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Lecture Comments (8)

1 answer

Last reply by: Professor Hovasapian
Wed Nov 4, 2015 9:35 PM

Post by Stephanie Bule on November 2, 2015

Hey Prof. Hovasapian. For the last example, the amino acid serine, shouldn't the side chain be CH2-OH? Wouldn't CH3-OH break the octet rule forming 5 total bonds since it's attached not only to the oxygen from the OH group, but also the carbon on the amino acid backbone? Thanks!

2 answers

Last reply by: Sally Acebo
Tue Jun 9, 2015 5:48 PM

Post by Sally Acebo on June 3, 2015

I think you forgot to put an extra H for the Nitrogen in the last example, the N of the peptide bond only has 2 bonds

2 answers

Last reply by: Archimedes S
Mon Sep 9, 2013 7:52 PM

Post by Archimedes S on September 8, 2013

Hi Prof. Hovasapian.  I've always been a bit confused about the term "hydrolysis".  In Ochem, most of the hydrolysis reactions we learned about were either acid or base catalyzed.  So should we think about hydrolysis as the reaction between the hydroxide or hydronium ions naturally in water, not as the water itself reacting?  I hope that makes sense...

Hydrolysis & Condensation Reactions


  • Intro 0:00
  • Hydrolysis and Condensation Reactions 0:50
    • Hydrolysis
    • Condensation
    • Example 1: Hydrolysis of Ethyl Acetate
    • Example 2: Condensation of Acetic Acid with Ethanol
    • Example 3
    • Example 4: Formation & Hydrolysis of a Peptide Bond Between the Amino Acids Alanine & Serine

Transcription: Hydrolysis & Condensation Reactions


So today's lesson, what I thought we'd do is take just a brief little sidestep, but I wanted to introduce two very, very important reactions that are going to come up all the time throughout the rest of the course; and they are the hydrolysis and the condensation reactions.0003

Up to now, we did this little chemistry review, where we talked about aqueous chemistry, where water is not just a medium, it's not just a solvent, where these reactions take place between these biological macromolecules and other things- it can actually act as a reactant or be produced as a product.0019

These are very, very important reactions.0039

They are ubiquitous in biochemistry, so I just wanted to introduce them, give you couple of examples of them, and then of course, as we go on in the course, you'll see them on a regular basis.0040

OK, let's see.0050

The first one- I'm going to give the definitions of both, and then I'm just going to just go ahead and give examples.0053

Hydrolysis will be our first reaction and it literally means breaking up by water - hydrolysis.0059

Hydrolysis, it is the use of water as a reactant - let me actually write H20 instead of water - the use of H20 as a reactant to split a single molecule into 2 molecules, 2 parts or 2 molecules, each of those parts will more often than not, be a molecule, where the components of water, of H20 - and again, it's best to think of H20 as an H+ and an OH-, those are the two components of water - end up one on each molecule.0071

So, what happens is that water comes in, it breaks it up, and the H ends up on one molecule, the OH ends up on the other.0147


That's hydrolysis, and the reverse of that is called condensation, and you'll see why we use the term condensation in just a second.0157

You know condensation as, if you have a cold glass, you put it some place, the water in the air will actually condense onto the glass.0166

It goes from the gas phase to the liquid phase; you're actually producing water.0177

They call this a condensation reaction, and this you’ll see in a second, because you are actually producing water in this reaction.0180

Now, this is when two molecules react to form a single molecule, and where H20 is eliminated as a product.0187

In other words, the H from one molecule, the OH from the other molecule, are pulled off, they are stuck together and it's released as water.0226

So, once we pull them off and stick those together and release them of water, the two empty spaces, those two atoms, actually, and the bonding, so two molecules go to one.0235


Let's go ahead and just do some examples.0246

I'll just write here "These are the reverse of each other.".0248

If you know the mechanism of one, you know the mechanism of the other.0259


I'm going to go to blue to do my examples here.0265

Example 1, now, I'm going to write a hydrolysis reaction.0268

So, because of the reverse of each other, we can just choose a double arrow.0274

In forward direction, it's one type of reaction; in the reverse direction, it's the other type of reaction.0276

It just depends on which one you want to concentrate on, but I'm going to list them individually with just single arrows; and then at the end, I'll do an example with the double arrow - at least I think that's what I did.0282


Example 1: this is going to be the hydrolysis of ethyl acetate.0294

Now, hopefully, you'll remember a little bit of your organic chemistry, if not, we'll do it right here.0314

