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Lipids consist of two parts1. Glycerol 2. Fatty Acids
a. Saturated fatty acids b. Unsaturated fatty acids
.Monounsaturated . Polyunsaturated
Figure 3 : Formation of TG Figure 3 : Formation of TG
Table 1 : Saturated fatty acids
Table 2 : Unsaturated fatty acids
Lipids are classified as simple or complex
1. Simple lipid a. Fatty acids
b. neutral fats (monoglyceride,
diglycerde, and triglyceride)
c. waxes
2. Complex lipids
a. Phospholipids
b. Glycolipids
c. Lipoproteins
3. Derived lipids
Figure 1 : Triglyceride Figure 1 : Triglyceride
Figure 2 : Phosphatidic acidFigure 2 : Phosphatidic acid
Omega Fatty acid
Cis- Trans Fatty acid
Function of Fat
. Energy
. Essential nutrient
. Flavor and Satisfaction
. Adipose Tissue
. Cell membrane Structure
Fat in Food
Fat in Body
Food Sources of Fat
. Meat Fat (bacon, sausage….)
. Dairy Fats and products (cream, butter, cheese..)
. Egg yolk
. Monounsaturated , polyunsaturated Fatty acid
. Vegetable oil (safflower, corn, soybean, cottonseed, olive oil)
Animal Fats
Plant Fat
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
Digestion of lipids
1. In mouth
mechanical digestion
Lingual Lipase
1. In mouth
mechanical digestion
Lingual Lipase
2. In stomach
mechanical digestion
Gastric lipase
2. In stomach
mechanical digestion
Gastric lipase
3. In small intestine
Bile acid, Pancreatic Lipase,
Cholesterol esterase, Phospholipase
3. In small intestine
Bile acid, Pancreatic Lipase,
Cholesterol esterase, Phospholipase
Triglycerid
es
2 fatty acids + Mono glycerides
3 fatty acids + glycerolTriglycerid
es
Triglycerid
es
1 fatty acids + Diglycerides
Absorption of lipids
Figure 4 : Absorption of fat. Figure 4 : Absorption of fat.
Transportation of lipids
Source Destination Major lipids Functions
Chylomicrons
Intestine Many organs Triglycerides, other lipids
Deliver lipids of dietary origin to
body cell.
VLDLs Liver Many organs Triglycerides, Cholesterol
Deliver endogenously produced
triglycerides to body cells.
LDLs Intraviscular removal of triglycerides from VLDL
Blood vessels, Liver
Cholesterol Deliver endogenously produced cholesterol to various organs.
HDLs Liver and intestine
Liver and steroid-hormone-producing glands
Cholesterol Remove and degrade
Cholesterol.
Table 3 Lipids are transported in the plasma as lipoproteins.
Lipids Metabolism
. Liver and Adipose tissue play a central
role in lipid metabolism.
. Adipose tissue is the main store of
triglyceride in the body.
. Lipid metabolism either lipolysis or
lipogenesis.
. Fatty acids are both oxidized to acetyl CoA and synthesized from acetyl CoA.
Lipolysis . Complete hydorlysis of triglyceride yeild
gelycerol and 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
Long chain fatty acids penetrate the inner -Mitochinderial membrane as carnitine derivatives.
Figure 5 : Role of carnitine in the transport of long chain fatty acids. Figure 5 : Role of carnitine in the transport of long chain fatty acids.
β - oxidation pathway of fatty acids . Many tissues are capable of oxidizing
fatty acids in the mitochondria by β - oxidation
pathway.
. The chain is broken between the α (2)
and β (3) carbon atoms.
Figure 6 : Overview of β - oxidation pathway of fatty acids Figure 6 : Overview of β - oxidation pathway of fatty acids
β - oxidation of fatty acids (Figure 7)
The products of oxidation of fatty acids Oxidation 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 CoA productFigure 8 : acetyl CoA product
Oxidation of unsaturated fatty acids occurs by
amodified β - oxidation pathway (figure9)
Ketone bodiesKetogenesis occurs when there is a high rate of
fatty acid oxidation in the Liver (figure 10).
Aceto acetyl CoA
Acetyl CoA
Acetoacetate
Acetone β -hydroxy butyrate
Acetyl CoA
CoA
CoA
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 CoAFigure 11 : Biosynthesis of Malonyl CoA
. Acetyl CoA transfer to the cytoplast across the
mitochondrial membrane in the form of citrate
Figure 12 : Conversion the citrate to Oxaloacetate and Acetyl CoA.Figure 12 : Conversion the citrate to Oxaloacetate and Acetyl CoA.
. The enzymes involved in fatty acid synthesis are
arranged in a complex called the fatty acid
synthase system.
The steps in the synthesis of fatty acid ( Figure 13)
Cholesterol
Figure 14 : CholesterolFigure 14 : Cholesterol
. Cholesterol is not an energy
producing nutrient.
. It is an essential structural
component 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 found in most tissues.
Acetyl CoA is the source of all carbon atoms in cholesterolAcetyl CoA is the source of all carbon atoms in cholesterol
Squalene
β -hydroxy- β- methylglutaryl
CoA
Mevalonate
Farmesyl pyrophosphate
Acetyl CoA
CoA
Acetoacetyl CoA
CoA
Acetyl CoA
HMG-CoA
reductase
Cyclization
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 Human Metabolism, West Puplishing Company. Lehninger, A., Nelson, D., Cox, M.,(1993) Principles of Biochemistry, 2nd edtion. Worth Puplishers. Murray, R., Granner, D., Mayes, P., Rodwell, V., (1996) Haper’s Biochemistry, 24th edition, Prentic-Hall International, Inc. Seeley, R., Stephens, T., Tate, P., (1992) Anatomy and Physiology,Mosby Yearbook.
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 Human Metabolism, West Puplishing Company. Lehninger, A., Nelson, D., Cox, M.,(1993) Principles of Biochemistry, 2nd edtion. Worth Puplishers. Murray, R., Granner, D., Mayes, P., Rodwell, V., (1996) Haper’s Biochemistry, 24th edition, Prentic-Hall International, Inc. Seeley, R., Stephens, T., Tate, P., (1992) Anatomy and Physiology,Mosby Yearbook.
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