1. The document discusses lipid classes and metabolism. It defines the main lipid classes including fatty acids, triacylglycerols, phospholipids, sphingolipids, and isoprenoids. 2. Saponification is described as the hydrolysis of fatty acids from glycerol by a base, forming soaps. 3. Fatty acid degradation and biosynthesis are compared. β-oxidation in the mitochondria degrades fatty acids in four steps to generate acetyl-CoA for the citric acid cycle, while fatty acid synthesis in the cytoplasm builds fatty acids like palmitate from acetyl-CoA and malonyl-ACP.

1. At the end of the class, you should be able to:
1. State the classes of lipid
2. Explain what is saponification  LAB
3. Explain fatty acid degradation in ß-oxidation
4. Explain fatty acid biosynthesis using Palmitate as an example
LIPID

6. Lipid classes
May be classified in many different ways
Can be subdivided into :
1. Fatty acids & their derivatives
2. Triacylglycerol (TAGs)
3. Wax esters
4. Phospholipids
5. Sphingolipids
6. Isoprenoids

7. Some naturally occurring fatty acids:
SFA (saturated fatty acids):
- 4:0 Butyric acid - Milk fat
- 12:0 Lauric acid - coconut oil
- 14:0 Myristic acid - Coconut oil, palm nut oil, most animal and plant fats
- 16:0 Palmitic acid - Animal and plant fats
- 18:0 Stearic acid - Mostly animal fats and some plant fats
- 20:0 Arachidic acid - Peanut oil
MUFA (monounsaturated fatty acids):
- 16:1 Palmitoleic acid - Marine oils, small amount in animal and plant oils
- 18:1 Oleic acid - palm oil and animal fats
PUFA (polyunsaturated fatty acids):
- 18:2 Linoleic acid - Corn, safflower, soybean, cottonseed, sunflower seed and
peanut oil
- 18:3 Linolenic acid - Linseed (flax), soybean and other seed oils
- 20:4 Arachidonic acid - Animal fats
Essential fatty acids (EFA):
- Linoleic acid (18:2) and linolenic acid (18:3)
are essential fatty acids (human body cannot synthesize these fatty acids due to lack
of desaturase enzymes)17

8. What is it?

9. In saponification,
1. a water molecule is removed from a fatty acid or an ester.
2. sodium stearate, sodium oleate or sodium palmitate is formed.
3. it is precipitated from the solution by addition of NaCl.
4. the addition makes the sodium salt of fatty acid partially insoluble in water.
5. the product then separates out of the solution
6. the remaining solution has glycerol and sodium chloride.
function?
http://educationalelectronicsusa.com/c/org_mat-V.htm

10. anabolism
catabolism
metabolism

12. Lipid metabolism
serum glucose
Insulin promotes TAGs synthesis =lipogenesis
Insulin facilitates transport of glucose to adipocytes
Adipocytes cannot synthesize TAGs when glucose
levels are low
E levels
Body’s fat stores are mobilized = lipolysis
Several hormones stimulate hydrolysis of TAGs in
adipose tissue  glycerol & fatty acid

13. Introducing the intermediate in lipid metabolism…

16. Q: How do we generate energy from fatty acid?

17. 3primary resources of fatty acids for
energy metabolism
1. Dietary triacylglycerols
2. Triacylglycerols synthesized in the liver
3. Triacylglycerols stored in adipocytes as lipid
droplets

18. What?
Where?
Why?
How?
http://www.rose-hulman.edu/~brandt/Chem331/Lipid_Breakdown.pdf
Fatty acids degradation

19. • Fn to generate E
• Occur in mitochondria and
peroxisomes
• Remove 2C from carboxyl end of
fatty acids
ß-oxidation
• To degrade odd-chain or branched
chain molecules
 α-oxidation
Fatty acids degradation

21. Triacylglycerols are combined with dietary cholesterol
and proteins to form LIPOPROTEIN
Lipase catalyses hydrolysis of ester linkages in fats
Fatty acids are taken up into the intestinal mucosa
They are resynthesized into triacylglycerols

24. • Triacylglycerol are transported by chylomicrons
• Chylomicrons are one of the plasma lipoproteins
• released by exocytosis from enterocytes into lacteals, lymphatic vessels
originating in the villi of the small intestine
• during the circulation, chylomicron accept apolipoprotein C-II from HD
Lipoproteins.
•APOC2 is a cofactor for lipoprotein lipase activity
• Fatty acids that have been delivered to muscle tissue via blood
capillaries diffuse through cell plasma membrane into the cytoplasm
• From cytoplasm/cytosol it will undergo degradation in the matrix
mitochondria.
• HOW?

