Chapter 4 Flashcards
active site
Region on the surface of an enzyme that binds to a substrate
molecule and catalyzes its chemical transformation.
allosteric
Describes a protein that can exist in multiple conformations
depending on the binding of a molecule (ligand) at a
site other than the catalytic site; such changes from one
conformation to another often alter the protein’s activity or
ligand affinity.
α-helix
Folding pattern, common in many proteins, in which a
single polypeptide chain twists around itself to form a rigid
cylinder stabilized by hydrogen bonds between every fourth
amino acid.
amino acid sequence
The order of the amino acid subunits in a protein chain.
Sometimes called the primary structure of a protein.
antibody
Protein produced by B lymphocytes in response to a foreign
molecule or invading organism. Binds to the foreign
molecule or cell extremely tightly, thereby inactivating it or
marking it for destruction.
antigen
Molecule or fragment of a molecule that is recognized by
an antibody.
β-sheet
Folding pattern found in many proteins in which neighboring regions of the polypeptide chain associate side-by-side with each other through hydrogen bonds to give a rigid, flattened structure.
binding site
Region on the surface of a protein, typically a cavity or
groove, that interacts with another molecule (a ligand)
through the formation of multiple noncovalent bonds.
C-terminus
The end of a polypeptide chain that carries a free carboxyl
group (–COOH).
coenzyme
Small molecule that binds tightly to an enzyme and helps it
to catalyze a reaction
coiled-coil
Stable, rodlike protein structure formed when two or more
α helices twist repeatedly around each other.
conformation
Precise, three-dimensional shape of a protein or other
macromolecule, based on the spatial location of its atoms
in relation to one another
disulfide bond
Covalent cross-link formed between the sulfhydryl groups
on two cysteine side chains; often used to reinforce a
secreted protein’s structure or to join two different proteins
together.
enzyme
A protein that catalyzes a specific chemical reaction.
feedback inhibition
A form of metabolic control in which the end product of
a chain of enzymatic reactions reduces the activity of an
enzyme early in the pathway.