Deck 8: Cell-Cell Interactions

Question 1

All of the following can be proteins found in the extracellular matrix of animal cells except

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

Answer 1

C

Question 2

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.The cells of the sponges dissociated.Wilson 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)There are enzymes involved in the assembly of the sponge organism,and the two different species had two different enzymes functioning in reassembly.
B)The disassembled cells formed bonds with any of the cells in the mixture.However,once the organism was completely assembled,an enzyme changed all cells to the same pigment.
C)The molecules responsible for cell-cell adhesion were different in the two different species of sponge.
D)One cell functions as the nucleus for each organism,attracting only cells of the same pigment.

Answer 2

C

Question 3

A gap junction is a channel that connects adjacent cells.What kinds of substances can pass through a gap junction?

A)ions that can regulate heartbeat
B)raw materials for protein synthesis
C)subunits of nucleic acids
D)all of these substances

Answer 3

D

Question 4

What is a major difference in the extracellular matrix (ECM)between plant and animal cells?

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 largely protein based.
C)Plant and animal ECMs are quite similar in structure and function.
D)Plant ECM components are released extracellularly by the Golgi stacks,whereas lysosomes function in this capacity in animal cells.

Question 5

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)Golgi apparatus.
D)intracellular electrical currents.

Question 6

Plant cells are typically exposed to a hypotonic environment.Therefore,you would expect

A)a microscopic space between the plasma membrane and the cell wall.
B)occasional contact between the plasma membrane and the cell wall.
C)the plasma membrane to exert outward force on the cell wall.
D)no communication between the cell wall and the cell membrane.

Question 7

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

A)adhesion of adjacent cells
B)to keep the cell walls of adjacent cells from dehydrating
C)to maintain the plant circulatory system
D)for gas and nutrient exchange between adjacent cells

Question 8

Cancer cells can survive without being attached to other cells or to a substratum.This feature contributes to their ability to

A)grow rapidly.
B)contribute to an increased blood supply.
C)attach to healthy body cells.
D)spread to other parts of the body.

Question 9

Streptococcus mutans is a common oral bacterium that forms dental plaque,which,if not removed,often results in tooth decay.What component of S.mutans is responsible for the formation of dental plaque?

A)digestive enzymes released by the organism
B)waste products excreted by the organism
C)extracellular matrix materials of the organism
D)proteins found in the cell wall of the organism

Question 10

For a tissue or an organ to function as a unit,

A)there must be a signal molecule to which all cells in the tissue or organ can respond.
B)there must be cell-cell communication among the cells within a tissue or organ.
C)the cells within the tissue or organ must be able to depolarize to create cell signals.
D)the tissue or organ must be composed of all of the same type of cells.

Question 11

If cancer cells detach from neighboring cells,what is a likely outcome of this event?

A)loss of desmosomes
B)loss of surface hormone receptors
C)loss of G-proteins
D)loss of second messenger molecules

Question 12

Anorganic bone matrix (ABM)is a material commonly used in bone grafts.Scientists compared ABM with ABM-peptide.The peptide that was bound to ABM was 15 amino acids long,derived from the extracellular matrix molecule,collagen.The researchers found that anchorage-dependent cells were more likely to adhere to and grow on the ABM-peptide than on ABM alone.What conclusion might be drawn from this research?

A)Anorganic bone matrix is not an effective material for use in bone grafts.
B)Attaching the peptide to ABM enhances the likelihood of success of the bone graft.
C)The immune system is more likely to reject the ABM-peptide than the ABM.
D)The peptide would have no effect on the success of the bone graft.

Question 13

Why are receptors for steroid hormones located inside the cell rather than on the membrane surface?

A)The receptors can be stimulated to exit to the membrane surface under conditions in which a cell needs to be regulated by the steroid hormone.
B)Steroid hormones are lipid soluble and thus can readily diffuse through the lipid bilayer that makes up the cell membrane.
C)The receptors are repressible,meaning they are actively altering cell function unless the target hormone is present.
D)Cells with steroid hormone receptors inside the cell are not able to respond to steroid hormones.

Question 14

Scientists have found that extracellular matrix components may induce specific gene expression in embryonic tissues such as the liver and testis.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 15

Tight junctions are cell-cell junctions found between adjacent cells of the epithelium that lines the small intestine.What is the function of these cellular junctions?

A)to attach epithelial cells to a basement membrane
B)to seal the epithelium and prevent movement of substances between cells
C)to recognize pathogenic organisms present in the lumen of the small intestine
D)to release digestive enzymes into the intestinal lumen

Question 16

Transport of materials across a cell membrane

A)is selective.
B)always takes place from a region of greater concentration to a region of lesser concentration.
C)is an energy-requiring process regardless of the chemical properties of the substance being transported.
D)requires a carrier molecule in the membrane regardless of the chemical properties of the substance being transported.

Question 17

Put the following events in the process of signal-transduction in order: 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)3,1,2,5,4
C)3,1,5,2,4
D)1,3,4,2,5

Question 18

Which of the following statements is false?

A)Growing plant cells release expansins,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 and quits growing with the formation of the tertiary cell wall.
D)Pectin is a component of the cell wall that attracts and holds water.

