42 Questions
What functional group of NAD+ is involved in the reaction?
Carbon on the nicotinamide ring opposite the positively charged nitrogen
What is the role of the histidine nitrogen in the reaction?
To bind the dissociable proton on lactate
What is the function of the zinc atom in the active site?
To stabilize the negative charge on the oxygen
What is the partner of ethanol in the reaction?
NAD+
What happens to the proton removed from ethanol?
It is used to reduce NAD+ to NADH
What is the role of the serine side chain -OH in the reaction?
To pull the proton away from ethanol
What is the result of the oxidation reaction?
Ethanol is oxidized to acetaldehyde
What can metal ions do in their coordination spheres?
Bind multiple ligands
What is the common characteristic of all digestive enzymes?
They are all hydrolases
What type of enzyme is chymotrypsin?
Protease
What is the result of the reaction catalyzed by pyrophosphatase?
Formation of 2 inorganic phosphates
What type of reaction is catalyzed by lyases?
Cleavage of bonds by means other than hydrolysis or oxidation
What is the role of a carbonyl carbon in lyase-catalyzed reactions?
To act as an electron sink
What type of enzyme is an aldolase?
Lyase
What is the result of the action of dehydratases?
Removal of the elements of water
What is the term for enzymes that catalyze the cleavage of high-energy phosphate bonds?
Pyrophosphatases
What does the enzyme substitute for the coenzyme in the reaction?
The functional group of an active-site amino acid residue
What effect would the mutation in glucokinase have on the reaction?
It would probably affect the binding of ATP or a subsequent step in the reaction sequence
What is the role of lysozyme in the human immune system?
It cleaves glycosidic linkages in bacterial cell walls
What is the pH optimum of the purified lysozyme enzyme?
5.2
What are the two acidic residues at the active site of lysozyme?
E35 and D52
What is the pKa of E35?
5.9
What is the primary ionization state of E35 at the pH optimum of the enzyme?
Protonated
What is the primary ionization state of D52 at the pH optimum of the enzyme?
Ionized
What role does histidine play in an enzyme?
Base catalyst
At which pH would an enzyme exhibit maximal activity if the pKa of the histidine residue is 6.2?
6.2
What type of inhibitor is penicillin?
Suicide inhibitor
What is affected by the use of penicillin in susceptible targets?
Bacterial cell wall
What is the role of vitamins in enzyme activities?
Act as coenzymes
What is characteristic of coenzymes?
Complex, nonprotein organic molecules
What is the basis for the treatment of maple syrup urine disease with thiamin?
Mutation in the enzyme led to a loss of TPP
What is the enzyme deficient in maple syrup urine disease?
Branched-chain α-keto acid dehydrogenase
What type of bond is formed between a covalent inhibitor and the active site of the enzyme?
Covalent bond
What is the primary target of medications aimed to inhibit enzymes?
Active site
What is the characteristic of coenzymes after a catalytic reaction?
They are reversibly bound to apoenzymes
What is the function of the active site in an enzyme?
To bind both the substrate and cofactor
What is the role of functional groups in the active site?
They participate in binding both the substrate and cofactor
Which type of inhibitor forms a bond with the active site without the enzyme altering the structure of the inhibitor?
Covalent inhibitor
What is the characteristic of coenzymes made up of amino acids?
They are reversibly bound to apoenzymes
What is the primary function of a coenzyme?
To facilitate catalysis
What is the result of a covalent inhibitor binding to the active site?
The enzyme is inhibited
What is the characteristic of enzyme inhibition by medications?
It is an irreversible process
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