Lipids

Description

Start From : 1- definition 2- function 3- classification (A- simple lipids B- Compound lipids C- Derived lipids D- polyprenoid ) 4- Fatty acids
Ahmed Ahdmmtq
Mind Map by Ahmed Ahdmmtq, updated more than 1 year ago
Ahmed Ahdmmtq
Created by Ahmed Ahdmmtq almost 7 years ago
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Resource summary

Lipids
  1. Definition
    1. - Heterogeneous group of compounds which are soluble in organic solvents and insoluble in water.
      1. - Not polymers.
        1. - Related to fatty acids.
        2. Function
          1. - Important dietary constituents, because of their high energy value.
            1. - Fate soluble vitamins D,E,K,A. (DEKA).
              1. - Lipids act as thermal insulator in subcutaneous tissues and around certain organs.
                1. - Act as electrical insulator around myelinated nerves.
                  1. - Cell membrane structure.
          2. Classification
            1. Simple Lipids
              1. Ester of (fatty acids + alcohol)
                1. Tag
                  1. Oils or fat (Triacylglycerol)
                    1. - They are Ester of ( fatty acids + Glycerol )
                      1. Simple Triacylglycerol
                        1. If the three fatty acids are the same
                        2. Mixed Triacylglycerol
                          1. If the three fatty acids are not the same
                          2. Function
                            1. - Main storage form of fatty acids.
                              1. They provide sufficient energy for survival for several weeks of starvation.
                                1. - Can be stored in large amount as it is hydrophobic
                                  1. - acts as insulator for heat
                                    1. - supports internal viscera
                            2. Solid or liquid ?
                              1. Solid Form
                                1. If the fatty acid chain is long or saturated (fat)
                                2. Liquid form
                                  1. If the fatty acid chain is short or unsaturated (oils)
                                  2. ( In room temp )
                              2. Wax
                                1. - Ester of ( fatty acid + high molecular monohydric alcohol)
                                  1. (alcohol has 16~30 carbon)
                                    1. As : Bee wax, Lanoline
                            3. Compound lipids
                              1. Esters of fatty acids with alcohols containing additional groups
                                1. Lipoproteins
                                  1. contain protein
                                  2. Sulfolipids
                                    1. contain sulphate
                                    2. Glycolipids
                                      1. contain carbohydrates
                                        1. - Contain ( Ceramide + carbohydrate )
                                          1. Contain Ceramide+ two or more monosaccharides+ one or more sialic acid.
                                            1. The principle sialic acid is gangliosides is N-acetyl neuraminic acid (NANA).
                                              1. They are present in ganglion cells of nervous system.
                                                1. They act as receptor or for cell- cell recognition.
                                                  1. Act as receptor e.g. for Cholera toxin in human intestine.
                                                    1. *All glycolipids and sphingomyelin contain Sphingosine alcohol and are referred as Sphingolipids*
                                        2. Cerebrosides
                                          1. ( Ceramide monohexosides )
                                            1. Contain Ceramide that is attached to monosaccharide unit by β-glycosidic bond
                                              1. Galactocerebrosides
                                                1. .Present in brain & nervous tissue
                                                2. Glucocerebrosides
                                                  1. .Present in extra neural tissue
                                            2. Sulfatides
                                              1. Contain galactocerebroside + sulfate
                                              2. Gangliosides
                                              3. Phospholipids
                                                1. contain phosphate
                                                  1. Glycerophospholipids
                                                    1. ( phosphoglycerides )
                                                      1. - They are polar, ionic lipids
                                                        1. Acidic phospholipids:
                                                          1. They are phospholipids with (-1) net charge or more at physiological PH (7.4).
                                                            1. Example: Phosphatidyl serine, inositol, glycerol and cardiolipin
                                                              1. They play a role in blood coagulation.
                                                                1. Antibodies against acidic phospholipids lead to recurrent thrombosis and recurrent fetal loss (antiphospholipids syndrome)
                                                        2. Phosphatidic acid
                                                          1. - An Intermediate in the synthesis of TAG, phospholipid (parent compounds).
                                                            1. It isn’t common constituents in tissue.
                                                          2. Phosphatidyl choline
                                                            1. ( lecithin )
                                                              1. ( Dipalmityl lecithin )
                                                                1. ( lung surfactant )
                                                                  1. - It contains palmitic acid at C1,2
                                                                    1. - It decreases the surface tension in the lung alveoli.
