Fatty acid composition of nearly fats and oils

 

Fatty acid composition of nearly fats and oils

Fatty acids are chemically bound in triglycerides in almost all natural (vegetable and animal) oils and fats. Contrary to popular belief, natural fats and oils do not contain any free (chemically unbound) fatty acids but glycerol esters of the fatty acids.

physiology

Fats and oils are essential human nutrients. Among other things, they are needed in the human body as

·        Energy supplier (so-called reserve material ),

·        Insulators against cold,

·        Solvent for only fat-soluble substances such as some vitamins,

·        Protective padding for internal organs and the nervous system,

·        Part of the cell membrane.

Fats as energy stores

Besides carbohydrates ( sugar, starch, and glycogen ), fats are the most important energy stores in cells. The physiological calorific value of 37 kJ / g fat is more than twice as high as that of carbohydrates and proteins (17 kJ / g). [1]

 

The depot fat as an energy store in the human body comes from the fat contained in food or other macronutrients (carbohydrates, proteins), which can ultimately be converted into fat over several intermediate stages of energy. It is controversial to what extent the conversion of the macronutrient fat, carbohydrates and proteins directly contribute to adipose tissue formation. Such a connection is established, especially from the point of view of calorie theory. Other mammals can easily make depot fats from an excess of energy in their food.

 

The density of human adipose tissue is 0.94 kg / l, the physiological calorific value (energy content) is around 29,000  kJ / kg (7,000 kcal / kg). The difference to 37,000 kJ / kg of fat results from the fact that the fatty tissue does not consist of pure fat. In the blood of people who Gesamttriglyceride is determined and are, as such, in addition to the blood fats' cholesterol level. The normal level of triglycerides in the blood is 70 to 170 mg/dl.

 

According to the German Nutrition Society (DGE), a fat intake of 60 to 80 g per day is sufficient for an adult, which corresponds to 25 percent of the energy consumed from food. There may well be small excesses, provided that the fat intake is balanced out in the following days. Women should consume a maximum of approx. 420 g and men approx. 560 g of fat per week. This calculation is based on an assumed energy requirement of approx. 10 to 13.4 MJ per day (= 2,400 to 3,200 kcal / d). For example, this would correspond to a 40-year-old office worker with bodyweight between 80 kg and 107 kg who does not participate in regular sports. Only determining the actual resting metabolic rate and the individual physical activity allows an exact determination of needs. Concomitant diseases must also be taken into account.

 

Trans fatty acids can stress the body and lead to vascular damage.

 

Biosynthesis of fats

The triacylglycerols are built up from the components glycerol and fatty acids in several reaction steps.

 

First, the fatty acid is activated using one of several fatty acid CoA ligases and glycerol using one of the glycerol kinases. The end products acyl-CoA and glycerine-3-phosphate react to form lysophosphatidic acid, catalyzed by the enzyme glycerine phosphate O- acyltransferase. Another fatty acid molecule is transferred by the acylglycerol-3-phosphate- O- acyltransferase, resulting in phosphatidic acid. One of the phosphatidate phosphatases splits off phosphate, whereby diacylglycerol remains. Finally, the diacylglycerol- O- acyltransferase transfers a third fatty acid molecule to the triacylglycerol. [8th]

 

Breakdown of fats

In fat cells, triacylglycerols are surrounded by a shell made from the protein complex Perilipin: CGI-58, which, depending on the degree of phosphorylation, prevents the breakdown of fats through hydrolysis. The enzyme hormone-sensitive lipase (HSL) is responsible for starting the analysis and is subject to both positive ( catecholamines, ACTH, glucagon ) and negative regulation ( insulin ).

 

The triacylglycerols are broken down into twelve steps: after phosphorylation of the HSL and its dimerization, the protein layer around the lipids is broken up with catecholamines or glucagon, perilipin separates from CGI-58 and is phosphorylated by protein kinase A and later recycled with protein phosphatase 1. HSL gets close to the lipids; their hydrolysis activity is enhanced by complexation with FAB4. This is how cholesterol esters are made fatty acids and cholesterol and from triacylglycerol glycerol and three fatty acid molecules. Dephosphorylation of HSL terminates the process; the phosphatase's identity that catalyzes this reaction is unknown. The course of the entire metabolic

webtechradar