chapter 4 Flashcards
Why binding is important in Physiology?
Binding of molecules to receptors causes changes in cells and serves in transporting, communicating and affecting the overall functions of organs
examples of molecules binding
- hormones
- enzymes
- neurotransmitters
- gases
Competition
The presence of multiple ligands able to bind to the same site
Agonist
Binds and triggers response, goal is to activate or increase an action. Often mimics a natural produced ligand
-Ex. Decongestant-mimic epinephrine but on a subtype receptor of epi
Antagonist
Molecule that does NOT activate as the natural ligand would. Often occupies the site so the natural ligand and its effect does not occur.
-Ex. Antihistamine-a histamine blocker by occupying those binding sites
what is a ligand and are the forces
any molecule or ion that is bound to a protein by one of the following forces:
- electrical attractions
- Weaker attractions due to hydrophobic forces between nonpolar regions on the two molecules
active site
region of a protein to which a ligand binds
When a ligand binds to a protein the proteins’ specific function may either be _____ or _____
activated or inhibited
Chemical specificity
in order to bind properly proteins must have the right conformational shape
-A single protein may have multiple active sites for multiple ligands OR multiple sites for one ligand
Chemical specificity ; the active (binding) site determines ________________
the type of chemical that is bound
Some sites only bind ____ ligand while others can bind _____ ligands
one; many
example:Drugs. The more sites a drug binds to, the higher the chance of unwanted side-effects.
substrate=
enzyme=
substrate=ligand
enzyme=protein
enzyme characteristics (4 main ones_
- can be defined as protein catalyst (speeds up reaction)
- Increases the rate of a reaction or Lowers the activation energy of the reaction
- enzyme itself is unchanged (a single catalyst molecule can act over and over again to catalyze many reactions)
- Enzymes end in -ase
shape of active site on the enzyme provides basis for ______ _______.
enzymes specificity
–substrate comes and binds to an enzyme; lock and key model–>if substrate doesn’t fit it can’t bind there.
the strength of ligand protein is a property of the binding site known as _____
affinity
specificy depends on _____ of binding site
shape
affinity depends on the ____ of attraction in binding site of protein to ligand
strength
what does the affinity of a binding site for a ligand determine ?
how likely it is that a bound ligand will leave the protein surface and return to its unbound state.
what does the term saturation refer to
the fraction of total active sites that are occupied at any given time.
the percent saturation depends on
- the concentration ligand
- affinity
chemical reactions involve breaking of chemical bonds into _____ (reactant/products) and the making of new chemical bonds in ______ (reactant/product)
reactant, products
energy is added or released and doesn’t disappear (true or false)
true
4 determinants of chemical reaction rates
- reactant concentrations (higher concentration–>faster reaction rate)
- activation energy (higher activation energy; slower reaction rate)
- Temperature (higher temp–>faster reaction rate)
- Catalyst (presence of catalyst–>faster reaction rate)
