
C) actins
D) fibronectins

Answer 14

integrins

Question 15

Plasmodesmata in plant cells are most similar in function to which of the following structures in animal cells?
A) peroxisomes
B) desmosomes
C) gap junctions
D) extracellular matrix
E) tight junctions

Answer 15

gap junctions

Question 16

Ions can travel directly from the cytoplasm of one animal cell to the cytoplasm of an adjacent cell through ________.
A) plasmodesmata
B) intermediate filaments
C) tight junctions
D) desmosomes
E) gap junctions

Answer 16

gap junctions

Question 17

For a tissue or an organ to function as a unit, ________.
A) there must be a signal molecule recognized by all cells in the tissue or organ
B) there must be cell—cell communication among the cells within a tissue or organ
C) the tissue or organ must perform similar functions
D) the tissue or organ must be composed of all of the same type of cells

Answer 17

there must be cell—cell communication among the cells within a tissue or organ

Question 18

In plant cells, the middle lamella ________.
A) allows adjacent cells to adhere to one another
B) prevents dehydration of adjacent cells
C) maintains the plant’s circulatory system
D) allows for gas and nutrient exchange among adjacent cells

Answer 18

allows adjacent cells to adhere to one another

Question 19

Where would you expect to find tight junctions?
A) in the epithelium of an animal’s stomach
B) between the smooth endoplasmic reticulum and the rough endoplasmic reticulum
C) between plant cells in a woody plant
D) in the plasma membrane of prokaryotes

Answer 19

in the epithelium of an animal’s stomach

Question 20

H. V. Wilson worked with sponges to gain some insight into exactly what was responsible for holding adjacent cells together. He exposed two species of differently pigmented sponges to a chemical that disrupted the cell—cell interaction (cell junctions), and the cells of the sponges dissociated. Wilson then mixed the cells of the two species and removed the chemical that caused the cells to dissociate. Wilson found that the sponges reassembled into two separate species. The cells from one species did not interact or form associations with the cells of the other species. How do you explain the results of Wilson’s experiments?
A) The two species of sponge had different enzymes that functioned in the reassembly process.
B) The molecules responsible for cell—cell adhesion (cell junctions) were irreversibly destroyed during the experiment.
C) The molecules responsible for cell—cell adhesion (cell junctions) differed between the two species of sponge.
D) One cell functioned as the nucleus for each organism, thereby attracting only cells of the same pigment.

Answer 20

The molecules responsible for cell—cell adhesion (cell junctions) differed between the two species of sponge.

Question 21

A gap junction is a channel that connects adjacent cells. Which one of the following
cannot pass through a gap junction?
A) ions that can regulate heartbeat
B) amino acids
C) nucleotides
D) ribosomes

Answer 21

ribosomes

Question 22

Intercalated discs are cell—cell junctions found between cardiac muscle cells. One feature of these intercalated discs is that they contain a large number of gap junctions, which means that ________.
A) an extension of smooth endoplasmic reticulum goes through the gap junction, making it continuous from one cardiac muscle cell to the next
B) water ions and small molecules can readily pass from one cardiac muscle cell to the next
C) cardiac cells can function independently when necessary
D) RNA from one cardiac muscle cell can be transported into an adjacent cell through
the gap junction

Answer 22

water ions and small molecules can readily pass from one cardiac muscle cell to the next

Question 23

Plasmodesmata are cell—cell junctions that are found between ________.
A) individual cardiac cells in heart muscle tissue
B) adjacent plant cells
C) adjacent animal cells in the same tissue type
D) the plasma membrane of actively dividing prokaryotes

Answer 23

adjacent plant cells

Question 24

Pemphigus vulgaris is an autoimmune disorder in humans in which antibodies are produced against the cadherins of desmosomes. The blistering of the skin and mucous membranes characteristic of this disorder is probably a result of ________.
A) a decrease in flexibility of the cell membrane
B) an inadequate number of G-protein receptors
C) inadequate production of cytoskeletal proteins
D) a loss in cell—cell adhesion

Answer 24

a loss in cell—cell adhesion

Question 25

A cell with membrane-bound proteins that selectively bind a specific hormone is called that hormone’s ________.
A) secretory cell
B) plasma cell
C) endocrine cell
D) target cell
E) regulatory cell

Answer 25

target cell

Question 26

Different body cells can respond differently to the same peptide hormones because ________.
A) different target cells have different sets of genes
B) each cell converts that hormone to a different metabolite
C) a target cell’s response is determined by the components of its signal transduction
pathways
D) the circulatory system regulates responses to hormones by routing the hormones to
specific targets
E) the hormone is chemically altered in different ways as it travels through the
circulatory system

Answer 26

a target cell’s response is determined by the components of its signal transduction
pathways

Question 27

Which of the following is characteristic of a steroid hormone action?
A) protein phosphorylation
B) cell-surface receptor binding
C) internal receptor binding
D) second messenger activation

