Question 1

Integrins are integral membrane proteins.They are often attached to

Accepted Answer

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

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?

Accepted Answer

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. 
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. C

Question 3

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

Accepted Answer

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

Question 4

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?

Accepted Answer

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. 
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 5

Plasmodesmata are cell-cell junctions that can be found between

Accepted Answer

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

Question 6

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?

Accepted Answer

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. 
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 7

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?

Accepted Answer

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 
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 8

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

Accepted Answer

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. 
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 9

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

Accepted Answer

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

Question 10

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

Accepted Answer

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. 
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 11

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

Accepted Answer

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. 
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 12

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

Accepted Answer

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

Question 13

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

Accepted Answer

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. 
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 14

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

Accepted Answer

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. 
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 15

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

Accepted Answer

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

Question 16

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.

Accepted Answer

A) 1,2,3,4,5 
B) 3,1,2,5,4 
C) 3,1,5,2,4 
D) 1,3,4,2,5 
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 17

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?

Accepted Answer

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

Question 18

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

Accepted Answer

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. 
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 19

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

Accepted Answer

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. 
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 20

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?

Accepted Answer

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 
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

Exam 8: Cell-Cell Interactions

Integrins are integral membrane proteins.They are often attached to

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

Plasmodesmata are cell-cell junctions that can be found between

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?

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?

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

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

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

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

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

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

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

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

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

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?

Biology and the Tree of Life

Water and Carbon: the Chemical Basis of Life

Protein Structure and Function

Nucleic Acids and the Rna World

An Introduction to Carbohydrates

Lipids, membranes, and the First Cells

Inside the Cell

Cellular Respiration and Fermentation

Photosynthesis

The Cell Cycle

Meiosis

Mendel and the Gene

Dna and the Gene: Synthesis and Repair

How Genes Work

Transcription, RNA Processing, and Translation

Control of Gene Expression in Bacteria

Control of Gene Expression in Eukaryotes

Analyzing and Engineering Genes

Genomics

Principles of Development

An Introduction to Animal Development

An Introduction to Plant Development

Evolution by Natural Selection

Evolutionary Processes

Speciation

Phylogenies and the History of Life

Bacteria and Archaea

Protists

Green Algae and Land Plants

Fungi

An Introduction to Animals

Protostome Animals

Deuterostome Animals

Viruses

Plant Form and Function

Water and Sugar Transport in Plants

Plant Nutrition

Plant Sensory Systems, signals, and Responses

Plant Reproduction

Animal Form and Function

Water and Electrolyte Balance in Animals

Animal Nutrition

Gas Exchange and Circulation

Electrical Signals in Animals

Animal Sensory Systems and Movement

Chemical Signals in Animals

Animal Reproduction

The Immune System in Animals

An Introduction to Ecology

Behavioural Ecology

Population Ecology

Community Ecology

Ecosystems

Biodiversity and Conservation Biology

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