Enzymes: Kinetics and Thermodynamics Flashcards
What is the difference between kinetics and thermodynamics in a reaction?
Thermodynamics is how favorable a reaction is.
Kinetics is how fast a reaction is.
Describe the major enzyme classifications and major reaction catalyzed by each.
Oxidoreductases- oxidation/reduction
Transferases- transfers functional groups
Hydrolases- cleaves bond with water
Lyases- addition rxn to a double bond making a single bond
Isomerases- switches form one isomer of a molecule to another isomer
Ligase- using ATP hydrolysis to form a new bond
Explain whether enzymes catalyze reactions through changes in rate and/or equilibrium
Enzymes catalyze reactions by decreasing the activation energy needed for the reaction to occur. Enzymes change the rate of which the reaction occurs but does not affect equilibrium at all.
Compare the characteristics of Michaelis-Menton and an allosteric enzyme kinetics and their roles in cellular pathways
Michaelis-Menton kinetics enzymes work through single, independent, active sites and have a rapid “on or off” activity (anytime substrate is present they are working).
Allosteric kinetics enzymes have multiple, dependent, active sites that have a slower variable activity (threshold needs to be met for them to work).
Define the terms Vmax, Km, and kcat and how their values relate to the catalysis of a reaction.
Vmax- is the maximum rate of a reaction when the enzyme is saturated with substrate
Km- the substrate concentration at which the reaction is at 1/2 Vmax
kcat- the slowest, rate-limiting, step in any enzymatic reaction
Explain the need and the nomenclature for zymogens and isozymes.
There is a need for zymogens so that they do not begin to catalyze reactions before they are needed. This stops enzymes such as those in the stomach from breaking down the body cells instead of the proteins ingested. They have a prefix of pro- or a suffix of -ogen.
Isozymes have different structures from each other but catalyze the same reactions. As different tissues have different environments (ie. pH) different structures will protect the enzymes to do what they are needed for. The naming of isozymes is tissue specific.
