Sheet #6 Lecture (Lipids and Membranes) Lecture Date :- 22-7-2018 Done By :- Ahmad Dabbour Edited By :- Amal Haj Ahmad Doctor :- Nabil Amer

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Lipids and Membranes

Functions Of Lipids

Functions of Lipids Source of energy Cellular membranes Excellent insulators Thermal insulators Electrical insulators (in membranes) Special roles: Signals Hormones, Mediators, or growth factors. Coenzymes Vitamins

Doctor notes (1) : # Carbohydrates are immediate source of energy (consume firstly in most organs) but lipids are Long- term source of energy . # Excellent insulators : subcutaneous fascia under body skin . ( seen in animals) . # Protection : all organs are surrounded by lipids , and these fats can leads to stones and pain in kidney for example when you burn it in severe diet . # Lubricants : maintain the integrity of membranes and skin .

Doctor notes (2) : # Vitamins : Fat-soluble vitamins: A,D,E,K … # In Brain tissue : there is no interstitial fluid in brain tissues, and Lipids work an important role in brain function( communication mainly) with Blood-Brain-Barrier . # In receptors and steroids hormones .

Lipids Lipids: a heterogeneous class of naturally occurring organic compounds classified together on the basis of common solubility properties insoluble in water, but soluble in nonpolar organic solvents including diethyl ether, chloroform, methylene chloride, and acetone Amphipathic in nature Lipids include Open Chain forms fatty acids, triacylglycerols, sphingolipids, phosphoacylglycerols, glycolipids, lipid-soluble vitamins prostaglandins, leukotrienes, and thromboxanes Cyclic forms cholesterol, steroid hormones, and bile acids

Doctor notes (3) : Proteins are soluble in water , because that some lipids are circulating and moving in the body by connection with specific proteins (Lipo-proteins). ## Amphipathic : means have two different parts : one soluble in water (less) , and another part in-soluble in water (most abundant ) ,like cholesterol . # Open-chain Forms : have no rings . # Cyclic Forms : have rings.

Fatty Acids Fatty acid: an unbranched-chain carboxylic acid, most commonly of 12 - 20 carbons, derived from hydrolysis of animal fats, vegetable oils, or phospholipids of biological membranes Usually contain even numbers of carbons (can contain odd, depending on how they are biosynthesized) • FA that contain C=C, are unsaturated: If they contain only C-C bonds, they are saturated Length of fatty acid plays a role in its chemical character

Doctor notes (4): ## odd numbers of carbons in fatty acid chain are rare. ## You must know the length of the chain (Number of carbon atoms ) on all these fatty acids, and the saturated and un-saturated chains.

## 16 Carbon -Saturated Fig. 8-1a, p. 194

## 18 Carbon -Saturated Fig. 8-1b, p. 194

## 18 Carbon -Unsaturated -(1 C=C) Fig. 8-1c, p. 194

## 18 Carbon -Unsaturated (2 C=C) Fig. 8-1d, p. 194

## 18 Carbon -Unsaturated (3 C=C) Fig. 8-1e, p. 194

## 20 Carbon -Unsaturated (4 C=C) Fig. 8-1f, p. 194

In most unsaturated fatty acids, the cis isomer predominates; the trans isomer is rare. Unsaturated fatty acids have lower melting points than their saturated counterparts; the greater the degree of unsaturation, the lower the melting point. 18

Doctor notes (5): ## cis : means that there is a double bond , and there is an angle . ## Trans : means straight .

Fatty Acids 20

Fatty Acids 21

Doctor Notes (6) : ## In Saturated Fatty acids : the longest chain has the highest melting point . ## In Un-Saturated Fatty acids : the chain which has the lowest number of double bonds , has the highest melting point . ## You must know each fatty acid in this Formula , and the general criteria for the melting point (highest , lowest ) .

In the shorthand notation for fatty acids saturated FA: the number of carbons then (:) then (0) are shown unsaturated FA: the number of carbons then (:) then the number and location of double bonds in the chain raised above delta symbol (Δ) are shown, separated by a colon Note: Counting starts from C of COOH Examples: palmitic (16:0), stearic (18:0), and oleic acids (18:1Δ9) = double bond between C9 and C10 ## Oleic acid are found in olive oil (زيت الزيتون) . ## C of COOH : alpha carbon.

Essential Fatty Acids They have to be supplied in the diet without exception. They are all polyunsaturated fatty acids: the C20 fatty acid arachidonic acid (20:4 Δ 5,8,11,14) and the two C18 acids linoleic acid (18:2 Δ 9,12) and linolenic acid (18:3 Δ 9,12 ,15 ). The animal organism requires arachidonic acid to synthesize eicosanoids.

Doctor Notes (7) : ## Linoleic acid (found in cell membrane ) , and give us the arachidonic acid . ## Our body can synthesize one double-bond fatty acids only, because that all the essential fatty acids have more than one double bond .

Nutritional fats contain palmitic, stearic, oleic acid, and linoleic acid particularly often. Unsaturated fatty acids are usually found at the central C atom of glycerol.

Omega-3 fatty acid Also called ω-3 fatty acids or n-3 fatty acids are polyunsaturated fatty acids (PUFAs) with a double bond (C=C) at the third carbon atom from the end of the carbon chain. which is considered the beginning of the chain, thus "alpha", and the methyl (-CH3) end, which is considered the "tail" of the chain, thus "omega"; the double bond is at omega minus 3 (not dash 3). One way in which a fatty acid is named is determined by the location of the first double bond, counted from the methyl end, that is, the omega (ω-) or the n- end. ## omega-3 ,omega-6 … are found in sea food (mainly in fish ) , and important for Brain health and memory .

