Enzyme Kinematics Flashcards
(25 cards)
How do enzymes function?
Lower activation energy
What category of macromolecules are enzymes?
Proteins (except ribozymes)
What is the optical specificity of enzymes?
Only act on D-isomer of sugars, or L-isomer of amino acids
What happens to enzymes in a reaction?
E + S -> ES -> E + P
Enzymes are not used up
What do enzymes do to the equilibrium constants?
Enzymes do not alter equilibrium constants
What do enzymes do to the free energy (^G)?
Enzymes do not change the free energy for the reaction
Exergonic reactions are reactions with a ____ and ____ or ____
-/ve ^G
Spontaneously occur or may generate energy
Endergonic reactions are reactions with a ____ and ____
+^G
Require energy input to occur
What are 2 factors that affect enzymes?
Temperature
pH
What happens when temperature increases?
- Rate of reaction increases
- Proteins denature at >102°F
What happens when temperature decreases?
Reaction rate slows down at <98°F
What enzymes work at acidic pH (1.5-2.0)?
Pepsin in stomach
What enzymes work at neutral pH (7.3-7.4)?
Carbonic anhydrase in RBC
What enzymes work at basic pH (8.0-9.0)?
Trypsin in small intestines
Name 2 experimental plots used to determine Km and Vmax? Which is better?
Eadie-Hofstee > Lineweaver-Burke
What are the 3 types of enzyme inhibition?
Competitive
Non-competitive
Irreversible/poisons
Competitive inhibition
a. Reversible/irreversible
b. Binding site
c. Molecule looks like ____
d. Effect on Vmax
e. Effect on Km
a. Reversible
b. Competitor binds at active site
c. Molecule looks like S
d. No effect on Vmax
e. Increases Km
Non-Competitive inhibition
a. Reversible/irreversible
b. Binding site
c. Molecule appearance
d. Effect on Vmax
e. Kinetics explained by ____
a. Reversible
b. Binds at Allosteric site
c. Molecule does not look like S
d. Decreases Vmax
e. Kinetics explained by Hill equation/plot
Examples of Irreversible/poisonous
Heavy metals (silver, mercury)
Nerve gas
Carbon monoxide (CO)
Cyanide (CN)
What enzymes have competitive inhibition?
Most enzymes
What enzymes have non-competitive inhibition?
Allosteric enzymes & Hb
What is the Michaelis-Menten curve?
Describes effects of substrate concentration on activity of many (not all) enzymes
What is Vmax?
Maximum velocity of reaction
What is Km?
- Concentration of substrate at which reaction occurs at rate of 1/2 Vmax
- estimated physiological concentration of substrate
