Question 1

Which of the following is an enzyme that temporarily undergoes covalent catalysis as part of its mechanism?

Accepted Answer

All of the choices listed, papain, chymotrypsin, caspase, and elastase, are examples of enzymes that utilize covalent catalysis as part of their mechanism. This involves the formation of a transient covalent bond between the enzyme and the substrate during the reaction process.

Question 2

What process converts chymotrypsinogen to chymotrypsin?

Accepted Answer

Chymotrypsinogen is converted to chymotrypsin through peptide bond cleavage. This is a common mechanism for activating zymogens or proenzymes, where an inactive form is converted to an active form by cleaving specific peptide bonds.

Question 3

What modification is made to DNA that protects the host DNA from cleavage by host restriction endonucleases?

Accepted Answer

Methylation is the modification made to DNA that protects host DNA from cleavage by host restriction endonucleases. This involves the addition of methyl groups to the DNA, typically at adenine or cytosine bases, which prevents the restriction enzymes from recognizing and cutting the DNA.

Question 4

Myosins hydrolyze _____________ in a controlled manner and use the free energy of hydrolysis to promote conformational changes within myosin itself.

Accepted Answer

The answer of Myosins hydrolyze _____________ in a controlled manner...

Question 5

What structures found in proteins are named for the fact that they interact with phosphoryl groups?

Accepted Answer

P-loops are named for their interaction with phosphoryl groups, as they are involved in binding and hydrolyzing phosphate groups in ATP or GTP, which is a critical function in many cellular processes.

Question 6

In trypsin, the specificity pocket contains a/an ______________ residue that binds to the positive charge of the K or R residue of the substrate.

Accepted Answer

The answer of In trypsin, the specificity pocket contains a/an...

Question 7

In proteases such as papain, a ___________________ residue is activated by hydrogen-bonding to a histidine residue.

Accepted Answer

The answer of In proteases such as papain, a ___________________...

Question 8

Which of the following techniques allows investigators to test the role of individual amino acids in the determination of enzyme structure/function relationships even if the investigated amino acid is not present in the active site?

Accepted Answer

Site-directed mutagenesis is a molecular biology method that allows for the creation of specific, targeted changes in a gene, thereby altering the amino acid sequence of the encoded protein. This technique can be used to investigate the role of individual amino acids in enzyme structure and function, including those not located in the active site, by observing the effects of these changes on the enzyme's activity, stability, and other properties.

Question 9

What type of symmetry is created by inverted repeats in double-stranded DNA?

Accepted Answer

Two-fold rotational symmetry is created by inverted repeats in double-stranded DNA, where the sequence on one strand is a reverse complement of the sequence on the opposite strand, allowing the molecule to be rotated 180 degrees and still align with itself.

Question 10

In chymotrypsin, the tetrahedral intermediate transition state is stabilized by a structural feature referred to as the "___________________" hole.

Accepted Answer

The answer of In chymotrypsin, the tetrahedral intermediate transition state...

Question 11

The mechanism of chymotrypsin involves the formation of an unstable __________________ -shaped intermediate that is stabilized by the oxyanion hole.

Accepted Answer

The answer of The mechanism of chymotrypsin involves the formation...

Question 12

What metal ion is frequently found in enzyme active sites that act on phosphate-containing substrates?

Accepted Answer

Magnesium (Mg) ions are frequently found in the active sites of enzymes that act on phosphate-containing substrates, as they can interact with the phosphate groups to facilitate binding and catalysis.

Question 13

What type of assay allows analysis of an enzyme catalyzed reaction in milliseconds?

Accepted Answer

Stopped-flow is a technique specifically designed to observe fast biochemical reactions by rapidly mixing reactants and measuring the reaction progress in milliseconds.

Question 14

Effective protease inhibitors are often _________________ for one enzyme.

Accepted Answer

The answer of Effective protease inhibitors are often _________________ for...

Question 15

The reaction center of most carbonic anhydrases is a zinc ion bound to water and _______________ residues of the enzyme.

Accepted Answer

The answer of The reaction center of most carbonic anhydrases...

Question 16

Kinetic studies on myosins, in the presence and absence of divalent cations, show that ________________ is the true substrate for this enzyme.

Accepted Answer

The answer of Kinetic studies on myosins, in the presence...

Question 17

What type of reaction is catalyzed by proteases?

Accepted Answer

Proteases catalyze the hydrolysis of peptide bonds in proteins, breaking them down into smaller peptides or amino acids.

Question 18

What metal ion is required by carbonic anhydrase for activity?

Accepted Answer

Carbonic anhydrase requires a zinc (Zn) ion for its enzymatic activity, where the zinc ion plays a crucial role in the catalysis of the conversion between carbon dioxide and water to bicarbonate and protons.

Question 19

A-T base pairs, which contain _____ hydrogen bonds, are more easily interrupted than G-C base pairs with _______ hydrogen bonds.

Accepted Answer

The answer of A-T base pairs, which contain _____ hydrogen...

Question 20

The catalytic mechanism ofcarbonic anhydrase, in which the substrates are simply oriented to stabilize the transition state, is called ___________________.

Accepted Answer

The answer of The catalytic mechanism ofcarbonic anhydrase, in which...

Quiz 9: Catalytic Strategies