LIPIDS AND FATTY ACIDS

LIPIDS AND FATTY ACIDS

1. There are two types of lipids that work in the human body. The differences are found in the fatty acid tail.

   • SATURATED FATS
     • They don´t have any double bonds in their fatty acid chain. They are found in most animal origin products. The body can produce some saturated fats by itself, and they can be used by the organism as an energy reservoir, but if consumed in excess, they cause cholesterol quantities to rise up, which can cause cardiovascular diseases and weight gain. Both can lead to severe health issues. This type of fat trends to be solid in room temperatures
       • Some examples of saturated fatty acids are the palmitic acid (16:0) and the lauric acid (12:0)
   • UNSATURATED FATS
     • These fats must be consumed in the diet, as is impossible for the body to produce them. They are found in vegetable origin products and fish meat. The unsaturated fats have been comprobed to be healthier than the saturated fats, as they reduce the cardiovascular risk disease, and they don´t suppose an increase in the cholesterol. They also play a role in the nervous system functions
       • Some examples of unsaturated fatty acids are the EPA (20:5) and DHA (22:6) which are known as omega-3 fatty acids
   • Lipids also have a nomenclature based on their number of carbons and double bonds
   • LIipids can also be found in cis-trans isomery. Most fatty acids are found in the naure in the cis configuration, but after some reactions and processes they change into the trans configuration, which makes them to adopt similar characteristics to the saturated fatty acids, as higher melting point (which cause them to be solid at room temperature), or cholesterol increase in the body

2. Lipids are organic molecules whose most remarkable characteristic is that they are amphipatic molecules, due to their structure: they are composed by a fatty acid attached to glycerol. The fatty acids have nonpolar 'tails' of carbon chains attached to a polar head that is a carboxylic acid. Lipids can also have phosphorus, sulfur or nitrogen in their structures, and despite they are not water soluble, they can be dissolved in organic solvents.

   • Their nomenclature can be with common numbers, which starts from the tail and ends in the head. The other way uses greek letters which starts after the first carbon of the carboxylic acid of the head of the lipid. That is going to be the alpha carbon, and so on in alphabetical order.
     • Due to their properties, lipids can be used in reactions that modify some of their characteristics or produce other type of compounds
       • ESTERIFICATION
         • Is the reaction where an alcohol blind covalently with the carboxylic acid of a lipid in order to form an ester. This makes the molecule completely homophobic. This reaction is used by the body to construct triglycerides
       • SAPONIFICATION
         • Is the reaction that occurs between a lipid and a basic compound in order to produce soap, which dissolves in water forming micelles
       • SELF-OXIDATION
         • It only occurs to the unsaturated fatty acids of the lipids. Their double bond react with oxygen, which provokes the rupture of the fatty acid tail to produce aldehydes

3. The lipids enter the body as triacylglycerol (triglycerides), and get distributed along the body by the chylomicrons. Once they are in the organism, they suffer of several processes that allow the body to profit these molecules as they can be used to produce massive amounts of energy but slowlier than with other molecules such as glucose

   • BETA OXIDATION
     • This process starts with the lipolysis of the triglycerides, which produce free fatty acids and glycerol. The fatty acids get oxidized into acetyl CoA chains by an enzyme, and subsequently this chains are converted into smaller molecules of acetyl CoA so it can be used in the Krebs cycle or in the ketogenesis
   • KETOGENESIS
     • This process starts with the acetyl CoA obtained from the beta oxidation of the fatty acids. The acetyl CoA is converted into acetoacetyl CoA by an enzyme and then into acetoacetate, which rupture produces the ketone bodies that will be used in ketolysis to produce energy when needed.
   • ESTERIFICATION
     • Is the reaction where the fatty acid chains attach to an alcohol, particuraly glycerol, in order to produce triacylglycerol or triglycerides. This reaction can also produce monoglycerides or diglycerides
   • The beta oxidation occurs in the liver, and in the extra hepatic tissues like skeletal muscle or the brain, the ketogenesis is used for energy production. The lipids are also storaged in the adipose tissue, which works as a fatty acid provider to the liver when energy needs to be produced.
   • Lipids are degraded in the body by an enzyme called lipase. There are many types of lipases that perform diferent functionsin the organism
     • SALIVARY AND PANCREATIC LIPASE
       • This lipases are used in the digestion, and contribute to the triacylglycerol degradation
     • HEPATIC LIPASE
       • This lipase degrades prevent the plaque formation in the blood vessels through the degradation of some lipoproteins
     • LIPOPROTEIN LIPASE
       • It hydrolyzes the triglycerides in the lipoproteins, specially VLDL and chylomicrons. It also increases the cell uptake of the chylomicron remnants and cholesterol
     • HORMONE-SENSITIVE LIPASE
       • It reacts to some hormones to break down the triglycerides into fatty acids to eventually produce energy or not as appropriate
     • PHOSPHOLIPASE
       • It hydrolyzes phospholipids into fatty acids

4. The lipids are mobilized through the body by the lipoproteins as they can´t flow through the bloodstream by themselves

   • CHYLOMICRONS
     • They transport lipids absorbed from the intestine to adipose, cardiac, and skeletal muscle tissue. During its way and in the tissues mentioned, its triglyceryde content is hydrolyzed by the lipoprotein lipase, leaving a chylomicron remnant which is able to enter the liver
     • VERY LOW DENSITY LIPOPROTEINS (VLDL)
       • These are produced in the liver, after the lipids that arrived in the chylomicron remnant are hydrolyzed. It transports, mainly, cholesterol, and in the bloodstream it transform into LDL and IDL
       • LOW DENSITY LIPOPROTEINS (LDL)
         • They transport lipids into the cells constantly. They are associated with progression of atherosclerosis as they travel for very small vessels, which are most likely to get plugged
         • INTERMEDIATE DENSITY LIPOPROTEINS
           • They are similar to the LDL as their function is the same. However, this one contents more cholesterol than the LDL
           • HIGH DENSITY LIPOPROTEIN
             • They transport cholesterol to the liver, as well as to adrenals, testes and ovaries, where the fats are used in the hormone production. Are the less likely to contribute to the atherosclerosis due to their very small size

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