Lecture 14: Introduction to Enzymes Flashcards
what are enzymes?
biological catalysts; capable of speeding up reaction rates without being permanently altered themselves
most enzymes are ___ (what type of biomolecule)
proteins
the rate of reaction depends on what 2 factors?
- concentrations of reactants/products
2. activation energy of reaction
in most biological reactions, the concentrations are ___ and the activation energies are ___
low; high
without catalysts, what would be the fate of biological reactions?
occur too slow to maintain life
enzymes accelerate ___ while not changing ___ of the reaction
arrival to equilibrium; thermodynamic favourability
what are the 6 classes of enzymes?
- transferase
- hydrolase
- oxidoreductase
- ligase
- lyase
- isomerase
give an example of oxidoreductase
alcohol dehydrogenase
function of oxidoreductase enzymes
catalyse oxidation-reduction reactions
oxidoreductase enzymes result in 1-2 ___ reactions that involve changes in __/___ atoms
electron transfer; H or O
ethanol is oxidized to ___
acetaldehyde
give an example of transferase
glucose kinase
function of transferase enzymes
catalyse transfer of functional groups from one molecule to another
what functional groups can be transferred by transferase?
amino, acyl, methyl, carbonyl, carboxyls, phosphoryl
example of hydrolase
protease
what is the function of hydrolase?
catalyze cleavage of molecule by adding water (hydrolysis)
what bonds are typically acted upon by hydrolase?
C-O, C-N and O-P
example of lyase
pyruvate decarboxylase
function of lyase enzymes
catalyze reactions in which CO2, H2O, NH3 are removed to form a double bond, or are added to a double bond
example of isomerase
alanine racemase
function of isomerase enzymes
catalyze intramolecular rearrangement (moving functional groups within the molecule
example of ligase
pyruvate carboxylase
function of ligase enzymes
catalyze reactions in which 2 molecules are joined at the expense of an ATP molecule (or similar molecule)
how are most enzymes named?
by their substrates/reactions and the suffix “ase”
what is Gibb’s Free energy?
energy available to do work
enthalpy change represents__
the amount of heat produced/absorbed in a reaction
entropy change represents ___
change in system order
gibb’s free energy is independent of ___
the path of transmission
does gibb’s free energy provide information on reaction rate?
no
when delta G is negative, the reaction will occur___
spontaneously (no energy input needed)
when delta G is positive, the reaction will occur___
non-spontaneously (needs energy input)
when delta G = 0, the reaction is __
at equilibrium
T/F enzymes alter reaction equilibria
false
the ___ determines the equilibrium of reaction (how much product is made)
free energy difference between reactants and products
enzymes determine what about reaction equilibrium?
how fast equilibrium is reached
enzymes increase reaction rates by decreasing __
activation energy
what is a transitionstate?
a fleeting molecular structure intermediate to reactant and product; least stable and highest energy
how do enzymes lower activation energy?
by altering reaction pathway to form a more stable transition state
the difference in energy between the substrate and transition state is the ___
activation energy
