,BIOD 101 Module 5 | Essential Biology I | Portage Learning |
Questions & Verified Answers | 2026 Edition
1. Which of the following best describes the role of scaffolding proteins in cell signaling?
A) They catalyze the phosphorylation of downstream target molecules
B) They physically support and organize proteins involved in signaling pathways
C) They transport signaling molecules across the plasma membrane
D) They hydrolyze GTP to GDP to terminate signaling
Correct Answer: They physically support and organize proteins involved in signaling pathways
Rationale: Scaffolding proteins are structural proteins that organize and physically support other
proteins involved in signaling pathways. By bringing signaling components into close proximity, they
increase the efficiency and specificity of signal transduction. They do not catalyze reactions or hydrolyze
nucleotides.
2. What type of signaling occurs when a cell releases vesicles containing a signaling ligand that binds to
nearby target cells?
A) Autocrine signaling
B) Endocrine signaling
C) Paracrine signaling
D) Synaptic signaling
Correct Answer: Paracrine signaling
Rationale: Paracrine signaling is local-range signaling in which cells release vesicles containing signaling
ligands that attach to nearby target cells. This type of signaling is important for development and the
release of growth factors. The ligands act on cells in the immediate vicinity of the signaling cell.
3. What is the primary function of a ligand in cell signaling?
A) To hydrolyze GTP to GDP
,B) To act as a second messenger within the target cell
C) To bind with specificity to a receptor and cause a change in the target cell
D) To phosphorylate proteins in the signaling cascade
Correct Answer: To bind with specificity to a receptor and cause a change in the target cell
Rationale: A ligand is a molecule that has specificity for a given receptor. When a ligand binds to its
receptor, it causes a conformational change that initiates a signaling cascade within the target cell.
Ligand-receptor specificity ensures that only appropriate target cells respond to the signal.
4. During synaptic signaling, what is released from the pre-synaptic cell to communicate with the post-
synaptic cell?
A) Hormones
B) Neurotransmitters packaged in vesicles
C) Growth factors
D) Intracellular second messengers
Correct Answer: Neurotransmitters packaged in vesicles
Rationale: In synaptic signaling, an electrical signal is sent to the synapse, triggering the release of
neurotransmitters that are packaged in vesicles. These neurotransmitters bind to receptors on the post-
synaptic target cell. Synaptic signaling is a form of local-range signaling with rapid action.
5. What is a synapse?
A) A large gap between a signaling cell and a target cell in endocrine signaling
B) A small gap between a signaling cell and a target cell in synaptic signaling
C) The site where hormones bind to receptors in the circulatory system
D) The region of a cell where ligands are produced
Correct Answer: A small gap between a signaling cell and a target cell in synaptic signaling
, Rationale: A synapse is a small gap between the signaling cell (pre-synaptic cell) and the target cell (post-
synaptic cell). Neurotransmitters are released across this gap to transmit signals from one neuron to
another or to a target cell such as a muscle or gland.
6. Which type of signaling involves a cell releasing a ligand that binds to receptors on its own surface?
A) Paracrine signaling
B) Synaptic signaling
C) Autocrine signaling
D) Endocrine signaling
Correct Answer: Autocrine signaling
Rationale: Autocrine signaling occurs when a cell signals itself by releasing a ligand that binds to
receptors on its own surface. In this type of signaling, the cell acts as both the sender and the receiver.
Autocrine signaling is most commonly found in immune cells and in metastasis.
7. Which type of signaling transmits ligands over long distances via the circulatory system?
A) Paracrine signaling
B) Synaptic signaling
C) Autocrine signaling
D) Endocrine signaling
Correct Answer: Endocrine signaling
Rationale: Endocrine signaling involves the transmission of ligands (hormones) over long distances via
the circulatory system. Hormones are released into the bloodstream and travel throughout the body,
but they only bind to cells that have specific receptors for that hormone.