25. Chylomicrons

28. Lipid metabolism
1. Fatty acids must get into mitochondrial matrix to be degraded.
How to get in ?
Fatty acid Fatty acyl CoA
ATP AMP
+PPi
CoASH
• f.a. are activated to form fatty acyl CoA by acyl-CoA synthetase
• CoA is the acyl carrier
• Fatty acyl CoA can enter into intermembrane space

29. 2. Fatty acyl-CoA degradation occur inside mitochondrial matrix & can’t
across the inner membrane.
How to get into the matrix ?
By using a carrier = carnitine
Acylcarnithine
carnitine
CoASH
Carnitine acyltransferase I
Enter matrix
Transport by a
carrier protein
Acyl-CoA
Fatty acid degradation

30. 3. Now Acylcarnithine has enter the matrix.
How to form back into fatty acyl-CoA ?
Acylcarnithine carnithine
CoASH Acyl-CoA
Intermembrane space
Transport back by
carrier protein
Fatty acid degradation

31. Fatty acid degradation

34. β-oxidation
Occur in 4 steps
1. Oxidation/Dehydrogenation = removal of electrons
2. Hydration = add water
3. Oxidation = remove more electrons
4. Thiolysis (Carbon-Carbon bond cleavage) = remove acetyl-CoA
4. What happen to fatty acyl-CoA ?
How to degrade acyl CoA and generate E?
Fatty acid degradation
Animation: http://www.uwsp.edu/chemistry/tzamis/boxanim.gif
http://medstat.med.utah.edu/kw/biochem_animations/betaox.html

35. 1. Oxidation : -electrons, -2H
Forms double bond
2.Hydration
Form –OH
3. Oxidation : - more electrons, -
2H
Forms C=O
4. Thiolysis :+ CoASH & cleave to -acetyl-CoA
Fatty acid degradation

36. After ß-oxidation of one cycle:
1. One FADH2
2. One NADH
3. One acyl-CoA
4. One acetyl –CoA
To determine total ATP, you must know number of ß-oxidation cycle.
Fatty acid degradation

37. • Most of acetyl CoA is used by TCA cycle or isoprenoid
synthesis
• But some acetyl CoA follow alternate pathway:
•During fasting/starvation  glycolysis ↓ [OAA become
depleted and could not accept acetyl-CoA] and
gluconeogenesis ↑
•Therefore the excess of acetyl CoA  is converted to ketone
bodies by ketogenesis (occur in matrix of liver mitochondria)
•Ketone bodies = acetoacetate, ß-hydroxybutarate, acetone
•They are water soluble lipids and can be readily
transported in the blood plasma
• Ketone bodies can be used to generate E (as a substitute
to glucose) in brain, cardiac & skeletal muscle

39. Question:
What happen if our diet contain:
Low in fat?
High carbohydrate ?

41. FATTY ACID BIOSYNTHESIS
• Occur in cytoplasm / chloroplast (plants)
•In adults = mainly liver cells and adipocytes, some in
mammary gland during lactation
• Synthesize when diet is low in fat and/or high in
carbohydrate.
• Most are synthesized from glucose:
• Glucose  Pyr transport to mitochondrion  acetyl –CoA
 citrate  citric acid cycle OR into the cytoplasm to make
fatty acids
• fatty acids are synthesized by the repetitive addition of two-
carbon to the growing end of hydrocarbon chain.
Fatty acids biosynthesis
Acetyl-CoA can be formed by ß-oxidation or decarboxylation of pyruvate
Animation:http://www.uwsp.edu/chemistry/tzamis/fasynthanim2003.gif

42. • The usual product of fatty acid anabolism is Palmitate (16C, saturated)
• during two carbon-elongation, malonyl-ACP is used
• Malonyl ACP is the main substrate
•There are 6 steps in one cycle of synthesis.
• involves ACP as the acyl carrier protein
1. Priming the system by acetyl-CoA
2. ACP-malonyltransferase reaction
3. Condensation
4. First reduction
5. Dehydration
6. Second reduction

43. Fatty acids biosynthesis e.g. palmitate
1. Priming
One acetyl-CoA is required for each
molecule of palmitate produced
2. ACP-malonyltransferase reaction
Malonyl is transfer to the system
3. Condensation
Formation of acetoacetyl-ACP
CO2 is released
4. First reduction
Use NADPH as reducing agent
5. Dehydration
Water is removed
6. Second reduction
Use NADPH as reducing agent
Cycle repeats 6 more time
to produce 16C palmitate

44. Do this:
Study the differences
between ß-oxidation
and fatty acid
synthesis.

49. Lipid classes
1. Fatty acids
• monocarboxylic acids that occur in Triacylglycerol,
phospholipids & sphingolipids
• saturated @ unsaturated
2. Triacylglycerols
• are esters of glycerol with 3 fatty acids.
• if solid at room temp.  fat (mostly saturated f.a)
• if liquid at room temp  oil (mostly unsaturated f.a)
• major storage & transport form of f.a
• important E storage (8x glycogen)
• less oxidized than carbohydrate
 its oxidation releases more E

50. Nonpolar hydrophobic tail
CH3
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
CH2
C
O
O
“Polar” hydrophilic head
Fatty acid :12-20 C
Triacylglycerol @ triglyceride
Before a fat can be oxidized, it
must be hydrolyzed to the
anion acid and glycerol.
Biologically this is done by
lipases.
Chemically base hydrolysis is
called saponification.
Lipid classes
H

51. Lipid classes
saponification
CH2
CH
CH2
O
O
O C
O
C
O
C
O
R3
R3
R3
3 KOH
CH2
CH
CH2
OH
OH
OH +
KO C
O
R3
K salt of a fatty acid
3
2

52. Lipid classes
3. Phospholipids
• structural components of membrane
• 2 types : phosphoglycerides & sphingomyelins
4. Sphingolipids
• Important comp. of animal & plant membranes
• Contain long chain amino alcohol: sphingosine (animal) &
phytosphingosine (plants)
5. Isoprenoids
Molecule containing repeating 5C isoprene
Consist of terpenes & steroids
6. Wax esters
Complex mixtures of non polar lipids
Serve as protecting coat