2. Lipids for Lecturing

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Lipids: Fats & Oils


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Lipids consist of two parts1. Glycerol2. Fatty Acids

a. Saturated fatty acidsb. Unsaturated fatty acids

.Monounsaturated . Polyunsaturated Figure 3 : Formation of TG


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Saturated vs. unsaturatedsaturated unsaturated


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Table 1 : Saturated fatty acid s


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Table 2 : Unsaturated fatty acids


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Lipids are classified as simple or complex

1. Simple lipida. Fatty acidsb. neutral fats (monoglyceride,

diglycerde, and triglyceride)

c. waxes

2. Complex lipids

a. Phospholipids

b. Glycolipids

c. Lipoproteins

3. Derived lipids

Figure 1 : Triglyceride

Figure 2 :

Phosphatidic acid


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Phospholipids Structure:

glycerol + 2 fatty acids + PO 4

PO 4 negatively charged

Its just like a penguin A head at one end& a tailat the other !


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Omega Fatty acid


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Cis- Trans Fatty acid


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Function of Fat

Energy

Essential nutrient

Flavor and Satisfaction

Adipose Tissue

Cell membrane Structure

Fat in Food

Fat in Body


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Food Sources of Fat

. Meat Fat (bacon, sausage.)

. Dairy Fats and products (cream, butter, cheese..)

. Egg yolk

. Monounsaturated, polyunsaturated Fatty acid. Vegetable oil (saf flower, corn, soybean, cottonseed, olive oil)

Animal Fats

Plant Fat


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Characteristics Of Food Fat Sources

. Butter, margarin, salad oils and dressing,shirteninig fat meat

. Chees, cream portion of homogenised milk, egg yolk,nuts, seeds, olives..

Visible Fat

Invisible Fat


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Digestion of lipids

1. In mouth

mechanical digestion

Lingual Lipase

2. In stomach

mechanical digestion

Gastric lipase


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3. In small intestine

Bile acid, Pancreatic Lipase, Cholesterol esterase,

Phospholipase

Triglycerides 2 fatty acids + Mono glycerides

3 fatty acids + glycerolriglycerides

Triglycerides 1 fatty acids + Diglycerides


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Absorption of lipids

Figure 4 : Absorption of fat.


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Transportation of lipids

Source Destination Major lipids Functions

Chylomicrons Intestine Many organs Triglycerides,other lipids

Deliver lipids ofdietary origin to

body cell.

VLDLs Liver Many organs Triglycerides,Cholesterol Deliverendogenouslyproduced

triglycerides tobody cells.

LDLs Intraviscularremoval of

triglycerides fromVLDL

Blood vessels,Liver

Cholesterol Deliverendogenously

producedcholesterol to

various organs.

HDLs Liver and intestine Liver and steroid-hormone-producing glands

Cholesterol Remove anddegrade

Cholesterol.

Table 3 Lipids are transported in the plasma as lipoproteins.


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Lipids Metabolism

. Liver and Adipose tissue play a central role in lipidmetabolism.

. Adipose tissue is the main store of triglyceride in thebody.

. Lipid metabolism either lipolysis or lipogenesis.

. Fatty acids are both oxidized to acetyl CoA andsynthesized from acetyl CoA.


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Lipolysis

. Complete hydorlysis of triglyceride yeild gelyceroland 3 fatty acids.

. Fatty acids oxidiation take place in the

mitochonderia.. Fatty acids are activated before being catabolized(oxidized).

Fatty acid + ATP + CoA Acyl CoA + AMP

+ PPi


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Long chain fatty acids penetrate the inner -Mitochinderialmembrane as carnitine derivatives.

Figure 5 : Role of carnitine in the transport of long chain fatty

acids.


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- oxidation pathway of fatty acids

. Many tissues are capable of oxidizing fatty acids inthe mitochondria by - oxidation pathway.

. The chain is broken between the ( 2) and ( 3)

carbon atoms.

Figure 6 : Overview of - oxidation pathway of fatty acids


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- oxi tion of fatty acids Figure 7)


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The products of oxidation of fatty acidsOxidation of fatty acids produces a large quantity of ATP,

example : Palmitic acid (C:16 )

7 cycles from 7 NADH + 7 FADH2(7 x5 = 35 ATP)

7 cycles from 8 Acetyl CoA

(8 x 12 = 96 ATP)

2 ATP for the initial activation

of fatty acid( 35 +96 2 = 129 molecule of ATP)

Figure 8 : acetyl CoAproduct


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Oxidation of unsaturated fatty acids occurs by amodified - oxidation pathway (figure9)


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Ketone bodies Ketogenesis occurs when there is a high rate of fatty acid

oxidation in the Liver (figure 10).

Aceto acetyl CoA

Acetyl CoA

Acetoacetate

Acetone -hydroxy butyrate

Acetyl CoA

CoA

CoA


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Lipogenesis

. The body is capable of synthesizing fatty acids in the

cytoplast of the cell from starter ( acetyl CoA + malonyl CoA).

. Malonyl CoA is formed from Acetyl CoA

Figure 11 : Biosynthesis of Malonyl CoA


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. Acetyl CoA transfer to the cytoplast across the mitochondrialmembrane in the form of citrate

Figure 12 : Conversion the citrate to Oxaloacetateand Acetyl CoA.

. The enzymes involved in fatty acid synthesis are arranged in acomplex called the fatty acid synthase system.


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The steps in the synthesis of fatty acid Figure 13)


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Cholesterol

Figure 14 : Cholesterol

. Cholesterol is not an energyproducing nutrient.

. It is an essential structuralcomponent of membrane of the outer layer of plasma lipoprotien.

Bile acids and steriod hormones are formed from cholesterol.

. Cholesteryl ester is a storage form of cholesterol which is foundin most tissues.


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Acetyl CoA is the source of all carbon atoms in cholesterol

Squalene

-hydroxy- - methylglutaryl CoA

Mevalonate

Farmesyl pyrophosphate

Acetyl CoA

CoA

Acetoacetyl CoA

CoA

Acetyl CoA

HMG-CoA

reductase

Cyclization


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References

Brene, R., Levy, M., Koeppen, B., Stanton, B., 2004) Physiology ,Fifth edition. Mosby.

Fox, S., 2004) Human Physiology , Eighth edition. Mc Graw Hill.

Hunt, S., Groff, J., 1997) Advanced Nutrition and HumanMetabolism, West Puplishing Company.

Lehninger, A., Nelson, D., Cox, M., 1993) Principles ofBiochemistry , 2nd edtion. Worth Puplishers.

Murray, R., Granner, D., Mayes, P., Rodwell, V., 1996) Hapers Biochemistry , 24th edition, Prentic-Hall International, Inc.

Seeley, R., Stephens, T., Tate, P., 1992) Anatomy andPhysiology, Mosby Yearbook.


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2. Lipids for Lecturing