AP BIO UNIT 4 EXAM 2025 QUESTIONS
AND ANSWERS
Chemicals that are secreted from antigen-presenting cells then activate helper T cells. -
ANS 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 describes the role of cell-to-cell communication during a response
to an invasion of antigens?
They allow the movement of molecules from one cell to another, enabling communication
between cells. - ANS 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 describes a primary function of plasmodesmata?
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,The hormone is released into the bloodstream where it can be transported to all cells with the
correct receptors. - ANS 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?
cAMP results in the activation of an enzyme that amplifies the signal by acting on many
substrate molecules. - ANS 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?
it is a ligand that activates the signal transduction pathway of the activation of AMPK. -
ANS 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.
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, By blocking AMPK with an inhibitor, researchers found that AMPK activation is required for
metformin to produce an inhibitory effect on glucose production by liver cells.
Which of the following best describes the component that metformin represents in a signal
transduction pathway that regulates glucose production in the liver?
A ligand binds to a receptor. - ANS Which of the following steps in a signaling pathway
typically occurs first once a chemical messenger reaches a target cell?
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. - ANS During a fight-
or-flight response, epinephrine is released into the body's circulatory system and transported
throughout the body. Some cells exhibit a response to the epinephrine while other cells do not.
Which of the following justifies the claim that differences in components of cell signaling
pathways explain the different responses to epinephrine?
If the SRY gene is absent or nonfunctional, the embryo will exhibit female sexual development. -
ANS Signal transduction may result in changes in gene expression and cell function, which
may alter phenotype in an embryo. An example is the expression of the SRY gene, which
triggers the male sexual development pathway in mammals. This gene is found on the Y
chromosome.
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AND ANSWERS
Chemicals that are secreted from antigen-presenting cells then activate helper T cells. -
ANS 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 describes the role of cell-to-cell communication during a response
to an invasion of antigens?
They allow the movement of molecules from one cell to another, enabling communication
between cells. - ANS 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 describes a primary function of plasmodesmata?
1 Copyright ©2025 FYNDLAY ALL RIGHTS RESERVED.
,The hormone is released into the bloodstream where it can be transported to all cells with the
correct receptors. - ANS 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?
cAMP results in the activation of an enzyme that amplifies the signal by acting on many
substrate molecules. - ANS 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?
it is a ligand that activates the signal transduction pathway of the activation of AMPK. -
ANS 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.
2 Copyright ©2025 FYNDLAY ALL RIGHTS RESERVED.
, By blocking AMPK with an inhibitor, researchers found that AMPK activation is required for
metformin to produce an inhibitory effect on glucose production by liver cells.
Which of the following best describes the component that metformin represents in a signal
transduction pathway that regulates glucose production in the liver?
A ligand binds to a receptor. - ANS Which of the following steps in a signaling pathway
typically occurs first once a chemical messenger reaches a target cell?
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. - ANS During a fight-
or-flight response, epinephrine is released into the body's circulatory system and transported
throughout the body. Some cells exhibit a response to the epinephrine while other cells do not.
Which of the following justifies the claim that differences in components of cell signaling
pathways explain the different responses to epinephrine?
If the SRY gene is absent or nonfunctional, the embryo will exhibit female sexual development. -
ANS Signal transduction may result in changes in gene expression and cell function, which
may alter phenotype in an embryo. An example is the expression of the SRY gene, which
triggers the male sexual development pathway in mammals. This gene is found on the Y
chromosome.
3 Copyright ©2025 FYNDLAY ALL RIGHTS RESERVED.
