MCAT Extra Biochem Flashcards
What are four ways enzymes can catalyze reactions?
- Acid/Base Catalysis
- Covalent Catalysis
- Electrostatic Catalysis
- Proximity and Orientation Effects
What is acid/base catalysis?
Enzymes act as either enzymes or bases, which can for example, help move protons around
What is covalent catalysis?
Enzymes form a covalent bond with another molecule, usually the target
For example, an enzyme could be an electron carrier or electron sink
What is electrostatic catalysis?
Stabilizing the negative charge on a molecule, like DNA replication molecules that stabilize negative charges on DNA with magnesium ions
What is catalysis through proximity and orientation effects?
Enzymes bring two molecules together in the right orientation to allow them to react more quickly
What is the transition state of a reaction?
The highest-energy point on a reaction coordinate, and therefore the most unstable point
Describe the progression of enzyme-substrate fit during the reaction process
Initially, they do not bind perfectly, but then both the enzyme and substrate change their conformation slightly so that they fit tightly together, and then at the end of the reaction the substrate no longer fits perfectly in the enzyme – this is the induced fit model
At what point is the enzyme most tightly bound to its substrate?
During the transition state
Do enzymes necessarily bind one substrate?
No – sometimes they have binding sites for more than one substrate
What do transferases do?
They move some functional group from one molecule to another
What do ligases do?
Ligases catalyze reactions between to molecules that are combining to form a complex together
What do oxidoreductases do?
An oxidase takes electrons away from a molecule
A reductase gives electrons to a molecule
These enyzymes can catalyze forward and back reactions
Lactate dehydrogenase is an example because it removes a hydride group, thereby oxidizing a molecule
What do isomerases do?
Convert a molecule to one of its isomers
What do hydrolases do?
They use water to cleave one molecule into two molecules
What do lyases do?
They catalyze the dissociation of one molecule into two molecules without using water like hydrolases do, and without using oxidation or reduction
