Lecture 3 Flashcards
What is the membrane ?
A selectively permeable barrier between the extracellular environment and the cytosol.
Why are differences in concentrations important ?
For cell function.
What are the purpose of the mechanisms in place ?
To allow the cell to maintain the concentrations inside and outside the membrane, these mechanisms depend on the transport of ions across the plasma membrane.
What is the plasma membrane made up of ?
A lipid bilayer - contains integral, extracellular and cytosolic proteins.
What are integral proteins ?
They span the width of the membrane, there are different types.
What are examples of peripheral proteins ?
Extracellular and cytosolic proteins.
Why is there a bilayer ?
Because the plasma membrane is two molecules thick and has both hydrophobic and hydrophilic characteristics of polar lipids resulting in this arrangement.
Why is the lipid bilayer important ?
To allow the plasma membrane to function because they depend on the environment (i.e. ion concentration) of the lipid bilayer for their function.
How are drugs distributed throughout the body ?
By the use of blood and bodily fluids.
How are drugs able able to act on individual cells in the body ?
Because drugs are able to bind to protein receptors.
Where are receptors found ?
On the outer membrane of the cells but also found on enzymes within the cell.
What are receptors ?
They are typically integral membrane proteins at the plasma membrane.
How can receptors be altered ?
By altering the concentration of the agonist (ligand).
Increased: up-regulation
Decreased: down-regulation
Factors that influence how drugs work
Absorption, distribution, metabolism, excretion.
Absorption
This is dependent upon a variety of factors, e.g. influenced by the solubility of the drug in the blood.
Distribution
Drugs may bind to the plasma proteins so there is a ratio of bound/free drug, only free drug molecules can bind to the receptor to exert effect.
Metabolism
It is important for dugs to be broken down (i.e. metabolised) in the body so the drug can be inactivated and excreted.
Excretion
To ensure that the drugs are excreted and leave the body, most commonly via urine.
How are biological responses exerted ?
The drugs recognise and bind to the receptors exerting a biological response.
Ligands are…
.. drugs.
What are ligands ?
They are chemicals (synthetic or natural) that can bind to receptors, they can be classified as agonists or antagonists.
How do agonists work ?
They are able to activate receptors and the cell responds. They have two important properties: affinity and efficacy.
Affinity
The strength with which a ligand binds to a receptor.
Efficacy
Hoe effective/efficient the agonist is in inducing a response (i.e. a conformational change/3D change in the receptor).