Pharmacology Flashcards
(49 cards)
Why must cells communicate
to coordinate complex activities
Explain specificity of intercellular signals
Chemical signals released from one cell produces a response only in those cells that express the right receptor. Different receptors for the same chemical signals can produce different responses in different cells - allows for specificity: the right response from the right cells
What can intercellular signalling molecule response include
Changes in:
* Secretory activity
* contractile activity
* metabolism
* membrane permenbility
* rate of proliferation or differentiation
What is the process of intercellular communication also called
signal transduction
What does the process of intercellular communication depent on
not sure if need to know
a range of receptors
Why are there 2 different types of receptor
- Intracellular receptors - lipophilic molecules which can diffuse directly through lipid bilayer (e.g. hormones)
- Cell surface receptors - hydrophilic signalling molecules, signal tranduced across membrane
Explain the action of lipidphilic (soluble) signalling molecules
- Dissolve through lipid bilayer of plasma membrane
- Bind to intacellular receptors in the cytosol (or nucleus)
- Reponse is triggered
Give NO and steroid hormones as examples of lipophilic signalling molecules
- NO (nitric oxide): binds to soluble guanylyl cyclase in the cytosol. Generates cGMP as a 2nd messenger that regulates cell activity
- Steroid hormones: recepotr is often transcription factor that regulats transcription in the nucleus
What are examples of primary messengers (1st)
neurotransmitters and hormones
Where must hydrophilic signalling molecules bind and how many are there?
To receptors on the cell surface: 4
Name all 4 types of cell surface receptor
- Receptor-channels
- G protein-coupled receptors (GPCRs)
- Receptor-enzymes
- Integrin receptors
3/4 are both catalytic receptors
Explain each of the 4 types of cell surface receptor
- Receptor-channels - also called ionotropic receptors and ligand binding opens/closes channel e.g. nicotinic acetylcholine receptors
- G protein-coupled receptors (GPCRs) - aka metabotropic receptors and do all their work via a middle man (G protein) which regulates enzyme activity/opens ion channel when ligand binds
- Receptor-enzymes - receptors with intrinsic enzyme activity (insulin receptors) or which are bound to an enzyme (cytokine receptors) - ligand binding to receptor-enzyme activates an intracellular enzyme
- Integrin receptors - receptors that interact with the cytoskeleton - ligand binding alters enzymes or the cytoskeleton
What will different G-protein couple to in GPCRs
different 2nd messenger systems
What could a G protein couple to in GPCRs
3
- Direct to ion channels: affects membrane potential and firing of action potentials (opens/closes ion channels)
- Adenylyl cyclase: produces cAMP as 2nd messenger after breaking down ATP. Regulates protein kinase A activity ( which phosphorylates target protiens and changes their activity)
- Phospholipase C: produce IP3 and DAG as 2nd messengers, releases Ca2+ and regulates protien kinase C activity. Phosphorylates target protiens and changes their activity
What does the phosphorylation of myosin by adenylyl cyclase pathway (GPCR) lead to?
smoother muscle contraction
Sources of Calcium
3
- Internal stores via IP3 - or Ca2+ - stimulated release Ca2+ from ER
- From outside the cell via voltage or ligand-gated Ca2+ channels - need neurotransmitter?
- Via inhibition of Ca2+ transport out of the cell
What G-protein messenger system release Ca2+
(and regulates protien kinase C activity)
Phospholipase C: produce IP3/DAG as 2nd messengers
What are the effects of Ca2+ in the cell
- Directly affect target protein (e.g. PKC)
- Bind to calmodulin which then activates target protein (e.g. Ca2+ - calmodulin dependent kinase - CamKinase)
- Works via some other Ca2+ binding protien (e.g. troponin)
How is intercellular signalling achieved
chemical signalling molecules acting on specific receptors
What are receptors and their intracellular signalling pathways at the site of action of?
Drugs
What can pharmacological agents be
- Endogenous - made by body (e.g. neurotransmitters and hormones)
- Exogenous - e.g. drugs
Define drug and give examples of possible sources
Any chemical agent that affects a biological system
Sources inc: natural products (from plants), synthetic drugs, biotechnology useing living systems (insulin) to make therapeutic agents, gene therapy
How do drugs act
by interacting with a binding receptor
Give 6 examples of receptors
- Cell surface receptors (B-adrenergic receptors)
- Intracellular receptors (steroid receptors)
- Ion channels (TTX blocks Na+ channels)
- Carriers (ouabain inhibits na/k ATPase)
- Enzymes (asprin/ibuprofen inhibit cyclooxygenase)
- nucleic acids (tumor promoters bind to DNA)
