Question 1

What does it mean to say that a signal is transduced?

Accepted Answer

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. 
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. B

Question 2

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

Accepted Answer

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

Question 3

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?

Accepted Answer

A)  inadequate insulin production 
B)  defective receptors 
C)  defective second messenger 
D)  overproduction of glucagon 
A)  inadequate insulin production 
B)  defective receptors 
C)  defective second messenger 
D)  overproduction of glucagon B

Question 4

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 ________.

Accepted Answer

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 
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 5

Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because ________.

Accepted Answer

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 
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

Question 6

Which of the following statements is FALSE?

Accepted Answer

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. 
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 7

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 ________.

Accepted Answer

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 
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

Question 8

Where would you expect to find tight junctions?

Accepted Answer

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 
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 9

What do the cell walls of plants and the extracellular matrix of animal cells have in common?

Accepted Answer

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. 
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.

Question 10

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 ________.

Accepted Answer

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 
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

Question 11

A cell with membrane-bound proteins that selectively bind a specific hormone is called that hormone's ________.

Accepted Answer

A)  secretory cell 
B)  plasma cell 
C)  endocrine cell 
D)  target cell 
E)  regulatory cell 
A)  secretory cell 
B)  plasma cell 
C)  endocrine cell 
D)  target cell 
E)  regulatory cell

Question 12

All of the following proteins may be found in the extracellular matrix of animal cells EXCEPT ________.

Accepted Answer

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

Question 13

Different body cells can respond differently to the same peptide hormones because ________.

Accepted Answer

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 
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

Question 14

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 ________.

Accepted Answer

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 
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

Question 15

Protein kinase is an enzyme that ________.

Accepted Answer

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 
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 16

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 ________.

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 17

Osteocytes are bone cells. Collagen fibers and calcium salts are found in abundance between and among the osteocytes. The collagen and calcium salts are ________.

Accepted Answer

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 
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

Question 18

Scaffolding proteins are ________.

Accepted Answer

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 
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

Question 19

Which of the following is characteristic of a steroid hormone action?

Accepted Answer

A)  protein phosphorylation 
B)  cell-surface receptor binding 
C)  internal receptor binding 
D)  second messenger activation 
A)  protein phosphorylation 
B)  cell-surface receptor binding 
C)  internal receptor binding 
D)  second messenger activation

Question 20

In signal transduction, phosphatases ________.

Accepted Answer

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 
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

Exam 11: Cellcell Interactions

What does it mean to say that a signal is transduced?

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

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 ________.

Lipid-soluble signaling molecules, such as testosterone, cross the membranes of all cells but affect only target cells because ________.

Which of the following statements is FALSE?

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 ________.

Where would you expect to find tight junctions?

What do the cell walls of plants and the extracellular matrix of animal cells have in common?

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 cell with membrane-bound proteins that selectively bind a specific hormone is called that hormone's ________.

All of the following proteins may be found in the extracellular matrix of animal cells EXCEPT ________.

Different body cells can respond differently to the same peptide hormones because ________.

Protein kinase is an enzyme that ________.

Osteocytes are bone cells. Collagen fibers and calcium salts are found in abundance between and among the osteocytes. The collagen and calcium salts are ________.

Scaffolding proteins are ________.

Which of the following is characteristic of a steroid hormone action?

In signal transduction, phosphatases ________.

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

Ecosystems and Global Ecology

Lipids, Membranes, and the First Cells

Inside the Cell

Energy and Enzymes: an Introduction to Metabolism

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

The Molecular Revolution: Biotechnology and Beyond

Genes, Development, and Evolution

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 and Development

Animal Form and Function

Water and Electrolyte Balance in Animals

Animal Nutrition

Gas Exchange and Circulation

Animal Nervous Systems

Animal Sensory Systems

Animal Movement

Chemical Signals in Animals

Animal Reproduction and Development

The Immune System in Animals

An Introduction to Ecology

Behavioral Ecology

Population Ecology

Community Ecology

Biodiversity and Conservation Biology

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