Biochemistry Chapter 2: Enzymes Flashcards
What are enzymes?
Enzymes are biological catalysts that are unchanged by the reactions they catalyze and are reusable
What are oxidoreductases?
Catalyze oxidation-reduction reactions that involve the transfer of elections.
What are transferases?
Transferases move a functional group from one molecule to another molecule.
What are hydrolases?
They catalyze cleavage with the addition of water.
What are lyases?
They catalyze cleavage without the addition of water and without transfer of electrons. The reverse reaction is often more important biologically.
What are isomerases?
They catalyze the interconversion of isomers, including both constitutional isomers and stereoisomers.
What are ligases?
Join two large biomolecules, often of the same type.
Exergonic reactions____energy
Endergonic reactions____energy
Exergonic reactions release energy.
Endergonic reactions absorb energy.
What do enzymes change about a reaction?
The rate at which equilibrium is reached, not the free energy or enthalpy.
How do enzymes act?
They stabilize the transition state by providing a favorable environment or bonding with the substrate
What does the lock and key theory hypothesize?
The lock and key theory hypothesizes that the enzyme and substrate are exactly complementary.
What does the induced fit model hypothesize?
enzyme and substrate undergo conformational changes to interact fully.
What are two molecules that enzymes can use?
metal cation COFACTORS or organic COENZYMES
What is saturation kinetics?
As the substrate concentration increases, the reaction rate does as well until a maximum value is reached.
What do cooperative enzymes show in their curve?
They show a sigmoidal curve because of the change in activity with substrate binding.
What can impact proteins’ ability to function?
temperature, pH and solution concentration
What is feedback inhibition?
a regulatory mechanism whereby the catalytic activity of an enzyme is inhibited by the presence of high levels of a product later in the pathway
What is reversible inhibition?
ability to replace the inhibitor with a compound of greater affinity or to remove it using mild laboratory treatment.
(competitive, noncompetitive, mixed, uncompetitive)
What is competitive inhibition? What does it do to the Vmax/Km?
Inhibitor is similar to the substrate and binds at the active site. It can be overcome by adding more substrate. Vmax does not change, Km increases.
What is noncompetitive inhibition?
Inhibitor binds with equal affinity to the enzyme and enzyme-substrate complex. Vmax decreases and Km is unchanged.
What is mixed inhibition?
when the inhibitor binds with unequal affinity to the enzyme and the enzyme-substrate complex. Vmax is decreased and Km is increased or decreased depending on which the inhibitor has a high affinity for.
What is uncompetitive inhibition?
When it only binds to the enzyme-substrate complex. Both Km and Vmax decrease.
What is irreversible inhibition?
Alters the enzyme in a way that the active site is unavailable for a prolonged duration or permanently; new enzyme molecules must be synthesized for the reaction to occur again.
Allosteric sites?
Where things other than substrate bind
What are zymogens?
precursors that are inactive & are activated by cleavage.