8. What is the name of the ligands released during endocrine signaling?
A) Neurotransmitters
Questions & Verified Answers | 2026 Edition
1. Which of the following best describes the role of scaffolding proteins in cell signaling?
A) They catalyze the phosphorylation of downstream target molecules
B) They physically support and organize proteins involved in signaling pathways
C) They transport signaling molecules across the plasma membrane
D) They hydrolyze GTP to GDP to terminate signaling
Correct Answer: They physically support and organize proteins involved in signaling pathways
Rationale: Scaffolding proteins are structural proteins that organize and physically support other
proteins involved in signaling pathways. By bringing signaling components into close proximity, they
increase the efficiency and specificity of signal transduction. They do not catalyze reactions or hydrolyze
nucleotides.
2. What type of signaling occurs when a cell releases vesicles containing a signaling ligand that binds to
nearby target cells?
A) Autocrine signaling
B) Endocrine signaling
C) Paracrine signaling
D) Synaptic signaling
Correct Answer: Paracrine signaling
Rationale: Paracrine signaling is local-range signaling in which cells release vesicles containing signaling
ligands that attach to nearby target cells. This type of signaling is important for development and the
release of growth factors. The ligands act on cells in the immediate vicinity of the signaling cell.
3. What is the primary function of a ligand in cell signaling?
A) To hydrolyze GTP to GDP
,B) To act as a second messenger within the target cell
C) To bind with specificity to a receptor and cause a change in the target cell
D) To phosphorylate proteins in the signaling cascade
Correct Answer: To bind with specificity to a receptor and cause a change in the target cell
Rationale: A ligand is a molecule that has specificity for a given receptor. When a ligand binds to its
receptor, it causes a conformational change that initiates a signaling cascade within the target cell.
Ligand-receptor specificity ensures that only appropriate target cells respond to the signal.
4. During synaptic signaling, what is released from the pre-synaptic cell to communicate with the post-
synaptic cell?
A) Hormones
B) Neurotransmitters packaged in vesicles
C) Growth factors
D) Intracellular second messengers
Correct Answer: Neurotransmitters packaged in vesicles
Rationale: In synaptic signaling, an electrical signal is sent to the synapse, triggering the release of
neurotransmitters that are packaged in vesicles. These neurotransmitters bind to receptors on the post-
synaptic target cell. Synaptic signaling is a form of local-range signaling with rapid action.
5. What is a synapse?
A) A large gap between a signaling cell and a target cell in endocrine signaling
B) A small gap between a signaling cell and a target cell in synaptic signaling
C) The site where hormones bind to receptors in the circulatory system
D) The region of a cell where ligands are produced
Correct Answer: A small gap between a signaling cell and a target cell in synaptic signaling
, Rationale: A synapse is a small gap between the signaling cell (pre-synaptic cell) and the target cell (post-
synaptic cell). Neurotransmitters are released across this gap to transmit signals from one neuron to
another or to a target cell such as a muscle or gland.
6. Which type of signaling involves a cell releasing a ligand that binds to receptors on its own surface?
A) Paracrine signaling
B) Synaptic signaling
C) Autocrine signaling
D) Endocrine signaling
Correct Answer: Autocrine signaling
Rationale: Autocrine signaling occurs when a cell signals itself by releasing a ligand that binds to
receptors on its own surface. In this type of signaling, the cell acts as both the sender and the receiver.
Autocrine signaling is most commonly found in immune cells and in metastasis.
7. Which type of signaling transmits ligands over long distances via the circulatory system?
A) Paracrine signaling
B) Synaptic signaling
C) Autocrine signaling
D) Endocrine signaling
Correct Answer: Endocrine signaling
Rationale: Endocrine signaling involves the transmission of ligands (hormones) over long distances via
the circulatory system. Hormones are released into the bloodstream and travel throughout the body,
but they only bind to cells that have specific receptors for that hormone.
8. What is the name of the ligands released during endocrine signaling?
A) Neurotransmitters
