Card Set Information
Enzymes biochemistry NSU
Introduction to Enzymes
What is an enzyme?
a protein catalyst for specific biochemical reactions
What does an enzyme affect?
they speed up reactions by lowering the activation energy of a reaction. Gibbs free energy is altered.
What does an enzyme not affect?
Keq and deltaG are not affected by enzymes
Name 2 models used to describe enzyme specificty and/or catalytic activity
The lock and key model
The induced fit model
What is a prosthetic group?
Small non-protein organic molecule that tightly binds to the enzyme's active site.
When the prosthetic group is attached, an apoenzyme becomes a holoenzyme
Name the 6 classes of enzymes
What is the michaelis menton equation and what do the terms mean?
Km = constant value for specific substrate, Michalis constant
Vmax = maximum velocity of rxn
[S] = substrate reaction
V = velocity of reaction
In an Michaelis-Menten plot, where is Vmax and how do you find Km?
Vmax is found when [S] is very high. Where all the enzyme is converted to the ES complex.
Km is determined by finding [S] when V = 1/2 Vmax
A lineweaver-burk plot is also called a _________ ______ plot.
What are the vertical and horizontal intercepts of the lineweaver-burk plot?
vertical = 1/Vmax
horizontal = -[1/Km]
What is plotted in a Michaelis-Menten plot?
[1/V] vs. 1/[S]
What are the advantages of the Eadie-Hofstee plot?
It will give more evenly spaced data points, not clustered like the LB plot
What distinguishes a competitor inhibitor from the rest?
They bind directly to the active site.
They can be overcome by increasing [S]
What does the inhibitor bind with for competitive, non competitive, and uncompetitive inhibition?
competitive = active site
non competitive = react w/ enzyme to reduce its effectiveness to bind with substrate
uncompetitive = bind with the ES complex (irreversible) to form the ESI complex
What does the sigmoid V vs [S] plot as well as a curved lineweaver-burk plot indicate?
indicates allosteric enzyme reaction
positive cooperativity of the enzyme
On the Lineweaver-Burk plots are the vertical and horizontal intercepts the same or different for a.) competitive, b.) non-competitive and c.) uncompetitively inhibited reactions?
On Linewaver-Burk plots:
A) Competitive inhibitors show a steeper slope than uninhibited reactions, but have the same 1/Vmax point.
B) Noncompetitive inhibitors show a steeper slope, but have the same -1/Km point.
C) Uncompetitive Inhibitors show the same slope, but shifts the curve left, showing a greater -1/Km value.