APEX-ANS EXAM QUESTIONS AND
ANSWERS 2026 COMPLETE EXAM
PREP WITH VERIFIED SOLUTIONS
◉ Signal transduction
Answer: Cell converts extracellular signal into an intracellular response
◉ Where are most receptors located?
Answer: Embedded in the cell membrane
◉ 3 types of membrane bound receptors
Answer: -Ion channel
-G-protein coupled receptor
-Enzyme linked receptor
◉ Ion channels definition and examples
Answer: Allow or inhibit ions from moving along their concentration
gradients
ex) voltage gated sodium channel in a neuron
Nicotinic N (ANS, CNS), Nicotinic M (NMJ)
◉ A G-protein coupled receptor works in one of two ways:
Answer: 1.Opens or closes an ion channel
,2.Activates or inhibits an enzyme inside the cell
◉ Example of a G-protein coupled receptor that opens/closes an ion
channel
Answer: Muscarinic-2 receptor in the SA node
(all muscarinic receptors??? - may not be true)
◉ Example of a G-protein coupled receptor that activates/inhibits an
enzyme inside the cell
Answer: Alpha-1 receptor in vascular smooth muscle
(All Alpha, Beta, Dopamine, Histamine, Vasopressin - this may not be
true!!)
◉ Enzyme Linked Receptors are also ________.
At rest the ELR is __________.
When does it become activated?
Answer: ELRs are also enzymes.
At rest the catalytic domain is inactive.
,When the signal binds, catalytic domain becomes activated.
◉ Example of enzyme linked receptor
Answer: Insulin receptor in skeletal muscle, linked to tyrosine kinase
◉ How do intracellular receptors work?
Answer: A signal diffuses through the cell membrane and binds to a
receptor located inside of the cell
◉ Example of intracellular receptor
Answer: Steroids bind to receptors in the cytoplasm
-Thyroid hormone binds to receptors in the cell nucleus
◉ Order of how a cellular response is elicited for GPCR
Answer: First Messenger--> GPCR--> Effector --> Second messenger --
> Cellular Response
◉ What is a first messenger?
Answer: A ligand that binds to the GPCR
Could be endogenous (neurotransmitter or hormone) or exogenous
(drug)
, ◉ Protein structure of GPCR:
Where is the receptor located?
Where is the G -protein located?What it is made up of?
Answer: The receptor is located is outside the cell membrane.
G-protein is located inside the cell and is made up of the alpha, beta,
gamma subunits
◉ What are the G-stimulatory proteins? What do they do?
Answer: -Gs or Gq
-They turn on an effector
◉ What is the G-inhibitory protein?
what do they do?
Answer: -Gi
-Turn off the effector
◉ 3 subunits of a G protein
Answer: Alpha, beta, and gamma
◉ What happens when ligand binds GPCR? (4)
Answer: 1. Ligand binding outside receptor activates G-protein
ANSWERS 2026 COMPLETE EXAM
PREP WITH VERIFIED SOLUTIONS
◉ Signal transduction
Answer: Cell converts extracellular signal into an intracellular response
◉ Where are most receptors located?
Answer: Embedded in the cell membrane
◉ 3 types of membrane bound receptors
Answer: -Ion channel
-G-protein coupled receptor
-Enzyme linked receptor
◉ Ion channels definition and examples
Answer: Allow or inhibit ions from moving along their concentration
gradients
ex) voltage gated sodium channel in a neuron
Nicotinic N (ANS, CNS), Nicotinic M (NMJ)
◉ A G-protein coupled receptor works in one of two ways:
Answer: 1.Opens or closes an ion channel
,2.Activates or inhibits an enzyme inside the cell
◉ Example of a G-protein coupled receptor that opens/closes an ion
channel
Answer: Muscarinic-2 receptor in the SA node
(all muscarinic receptors??? - may not be true)
◉ Example of a G-protein coupled receptor that activates/inhibits an
enzyme inside the cell
Answer: Alpha-1 receptor in vascular smooth muscle
(All Alpha, Beta, Dopamine, Histamine, Vasopressin - this may not be
true!!)
◉ Enzyme Linked Receptors are also ________.
At rest the ELR is __________.
When does it become activated?
Answer: ELRs are also enzymes.
At rest the catalytic domain is inactive.
,When the signal binds, catalytic domain becomes activated.
◉ Example of enzyme linked receptor
Answer: Insulin receptor in skeletal muscle, linked to tyrosine kinase
◉ How do intracellular receptors work?
Answer: A signal diffuses through the cell membrane and binds to a
receptor located inside of the cell
◉ Example of intracellular receptor
Answer: Steroids bind to receptors in the cytoplasm
-Thyroid hormone binds to receptors in the cell nucleus
◉ Order of how a cellular response is elicited for GPCR
Answer: First Messenger--> GPCR--> Effector --> Second messenger --
> Cellular Response
◉ What is a first messenger?
Answer: A ligand that binds to the GPCR
Could be endogenous (neurotransmitter or hormone) or exogenous
(drug)
, ◉ Protein structure of GPCR:
Where is the receptor located?
Where is the G -protein located?What it is made up of?
Answer: The receptor is located is outside the cell membrane.
G-protein is located inside the cell and is made up of the alpha, beta,
gamma subunits
◉ What are the G-stimulatory proteins? What do they do?
Answer: -Gs or Gq
-They turn on an effector
◉ What is the G-inhibitory protein?
what do they do?
Answer: -Gi
-Turn off the effector
◉ 3 subunits of a G protein
Answer: Alpha, beta, and gamma
◉ What happens when ligand binds GPCR? (4)
Answer: 1. Ligand binding outside receptor activates G-protein
