CCBC BIO 110 Exam 2 Questions with Verified Answers
2026/2027 New Update
A ion channel linked receptor - answer -acts as a gate when the receptor changes shape. When
a signal molecule binds as a ligand to the receptor, the gate allows specific ions, such as Na+ or
Ca2+, through a channel in the receptor( Example: acetylcholine effects muscle contraction).
- G-protein-linked (coupled) receptor (GPCRs) - answer -are the largest family of cell-surface
receptors. A GPCR is a plasma membrane receptor that works with the help of a G protein. The
G protein acts as an on/off switch: If GDP is bound to the G protein, the G protein is inactive
(Example: GPCRs role in sense of smell, vision, etc).
Enzyme-Linked (tyrosine kinase) Receptors (RTKs) - answer -are membrane receptor enzymes
that attach phosphates to amino acid tyrosine. A receptor tyrosine kinase can trigger multiple
signal transduction pathways at once. Abnormal functioning of RTKs is associated with many
types of cancers.
Intracellular receptor proteins - answer -are found in the cytosol or nucleus of target cells. Small
or hydrophobic chemical messengers can readily cross the membrane and activate receptors.
Examples of hydrophobic messengers are the steroid and thyroid hormones of animals. An
activated hormone-receptor complex can act as a transcription factor, turning on specific genes.
Signal transduction: - answer -a cell converts an extracellular signal into an intracellular signal,
and relays the signal
1|Page
,(Signal transduction continued) - answer -- Signal transduction usually involves multiple steps
and typically involves a chain of molecules that relay information. Multistep pathways can
amplify a signal: A few molecules can produce a large cellular response. They provide more
opportunities for coordination and regulation of the cellular response
(Signal transduction continued too) - answer -The molecules that relay a signal from receptor to
response are mostly proteins. Like falling dominoes, the receptor activates another protein,
which activates another, and so on, until the protein producing the response is activated. At
each step, the signal is transduced into a different form, usually a shape change in a protein.
-In many pathways, the signal is transmitted by a cascade of protein phosphorylations. - answer
-Protein kinases transfer phosphates from ATP to protein, a process called phosphorylation.
Protein phosphatases remove the phosphates from proteins, a process called
dephosphorylation. This phosphorylation and dephosphorylation system
acts as a molecular switch, turning activities on and off or up or down, as required.
.
G proteins - answer -are activated by binding to GTP, and deactivated by GTP hydrolysis to GDP.
The extracellular signal molecule (ligand) - answer -that binds to the receptor is a pathway's
"first messenger". Second messengers are small, nonprotein, water-soluble molecules or ions
that spread throughout a cell by diffusion. Second messengers are produced in pathways
initiated by GPCRs and RTKs. Cyclic AMP (cAMP), inositol thiphosphate (IP3), diacylglycerol
(DAG) and calcium ions are common second messengers. Second messengers greatly amplify
the original signal.
2|Page
, Response: a signal is converted into a response that alters some cell process. - answer --
Ultimately, a signal transduction pathway leads to regulation of one or more cellular
activities. The response may occur in the cytoplasm or in the nucleus.
- Many signaling pathways regulate the synthesis of enzymes or other proteins, usually by
turning genes on or off in the nucleus. The final activated molecule in the signaling pathway
may function as a transcription factor.
- Other pathways regulate the activity of enzymes rather than their synthesis.
- Signaling pathways can also affect the overall behavior of a cell, for example, changes in
cell shape.
Fine-tuning of the response:
There are four aspects of fine-tuning to consider - answer -• Amplifying the signal (and thus the
response). Enzyme cascades amplify the cell's response. At each step, the number of activated
products is much greater than in the preceding step.
• Specificity of the response. Different kinds of cells have different collections of proteins. These
different proteins allow cells to detect and respond to different signals. Even the same signal
can have different effects in cells with different proteins and pathways. Pathway branching and
"cross-talk" further help the cell coordinate incoming signals.
• Overall efficiency of response, enhanced by scaffolding proteins. Scaffolding proteins are large
relay proteins to which other relay proteins are attached.
They can increase the signal transduction efficiency by grouping together
different proteins involved in the same pathway.
