Biochemistry : Hydrolases

Study concepts, example questions & explanations for Biochemistry

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Example Questions

Example Question #17 : Protein Structure And Functions

Lysosomal enzymes are predominantly __________.

Possible Answers:

kinases

isomerases

decarboxylases

hydrolases

oxidases

Correct answer:

hydrolases

Explanation:

The lysosome is the "stomach" of the cell. It contains many hydrolytic enzymes to digest and recycle the monomers used to form old polymers. Remember the opposite of dehydration/condensation synthesis is hydrolysis. Hydrolysis reactions use water to break bonds in polymers, yielding monomers that can be recycled and reused in anabolic pathways.

Example Question #1 : Hydrolases

Which of the following best describes how a lysozyme works?

Possible Answers:

It hydrolyzes bonds in lipids, causing a split in a fatty acid chain.

It is responsible for the cleaving of amino acid chains via the ping-pong mechanism.

It cuts a polysaccharide relatively slowly, facilitating a random, spontaneous collision between water and the sugar, with little intervention.

It cleaves the phosphodiester bond in nucleic acids, via hydrolysis.

It cuts the bond in a polysaccharide, by holding six sugars in a row in its active site, and adding a water molecule, causing hydrolysis.

Correct answer:

It cuts the bond in a polysaccharide, by holding six sugars in a row in its active site, and adding a water molecule, causing hydrolysis.

Explanation:

Lysozymes speed up by many times the hydrolysis of polysaccharides, by adding the water molecule to sugars linked in its enzyme-substrate complex. If left alone without the lysozyme, this hydrolysis would occur relatively infrequently, because it requires a large activation energy which would be supplied only by rare random collisions. The amino acid cleavage enzyme which uses the ping-pong mechanism is chymotrypsin. The enzyme which breaks nucleic acid phosophodiester bonds is phosphodiesterase. Fats are hydrolyzed by lipases, not lysozymes.

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