Binding Sites, Enzymes, Chemical Signalling Flashcards
What is a ligand?
any molecule or ion that is bound to a protein by electrical attraction or hydrophobic attraction
What does the binding of a ligand do to a protein?
It changes the conformation of the protein
What is necessary for a ligand to bind to a protein?
the charges and conformational shapes must be complementary
What is the affinity of a binding site to a ligand?
The strength of a ligand-protein binding, and the likeliness that the ligand will stay bound rather than returning to its unbound state
What factors determine the percent saturation of a binding site with ligands?
- Concentration of unbound ligand
- affinity of the binding site for the ligand
What are the two ways to control protein activity?
- Changing protein shape to alter ligand binding
- Regulating protein synthesis and breakdown
What are the two mechanisms in cells that alter protein shape?
- Allosteric Modulation
- Covalent Modulation
What is allosteric modulation?
When a protein has two binding sites and the binding of a protein to one of the sites alters the shape of the other.
What is cooperativity?
When a ligand binds to the first of several functional sites on a molecule, inducing a change that increases the affinity of other functional sites
What is covalent modulation?
The covalent bonding of charged chemical groups to some of the protein’s side chains.
What is a common type of covalent modulation?
Phosphorylation
what is the name for an enzyme that adds phosphate to another protein?
Kinase
What is catabolism?
the break down of organic molecules
What is anabolism, bro?
the synthesis of organic molecules
What is the Law of Mass Action?
The concentration of reactants and products can determine the direction at which the net reaction proceeds
What is the activation energy threshold?
Sufficient energy to overcome the mutual repulsion from electrons surrounding the atoms allowing them to collide
What is a cofactor?
A trace metal (like Mg, Zinc, Cu, Fe) that binds to an enzyme changing its conformation so that it can bind substrate
What is a coenzyme?
An organic molecule which directly participates as one of the substrates in a reaction
What are the three main factors affecting enzyme mediated ractions?
Substrate concentration
Enzyme concentration
Enzyme Activity
How does substrate concentration affect rate of enzyme mediated reactions?
Increases until saturated
How does enzyme concentration affect rate of enzyme mediated reactions?
Increasing enzyme concentration increases the max rate (shift upwards in diagram).
How does enzyme activity affect the rate of enzyme mediated reactions?
Increasing affinity through allosteric or covalent modulation increases the steepness of the diagram (think as efficiency)
What is the difference between a neurotransmitter and a hormone?
Hormone = slow function over great distance Neurotransmitter = rapid fuction over short distance
What is down-regulation of receptors?
Where extra-cellular concentration of a messenger is maintained, the number of receptors on target cells is decreased, reducing the cell responsiveness to the chemical messenger
