apbio unit 4 collegeboard mcq questions
and answers with solutions
An antigen can induce an immune response in a host organism. Antigens are targeted by
antibodies that are produced by the organism’s immune system in response to contact with the
antigen. Antibodies are specific to antigens. Many different cell types are involved in immune
responses.
Which of the following best explains the role of cell-to-cell communication during a response to
an invasion of antigens?
a.Chemicals that are secreted from antigen-presenting cells then activate helper T cells.
b.A macrophage cell engulfs a pathogen in the blood.
c.Antigens attaching to receptors on memory B cells stimulate the memory B cells to become
plasma cells.
d.Antigen-presenting cells engulf antigens at the first exposure.
a.Chemicals that are secreted from antigen-presenting cells then activate helper T cells.
Adjacent plant cells have narrow channels called plasmodesmata that pass through the cell
walls of the connected cells and allow a cytoplasmic connection between the cells.
Which of the following statements best explains a primary function of plasmodesmata?
a. They allow the movement of molecules from one cell to another, enabling communication
between cells.
b. They prevent the cell membrane from pulling away from the cell wall during periods of
drought.
c.They eliminate the need to produce signaling molecules and eliminate the need for cells to
have receptors for signaling molecules.
d.They increase the surface area available for attachment of ribosomes and thus increase
protein synthesis.
a. They allow the movement of molecules from one cell to another, enabling communication
between cells.
,A hydrophilic peptide hormone is produced in the anterior pituitary gland located at the base of
the brain. The hormone targets specific cells in many parts of the body.
Which of the following best explains a possible mechanism that would enable the hormone to
efficiently reach all of the target cells in the body?
A.The hormone interacts with the nerves at the base of the brain and directs signals to the
target cells through the nervous system.
B.The hormone diffuses into target cells adjacent to the anterior pituitary gland, where the
hormone is degraded.
C.The hormone is released into the bloodstream where it can be transported to all cells with the
correct receptors.
D.The hormone moves through cytoplasmic connections between cells until it has reached all
cells with the correct intracellular binding sites.
C.The hormone is released into the bloodstream where it can be transported to all cells with the
correct receptors.
G proteins are a family of receptor proteins that are involved in transmitting signals from
outside a cell to inside a cell. When a signaling molecule binds to a G protein, the G protein is
activated. The G protein then activates an enzyme that produces a second messenger called
cAMP.
Which of the following describes a critical role of cAMP during the transduction stage of a G
protein signal transduction pathway?
A. cAMP carries the signal to the nucleus of the cell and results in new sequences of nucleotides
being added to the cell’s DNA.
B. cAMP binds the extracellular signal molecule and carries it to the intracellular target specified
by the signal.
C. cAMP modifies a specific monomer so that it can be added to an elongating structural
macromolecule.
D. cAMP results in the activation of an enzyme that amplifies the signal by acting on many
substrate molecules.
D. cAMP results in the activation of an enzyme that amplifies the signal by acting on many
substrate molecules.
, Metformin is a drug used to treat type 2 diabetes by decreasing glucose production in the liver.
AMP-activated protein kinase (AMPK) is a major cellular regulator of glucose metabolism.
Metformin activates AMPK in liver cells but cannot cross the plasma membrane.
Which of the following best describes the component that metformin represents in a signal
transduction pathway that regulates glucose production in the liver?
A. It is a secondary messenger that amplifies a signal through a cascade reaction.
B. It is a ligand that activates the signal transduction pathway of the activation of AMPK.
C. It is an allosteric regulator that binds to a crucial section of the DNA that makes the enzymes
needed for glucose uptake.
D. It is a competitive inhibitor that binds to glucose and prevents it from entering the cell.
B. It is a ligand that activates the signal transduction pathway of the activation of AMPK.
Which of the following steps in a signaling pathway typically occurs first once a chemical
messenger reaches a target cell?
A. Specific genes are activated.
B. A second messenger molecule is produced.
C. A ligand binds to a receptor.
D. Specific proteins are synthesized.
C. A ligand binds to a receptor.
We have an expert-written solution to this problem!
Which of the following justifies the claim that differences in components of cell signaling
pathways explain the different responses to epinephrine?
A. Cell signaling depends on the ability to detect a signal molecule. Not all cells have receptors
for epinephrine. Only cells with such receptors are capable of responding.
