Biochem Class Flashcards
Cofactor
a substance (other than the substrate) whose presence is essential for the activity of an enzyme.
Coenzyme
A coenzyme is a substance that works with an enzyme to initiate or aid the function of the enzyme. It can be considered a helper molecule for a biochemical reaction. Coenzymes are small, nonproteinaceous molecules that provide a transfer site for a functioning enzyme.
Prosthetic Groups
A prosthetic group is a tightly bound, specific non-polypeptide unit required for the biological function of some proteins.
Holoenzyme
a biochemically active compound formed by the combination of an enzyme with a coenzyme.
Apoenzyme
An apoenzyme is an inactive enzyme, activation of the enzyme occurs upon binding of an organic or inorganic cofactor.
Activation Energy Barrier
Enzymes lower the activation energy to a point where a small amount of available heat can push the reactants to a transition state.
Lock and Key Model
A model for enzyme-substrate interaction suggesting that the enzyme and the substrate possess specific complementary geometric shapes that fit exactly into one another.
Induced Fit Model
asserts that when the active site on the enzymes makes contact with the proper substrate, the enzyme molds itself to the shape of the molecule.
Michaelis-Menten Equation
Michaelis-Menten Constant
Km is the Michaelis-Menten constant which shows the concentration of the substrate when the reaction velocity is equal to one half of the maximal velocity for the reaction. It can also be thought of as a measure of how well a substrate complexes with a given enzyme, otherwise known as its binding affinity.
Kcat (K2) and VMax
Competitive Inhibitor
Uncompetitive Inhibitor
Noncompetitive/Mixed Inhibition
Oxidoreductases
Transfer electrons between molecules (catalyze oxidation-reduction rxns)
Ex: Lactate Dehydrogenase in Glycolysis
Transferase
Transfer functional groups between molecules.
Ex: Aminotransferases in amino acid synthesis and degradation shuffle amine groups between donor and acceptor molecules.
Hydrolases
Cleave molecules by the addition of water.
Ex: Trypsin, a proteolytic enzyme (breaks down proteins)
Lyases
Add atoms or functional groups to a double bond or removes them to form double bonds.
Ex: Lyase fumarate is crucial to aerobic fuel metabolism
Isomerases
Move functional groups within a molecule
Ex: Triose phosphate isomerase in glycolysis
Ligases
Join 2 molecules in a reaction powered by ATP hydrolysis
Ex: DNA ligase, an important enzyme in DNA replication
Ligand
Globins
The globins are a superfamily of heme-containing globular proteins, involved in binding and/or transporting oxygen.
Bohr Effect
Low pH and high carbon dioxide promote the release of oxygen.
The pH difference between lungs and metabolic tissues increases efficiency of the O2 transport.
Hemoglobin and CO2 Transport
Allosteric Enzymes
Binding of a ligand to one site affects the binding properties of a different site on the same protein.
– can be positive or negative
– homotropic • The normal ligand of the protein is the allosteric regulator.
– heterotropic • A different ligand affects binding of the normal ligand.
Cooperativity = positive homotropic regulation
Cooperativity
For Effective Transport Affinity Must Vary with pO2 It must be a protein with multiple binding sites. Binding sites must be able to interact with each other. This phenomenon is called cooperativity.
Ex: Hemoglobin binds O2 cooperatively
AA’s with Hydrophobic Side Chains
Aliphatic: Alanine, Isoleucine, Leucine, Methionine, Valine, Glycine
Aromatic: Phenylalanine, Tryptophan, Tyrosine (and kinda Proline)
AA’s with Polar, Neutral Side Chains
Asparagine, Cysteine, Glutamine, Serine, Threonine, Tyrosine
Acidic AA’s with Electrically Charged Side Chains
Aspartic Acid, Glutamic Acid
AA’s with Basic Side Chains
Lysine, Arginine, Histidine