                                                                      1. - It is synthesized around time of birth.
                                                                        1. - Deficiency of lung surfactant in premature babies causes respiratory distress syndrome (RDS).
                                                            2. Phosphatidyl serine
                                                              1. phosphatidyl ethanolamine
                                                                1. - They have role in blood coagulation.
                                                                  1. - They are found in the cell membrane.
                                                                    1. (cephalin)
                                                                    2. Phosphatidyl inositol
                                                                      1. Phosphatidyl inositol 4,5 bisphosphate acts as second messenger in signal transduction and present in cell membrane.
                                                                        1. *inositol is a cyclic hexahydric alcohol*
                                                                      2. Phosphatidyl glycerol
                                                                        1. Present in mitochondrial membrane and is the precursor of cardiolipin.
                                                                        2. Cardiolipin (Diphosphatidyl glycerol)
                                                                          1. - Present in mitochondrial membrane -It has some immunological properties.
                                                                          2. Lysophospholipid
                                                                            1. (lysophosphatidyl choline) (lysolecithin)
                                                                              1. - This type of phospholipid with free OH in C2.
                                                                                1. - They are important intermediates in metabolism and phospholipid interconversions.
                                                                            2. Plasmalogens
                                                                              1. - Resemble phospholipids, except: they have ether link in C1 not ester link.
                                                                                1. - Represent 10-30% of phospholipids in brain and heart.
                                                                                  1. - Example: Ethanolamine plasmalogen.
                                                                          3. Sphingophospholipid
                                                                            1. ( Sphingomyelin )
                                                                              1. Ceramide
                                                                                1. fatty acid
                                                                                  1. Sphingosine
                                                                                    1. Serine
                                                                                      1. ( amino acid )
                                                                                      2. (palmitate)
                                                                                        1. ( fatty acid )
                                                                                    2. Phosphocholine
                                                                                    3. Functions of phospholipids
                                                                                      1. 1- They serve as structural component of membranes
                                                                                        1. They are important for mobilization of triacylglycerol from liver preventing the development of fatty liver
                                                                                          1. 2- They form the surface layer of lipoprotein structure, which help in lipid transport in blood.
                                                                                            1. 3- They solubilize cholesterol in bile, and prevent the formation of cholesterol stones
                                                                                          2. Important notes on phospholipids:
                                                                                            1. • Most phospholipids contain more than one kind of fatty acids.
                                                                                              1. • Saturated fatty acid is attached to C1. While, unsaturated fatty acid is attached to C2 except in Dipalmityl lecithin
                                                                                                1. • Phospholipase A2 enzyme attacks C2 position leads to removal of unsaturated fatty acid at C2.
                                                                                      2. Derived lipids
                                                                                        1. These are produced from the hydrolysis or digestion of simple or compound lipids.
                                                                                          1. Fatty acids
                                                                                            1. properties
                                                                                              1. They are mono carboxylic (only one –COOH-), which is completely ionized in plasma.
                                                                                                1. Fatty acids are amphipathic as it contain hydrophilic part and hydrophobic part.
                                                                                                  1. They have long straight chains Except, phytanic acid is branched.
                                                                                                    1. - Up to five carbon : short chain fatty acid
                                                                                                      1. - 5~10 : medium fatty acid
                                                                                                        1. - More than 10 : long chain
                                                                                                          1. Fatty acids in human have even number of carbon atoms. plants have odd number.
                                                                                                            1. Some fatty acids contain a hydroxyl group as ( cerebronic acid)
                                                                                                              1. Saturated
                                                                                                                1. Unsaturated
                                                                                                                  1. Mono-unsaturated
                                                                                                                    1. Poly-unsaturated
                                                                                                                      1. Essential fatty acids
                                                                                                                        1. polyunsaturated fatty acids
                                                                                                                          1. Can't be synthesized inside the body.
                                                                                                                            1. They should be taken in diet for synthesis of other members of ω3,ω6 family.
                                                                                                                              1. Linoleic acid
                                                                                                                                1. (18:2 Δ9,12 ω6)
                                                                                                                                  1. Constitutes about 60-80% of total fatty acid in dietary oils as corn oil, sunflower oil, and soyabean oil.
                                                                                                                                2. Linolenic acid
                                                                                                                                  1. (18:3 Δ9,12 ,15 ω3)
                                                                                                                                    1. Present in small amount in plant oil in association with linoleic acid, particularly present in linseed oil
                                                                                                                                  2. Arachidonic acid
                                                                                                                                    1. - Present in (arachis oil) Peanut oil. Present in small amount in plant oil in association with linoleic acid
                                                                                                                                      1. - It may not be essential to take Arachidonic acid in diet if there is an adequate supply of linoleic acid.
