LIPIDS . Digestion .. Absorption .. Transportation .. Metabolism. Dina Trabzuni. Lipids consist of two parts Glycerol Fatty Acids a. Saturated fatty acids b. Unsaturated fatty acids . Monounsaturated . Polyunsaturated. Figure 3 : Formation of TG. Table 1 : Saturated fatty acids .
Digestion .. Absorption ..
Transportation .. Metabolism
Figure 3 : Formation of TG
Figure 1 : Triglyceride
Figure 2 : Phosphatidic acid
. Essential nutrient
. Flavor and Satisfaction
. Adipose Tissue
.Cell membrane Structure
Fat in Food
Fat in Body
. 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)
. Butter, margarin, salad oils and dressing,shirteninig fat meat
. Chees, cream portion of homogenised milk, egg yolk, nuts, seeds, olives…..
2 fatty acids + Mono glycerides
1 fatty acids + Diglycerides
3 fatty acids + glycerol
Figure 4 : Absorption of fat.
Table 3Lipids are transported in the plasma as lipoproteins.
. 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.
. 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.
. 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
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 product
Oxidation of unsaturated fatty acids occurs by amodified β - oxidation pathway (figure9)
Ketogenesis occurs when there is a high rate of fatty acid oxidation in the Liver (figure 10).
Aceto acetyl CoA
β -hydroxy butyrate
. 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
. 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.
. The enzymes involved in fatty acid synthesis are arranged in a complex called the fatty acid synthase system.
. Cholesterol is not an energy producing nutrient.
Figure 14 : Cholesterol
Acetyl CoA is the source of all carbon atoms in cholesterol
β -hydroxy- β- methylglutaryl CoA
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