Module 12 Flashcards
Enzymes catalyze biological reactions by __________. They can __________ a reaction but they do not __________. Doubling the substrate concentration will __________ the maximum rate of the enzyme-catalyzed reaction.
lowering the activation energy; speed up; alter the equilibrium; not affect
In a protein, an alpha-helix is a type of __________ structure; the three-dimensional configuration of a globular protein is an example of a/an __________ structure; the particular amino acid sequence is the __________ structure; and an association of multiple peptide chains represents a __________ structure.
secondary; tertiary; primary; quaternary
In the __________ model of enzyme action, the __________ and the __________ react and adapt to one another in order to initiate catalysis. During catalysis, they pass through the __________ before the product emerges.
induced fit; active site; substrate; transition state
Based on the conventions for naming enzymes, which of the following names would best apply to an enzyme that removes an amino group from tyrosine and adds it to a precursor to form glutamate?
tyrosine transaminase
Nonprotein prosthetic groups which facilitate the activity of certain enzymes are called __________. The polypeptide portion of such an enzyme is called the __________ and the enzyme/prosthetic group complex is called the __________.
cofactors; apoenzyme; holoenzyme
An alpha-amino acid has a/an __________ and a/an __________ on the alpha carbon; in aqueous solution at pH = 7, the molecule exists as a __________.
carboxyl; amino; zwitterion (the carboxyl group is deprotonated and negatively charged; the amino group is protonated and positively charged.)
When the pH of a protein-containing solution gradually rises or falls, a certain pH value is reached wherein the protein has an equal number of positive and negative charges. This value is called the protein’s __________ ; at this pH, the proteins tend to __________.
isoelectric point; coagulate - Depending on its individual amino acid composition, a given protein will have an overall characteristic electric charge. Charged molecules are water-soluble. When the pH of the solution is varied, it may reach a point where the protein loses its positive or negative charge due to protonation or deprotonation of the functional groups in the amino acid side chains. Uncharged proteins cease to repel one another and can coagulate and precipitate out of solution.
When the free functional groups of two amino acids combine (as in a protein), the bond formed between them is a type of __________ specifically called a/an __________ bond. It is stabilized by __________.
amide; peptide; resonance - This is a type of amide bond that is stabilized by resonance delocalization involving the electrons of the carbonyl function, somewhat like a keto-enol tautomer. As a result, the bond is planar and relatively rigid; this allows proteins to assume definite shapes.
Enzyme X has two binding sites: one for its substrate and one for the ultimate product made by the biosynthetic pathway in which X participates. Therefore, Enzyme X is __________ and is probably regulated by __________. There is a drug, Z, which mimics this enzyme’s substrate and can reduce its activity by temporarily binding to its active site. Drug Z is called a/an __________ of the enzyme.
allosteric; feedback inhibition; reversible competitive inhibitor
An enzyme which functions to oxidize a molecule of D-glucose by changing a hydroxyl group to a ketone group, but which will not oxidize L-glucose, is said to exhibit __________ .
stereochemical specificity