Answer 27

internal receptor binding

Question 28

The receptors for steroid hormones are located inside the cell instead of on the membrane surface like most other signal receptors. This is NOT a problem for steroids because ________.
A) the receptors can be readily stimulated to exit and relocate on the membrane surface
B) steroids do not directly affect cells but instead alter the chemistry of blood plasma
C) steroid hormones are lipid soluble, so they can readily diffuse through the lipid
bilayer of the cell membrane
D) steroids must first bond to a steroid activator, forming a complex that then binds to
the cell surface

Answer 28

steroid hormones are lipid soluble, so they can readily diffuse through the lipid
bilayer of the cell membrane

Question 29

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.
A) 1, 2, 3, 4, 5
B) 3, 1, 2, 4, 5
C) 3, 1, 5, 2, 4
D) 1, 2, 5, 3, 4

Answer 29

3, 1, 5, 2, 4

Question 30

Protein kinase is an enzyme that ________.
A) functions as a second messenger molecule
B) serves as a receptor for various signal molecules
C) activates or inactivates other proteins by adding a phosphate group to them
D) produces second messenger molecules

Answer 30

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

Question 31

Hormones are chemical substances produced in one organ that are released into the bloodstream and affect the function of a target organ. For the target organ to respond to a particular hormone, it must ________.
A) modify its plasma membrane to alter the hormone entering the cytoplasm
B) be from the same cell type as the organ that produced the hormone
C) experience an imbalance that disrupts its normal function
D) have receptors that recognize and bind the hormone molecule

Answer 31

have receptors that recognize and bind the hormone molecule

Question 32

Steroid hormones bind to receptors inside the cell and alter their conformation. The hormone—receptor complex is then transported into the nucleus, where it can directly affect gene expression. To get from the location where the receptor binds the hormone to its site of action, the hormone—receptor complex must ________.
A) undergo another conformational change
B) become water-soluble by binding to a carrier molecule
C) be transported through the nuclear pore complex
D) enter the smooth endoplasmic reticulum

Answer 32

be transported through the nuclear pore complex

Question 33

Not all intercellular signals require transduction. Which one of the following signals would be processed without transduction?
A) a lipid-soluble signal
B) a signal that is weakly bound to a nucleotide
C) a signal that binds to a receptor in the cell membrane
D) a signal that binds to the ECM

Answer 33

a lipid-soluble signal

Question 34

Blood sugar is regulated by two pancreatic hormones—insulin and glucagon. When blood sugar rises, insulin is released; it binds to receptors and, through signal transduction, results in an increase in glucose uptake by cells, which effectively lowers blood glucose levels. When blood sugar decreases, glucagon is released, binds to cell receptors, and causes glucose to be released into circulation, thereby increasing blood glucose levels. Diabetes mellitus is a disorder that results from excessively high levels of blood glucose. Type II diabetics have normal to elevated levels of insulin. What, then,
might be causing their elevated blood glucose levels?
A) inadequate insulin production
B) defective receptors
C) defective second messenger
D) overproduction of glucagon

Answer 34

defective receptors

Question 35

What does it mean to say that a signal is transduced?
A) The signal enters the cell directly and binds to a receptor inside.
B) The physical form of the signal changes from one form to another.
C) The signal is amplified, such that even a single molecule evokes a large response.
D) The signal triggers a sequence of phosphorylation events inside the cell.

Answer 35

The physical form of the signal changes from one form to another.

Question 36

A G-protein receptor with GTP bound to it ________.
A) is in its active state
B) signals a protein to maintain its shape and conformation
C) will use cGMP as a second messenger
D) directly affects gene expression

Answer 36

is in its active state

Question 37

Acetylcholine is a neurotransmitter that binds to receptors on skeletal muscle cells.
The receptor—signal complex brings about a series of events that result in contraction of skeletal muscle. Venom from black widow spiders causes an explosive release of acetylcholine. What would that do to its victims?
A) The victim’s muscles would be unable to contract.
B) The victim’s muscles would be unable to relax.
C) The victim’s cell receptors would no longer be able to bind regulatory hormones.
D) The victim’s cell receptors would be able to bind regulatory hormones but at a rate
greatly exceeding normal rates.

Answer 37

The victim’s muscles would be unable to relax.

Question 38

One of the major categories of receptors in the plasma membrane reacts by forming dimers, adding phosphate groups, and then activating relay proteins. Which type does this?
A) G-protein—coupled receptors
B) ligand-gated ion channels
C) steroid receptors
D) receptor tyrosine kinases

Answer 38

receptor tyrosine kinases

Question 39

In general, a signal transmitted via phosphorylation of a series of proteins ________.
A) results in a conformational change to each protein
B) requires binding of a hormone to an intracellular receptor
C) activates a transcription event
D) generates ATP in the process of signal transduction
E) occurs within the outer plasma membrane

Answer 39

results in a conformational change to each protein

Question 40

In signal transduction, phosphatases ________.
A) move the phosphate group of the transduction pathway to the next molecule of a series
B) prevent a protein kinase from being reused when there is another extracellular signal
C) amplify the transduction signal so it affects multiple transducers
D) amplify the second messengers such as cAMP
E) inactivate protein kinases and turn off the signal transduction

Answer 40

inactivate protein kinases and turn off the signal transduction

Question 41

At puberty, an adolescent female body changes in both structure and function of several organ systems, primarily under the influence of changing concentrations of estrogens and other steroid hormones. How can one hormone, such as estrogen,
mediate so many effects?
A) Estrogen is produced in very large concentration by nearly every tissue of the body.
B) Each cell responds in the same way when steroids bind to the cell surface.
C) Estrogen is kept away from the surface of any cells not able to bind it at the surface.
D) Estrogen binds to specific receptors inside many kinds of cells, each with different responses.
E) Cells metabolize steroids in different ways, producing by-products that stimulate
tRNA production.

