Biochem Class

Question 1

Cofactor

Answer 1

a substance (other than the substrate) whose presence is essential for the activity of an enzyme.

Question 2

Coenzyme

Answer 2

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.

Question 3

Prosthetic Groups

Answer 3

A prosthetic group is a tightly bound, specific non-polypeptide unit required for the biological function of some proteins.

Question 4

Holoenzyme

Answer 4

a biochemically active compound formed by the combination of an enzyme with a coenzyme.

Question 5

Apoenzyme

Answer 5

An apoenzyme is an inactive enzyme, activation of the enzyme occurs upon binding of an organic or inorganic cofactor.

Question 6

Activation Energy Barrier

Answer 6

Enzymes lower the activation energy to a point where a small amount of available heat can push the reactants to a transition state.

Question 7

Lock and Key Model

Answer 7

A model for enzyme-substrate interaction suggesting that the enzyme and the substrate possess specific complementary geometric shapes that fit exactly into one another.

Question 8

Induced Fit Model

Answer 8

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.

Question 9

Michaelis-Menten Equation

Answer 9

Question 10

Michaelis-Menten Constant

Answer 10

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.

Question 11

Kcat (K2) and VMax

Answer 11

Question 12

Competitive Inhibitor

Answer 12

Question 13

Uncompetitive Inhibitor

Answer 13

Question 14

Noncompetitive/Mixed Inhibition

Answer 14

Question 15

Oxidoreductases

Answer 15

Transfer electrons between molecules (catalyze oxidation-reduction rxns)

Ex: Lactate Dehydrogenase in Glycolysis

Question 16

Transferase

Answer 16

Transfer functional groups between molecules.

Ex: Aminotransferases in amino acid synthesis and degradation shuffle amine groups between donor and acceptor molecules.

Question 17

Hydrolases

Answer 17

Cleave molecules by the addition of water.

Ex: Trypsin, a proteolytic enzyme (breaks down proteins)

Question 18

Lyases

Answer 18

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

Question 19

Isomerases

Answer 19

Move functional groups within a molecule

Ex: Triose phosphate isomerase in glycolysis

Question 20

Ligases

Answer 20

Join 2 molecules in a reaction powered by ATP hydrolysis

Ex: DNA ligase, an important enzyme in DNA replication

Question 21

Ligand

Answer 21

Question 22

Globins

Answer 22

The globins are a superfamily of heme-containing globular proteins, involved in binding and/or transporting oxygen.

Question 23

Bohr Effect

Answer 23

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.

Question 24

Hemoglobin and CO₂ Transport

Answer 24

Question 25

Allosteric Enzymes

Answer 25

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

Question 26

Cooperativity

Answer 26

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

Question 27

AA’s with Hydrophobic Side Chains

Answer 27

Aliphatic: Alanine, Isoleucine, Leucine, Methionine, Valine, Glycine

Aromatic: Phenylalanine, Tryptophan, Tyrosine (and kinda Proline)

Question 28

AA’s with Polar, Neutral Side Chains

Answer 28

Asparagine, Cysteine, Glutamine, Serine, Threonine, Tyrosine

Question 29

Acidic AA’s with Electrically Charged Side Chains

Answer 29

Aspartic Acid, Glutamic Acid

Question 30

AA’s with Basic Side Chains

Answer 30

Lysine, Arginine, Histidine