B. Cell signaling depends on the transduction of a received signal by the nervous system. Not all
cells are close enough to a synapse to receive the signal and respond.
and answers with solutions
An antigen can induce an immune response in a host organism. Antigens are targeted by
antibodies that are produced by the organism’s immune system in response to contact with the
antigen. Antibodies are specific to antigens. Many different cell types are involved in immune
responses.
Which of the following best explains the role of cell-to-cell communication during a response to
an invasion of antigens?
a.Chemicals that are secreted from antigen-presenting cells then activate helper T cells.
b.A macrophage cell engulfs a pathogen in the blood.
c.Antigens attaching to receptors on memory B cells stimulate the memory B cells to become
plasma cells.
d.Antigen-presenting cells engulf antigens at the first exposure.
a.Chemicals that are secreted from antigen-presenting cells then activate helper T cells.
Adjacent plant cells have narrow channels called plasmodesmata that pass through the cell
walls of the connected cells and allow a cytoplasmic connection between the cells.
Which of the following statements best explains a primary function of plasmodesmata?
a. They allow the movement of molecules from one cell to another, enabling communication
between cells.
b. They prevent the cell membrane from pulling away from the cell wall during periods of
drought.
c.They eliminate the need to produce signaling molecules and eliminate the need for cells to
have receptors for signaling molecules.
d.They increase the surface area available for attachment of ribosomes and thus increase
protein synthesis.
a. They allow the movement of molecules from one cell to another, enabling communication
between cells.
,A hydrophilic peptide hormone is produced in the anterior pituitary gland located at the base of
the brain. The hormone targets specific cells in many parts of the body.
Which of the following best explains a possible mechanism that would enable the hormone to
efficiently reach all of the target cells in the body?
A.The hormone interacts with the nerves at the base of the brain and directs signals to the
target cells through the nervous system.
B.The hormone diffuses into target cells adjacent to the anterior pituitary gland, where the
hormone is degraded.
C.The hormone is released into the bloodstream where it can be transported to all cells with the
correct receptors.
D.The hormone moves through cytoplasmic connections between cells until it has reached all
cells with the correct intracellular binding sites.
C.The hormone is released into the bloodstream where it can be transported to all cells with the
correct receptors.
G proteins are a family of receptor proteins that are involved in transmitting signals from
outside a cell to inside a cell. When a signaling molecule binds to a G protein, the G protein is
activated. The G protein then activates an enzyme that produces a second messenger called
cAMP.
Which of the following describes a critical role of cAMP during the transduction stage of a G
protein signal transduction pathway?
A. cAMP carries the signal to the nucleus of the cell and results in new sequences of nucleotides
being added to the cell’s DNA.
B. cAMP binds the extracellular signal molecule and carries it to the intracellular target specified
by the signal.
C. cAMP modifies a specific monomer so that it can be added to an elongating structural
macromolecule.
D. cAMP results in the activation of an enzyme that amplifies the signal by acting on many
substrate molecules.
D. cAMP results in the activation of an enzyme that amplifies the signal by acting on many
substrate molecules.
, Metformin is a drug used to treat type 2 diabetes by decreasing glucose production in the liver.
AMP-activated protein kinase (AMPK) is a major cellular regulator of glucose metabolism.
Metformin activates AMPK in liver cells but cannot cross the plasma membrane.
Which of the following best describes the component that metformin represents in a signal
transduction pathway that regulates glucose production in the liver?
A. It is a secondary messenger that amplifies a signal through a cascade reaction.
B. It is a ligand that activates the signal transduction pathway of the activation of AMPK.
C. It is an allosteric regulator that binds to a crucial section of the DNA that makes the enzymes
needed for glucose uptake.
D. It is a competitive inhibitor that binds to glucose and prevents it from entering the cell.
B. It is a ligand that activates the signal transduction pathway of the activation of AMPK.
Which of the following steps in a signaling pathway typically occurs first once a chemical
messenger reaches a target cell?
A. Specific genes are activated.
B. A second messenger molecule is produced.
C. A ligand binds to a receptor.
D. Specific proteins are synthesized.
C. A ligand binds to a receptor.
We have an expert-written solution to this problem!
Which of the following justifies the claim that differences in components of cell signaling
pathways explain the different responses to epinephrine?
A. Cell signaling depends on the ability to detect a signal molecule. Not all cells have receptors
for epinephrine. Only cells with such receptors are capable of responding.
B. Cell signaling depends on the transduction of a received signal by the nervous system. Not all
cells are close enough to a synapse to receive the signal and respond.