Ethyl acetate is an ester, and it looks like this.0319

Yes, that's fine, I'll go ahead and do it here.0325

When I draw my structures for organic compounds, I tend to draw out all the carbons.0328

Now, later as we go on, I'll probably end up drawing the line structures where two lines come in together, something like this.0333

This is a carbon, and that's a carbon, and that's a carbon, but for the time being, generally, even to this day, when I draw my structures, I tend to draw out all of the carbons because I’d like to see all of my carbons.0339

Actually, you know what I'm going to do, I'm going to go ahead and do this on the next page; excuse me.0354

I'll go ahead and leave this here.0358

Example 1: hydrolysis of ethyl acetate.0360

Let me go ahead and go to the next page.0362

This is the hydrolysis of ethyl acetate.0365

Let me rewrite it - hydrolysis of ethyl acetate - and it's going to look like this.0369

We have CH3, COO, CH2, CH3 - this is the ethyl part, this is the acetate part, it is an ester, ester is a carbon; it has this carbonyl group, and on that carbon, the carbonyl carbon, there's an oxygen, and that oxygen is attached to another carbon group, OK – plus H2O, it goes to CH3, COOH, + HO, CH2, CH3.0381

There we go; we've taken a single molecule, we've split it.0424

Now, let me do this one in red.0427

This hydrolysis, we've actually split it.0429

Now, notice, we split it actually right here.0432


That's where the hydrolysis takes place.0436

We are not going to worry about mechanisms just yet, we'll get to mechanisms a little bit later, but I just wanted you to recognize these reactions.0438

But notice, this oxygen over here is not this oxygen.0443

This oxygen actually comes from the water.0449

And again, we'll deal with mechanism later but the bond that we split is this one right here, and here are the elements of water.0452

There is your HOH, or actually, it's not that, that's just the reverse of what it is that I said, so let me erase this.0460

You can look at it that way.0472

Let me go back to blue and rewrite everything, so I have it in there.0477

There is an O here, and then H here.0480


Now, let me go to red, and my elements of water are right there.0485

You could have done it the other way, it's not a problem, but I just wanted you to realize that this OH, actually, this oxygen comes from the water; but again, that's a question of mechanism which we'll deal with later.0493

So, this is the hydrolysis- you are using water to split a molecule into two molecules - acidic acid and ethanol.0502

That's all.0511


Now, let's go ahead and see what we can do.0514

Let’s do example 2.0520

Now, we'll do the reverse; now, we'll do the condensation of acidic acid with ethanol.0526

We are going to do the reverse reaction.0540

We are just going to write it backwards, just the other way around.0542

What we have is CH3, COOH+, HO, CH3, CH3.0545

So, now, in this case, when this molecule of acidic acid and this molecule of ethanol come together, the elements of water are going to be released.0563

What you end up with is the ethyl acetate: CH3, COO.0572

You're probably wondering why didn't I just put the double arrow here?0579

Why do I have to rewrite it?0581

Well, part of it is just practice.0582

The idea is: it's one thing to see something on the page and think that you understand it; it's another thing to actually write out the structures and understand it.0585

The only way that you have full command of the material in your mind is if you are actually able to produce it with your hand.0594

That's why it is important, even for me at this point, I like to write things out.0600

Yeah, it takes a little bit longer, yeah I think that I understand it, but I know that when I write it out, when I produce it actively, it's very, very different than understanding it passively just by looking at it; so write things out, get in the habit of writing things out.0604

It is a little tedious, it is a little annoying- I know.0617

Biochemical molecules are going to get bigger and bigger and bigger, but if you want to have a total command of your biochemistry, which you want to have if you are going to go on in the biomedical sciences, you need to write them out.0620

Trust me on this one- active understanding better than passive understanding.0631

OK, sorry.0636

Alright, so this is going to be O, and then let's go ahead and write CH3, CH3 - we're doing the condensation, right, yes - + H2O.0638


Where are the elements of water that are coming together?0651

I'll do this in blue now.0655

Here, again, this is the bond that's being broken.0658

That's the bond that's being broken.0661

We won't worry about mechanism.0662

Those are the elements of water.0665

This H and this OH, they come together to form that water.0668

OK, good.0676

OK, let's do example number 3 here.0678

I wonder if I should do it on the next page; that's alright.0683

Example number 3, I think I've got enough room here.0686

This is going to be the hydrolysis of adenosine triphosphate, the hydrolysis of ATP.0689

