CPPS 304 LATEST 2026 EXAM QUESTIONS AND SOLUTIONS
RATED A+
✔✔Do drugs bind to receptors using covalent bonds - ✔✔no they are too strong
want the drug to be able to dissociate from the receptor so that its effects are not
permanent
✔✔What is competitive inhibition - ✔✔when 2 drugs that act on the same receptor site
are both present, the drug with the higher affinity and/or concentration will have a
greater chance of binding
✔✔Intrinsic activity - ✔✔refers to the ability of a drug to change the conformation of a
receptor to produce an effect
✔✔Is it possible for a drug to posses affinity but not intrinsic activity - ✔✔yes
the drug will bind the receptor, but not cause anything to happen
blocks other things from binding the receptor
✔✔Efficacy - ✔✔refers to the maximum desired response that a drug can produce
✔✔Agonist - ✔✔a drug that binds to the receptor and produces an effect
has affinity and intrinsic activity
✔✔Partial agonist - ✔✔has affinity for the receptor but possesses lesser intrinsic activity
lower efficacy and Emax compared to a full agonist on the same receptor
✔✔example of an agonist and partial agonist - ✔✔morphine - agonist (greater efficacy)
codeine - partial agonist
✔✔Antagonist - ✔✔a drug that can bind to a receptor but cannot activate it
has affinity
no intrinsic activity
✔✔Competitive antagonists are reversible - ✔✔
✔✔Noncompetitive antagonists are non-reversible - ✔✔
✔✔How do comp antagonists effect Emax and EC50 of a drug - ✔✔Emax stays the
same
EC50 stays the same
✔✔How do noncompliance antagonists effect Emax and EC50 of a drug - ✔✔Emax
decreases
EC50 often increases
,✔✔Examples of partial agonists (2) - ✔✔buprenorphine - partial agonist for opioid
receptor
pindolol - partial agonist for B1 receptors (Beta blocker)
✔✔What are inverse agonists - ✔✔Some receptors have a minimum amount of
constitutive activity even when no ligand is bound to them
Inverse agonists will bind to the receptors and reduce their basal activity
✔✔Example of inverse agonist - ✔✔famotidine - inhibits basal activity of H2 (histamine)
receptors
- decreases amount of gastric acid production
✔✔What are EC50 and Emax - ✔✔EC50 - the dose/concentration that produces 50% of
the maximal response
Emax - the maximal effect produced by a drug (measures efficacy)
✔✔Idiosyncratic effect - ✔✔an unpredictable adverse effect resulting from an unknown
mechanism
✔✔Iatrogenic Effect - ✔✔an adverse affect or complication caused unintentionally by a
healthcare professional
malpractice/usually preventable
✔✔Frequency distribution vs Cumulative frequency - ✔✔frequency distribution - each
bar shows the new number of people who respond to that dose (excludes people who
responded at lower doses
cumulative distribution - each bar shows the total amount of people that respond to that
dose (including those that first responded at lower doses)
✔✔What are ED50, TD50, LD50 - ✔✔ED50 - the effective dose in 50% of the
population
TD50 - the toxic dose in 50% of the population
LD50 - the lethal dose in 50% of the population
✔✔What is the therapeutic index equation - ✔✔TI= TD50/ED50 or LD50/ED50
A drug with a larger TI is usually safer
✔✔Therapeutic window - ✔✔the difference between the minimum doses to induce an
effective response and a toxic response
want plasma concentration levels to stay within this range
✔✔GPCRs - largest superfamily of proteins in animal genome (lots of drugs that target
them) - ✔✔
, ✔✔GPCR signalling - activation (3) - ✔✔1. binding of agonist to receptor promotes its
binding to inactive GDP-bound G-protein
2. Ga subunit exchanges GDP with GTP to activate
3. Ga subunit dissociates from complex to activate an amplifier
✔✔2 Major types of Ga subunits - ✔✔Gsa (stimulatory a) - transduce signals through
adenylyl cyclase (amplifier) - cAMP (2nd messager)
Gqa - transducer signals through phospholipase C-B (amplifier) - IP3/DAG (2nd
messengers)
✔✔Gsa pathway receptor and natural ligand - ✔✔AdrB2
epinephrine (relaxes airways)
✔✔Gqa pathway receptor and natural ligand - ✔✔M3 receptor
acetylcholine (constricts airways)
✔✔What type of receptors are GPCR and RTK - ✔✔extracellular
✔✔Steps to activate RTKs (3) - ✔✔1. in inactivated state, receptors present as
monomers
2. binding a ligand induces a conformational change and the receptors dimerize/activate
3. receptor dimers trans-phosphorylate each other and activate other downstream
effectors
✔✔Example of an RTK ligand and receptor - ✔✔ligand: epidermal growth factor (EGF)
receptor: EGFR
✔✔How do ligand gated ion channels work? - ✔✔the receptor is a protein with a
channel in the centre
an agonist binds to the receptor, causing it to open and allow specific ions to cross the
cell membrane
✔✔What are intracellular receptors used for - ✔✔drugs that can pass through the cell
membrane
ex. steroid hormones - estrogen
✔✔How intracellular receptors work (3) - ✔✔1. agonist enters the cell and binds to the
receptor in the cytoplasm
2. the drug-receptor complex enters the nucleus to stimulate transcription
3. leads to the synthesis of new proteins and enzymes
✔✔Theories for up/down regulation (4) - ✔✔1. chronic stimulation of receptors by
AGONISTS can lead to desensitization
2. chronic stimulation of receptors by ANTAGONISTS can lead to up-regulation
3. decreased receptor numbers/decreased signal transduction