• Termination of the signal. Termination of signal: Inactivation mechanisms
are an essential aspect of cell signaling. If ligand concentration falls, fewer receptors will be
bound. Unbound receptors revert to an inactive state
3|Page
2026/2027 New Update
A ion channel linked receptor - answer -acts as a gate when the receptor changes shape. When
a signal molecule binds as a ligand to the receptor, the gate allows specific ions, such as Na+ or
Ca2+, through a channel in the receptor( Example: acetylcholine effects muscle contraction).
- G-protein-linked (coupled) receptor (GPCRs) - answer -are the largest family of cell-surface
receptors. A GPCR is a plasma membrane receptor that works with the help of a G protein. The
G protein acts as an on/off switch: If GDP is bound to the G protein, the G protein is inactive
(Example: GPCRs role in sense of smell, vision, etc).
Enzyme-Linked (tyrosine kinase) Receptors (RTKs) - answer -are membrane receptor enzymes
that attach phosphates to amino acid tyrosine. A receptor tyrosine kinase can trigger multiple
signal transduction pathways at once. Abnormal functioning of RTKs is associated with many
types of cancers.
Intracellular receptor proteins - answer -are found in the cytosol or nucleus of target cells. Small
or hydrophobic chemical messengers can readily cross the membrane and activate receptors.
Examples of hydrophobic messengers are the steroid and thyroid hormones of animals. An
activated hormone-receptor complex can act as a transcription factor, turning on specific genes.
Signal transduction: - answer -a cell converts an extracellular signal into an intracellular signal,
and relays the signal
1|Page
,(Signal transduction continued) - answer -- Signal transduction usually involves multiple steps
and typically involves a chain of molecules that relay information. Multistep pathways can
amplify a signal: A few molecules can produce a large cellular response. They provide more
opportunities for coordination and regulation of the cellular response
(Signal transduction continued too) - answer -The molecules that relay a signal from receptor to
response are mostly proteins. Like falling dominoes, the receptor activates another protein,
which activates another, and so on, until the protein producing the response is activated. At
each step, the signal is transduced into a different form, usually a shape change in a protein.
-In many pathways, the signal is transmitted by a cascade of protein phosphorylations. - answer
-Protein kinases transfer phosphates from ATP to protein, a process called phosphorylation.
Protein phosphatases remove the phosphates from proteins, a process called
dephosphorylation. This phosphorylation and dephosphorylation system
acts as a molecular switch, turning activities on and off or up or down, as required.
.
G proteins - answer -are activated by binding to GTP, and deactivated by GTP hydrolysis to GDP.
The extracellular signal molecule (ligand) - answer -that binds to the receptor is a pathway's
"first messenger". Second messengers are small, nonprotein, water-soluble molecules or ions
that spread throughout a cell by diffusion. Second messengers are produced in pathways
initiated by GPCRs and RTKs. Cyclic AMP (cAMP), inositol thiphosphate (IP3), diacylglycerol
(DAG) and calcium ions are common second messengers. Second messengers greatly amplify
the original signal.
2|Page
, Response: a signal is converted into a response that alters some cell process. - answer --
Ultimately, a signal transduction pathway leads to regulation of one or more cellular
activities. The response may occur in the cytoplasm or in the nucleus.
- Many signaling pathways regulate the synthesis of enzymes or other proteins, usually by
turning genes on or off in the nucleus. The final activated molecule in the signaling pathway
may function as a transcription factor.
- Other pathways regulate the activity of enzymes rather than their synthesis.
- Signaling pathways can also affect the overall behavior of a cell, for example, changes in
cell shape.
Fine-tuning of the response:
There are four aspects of fine-tuning to consider - answer -• Amplifying the signal (and thus the
response). Enzyme cascades amplify the cell's response. At each step, the number of activated
products is much greater than in the preceding step.
• Specificity of the response. Different kinds of cells have different collections of proteins. These
different proteins allow cells to detect and respond to different signals. Even the same signal
can have different effects in cells with different proteins and pathways. Pathway branching and
"cross-talk" further help the cell coordinate incoming signals.
• Overall efficiency of response, enhanced by scaffolding proteins. Scaffolding proteins are large
relay proteins to which other relay proteins are attached.
They can increase the signal transduction efficiency by grouping together
different proteins involved in the same pathway.
• Termination of the signal. Termination of signal: Inactivation mechanisms
are an essential aspect of cell signaling. If ligand concentration falls, fewer receptors will be
bound. Unbound receptors revert to an inactive state
3|Page
