BMB 252 Exam 1 Questions with Correct Answers Latest Version 2025 Graded A+
What are the major components of a signaling cascade? - Answers Extra-cellular Signal molecules bind
to receptor proteins on the plasma membrane of the cell. This triggers inter-cellular signaling proteins to
induce a change in cell behavior through effector proteins.
What is the quorum sensing? - Answers The process of bacteria responding to chemical signals secreted
by their neighbors. It can regulate aggregation, motility, biofilm formation, spore formation, sexual
conjugation, etc.
Which processes in yeast require signaling pathways? - Answers Signal to mate, pheromone. Usually
divide through mitosis however.
Give examples of molecules which can act as signals. - Answers proteins
small peptides
amino acids
Nucleotides
steroids, retinoids
Fatty acids derivatives
dissolved gases (NO, CO)
What is the difference between signaling molecules, which bind to intracellular and cell-surface
receptors? - Answers Signals can bind to cell surface receptor (hydrophilic) or diffuse through the plasma
membrane (hydrophobic) and bind inside the cell.
What are the four forms of intercellular signaling? - Answers Contact Dependent, Paracrine, Synapse,
Endocrine.
What keeps the signal localized in paracrine signaling? - Answers quickly absorbed by other cells
degrade very quickly
Immobilized in extracellular matrix
blocked by antagonist binding to receptor or signal itself
What are the differences between synaptic and endocrine signaling (speed of signal delivery,
concentrations of signal, affinity of receptors, duration of signal)? - Answers Endocrine signaling is slow
requiring blood flow to transfer signals. It also has a low concentration of signals (hormones) but a high
affinity for its receptors. Synaptic signaling is fast (Electrical impulse 100 m/sec, diffusion of
neurotransmitter over less than 100 nm) however has a high concentrations of signals
(neurotransmitters) and a low affinity for receptors.
, What determines the speed of intracellular transmission in response to a signal? - Answers The distance,
type of signal, signal strength
What happens to the cell in the absence of the signals? - Answers Apoptosis.
What kinds of cellular responses can acetylcholine stimulate? Does it always bind to the same receptor?
- Answers Muscle cells contract in response to acetylcholine (a neurotransmitter)
Heart muscle cells relax in response to acetylcholine
What are gap junctions and what kind of molecules can pass through them? Make examples of
responses where gap junctions are important. - Answers Gap junctions = non selective channels
between two adjacent cells.
Bidirectional
Allow sharing of small signaling molecules:
Calcium ions
cAMP
ionic currents at electrical synapses (involved in defensive reflexes)
Proteins are too big to be transferred
Gap junctions are important in contact dependent signaling.
What type of signaling molecule can form gradients in development? - Answers morphogen
What molecules can act as signals for intracellular receptors? - Answers Nitric oxide (NO)
Carbon monoxide (CO)
What kind of receptors can NO bind (cell-surface or intracellular)? - Answers intracellular
What is the effect of NO on blood vessels? - Answers NO dilates blood vessel. Making them wider/larger.
What does NO bind to? - Answers Guanylyl cyclase
What is the function of guanylyl cyclase, phosphodiesterase? - Answers Guanylyl cyclase when binds to
NO relaxes smooth muscle cells. (GTP to cGMP). Phosphodiesterase cleaves the phosphodiester bond to
convert cGMP to GMP.
Which of them is blocked by viagra? - Answers viagra blocks phosphodiesterase
What prevents the gases NO and CO from spreading all over the body? - Answers Gas NO lifetime is 5-10
sec
What are the major components of a signaling cascade? - Answers Extra-cellular Signal molecules bind
to receptor proteins on the plasma membrane of the cell. This triggers inter-cellular signaling proteins to
induce a change in cell behavior through effector proteins.
What is the quorum sensing? - Answers The process of bacteria responding to chemical signals secreted
by their neighbors. It can regulate aggregation, motility, biofilm formation, spore formation, sexual
conjugation, etc.
Which processes in yeast require signaling pathways? - Answers Signal to mate, pheromone. Usually
divide through mitosis however.
Give examples of molecules which can act as signals. - Answers proteins
small peptides
amino acids
Nucleotides
steroids, retinoids
Fatty acids derivatives
dissolved gases (NO, CO)
What is the difference between signaling molecules, which bind to intracellular and cell-surface
receptors? - Answers Signals can bind to cell surface receptor (hydrophilic) or diffuse through the plasma
membrane (hydrophobic) and bind inside the cell.
What are the four forms of intercellular signaling? - Answers Contact Dependent, Paracrine, Synapse,
Endocrine.
What keeps the signal localized in paracrine signaling? - Answers quickly absorbed by other cells
degrade very quickly
Immobilized in extracellular matrix
blocked by antagonist binding to receptor or signal itself
What are the differences between synaptic and endocrine signaling (speed of signal delivery,
concentrations of signal, affinity of receptors, duration of signal)? - Answers Endocrine signaling is slow
requiring blood flow to transfer signals. It also has a low concentration of signals (hormones) but a high
affinity for its receptors. Synaptic signaling is fast (Electrical impulse 100 m/sec, diffusion of
neurotransmitter over less than 100 nm) however has a high concentrations of signals
(neurotransmitters) and a low affinity for receptors.
, What determines the speed of intracellular transmission in response to a signal? - Answers The distance,
type of signal, signal strength
What happens to the cell in the absence of the signals? - Answers Apoptosis.
What kinds of cellular responses can acetylcholine stimulate? Does it always bind to the same receptor?
- Answers Muscle cells contract in response to acetylcholine (a neurotransmitter)
Heart muscle cells relax in response to acetylcholine
What are gap junctions and what kind of molecules can pass through them? Make examples of
responses where gap junctions are important. - Answers Gap junctions = non selective channels
between two adjacent cells.
Bidirectional
Allow sharing of small signaling molecules:
Calcium ions
cAMP
ionic currents at electrical synapses (involved in defensive reflexes)
Proteins are too big to be transferred
Gap junctions are important in contact dependent signaling.
What type of signaling molecule can form gradients in development? - Answers morphogen
What molecules can act as signals for intracellular receptors? - Answers Nitric oxide (NO)
Carbon monoxide (CO)
What kind of receptors can NO bind (cell-surface or intracellular)? - Answers intracellular
What is the effect of NO on blood vessels? - Answers NO dilates blood vessel. Making them wider/larger.
What does NO bind to? - Answers Guanylyl cyclase
What is the function of guanylyl cyclase, phosphodiesterase? - Answers Guanylyl cyclase when binds to
NO relaxes smooth muscle cells. (GTP to cGMP). Phosphodiesterase cleaves the phosphodiester bond to
convert cGMP to GMP.
Which of them is blocked by viagra? - Answers viagra blocks phosphodiesterase
What prevents the gases NO and CO from spreading all over the body? - Answers Gas NO lifetime is 5-10
sec
