,BIOD 101 Module 5 | Practice Q&A | 2026/2027 | Biology | Portage
Learning | 100% PASS
1. What is a ligand?
A) A type of receptor found on the cell surface
B) A molecule that has specificity for a given receptor and causes a change
upon binding
C) An enzyme that transfers phosphate groups to proteins
D) A protein that hydrolyzes GTP to GDP
Correct Answer: A molecule that has specificity for a given receptor and
causes a change upon binding
Rationale: A ligand is a molecule that has specificity for a given receptor, and
the binding of a ligand to the given receptor causes a change. Ligands
include hormones, peptides, sugars, and small hydrophobic molecules.
2. Which of the following are the three types of cell surface receptors
discussed in the module?
A) G protein-coupled receptors (GPCRs), receptor tyrosine kinases (RTKs),
and ligand-gated ion channels
B) Autocrine receptors, paracrine receptors, and synaptic receptors
C) Intracellular receptors, nuclear receptors, and cytoplasmic receptors
D) Enzyme-linked receptors, ion channels, and G proteins
Correct Answer: G protein-coupled receptors (GPCRs), receptor tyrosine
kinases (RTKs), and ligand-gated ion channels
Rationale: The three types of cell surface receptors discussed in the module
are GPCRs, RTKs, and ligand-gated ion channels. These represent the major
classes of membrane-bound receptors.
,3. What nucleotide does a G protein bind to?
A) ATP
B) GDP
C) GTP
D) ADP
Correct Answer: GTP
Rationale: A G protein functions by binding to the nucleotide guanosine
triphosphate (GTP). G proteins are named for their ability to bind guanine
nucleotides.
4. What is the broad role of all G proteins?
A) Transferring phosphate groups to proteins
B) Hydrolyzing (breaking down) GTP to GDP
C) Opening ion channels in response to ligands
D) Transporting molecules across the membrane
Correct Answer: Hydrolyzing (breaking down) GTP to GDP
Rationale: While there are many different types of G proteins, they all share
the broad role of hydrolyzing (breaking down) GTP to GDP (guanosine
diphosphate).
5. What type of enzyme is a receptor tyrosine kinase (RTK)?
A) Phosphatase
B) Kinase
, C) Ligase
D) Hydrolase
Correct Answer: Kinase
Rationale: RTK stands for receptor tyrosine kinase. An RTK is a kinase, which
is an enzyme that transfers phosphate groups to a protein or another target
molecule from an ATP molecule.
6. What is the broad function of a kinase?
A) To hydrolyze GTP to GDP
B) To open ion channels in response to ligands
C) To transfer phosphate groups to a protein or another target molecule from
ATP
D) To remove phosphate groups from proteins
Correct Answer: To transfer phosphate groups to a protein or another target
molecule from ATP
Rationale: A kinase is an enzyme that transfers phosphate groups to a
protein or another target molecule from an ATP molecule. This process is
called phosphorylation.
7. Describe what happens when a ligand binds to the extracellular binding
site of a ligand-gated ion channel.
A) The channel is inactivated and closes
B) A conformational change occurs, eliciting the channel to open and allow
the passage of ions
C) The receptor is internalized into the cell
Learning | 100% PASS
1. What is a ligand?
A) A type of receptor found on the cell surface
B) A molecule that has specificity for a given receptor and causes a change
upon binding
C) An enzyme that transfers phosphate groups to proteins
D) A protein that hydrolyzes GTP to GDP
Correct Answer: A molecule that has specificity for a given receptor and
causes a change upon binding
Rationale: A ligand is a molecule that has specificity for a given receptor, and
the binding of a ligand to the given receptor causes a change. Ligands
include hormones, peptides, sugars, and small hydrophobic molecules.
2. Which of the following are the three types of cell surface receptors
discussed in the module?
A) G protein-coupled receptors (GPCRs), receptor tyrosine kinases (RTKs),
and ligand-gated ion channels
B) Autocrine receptors, paracrine receptors, and synaptic receptors
C) Intracellular receptors, nuclear receptors, and cytoplasmic receptors
D) Enzyme-linked receptors, ion channels, and G proteins
Correct Answer: G protein-coupled receptors (GPCRs), receptor tyrosine
kinases (RTKs), and ligand-gated ion channels
Rationale: The three types of cell surface receptors discussed in the module
are GPCRs, RTKs, and ligand-gated ion channels. These represent the major
classes of membrane-bound receptors.
,3. What nucleotide does a G protein bind to?
A) ATP
B) GDP
C) GTP
D) ADP
Correct Answer: GTP
Rationale: A G protein functions by binding to the nucleotide guanosine
triphosphate (GTP). G proteins are named for their ability to bind guanine
nucleotides.
4. What is the broad role of all G proteins?
A) Transferring phosphate groups to proteins
B) Hydrolyzing (breaking down) GTP to GDP
C) Opening ion channels in response to ligands
D) Transporting molecules across the membrane
Correct Answer: Hydrolyzing (breaking down) GTP to GDP
Rationale: While there are many different types of G proteins, they all share
the broad role of hydrolyzing (breaking down) GTP to GDP (guanosine
diphosphate).
5. What type of enzyme is a receptor tyrosine kinase (RTK)?
A) Phosphatase
B) Kinase
, C) Ligase
D) Hydrolase
Correct Answer: Kinase
Rationale: RTK stands for receptor tyrosine kinase. An RTK is a kinase, which
is an enzyme that transfers phosphate groups to a protein or another target
molecule from an ATP molecule.
6. What is the broad function of a kinase?
A) To hydrolyze GTP to GDP
B) To open ion channels in response to ligands
C) To transfer phosphate groups to a protein or another target molecule from
ATP
D) To remove phosphate groups from proteins
Correct Answer: To transfer phosphate groups to a protein or another target
molecule from ATP
Rationale: A kinase is an enzyme that transfers phosphate groups to a
protein or another target molecule from an ATP molecule. This process is
called phosphorylation.
7. Describe what happens when a ligand binds to the extracellular binding
site of a ligand-gated ion channel.
A) The channel is inactivated and closes
B) A conformational change occurs, eliciting the channel to open and allow
the passage of ions
C) The receptor is internalized into the cell
