Deck 8: Cell-Cell Interactions

Question 1

The receptors for steroid hormones are located inside the cell,instead of on the membrane surface like most other signal receptors.Why is this not a problem for steroids?

A)because the receptors can be readily stimulated to exit and relocate on the membrane surface
B)because receptors located inside cells are less susceptible to blockage by inhibitors located on or near the cell surface,so it serves as a protective mechanism
C)because steroid hormones are lipid soluble so can readily diffuse through the lipid bilayer of the cell membrane
D)because the receptors are repressible,meaning they are actively altering cell function unless the target hormone is present

Answer 1

C

Question 2

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 2

B

Question 3

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 3

B

Question 4

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

Question 5

What is the function of the middle lamella in plant cells?

A)It allows adjacent cells to adhere to one another.
B)It prevents dehydration of adjacent cells.
C)It maintains the plant's circulatory system.
D)It allows for gas and nutrient exchange among adjacent cells.

Question 6

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

Question 7

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

Question 8

Which of the following statements about quorum sensing is not accurate?

A)Quorum sensing is cell-cell communication in prokaryotes.
B)Quorum sensing is species specific.
C)Quorum sensing may result in biofilm formation.
D)Quorum sensing is particularly well studied because of its importance in understanding interactions between prokaryotes and eukaryotes.

Question 9

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,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 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 were irreversibly destroyed during the experiment.
C)The molecules responsible for cell-cell adhesion 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.

Question 10

Which of the following would you not find in a plant cell?

A)pectin
B)polysaccharides
C)collagen
D)lignin

Question 11

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.

Question 12

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

Question 13

A gap junction is a channel that connects adjacent cells.From substances listed,which one cannot pass through a gap junction?

A)ions that can regulate heartbeat
B)amino acids
C)nucleotides
D)ribosomes

Question 14

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.

Question 15

Of the following,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

Question 16

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

Question 17

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

Question 18

All of the following proteins may be found in the extracellular matrix of animal cells except _____.

A)collagen
B)fibronectin
C)actin
D)fibrillin

Question 19

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 hormone entering the cytoplasm
B)be from the same cell type as the organ that produced the hormone
C)experiencing an imbalance that disrupts its normal function
D)have receptors that recognize and bind the hormone molecule

Question 20

One characteristic of life and living systems is that they are able to adapt.Toward this end,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

Question 21

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

Question 22

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

Question 23

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

Question 24

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

Question 25

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.

Question 26

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 between the outside of the cell and the inside.
C)The signal is amplified,such than even a single molecule evokes a large response.
D)The signal triggers a sequence of phosphorylation events inside the cell.

Question 27

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