Question 19

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 and are not associated with the osteocytes.

Question 20

Integrins are integral membrane proteins.They are often attached to

A)membranes of intracellular organelles.
B)cytoskeletal proteins and molecules of the extracellular matrix.
C)pathogens.
D)glycogen molecules and other cellular inclusions.

Question 21

Intercalated disks are cell-cell junctions found between cardiac muscle cells.A feature of intercalated disks is a large number of gap junctions.This means

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 and small ions can readily pass from one cardiac muscle cell to the next.
C)the plasma membrane encompasses multiple cardiac muscle cells.
D)RNA from one cardiac muscle cell can be transported into an adjacent cell through the gap junction.

Question 22

Which of the following hormones stimulates fruit ripening?

A)insulin
B)ethylene
C)auxin
D)systemin

Question 23

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)have the same genetic makeup.
B)be from the same cell type as the organ that produced the hormone.
C)be experiencing a disruption in homeostasis.
D)have receptors that recognize and bind the hormone molecule.

Question 24

A kinase is an enzyme that

A)functions as a second messenger molecule.
B)serves as a receptor for various signal molecules.
C)adds a phosphate group to target molecules.
D)produces second messenger molecules.

Question 25

A G-protein receptor with GTP bound to it

A)is in its active state.
B)autophosphorylates its tyrosine residues.
C)will use cGMP as a second messenger.
D)directly affects gene expression.

Question 26

Pemphigus vulgaris is an autoimmune disorder in which antibodies are produced against the cadherins of desmosomes.The blistering seen in these individuals is probably a result of

A)a decrease in flexibility of the cell membrane.
B)inadequate numbers of G-protein receptors.
C)inadequate production of cytoskeletal proteins.
D)loss of cell-cell adhesion.

Question 27

The fact that a single signal-receptor complex results in the activation of several second messenger molecules enables the cell signal to be

A)terminated.
B)reflected.
C)altered.
D)amplified.

Question 28

Insulin is a hormone produced by the pancreas.When insulin binds to its receptor,which of the following will occur?

A)A G-protein will change its conformation to the "on" position thereby allowing the effector to be activated.
B)The G-protein will become active when GTP is replaced by GDP.
C)A receptor tyrosine kinase will change its conformation (i.e.form a dimer)thereby allowing phosphorylation to occur.
D)A receptor tyrosine kinase will dissociate into two monomers thereby allowing phosphorylation to occur.

Question 29

Cells of capillaries that nourish the cells of the central nervous system are joined by tight junctions,whereas the capillaries to most other organs are characterized by having large openings or clefts between adjacent cells.How would the difference in cell-cell connections affect their functions?

A)Capillaries of the blood-brain barrier are more likely to rupture.
B)The blood-brain barrier is more selective regarding the types of molecules that can pass out of circulation.
C)There is more pressure on the blood passing through the central nervous system than to other organs.
D)Capillaries of the central nervous system are more tightly anchored to adjacent tissues.

Question 30

Which of the following best describes the function of gap junctions?

A)They create direct connections between the cytoplasm of adjacent animal cells thereby permitting the exchange of water,small ions,and small molecules.
B)They occur when peripheral membrane proteins from neighboring cells line up thereby permitting the exchange of water,small ions,and small molecules.
C)They are intracellular receptors,which associate with signals entering the cell,and often regulate transcriptional processes.
D)They are second messengers that activate protein kinases.The protein kinases then activate or deactivate other proteins.

Question 31

How is the formation of a biofilm beneficial for bacterial cells?

A)It protects the bacterial cells from attack by the immune system or antibiotics.
B)It helps the bacterial cells to adhere to their surroundings.
C)It allows the bacterial cells to produce second messenger molecules.
D)It provided a direct linkage between the cytoskeleton and the ECM.

Question 32

Pseudomonas aeruginosa is a bacterium that can settle on human lung cells.P.aeruginosa can secrete a signalling molecule that recruits other P.aeruginosa cells.The result of this secretion is the formation of a

A)capsule.
B)slime layer.
C)biofilm.

Question 33

Hormones function as

A)cell receptors.
B)second messengers.
C)signal molecules.
D)neurotransmitters.

Question 34

Second messengers

A)can synthesize cAMP from AMP and ADP.
B)are intracellular kinases which lead to a cellular response.
C)are intracellular non-protein signalling molecules.
D)are signalling molecules which bind directly to the G-protein coupled receptor.

Question 35

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)Muscles would be unable to contract.
B)Muscles would be unable to relax.
C)Cell receptors would no longer be able to bind regulatory hormones.
D)G-protein receptors would all be inactivated.

Question 36

Blood sugar is regulated by two pancreatic hormones,namely 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,effectively lowering blood glucose.When blood sugar decreases,glucagon is released,binds to cell receptors,and causes glucose to be released into circulation.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 the elevated blood glucose levels?

A)inadequate insulin production
B)defective receptors
C)defective second messenger
D)inability to regulate gene expression

Question 37

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 receptor-hormone 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 38

Plasmodesmata are cell-cell junctions that can be found between

A)skeletal muscle cells.
B)plant cells.
C)cells of connective tissue in animals.
D)none of the above.