Karens Cards On Pharmocodynamics Flashcards
What is pharmacodynamics?
- What drugs do to the body
- How is works
What are Zwitterions?
Amino acids and proteins are Zwitterions. They can be both positively and negatively charged or nothing/neutral
What does an amino acid look like?
NH2 (nitrogen, hydrogen) - R- COOH (carbon, oxygen, hydrogen)
Amino group = N terminal
Carboxyl group = C terminal
1) What are positively charged ions known as?
2) What are negatively charged ions known as?
1) positively charged ions = cations
2) negatively charged ions = anions
Opposites attract:
Rods - positive = anode and negatives = cathode
What are the 4 functions of proteins in a cell membrane?
1) Transporters (form channels)
2) Linkers (form adhesion molecules, structure - can unlink and travel)
3) Receptors (carry messages)
4) Enzymes (spread up chemical reaction)
What is the electrical charge inside a cell?
Inside a cell is always negative charge
Outside a cell is always positive charge
What are the targets for drug actions?
RICE
R - receptors
I - ion channels
C - carrier molecules
E - Enzymes
There are 4 main types of receptors (superfamilies). What are they?
1) Inotropic - Ligand gated channels
2) Metabotropic - G protein coupled
3) Kinase linked
4) Nuclear
Describe characteristics of ligand gated channel receptors? (3)
1) Inotropic
2) Directly coupled to an ion channel
3) fastest (nerve/cardiac tissue)
Describe characteristics of G protein coupled receptor (4)
1) metabotropic
2) signalling cascade
3) second messenger system
4) fast - seconds
Describe characteristics of kinase linked receptors (2)
1) Enzyme amplifier
2) hours
Example - insulin
Describe characteristics of nuclear receptors (3)
1) within the cell (intracellular)
2) turns nucleus off
3) hours/days
Example - steroids
1) what is an agonist?
2) what is an antagonist?
1) an agonist activates, initiates a response, a natural response
2) an antagonist blocks receptors by preventing access to the site by the natural agonist
1) What is a competitive receptor?
2) What is a non competitive receptor?
1) Competitive = catipiller - concentration dependent
2) non competitive = Wedge/tap - doesn’t matter about concentration
What is Tachyphylaxis?
Desensitisation - rapidly decreasing response to a drug
Causes:
- change in receptors
- loss of receptors
- hiding receptors
What is an ion channel and what are the 4 main types of ion channels?
Ion channels exist in open and closed form (open allowing movement, closed preventing movement or inactive)
1) Ligand gated (intracellular)
2) Ligand gated (extracellular)
3) voltage gated
4) mechanically gated
Describe how the below ion channels are activated:
A) Ligand gated ion channels?
B) voltage gated ion channels?
C) mechanically gated ion channels?
A) Activated by the binding of endogenous ligands to a specific receptor which forms part of the ion channel
B) Activated following a change in voltage
C) Activated by the weight or force of a molecule hitting it open
Consider 5 features of ion channels
1) Over 100 types
2) Important for systems that require a rapid response (NS, renal, CVS)
3) Drugs either block (directly block the ion channel preventing movement) or modulate (indirect- the binding of a drug to the site of an associated receptor can either increase or decrease the likelihood of a channel being open)
4) Ions need the help of proteins to cross cell membrane (such as ion channels)
5) Ion channels don’t bind but form a channel through the membrane (they let in water and small ions pass)
What are the 4 characteristics of carrier molecules?
1) Transport a substance across a cell membrane
2) Carrier molecules can be ion, glucose or amino acids
3) They carry a specific molecule/shape
4) Some drugs target these carriers and block transport - common by inhibiting an enzyme ATP that provides the energy to drive them
Drugs can act to modulate the function of carrier molecules directly or indirectly….explain
Direct - Binds completely to the carrier preventing the binding of endogenous ligands
Indirect - Allosteric (binds to a separate site on the carrier and alters the 3D shape, preventing the binding of endogenous ligands
Allosteric = change in shape or activity
Endogenous = existing
What are the 2 main types of carrier molecules?
1) Energy dependent:
- can work across a concentrated gradient
- requires energy (usually ATP)
2) Energy independent:
- Transporters (single molecule in one direction)
- Symporters (2 different molecules in the same direction)
- Antiporters (2 molecules in opposite directions?
(Can only work down a concentrated gradient)
What are Enzymes? (2)
1) Enzymes are biological catalysts that speed up a chemical reaction
2) Enzymes have an active or catalytic site that binds substrates specifically (substrate fits shape like a key in a lock)
- chemical reaction
- then substrate forms into products
What does a substrate analogue do and how does it work? (2)
1) Mimic the substrate or feature of the substrate
2) Can act as a competitive inhibitor or a non competitive inhibitor
What are the characteristics of a competitive inhibitor? (4)
Substrate analogue
1) have a similar chemical structure (shape) and slows down a reaction rate
2) The inhibitor competes with the substrate to slow down the reaction
3 Binds at the active site
4) reversible
(Drugs help prevent harmful products or growth of foreign cells. Penicillin inhibits an enzyme which help bacteria grow)
What are the characteristics of a non competitive inhibitor? (4)
(Substrate analogue)
1) Bind to the enzyme but not at the active site
2) Still inhibit the reaction
3) Work by changing the enzyme shape, thus making it inactive
4) non reversible
(Aspirin)
What are the characteristics of a false substrate? (3)
1) Transformed by an enzyme to produce an abnormal non functioning product
2) Target a specific point in a pathway and often have less side effects as it’s more targeted
3) Fools the enzyme into thinking it’s metabolising
What are the characteristics of conversion of pro drugs? (3)
1) Most oral drugs are in the inactive form
2) They rely on conversion by enzymes (usually in the liver) to activate the drug
3) Pro drug is an active metabolite
Example - codeine - morphine
Drugs are either reversible or irreversible inhibitors….explain
Reversible - temporarily binds to the catalytic site
Irreversible- binds permanently to the enzyme making it terminally inactive. These require the production of new enzymes to re start activity
Aspirin - irreversible inhibitor
Penicillin - reversible inhibitor
