1. Fat molecules can be formed by dehydration synthesis and broken down by hydrolysis. We’ll look at both of these processes here.

2. We’ll start with the synthesis of fats.

3. If we take a molecule of glycerol, Glycerol + 3 Fatty Acids  A Fat + 3H 2 O

4. And combine it with 3 fatty acid molecules, Glycerol + 3 Fatty Acids  A Fat + 3H 2 O

5. We get a fat, Glycerol + 3 Fatty Acids  A Fat + 3H 2 O

6. And 3 molecules of water. Glycerol + 3 Fatty Acids  A Fat + 3H 2 O

7. This takes place using a process called dehydration synthesis. Let’s take a more detailed look at this process. Glycerol + 3 Fatty Acids  A Fat + 3H 2 O Dehydration Synthesis

8. 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. Glycerol

9. A fatty acid consists of a long chain of carbon and hydrogen atoms, Saturated Fatty Acid Carbon–Hydrogen Chain

10. 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 Acid COOH (Carboxyl Group)

11. 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 Acid Typically about 16-18 C atoms long

12. 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 Acid All single bonds between C atoms. Contains the maximum # of H atoms

13. Such a fatty acid is said to be a saturated fatty acid. Saturated Fatty Acid All single bonds between C atoms. Contains the maximum # of H atoms

14. 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 Acid At least one double bond between C atoms. Contains less H atoms

15. 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 Acid At least one double bond between C atoms. Contains less H atoms

16. Here is a molecule of glycerol. We have elongated the bonds between the carbon atoms in order to fit our molecular model better. Glycerol 3 Fatty Acids

17. And 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. Glycerol 3 Fatty Acids saturated unsaturated

18. These H atoms come off of the glycerol molecule during dehydration synthesis, so we’ll colour them red. These H atoms come off during dehydration synthesis

19. And these OH groups come off of the fatty acids during dehydration synthesis, so we’ll colour them blue. These OH groups come off during dehydration synthesis

20. Now we’ll look at the process of forming a fat molecule…

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

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

23. We’ll move the water molecule over here.

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

25. Which we’ll move over here…

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

27. And we’ll move its water molecule over here.

28. So now, we’ve 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)

29. So we can summarize by stating that glycerol, Glycerol + 3 Fatty Acids  A Fat + 3H 2 O +  + Dehydration Synthesis

30. Combines with 3 fatty acids, Glycerol + 3 Fatty Acids  A Fat + 3H 2 O +  + Dehydration Synthesis

31. To form a fat Glycerol + 3 Fatty Acids  A Fat + 3H 2 O +  + Dehydration Synthesis

32. And three molecules of water. Glycerol + 3 Fatty Acids  A Fat + 3H 2 O +  + Dehydration Synthesis

33. Now, we’ll have a look at hydrolysis of a fat molecule

34. We’ll start with a fat molecule and three water molecules. A Fat 3 H 2 O

35. 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 Fat 3 H 2 O

36. Let’s watch the whole process as the water molecules move in and break up the fat molecule. Hydrolysis

37. Now, we’ve got a molecule of glycerol and 3 molecules of fatty acids. Glycerol 3 Fatty Acids

38. Now we’ll summarize the process of hydrolysis: We start with a (click) fat molecule A Fat + 3H 2 O  Glycerol + 3 Fatty Acids  + Hydrolysis

39. And in the presence of the appropriate enzyme, we add three water molecules A Fat + 3H 2 O  Glycerol + 3 Fatty Acids  + Hydrolysis

40. And the fat breaks down into a glycerol molecule A Fat + 3H 2 O  Glycerol + 3 Fatty Acids  + Hydrolysis

41. 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 + 3H 2 O  Glycerol + 3 Fatty Acids  + Hydrolysis