EK Lecture 1 #8

[Fing Fang Foom]

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What molecule is a reactant in the breaking of the beta-1,4-glycoside linkages of cellulose and chitin?

Oxygen and alpha-1,4-glucosidases were easily eliminated so it comes down to water and beta-1,4-glucosidase. Water is responsible for breaking down most macromolecules so I chose water.

I am having trouble thinking about this. I only know that these are enzymes and are not reactants but I do not understand why. I chose the correct answer but I don't know why enzymes are not reactants. I had that memorized in general chemistry but I don't understand it.

I am thinking in terms of an experiment. If we put all of our stuff in the pot for our reaction do we say that catalysts are not reactants because all of the reactants have to be added to the pot before we add our catalyst? I know it seems silly but when I have applications for the things I am reading I am better able to understand things.

 

[apex954]

I dont think so, for the reason that enzymes aren' t considered reactant bcuz they r not used up, i.e they remain unchanged after d rxn...the key word in the question is 'reactant', i.e something that gets used up to become a product. So it doesn't matter if the prefix is glu or gly, as long it has -ase suffix, which usually indicates an enzyme, it will b d wrong answer, as enzymes are NOT reactant.

 

[blue0rchid]

water is the correct answer. It's called hydrolysis because water is added.
Anything with -ase is an enzyme and enzymes are catalysts, not reactants.

Think if enzymes like a chef. You may have all the food ingredients in the pot, but it won't come out edible. The chef would know which ingredient go in first with other ingredients, what heat level they should be cooked at, and for how long, then you'll have edible meal. hahaha sorry if i don't explain very well.

 

[movax]

What molecule is a reactant in the breaking of the beta-1,4-glycoside linkages of cellulose and chitin?

Oxygen and alpha-1,4-glucosidases were easily eliminated so it comes down to water and beta-1,4-glucosidase. Water is responsible for breaking down most macromolecules so I chose water.

I am having trouble thinking about this. I only know that these are enzymes and are not reactants but I do not understand why. I chose the correct answer but I don't know why enzymes are not reactants. I had that memorized in general chemistry but I don't understand it.

I am thinking in terms of an experiment. If we put all of our stuff in the pot for our reaction do we say that catalysts are not reactants because all of the reactants have to be added to the pot before we add our catalyst? I know it seems silly but when I have applications for the things I am reading I am better able to understand things.

Gross oversimplification here, but enzymes act as catalysts to lower the activation energy of the reaction (both forward and reverse). If you took away the enzyme, the reaction may proceed at some vastly reduced rate.

This question I think primarily relies on you knowing that the majority of bonds between biological molecules are broken via hydrolysis. Dehydration forms them (look at peptide bonds for instance), adding water back (hydrolyzing) breaks them.