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Synthesis and Hydrolysis of FatsFat molecules can be formed by dehydration synthesis and broken down by hydrolysis. Well look at both of these processes here. 1

Synthesis of FatsWell start with the synthesis of fats.2If we take a molecule of glycerol,

Glycerol + 3 Fatty Acids A Fat + 3H2O3And combine it with 3 fatty acid molecules,

Glycerol + 3 Fatty Acids A Fat + 3H2O4We get a fat,

Glycerol + 3 Fatty Acids A Fat + 3H2O5And 3 molecules of water.

Glycerol + 3 Fatty Acids A Fat + 3H2O6This takes place using a process called dehydration synthesis. Lets take a more detailed look at this process.

Glycerol + 3 Fatty Acids A Fat + 3H2ODehydration Synthesis7

Here is a molecule of glycerol, which can also be called glycerine or propane 1, 2, 3 triol. Notice it has 3 carbon atoms, each with an OH group attached to it.

Glycerol8

A fatty acid consists of a long chain of carbon and hydrogen atoms,

Saturated Fatty AcidCarbonHydrogen Chain9

And a COOH, or carboxyl group on the end. A carboxyl group has a double bonded oxygen atom and an OH group attached to a carbon atom

Saturated Fatty AcidCOOH(Carboxyl Group)10

In most cells, the fatty acid chains are typically about 16 18 carbon atoms long, but shorter ones do occur. We are representing a shorter one here so it fits better into our video frame. Just remember, these are usually longer in most common fats.

Saturated Fatty AcidTypically about 16-18 C atoms long11

Note in this particular fatty acid that all the bonds between carbon atoms are single covalent bonds and the carbon atoms in the chain are attached to the maximum number of Hydrogen atoms they can hold.

Saturated Fatty AcidAll single bonds between C atoms.Contains the maximum # of H atoms12

Such a fatty acid is said to be a saturated fatty acid.

Saturated Fatty AcidAll single bonds between C atoms.Contains the maximum # of H atoms13

Looking at another fatty acid, we see that this one has a double bond between two of the carbon atoms in the chain. Because each C atom can only have a total of 4 bonds, there are less bonds available for hydrogen atoms, so this molecule has less hydrogen atoms than a saturated fatty acid with the same # of C atoms.

Unsaturated Fatty AcidAt least one double bond between C atoms.Contains less H atoms14

Fatty acids with one or more double bonds between carbon atoms are called unsaturated fatty acids. Some contain one double bond, in various locations, and some contain 2 or more double bonds.

Unsaturated Fatty AcidAt least one double bond between C atoms.Contains less H atoms15Here is a molecule of glycerol. We have elongated the bonds between the carbon atoms in order to fit our molecular model better.

Glycerol3 Fatty Acids16And here are three fatty acid molecules. Many different fatty acids can form fats, some with longer or shorter chains, as well as some saturated ones with no double Carbon-carbon bonds and some unsaturated ones with one or more double carbon-carbon bonds. In this example we have two (click) saturated and one (click) unsaturated fatty acid.

Glycerol3 Fatty Acidssaturatedsaturatedunsaturated17

These H atoms come off of the glycerol molecule during dehydration synthesis, so well colour them red.

These H atoms come off during dehydration synthesis18

And these OH groups come off of the fatty acids during dehydration synthesis, so well colour them blue.

These OH groups come off during dehydration synthesis19

Now well look at the process of forming a fat molecule

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The molecules move closer together. Even though all the fatty acids join to glycerol at the same time, well watch them one by one here, to make is easier to understand.

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The top fatty acid bonds to the glycerol with dehydration synthesis, producing one water molecule

22

Well move the water molecule over here.

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Now, watch as the second fatty acid bonds to the glycerol by dehydration synthesis, producing another water molecule

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Which well move over here

25

And finally the third fatty acid moves in an joins the glycerol with another dehydration synthesis.

26

And well move its water molecule over here.

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So now, weve formed a fat. Fats can also be called (click) triglycerides. The prefix tri is used because it has 3 fatty acids.

A Fat (or Triglyceride)28

So we can summarize by stating that glycerol,

Glycerol +3 Fatty Acids A Fat + 3H2O

++Dehydration Synthesis29

Combines with 3 fatty acids,

Glycerol +3 Fatty Acids A Fat + 3H2O

++Dehydration Synthesis30

To form a fat

Glycerol +3 Fatty Acids A Fat + 3H2O

++Dehydration Synthesis31

And three molecules of water.

Glycerol +3 Fatty Acids A Fat + 3H2O

++Dehydration Synthesis32

Hydrolysis of FatsNow, well have a look at hydrolysis of a fat molecule33

Well start with a fat molecule and three water molecules.

A Fat3 H2O34

When the appropriate enzyme is present, the water molecules will break these bonds on the fat molecule, adding H atoms to the glycerol and OH groups to the fatty acids. This is the process of hydrolysis (or adding water to break up a large molecule)

A Fat3 H2O35

Lets watch the whole process as the water molecules move in and break up the fat molecule.

Hydrolysis36

Now, weve got a molecule of glycerol and 3 molecules of fatty acids.

Glycerol3 Fatty Acids37

Now well summarize the process of hydrolysis: We start with a (click) fat molecule

A Fat + 3H2O Glycerol +3 Fatty Acids

+Hydrolysis38

And in the presence of the appropriate enzyme, we add three water molecules

A Fat + 3H2O Glycerol +3 Fatty Acids

+Hydrolysis39

And the fat breaks down into a glycerol molecule

A Fat + 3H2O Glycerol +3 Fatty Acids

+Hydrolysis40

And three fatty acid molecules. Breaking down fats into glycerol and fatty acids by hydrolysis is a very important process in digestion of the foods we eat.

A Fat + 3H2O Glycerol +3 Fatty Acids

+Hydrolysis41