Unit 4 MRQ 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 describes the role of cell-to-cell communication during a
response to an invasion of antigens? - ANSWER 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 describes a primary function of plasmodesmata? - ANSWER 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? - ANSWER 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? - ANSWER 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. 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? - ANSWER 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? - ANSWER C: A ligand binds to a receptor
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? - ANSWER 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.
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. Which
statement provides the evidence to justify the claim that signal transduction may result in an
altered phenotype? - ANSWER B: If the SRY gene is absent or nonfunctional, the embryo will
exhibit female sexual development.
Researchers have discovered details about apoptosis (programmed cell death) by studying
embryologic development of a nematode worm, Caenorhabditis elegans. Apoptosis is a normal
developmental process in C. elegans. They found several genes involved in apoptosis, including
ced−9 and ced−3 . The ced−3 gene was found to promote cell death, and ced−9 to inhibit it. The
ced−9 gene serves as a regulator that prevents apoptosis in the absence of a signal promoting
apoptosis. Which of the following statements best justifies the claim that changes in the
expression of ced−9 in C. elegans can affect regulation of apoptosis in the cell? - ANSWER A: An
experiment showed that a mutation in the ced−9 gene led to excessive cell death in C. elegans.
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 describes the role of cell-to-cell communication during a
response to an invasion of antigens? - ANSWER 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 describes a primary function of plasmodesmata? - ANSWER 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? - ANSWER 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? - ANSWER 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. 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? - ANSWER 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? - ANSWER C: A ligand binds to a receptor
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? - ANSWER 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.
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. Which
statement provides the evidence to justify the claim that signal transduction may result in an
altered phenotype? - ANSWER B: If the SRY gene is absent or nonfunctional, the embryo will
exhibit female sexual development.
Researchers have discovered details about apoptosis (programmed cell death) by studying
embryologic development of a nematode worm, Caenorhabditis elegans. Apoptosis is a normal
developmental process in C. elegans. They found several genes involved in apoptosis, including
ced−9 and ced−3 . The ced−3 gene was found to promote cell death, and ced−9 to inhibit it. The
ced−9 gene serves as a regulator that prevents apoptosis in the absence of a signal promoting
apoptosis. Which of the following statements best justifies the claim that changes in the
expression of ced−9 in C. elegans can affect regulation of apoptosis in the cell? - ANSWER A: An
experiment showed that a mutation in the ced−9 gene led to excessive cell death in C. elegans.