RATED A+
✔✔Do drugs bind to receptors using covalent bonds - ✔✔no they are too strong
want the drug to be able to dissociate from the receptor so that its effects are not
permanent
✔✔What is competitive inhibition - ✔✔when 2 drugs that act on the same receptor site
are both present, the drug with the higher affinity and/or concentration will have a
greater chance of binding
✔✔Intrinsic activity - ✔✔refers to the ability of a drug to change the conformation of a
receptor to produce an effect
✔✔Is it possible for a drug to posses affinity but not intrinsic activity - ✔✔yes
the drug will bind the receptor, but not cause anything to happen
blocks other things from binding the receptor
✔✔Efficacy - ✔✔refers to the maximum desired response that a drug can produce
✔✔Agonist - ✔✔a drug that binds to the receptor and produces an effect
has affinity and intrinsic activity
✔✔Partial agonist - ✔✔has affinity for the receptor but possesses lesser intrinsic activity
lower efficacy and Emax compared to a full agonist on the same receptor
✔✔example of an agonist and partial agonist - ✔✔morphine - agonist (greater efficacy)
codeine - partial agonist
✔✔Antagonist - ✔✔a drug that can bind to a receptor but cannot activate it
has affinity
no intrinsic activity
✔✔Competitive antagonists are reversible - ✔✔
✔✔Noncompetitive antagonists are non-reversible - ✔✔
✔✔How do comp antagonists effect Emax and EC50 of a drug - ✔✔Emax stays the
same
EC50 stays the same
✔✔How do noncompliance antagonists effect Emax and EC50 of a drug - ✔✔Emax
decreases
EC50 often increases
,✔✔Examples of partial agonists (2) - ✔✔buprenorphine - partial agonist for opioid
receptor
pindolol - partial agonist for B1 receptors (Beta blocker)
✔✔What are inverse agonists - ✔✔Some receptors have a minimum amount of
constitutive activity even when no ligand is bound to them
Inverse agonists will bind to the receptors and reduce their basal activity
✔✔Example of inverse agonist - ✔✔famotidine - inhibits basal activity of H2 (histamine)
receptors
- decreases amount of gastric acid production
✔✔What are EC50 and Emax - ✔✔EC50 - the dose/concentration that produces 50% of
the maximal response
Emax - the maximal effect produced by a drug (measures efficacy)
✔✔Idiosyncratic effect - ✔✔an unpredictable adverse effect resulting from an unknown
mechanism
✔✔Iatrogenic Effect - ✔✔an adverse affect or complication caused unintentionally by a
healthcare professional
malpractice/usually preventable
✔✔Frequency distribution vs Cumulative frequency - ✔✔frequency distribution - each
bar shows the new number of people who respond to that dose (excludes people who
responded at lower doses
cumulative distribution - each bar shows the total amount of people that respond to that
dose (including those that first responded at lower doses)
✔✔What are ED50, TD50, LD50 - ✔✔ED50 - the effective dose in 50% of the
population
TD50 - the toxic dose in 50% of the population
LD50 - the lethal dose in 50% of the population
✔✔What is the therapeutic index equation - ✔✔TI= TD50/ED50 or LD50/ED50
A drug with a larger TI is usually safer
✔✔Therapeutic window - ✔✔the difference between the minimum doses to induce an
effective response and a toxic response
want plasma concentration levels to stay within this range
✔✔GPCRs - largest superfamily of proteins in animal genome (lots of drugs that target
them) - ✔✔
, ✔✔GPCR signalling - activation (3) - ✔✔1. binding of agonist to receptor promotes its
binding to inactive GDP-bound G-protein
2. Ga subunit exchanges GDP with GTP to activate
3. Ga subunit dissociates from complex to activate an amplifier
✔✔2 Major types of Ga subunits - ✔✔Gsa (stimulatory a) - transduce signals through
adenylyl cyclase (amplifier) - cAMP (2nd messager)
Gqa - transducer signals through phospholipase C-B (amplifier) - IP3/DAG (2nd
messengers)
✔✔Gsa pathway receptor and natural ligand - ✔✔AdrB2
epinephrine (relaxes airways)
✔✔Gqa pathway receptor and natural ligand - ✔✔M3 receptor
acetylcholine (constricts airways)
✔✔What type of receptors are GPCR and RTK - ✔✔extracellular
✔✔Steps to activate RTKs (3) - ✔✔1. in inactivated state, receptors present as
monomers
2. binding a ligand induces a conformational change and the receptors dimerize/activate
3. receptor dimers trans-phosphorylate each other and activate other downstream
effectors
✔✔Example of an RTK ligand and receptor - ✔✔ligand: epidermal growth factor (EGF)
receptor: EGFR
✔✔How do ligand gated ion channels work? - ✔✔the receptor is a protein with a
channel in the centre
an agonist binds to the receptor, causing it to open and allow specific ions to cross the
cell membrane
✔✔What are intracellular receptors used for - ✔✔drugs that can pass through the cell
membrane
ex. steroid hormones - estrogen
✔✔How intracellular receptors work (3) - ✔✔1. agonist enters the cell and binds to the
receptor in the cytoplasm
2. the drug-receptor complex enters the nucleus to stimulate transcription
3. leads to the synthesis of new proteins and enzymes
✔✔Theories for up/down regulation (4) - ✔✔1. chronic stimulation of receptors by
AGONISTS can lead to desensitization
2. chronic stimulation of receptors by ANTAGONISTS can lead to up-regulation
3. decreased receptor numbers/decreased signal transduction