Now, we'll talk about ATP later when we talk about bioenergetics.0699

Let me write the equation first - ATP 4- - and then, I'll do the structures.0703

Again, this is biochemistry, organic chemistry structures.0708

ATP + H2O is going to go to H, ADP, and I'll explain where that H comes from in just a minute.0713

2- + HPO42- - notice the charges' balance 2-, 2-, 4- on the right, 4- on the left.0722

It's very, very important.0731

Here is what the reaction looks like.0733

I'll write AD for adenosine, and here is what the triphosphate looks like: O, P, O, P.0737

And again, no worries, this is not about getting the structure here right now, and just recognize the hydrolysis and the condensation reactions.0745

We'll worry about what these look like later.0754

O, P, O, P, O, P, O and then we've got a double bond there, a double bond there, a double bond there.0755

We have a minus charge, a minus charge, a minus charge and a minus charge.0765

There are normally hydrogens on all of these; it's fully ionized.0769


It's fully ionized at body pH, so this is a 4- charge; that's what this is.0775

Now, plus H2O, this is going to be the hydrolysis part.0780


Now, let's go ahead and write- maybe I should've done it on the next page; that's OK, I think we've got some room here.0787

So, we've got adenosine, what we are going to end up with is O, P, O, P, O, double bond, double bond, single bond negative oxygen, single bond negative oxygen.0795

I'm going to go ahead and put an H right there, and then this is going to be plus, and I'm going to have H, O, P, O, that, O-, O-.0813

There we go.0828

Let me do this in red so that you see it; I'll go ahead and go back to red.0834

In this way, it is hydrolysis, in this way backwards going from ADP and inorganic phosphate to adenosine triphosphate, it is condensation.0848

That's it, that's all that is happening here- splitting up by water, this H2O, this is the distribution.0860

OH goes with one of them, H goes with the other.0866


Let's go ahead and do 1 final example here - a very, very important example, because starting with the next lesson, we are going to jump into biochemistry proper with the discussion of amino acids and proteins, and of course, proteins are just a long chain or short chain, doesn't matter, of amino acids, linked together by something called the peptide bond.0870

As far as this example is concerned, we are going to do an example of the formation and hydrolysis of the peptide bond.0892

Example number 4: formation and hydrolysis.0904

When we say formation and hydrolysis, we are talking about the condensation and hydrolysis of a peptide bond between and the amino acids that I chose.0915

And again, you don't have to know this yet because we haven't gotten to it yet.0933

This is just the reaction that is important.0937

In the next couple of lessons, you'll understand what is happening here.0938

I chose alanine and serine.0943


Here we go.0951

Let's see.0952

Let's go ahead and write it as N, C, C, OH.0953

I'll go ahead and write this as N3+, this is an H here, and this is a CH3 - that's our alanine – and then this is going to be plus.0965

I'll just do an N, H, and an H, and don't worry about why it is that I have 3 Hs here versus 2 Hs over on this side.0982

Again, we'll deal with all of that later.0991

Right now, it's just about the reaction.0992

That's C, C, OH, and here we have the H, and here we have serine which is going to be CH3OH.0995

OK, here we go.1007

When we put these together, you're going to end up with the following; you're going to end up with the peptide bond.1008

This is going to be N, C, C, N, C, C.1017

This is how I write out my peptide bonds: N, C, C, N, C, C.1024

Always keep it straight that way, and the carbonyl goes on the second one.1028

This one goes here.1034

Let me fill that in.1036

Let me go ahead and put the rest of it in here.1038

This goes there, this is an H, this is an H, this is a CH3, this is a CH3OH.1042

Now, we can go ahead and…plus H2O.1051

Now, I'll do this in blue.1058

These are the elements of water, right here.1060

N comes in, that is that.1064

The peptide bond that we're forming is between the carbonyl carbon of 1 amino acid and the nitrogen on the other amino acid.1074

That's the bond that's forming; that's called the peptide bond.1085

And again, we'll go through all of this later.1091

For the next several lessons, we are going to be talking about exclusively proteins, profoundly important biological macromolecule- the most abundant biological macromolecule in nature.1094

That's it, this is hydrolysis and this is condensation.1105

Hydrolysis is the breaking up of a molecule with a water, and condensation is when you put two molecules together and the elements of water are produced as a product.1110

You'll see these all the time.1118

OK, thank you for joining us here at

We'll see you next time for discussion of proteins, bye-bye.1123