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A combination of water-soluble and fat-soluble antioxidants is ideal, usually in the ratio of fat to water. In addition, rancidification can be decreased by storing fats and oils in a cool, dark place with little exposure to oxygen or free radicals, since heat and light accelerate the rate of reaction of fats with oxygen.
Chylomicron structure ApoA, ApoB, ApoC, ApoE (apolipoproteins); T (triacylglycerol); C (cholesterol); green (phospholipids). Chylomicrons transport lipids absorbed from the intestine to adipose, cardiac, and skeletal muscle tissue, where their triglyceride components are hydrolyzed by the activity of the lipoprotein lipase, allowing the released free fatty acids to be absorbed by the tissues.
The digestion products consisting of a mixture of tri-, di- and monoglycerides and free fatty acids, which, together with the other fat soluble contents of the diet (e.g. the fat soluble vitamins and cholesterol) and bile salts form mixed micelles, in the watery duodenal contents (see diagrams on the right). [27] [29]
These compounds are water-soluble and, thus, cannot protect fats from oxidation: For this purpose, the fat-soluble esters of ascorbic acid with long-chain fatty acids (ascorbyl palmitate or ascorbyl stearate) can be used as antioxidant food additives. Sodium-dependent active transport process enables absorption of Ascorbic acid from the intestine.
Dehydroascorbic acid has been used as a vitamin C dietary supplement. [9] As a cosmetic ingredient, dehydroascorbic acid is used to enhance the appearance of the skin. [10] It may be used in a process for permanent waving of hair [11] and in a process for sunless tanning of skin. [12]
Lipid metabolism is often considered the digestion and absorption process of dietary fat; however, there are two sources of fats that organisms can use to obtain energy: from consumed dietary fats and from stored fat. [5] Vertebrates (including humans) use both sources of fat to produce energy for organs such as the heart to function. [6]
Vitamins and minerals are essential to the proper functioning and maintenance of the human body. [114] There are 20 trace elements and minerals that are essential in small quantities to body function and overall human health. [114] Iron deficiency is the most common inadequate nutrient worldwide, affecting approximately 2 billion people. [115]
Mechanism for acid-catalyzed hydrolysis of an amide. Upon hydrolysis, an amide converts into a carboxylic acid and an amine or ammonia (which in the presence of acid are immediately converted to ammonium salts). One of the two oxygen groups on the carboxylic acid are derived from a water molecule and the amine (or ammonia) gains the hydrogen ion.