The three types of omega-3 fatty acids involved in human physiology are α-linolenic acid (ALA) (found in plant oils), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA)(both commonly found in marine oils). Common sources of plant oils containing the omega-3 ALA fatty acid include walnut, edible seeds, seed oil, algal oil, flaxseed oil, while sources of animal omega-3 EPA and DHA fatty acids include fish, fish oils, eggs from chickens fed EPA and DHA, squid oils. Dietary supplementation with omega-3 fatty acids does not appear to affect the risk of death, cancer or heart disease.

Triacylglycerols Triacylglycerol (triglyceride): an ester of glycerol with three fatty acids natural soaps are prepared by boiling triglycerides (animal fats or vegetable oils) with NaOH, in a hydrolysis reaction called saponification (Latin, sapo, soap)

Doctor Notes (8) : Simple type of triglycerides : has the same typical chains ( 3 fatty chains ) . Mixed type : has different chains(different type of fatty acids ) . ## glycerin : a viscous fluid , used in personal care preparations, often as a means of improving smoothness, providing lubrication . ## Mixed type mainly found in the body , to be made easily from any three fatty acids presents at this step. ## Triglycerides : mainly Fat-storage type found in body (under the skin ) …

Doctor Notes (9): ## when we take extra sugars our body will form it in triglyceride type (as a storage ) .. And this will lead to obesity … ## when there is no available sugars to burn , our body will return these triglyceride to become sugars again to be consumed and producing energy ,, (this will happen in fasting , sport …) .

Soaps Soaps form water-insoluble salts when used in water containing Ca(II), Mg(II), and Fe(III) ions (hard water)

Hydrolysis of Triglycerides Chemical hydrolysis, by saponification as mentioned earlier Enzymatic digestion by lipase enzyme

## According to the type of alkaline that is added, soap may be : Doctor Notes (10): ## According to the type of alkaline that is added, soap may be : Soft >>by adding KOH. Solid>>by adding NaOH.

Doctor Notes (11) : ## Pancreas : produces all digestive enzymes : - pepsin , chymotrypsin and Trypsinogen (protein ) . - amylase ( carbohydrates ) . - Lipase (Lipids ) . # #there is anther type of lipase in anther place , because that we called it “ pancreatic lipase “ .

Phosphoacylglycerols Phosphoacylglycerols (= phospholipids) are the second most abundant group of naturally occurring lipids found almost exclusively in plant and animal cell membranes, which typically consist of 40% -50% phosphoacylglycerols and 50% - 60% proteins the most abundant phosphoacylglycerols are derived from phosphatidic acid, a molecule in which glycerol is esterified with two molecules of fatty acid and one of phosphoric acid the three most abundant fatty acids in phosphatidic acids are palmitic (16:0), stearic (18:0), and linoleic (18:1)

Phosphatidic acid

Phosphatidic acid

Phosphatidic acid

Phosphatidyl esters Further esterification with a low-molecular-weight alcohol with phosphate group gives a phosphoacylglycerol or phosphatidyl ester the most common of these low-molecular-weight alcohols are:

Phosphatidyl esters

Phosphatidyl esters

Phosphatidyl esters

Phosphatidyl esters A lecithin ## Important (lecithin is found on membranes and chocolates and biscuits ) .

Pulmonary surfactant Molecular Dynamics simulation of DPPC lipid bilayer formation in two phase systems reduces surface tension

Diagram of the alveoli with both cross-section and external view

Respiratory Distress Syndrome Result from the Disruption of Lipid Metabolism Respiratory distress syndrome is a pathological condition resulting from a failure in the biosynthetic pathway for dipalmitoyl phosphatidyl choline. This phospholipid, in conjunction with specific proteins and other phospholipids, is found in the extracellular fluid that surrounds the alveoli of the lung, where it decreases the surface tension of the fluid to prevent lung collapse at the end of the expiration phase of breathing. Premature infants may suffer from respiratory distress syndrome because their immature lungs do not synthesize enough dipalmitoyl phosphatidyl choline ( Surfactant ). ## Premature infants : delivery on 7th or 8th mounth .

Waxes A complex mixture of esters of long-chain carboxylic acids and alcohols Found as protective coatings for plants and animals 50

Sphingolipids Contain sphingosine, a long-chain (18 C) aminoalcohol from which this class is named Found in plants and animals Abundant in nervous system choline

Glycolipids Glycolipid: a compound in which a carbohydrate is bound to an -OH of the lipid many glycolipids are derived from ceramides Ceramide + simple sugar= cereboside (found in nerves and brain cells)

FIGURE 8. 8 The structures of several important gangliosides FIGURE 8.8 The structures of several important gangliosides. Also shown is a space-filling model of ganglioside GM1. Fig. 8-8, p.190

Tay-Sachs disease It is caused by a failure of lipid degradation: an inability to degrade gangliosides. Gangliosides are found in highest concentration in the nervous system, particularly in gray matter, where they constitute 6 % of the lipids. Gangliosides are normally degraded inside lysosomes by the sequential removal of their terminal sugars but, in Tay-Sachs disease, this degradation does not occur. As a consequence, neurons become enormously swollen with lipid-filled lysosomes . An affected infant displays weakness and retarded psychomotor skills before 1 year of age. The child is demented and blind by age 2 and usually dead before age 3.

Tay-Sachs disease can be diagnosed in the course of fetal development Tay-Sachs disease can be diagnosed in the course of fetal development. Amniotic fluid is obtained by amniocentesis and assayed for β-N-acetylhexosaminidase activity.

Multiple sclerosis (MS) It is a demyelinating disease in which the insulating covers of nerve cells in the brain and spinal cord are damaged.This damage disrupts the ability of parts of the nervous system to communicate, resulting in a range of signs and symptoms, including physical, mental, and sometimes psychiatric problems.

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