Part 1
Define Energy
the potential to do work
Define Free Energy
Energy that can be used to do work.
Define entropy
A measure of the level of disorder
High entropy= more disorder(less ordered)
Low entropy= less disorder(more ordered)
*Think of Jenga blocks*
What are the two ways enzymes can be regulated? Define them.
Irreversible Inhibition: typically involves covalent modification of the enzyme(usually the active site) (Lecture 15 slide 46 example.)
Reversible Inhibition: a molecule binds to an enzyme in a non-covalent manner and alters enzyme confirmation.
What is the definition of potential energy? What is the definition of kinetic energy?
Potential energy is energy "stored" in an object.
Kinetic Energy is the energy of motion(at the molecular scale).
Define exergonic. What is the delta G? Spontaneous or non-spontaneous?
Define endergonic. What is the delta G? Spontaneous or non-spontaneous?
Exergonic: energy-releasing reactions. Reactants have more energy than products. Spontaneous. delta G<0
Endergonic: Energy-consuming reactions. Reactants have less energy than products. Non-spontaneous. deltaG>0
How does pH affect the reaction rate?
pH can change amino acid protonation(charge)
Define Competitive inhibition. What is its effect on vmax and Km?
Define noncompetitive inhibition. What is its effect on vmax and Km?
Competitive inhibitors compete with substrate for access to active site. When around, the Vmax is the same as when not, and the Km is higher when comp. inhibitors are around.
Noncompetitive inhibitors bind away from the active site and alter active site function-making it harder or impossible for substrate to bind. Vmax and Km are lower when noncompetitive inhibitor is present.
List the characteristics of Higher free energy
* Less stable(more bonds)
* More concentrated
* More ordered
* Greater work capacity
List the characteristics of Lower free energy
* More stable
* Less concentrated
* Less ordered
* lesser work capacity
What does Km mean?
Km describes the affinity of an enzyme has for its substrate.
Competitive:
* Similar to substrate structurally and chemically
* Compete with substrate for active site
* Adding substrate can overcome inhibition
Noncompetitive:
*No similarity to substrate
*Bind at a location other than the active site, changing shape of active site
* Adding substrate cannot overcome inhibition.
What are enzymes? What are their jobs/what do they do?
Enzymes are protein. Enzymes act as catalysts by lowering activation energy.
Enzymes have substrate specificity- having a higher binding affinity and/or catalytic activity on specific molecules to facilitate reactions through the enzymes active site.
What do enzyme catalysts do and what do they not do?
Enzymes....
-Do lower the energy of activation Ea
-Do increase the rate of the reaction
-does not change amount of energy released(i.e. doesn't change deltaG)
-doesn't change equilibrium constant, Keq
What does a low Km mean?
Enzyme holds the substrate tightly(high affinity) and is more efficient at converting it to product.(The catalyst is more efficient).
What does a high Km mean?
A high Km means that the enzyme holds the substrate loosely(low affinity) and is less efficient at converting it to product.
How do enzymes lower the activation energy of a reaction?
Enzyme holds reactants(substrates) close together in the right orientation of its active site for the reaction, reducing reliance on random collisions.
Enzyme can put a "strain" on existing bonds, making them easier to break.
List the 5 factors that affect the rate of a reaction.
*Substrate concenctration
*Enzyme concenctration
*temperature
*pH
*the presence/concentration of other ions
What does the curve "Plateau" mean?
The enzymes are all saturated with substrate, so there is no more work able to do, because every enzyme is busy.
R-groups interact with substrates at the active site and stabilize the transition state, so that the reaction can proceed with further interactions with R-groups.