                                                                                                                                        1. - It can be synthesized inside the body from linoleic.
                                                                                                                                          1. - It contains 20 carbons contains 4 double bonds, ( so it's more kinked )
                                                                                                                                            1. - Its U shape is very important in fluidity of biological membrane
                                                                                                                              2. The importance of essential fatty acids
                                                                                                                                1. - Are used for synthesis of prostaglandins and thromboxanes (Eicosanoids)
                                                                                                                                  1. - Enter in cell membrane structure.
                                                                                                                                    1. - Lower the cholesterol level in plasma.
                                                                                                                                      1. - Role in growth and development
                                                                                                                                        1. - Role of Linolenic acid in the formation of docosahexaenoic (DHA) acid (22:6 3), DHA is needed for normal brain & retina.
                                                                                                                              3. other ω-3 fatty acids
                                                                                                                                1. Eicosapentaenoic acid (20:5)
                                                                                                                                  1. Docosahexaenoic acid (22:6)
                                                                                                                                    1. Both are present in fish oil (Salmon) They protect from cardiovascular diseases
                                                                                                                                2. Notes
                                                                                                                                  1. The double bound are always separated from each other by methylene group (-CH2-)
                                                                                                                                    1. They are neither adjacent nor conjugated ( not alternating with single bonds )
                                                                                                                                      1. The presence of double bound produces ( Cis-trans ) isomerism
                                                                                                                                        1. The melting point of fatty acid decreases if the fatty acids are shorter and have more double bonds
                                                                                                                                          1. Short fatty acids (up to 5C) and medium chain fatty acids (6-10C) are liquid at room temp
                                                                                                                                            1. Longer chain fatty acids (more than 10C) are solid at room temp.
                                                                                                                                              1. Parent fatty acids :
                                                                                                                                                1. Fatty acid numbering : اسمع المحاضرة التانية على الدرايف
                                                                                                                                        2. Cis
                                                                                                                                          1. When the two bulky groups are at the same side of the bond
                                                                                                                                            1. - Less thermal stable, have lower melting temp
                                                                                                                                          2. Trans
                                                                                                                                            1. When the two bulky groups are at the opposite side of the bond
                                                                                                                                              1. - More thermal stable, need high melting temp.
                                                                                                                                                1. - They are nearer to in properties to the corresponding saturated fatty acid.
                                                                                                                                                  1. - They are metabolized like saturated fatty acids. So, they tend to increase cholesterol in blood.
                                                                                                                    2. glycerol
                                                                                                                      1. sphingosine
                                                                                                                    3. Polyprenoid Compounds
                                                                                                                      1. A group of compounds which contains isoprene units
                                                                                                                        1. Steroids
                                                                                                                          1. • They are compounds that have steroid nucleus.
                                                                                                                            1. Steroid nucleus is composed of 4 rings identified by A-BC- D, and formed of 19 carbons
                                                                                                                              1. The OH at C3 is often esterified with unsaturated fatty acid (cholesterol ester)
                                                                                                                                1. Cholesterol ester is the storage form inside the cell. Cholesterol and cholesterol ester present in animal fats not in plant fats.
                                                                                                                                  1. Blood cholesterol is either in free form (1/3 of total) or in ester form (2/3 of total).
                                                                                                                                    1. Free cholesterol is an amphipathic as it contains the OH group at C3 (hydrophilic).
                                                                                                                                      1. Cholesterol is an important constituent in cell membrane
                                                                                                                                        1. Plant sterol is ergosterol, the precursor of vitamin D2
                                                                                                                                          1. Bacteria do not contain sterol
                                                                                                                            2. Cholesterol
                                                                                                                              1. precursor of
                                                                                                                                1. Vitamin D
                                                                                                                              2. Fat soluble Vitamins (EKA)
                                                                                                                                1. Bile acids
                                                                                                                                  1. sex hormones
                                                                                                                                    1. adrenocortical hormones
                                                                                                                                    2. Terpenes
                                                                                                                                      1. in plants
                                                                                                                                        1. As essential oils in plants that have characteristics flavors . Example : limonene (from lemon oil)
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