Answer 41

Estrogen binds to specific receptors inside many kinds of cells, each with different responses.

Question 42

Scaffolding proteins are ________.
A) ladderlike proteins that allow receptor—ligand complexes to climb through cells from one position to another
B) microtubular protein arrays that allow lipid-soluble hormones to get from the cell membrane to the nuclear pores
C) large molecules to which several relay proteins attach to facilitate cascade effects
D) relay proteins that orient receptors and their ligands in appropriate directions to facilitate their complexing
E) proteins that can reach into the nucleus of a cell to affect transcription

Answer 42

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

Question 43

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because they ________.
A) are species specific
B) always lead to the same cellular response
C) amplify the original signal many times
D) counter the harmful effects of phosphatases
E) use a small and fixed number of molecules

Answer 43

amplify the original signal many times

Question 44

The activation of receptor tyrosine kinases is characterized by ________.
A) dimerization and phosphorylation
B) dimerization and IP3 binding
C) a phosphorylation cascade
D) GTP hydrolysis
E) channel protein shape change

Answer 44

dimerization and phosphorylation

Question 45

Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all
cells but affect only target cells because ________.
A) only target cells retain the appropriate DNA segments
B) intracellular receptors are present only in target cells
C) most cells lack the Y chromosome required
D) only target cells possess the cytosolic enzymes that transduce the testosterone
E) only in target cells is testosterone able to initiate the phosphorylation cascade
leading to activated transcription factor

Answer 45

intracellular receptors are present only in target cells

Question 46

Consider this pathway: epinephrine → G-protein-coupled receptor → G-protein →adenylyl cyclase → cAMP. The second messenger in this pathway is ________.
A) cAMP
B) G-protein
C) GTP
D) adenylyl cyclase
E) G-protein-coupled receptor

Answer 46

cAMP

Question 47

Which observation suggested the involvement of a second messenger in epinephrine’s effect on liver cells?
A) Enzymatic activity was proportional to the amount of calcium added to a cell-free extract.
B) Receptor studies indicated that epinephrine was a ligand.
C) Glycogen breakdown was observed only when epinephrine was administered to intact cells.
D) Glycogen breakdown was observed when epinephrine and glycogen phosphorylase were combined.
E) Epinephrine was known to have different effects on different types of cells.

Answer 47

Glycogen breakdown was observed only when epinephrine was administered to intact cells.

Question 48

The cancer-causing forms of the Ras protein are involved in which of the following processes?
A) relaying a signal from a growth-factor receptor
B) DNA replication
C) DNA repair
D) cell—cell adhesion
E) cell division

Answer 48

relaying a signal from a growth-factor receptor

Question 49

Which of the following statements about quorum sensing is FALSE? Quorum sensing ________.
A) is cell—cell communication in eukaryotes
B) is species specific
C) may result in biofilm formation
D) is particularly well studied because of its medical importance

Answer 49

is cell—cell communication in eukaryotes

Question 50

Forms of the Ras protein found in tumors usually cause which of the following?
A) DNA replication to stop
B) DNA replication to be hyperactive
C) cell-to-cell adhesion to be nonfunctional
D) cell division to cease
E) excessive cell division

Answer 50

excessive cell division

Question 51

When yeast cells of opposite mating types are in close proximity, cell changes occur inside those cells that result in the polymerization of actin filaments, allowing the yeast cells to mate. Those changes in cell behavior are initially due to signaling molecules
(pheromones) released by the yeast cells. Pheromones are ________.
A) a type of steroid hormone that diffuses through the plasma membrane causing cytoplasmic actin proteins to form filaments
B) a type of hormone that binds cell-surface receptors causing cytoplasmic actin proteins to form filaments
C) signaling molecules that bind cell-surface receptors causing yeast cells to become motile, insuring mating success
D) signaling molecules that cause the extracellular matrix of yeast cells to thicken in preparation for cell fusion
E) signaling molecules that cause intracellular G-proteins to be inhibited

Answer 51

a type of hormone that binds cell-surface receptors causing cytoplasmic actin proteins to form filaments

Question 52

When yeast cells of the “a” mating type are exposed to a solution of “α” pheromones ________.
A) those yeast cells will undergo cell division
B) actin filaments will form a cleavage furrow in the yeast cells
C) the yeast cells will fuse with each other
D) G-proteins will be activated in the cell-signaling pathway and the yeast cells will change shape
E) those yeast cells will undergo DNA replication

Answer 52

G-proteins will be activated in the cell-signaling pathway and the yeast cells will change shape