Carbs and lipids: Ch 8 Lecture

Lipids

% of Dietary Energy Intake derived from Fat, Protein, and Carbohydrates (CHO) in selected human populations, chimpanzees and Gorillas

Which are the two essential fatty acids?

- Linoleic (ω6, 18:2, Δ9,12) acid in plant oils - Linolenic (ω3, 18:3, Δ9,12,15) acid in plant oils

Chemical Classification of Lipids

- Non-esterified fatty acids (saturated, unsaturated, trans) - Glycerolipids (MAG, DAG, TAG) Glycerophospholipids (PE, PC, PS, PI..) - Glycoglycerolipids - Sphingolipids - Isoprenoids - Biological waxes - Steroids - Elicosanoids - Other lipids

How do lipids differ from carbs and proteins?

- Not large macromolecular polymers - No affinity for water

Glycoglycerolipids

- One of the two major classes of glycolipids • Compounds that have a mono- or oligosaccharide moiety linked glycosidically to the hydroxyl group of glycerol as well as fatty acyl or fatty alcohol chains attached to the other two positions of glycerol. • The glycosylphosphatidylinositol (GPI) anchor and GPI-anchored proteins are synthesized starting with membrane PtdIns. GPI-anchored proteins are involved in receptor mediated signal transduction pathways and membrane trafficking.

cis and trans fatty acids

- The orientation of hydrogen atoms around the Carbon double bond distinguishes "cis" fatty acids from "trans" fatty acids. Most unsaturated fatty acids found in nature have double bonds in the cis configuration. - A cis fatty acid is a carbon-carbon double bond in which the hydrogen atoms are positioned on the same side of the double bond. Trans fatty acids are a carbon-carbon double bond in which the hydrogen atoms are positioned on opposite sides of the double bonds.

Hydrogenation

- The process of converting unsaturated fats to saturated fats by adding hydrogen - the process of adding hydrogen to unsaturated fatty acids to make fat more solid and resistant to the chemical change of oxidation

Arachidic acid

- aka eicosanoic acid - a saturated fatty acid with a 20-carbon chain. - The salts and esters of arachidic acid are known as arachidates. - a minor constituent of cupuaçu butter (7%), perilla oil (0-1%), peanut oil (1.1-1.7%), corn oil (3%),[5] and cocoa butter (1%). - also constitutes 7.08% of the fats from the fruit of the durian species Durio graveolens

arachidonic acid

- an omega-6 fatty acid derived from linoleic acid - an omega-6 polyunsaturated fatty acid with 20 carbons and four double bonds; - present in small amounts in meat and other animal products and synthesized in the body from linoleic acid.

Why are n-3 fatty acids particularly important to the body?

- because they are hypolipidemic and antithrombotic - They are significant structural components of the phospholipid membranes of tissues throughout the body and are especially rich in the retina, brain, and spermatozoa, in which docosahexaenoic acid (DHA; 22:6 n−3) constitutes ≤36.4% of total fatty acids (1, 2). - Membrane fluidity is essential for proper functioning of these tissues. ---In the retina, where n−3 fatty acids are especially important, deficiency can result in decreased vision and abnormal electroretinogram results. These topics are explored extensively in the supplement. n−3 Fatty acids are essential fatty acids, necessary from conception through pregnancy and infancy and, undoubtedly, throughout life. It is not known whether there is need in the human diet for the entire spectrum of n−3 fatty acids from the 18-carbon α-linolenic acid (ALA; 18:3n−3) with 3 double bonds to the highly polyunsaturated DHA. Considering that DHA can be synthesized from ALA, is there a need for DHA in infant formulas? Or should DHA be supplied to infant formulas in addition to ALA? DHA is certainly transferred across the placenta to the fetus during pregnancy (3) and is always present in human milk along with other n−3 fatty acids, including ALA. Also, what is the proper ratio in the diet of dietary n−6 to n−3 fatty acids? An imbalance in this ratio can accentuate the n−3 fatty acid deficiency state, as is shown by several review articles in this supplement. The ratio of n−6 to n−3 fatty acids may have increased in industrialized societies because of increased consumption of vegetable oils rich in n−6 fatty acids, ie, linoleic acid (18:2n−6), and reduced consumption of foods rich in n−3 fatty acids. Because both n−3 and n−6 fatty acids are essential, the ratio of arachidonic acid (20:4n−6) to DHA may also be important. Another important feature of n−3 fatty acids is their role in the prevention and modulation of certain diseases that are common in Western civilization.

fatty acids

- chains of carbon atoms bonded to hydrogen atoms - fatty acids are carboxylic acids (amphipathic) - fatty acids consist of hydrocarbon chains fo differing lengths (short, medium, long) - degrees of unsaturation - short chain length and cis unsaturation enhance the fluidity of fatty acids and their derivatives - cis and trans fatty acids; hydrogenation

The delta (Δ) system

- counts from carboxyl end - the notation for linoleic acid is 18:2 Δ^9,12

the Omega (ω) System

- counts from the methyl end - the notation for linoleic acid is 18:2 ω-6 or 18:2 n-6

stearic acid

- is a saturated fatty acid with an 18-carbon chain. - The IUPAC name is octadecanoic acid. - It is a waxy solid and its chemical formula is C17H35CO2H. - Its name comes from the Greek word στέαρ "stéar", which means tallow. - The salts and esters of stearic acid are called stearates. As its ester, stearic acid is one of the most common saturated fatty acids found in nature following palmitic acid. - The triglyceride derived from three molecules of stearic acid is called stearin.

palmitic acid

- palmitate - primary end product of fatty acid synthesis - 16:0 Saturated w/ hydrogen Alkane

linolenic acid (omega 3)

- polyunsaturated fat sources, found in fish oil - (ω3, 18:3, Δ^9,12,15) acid in plant oils -has 18 carbon atoms but contains 3 double bonds and is found mostly in soybean, flaxseed and hempseed. - Linolenic acid is a type of fatty acid. - It can refer to either of two octadecatrienoic acids (i.e. with an 18-carbon chain and three double bonds, which are found in the cis configuration), or a mixture of the two. - Linolenate (in the form of triglyceride esters of linolenic acid) is often found in vegetable oils; traditionally, such fatty acylates are reported as the fatty acids: ----α-Linolenic acid, an omega-3 (n-3) fatty acid ----γ-Linolenic acid, an omega-6 (n-6) fatty acid

Function of lipids

- store energy - provide barriers - lubrication and conditioning for body surfaces - hormones and signals - regulation (act as sensors, receptors, etc)

Sphingolipids

-- Fatty acid is attached in amide linkage to the amino group of 18-carbon amino alcohol sphingosine backbone - Sphingosine + fatty acid forms ceramide - Ceramide + PC forms sphingomyelin (nerve cells) - 3 subclasses: • Sphingomyelins - sphingophosphatides • Cerebrosides - glycolipids • Gangliosides - glycolipids Contain a CHO moiety

carboxylic acid

-COOH (carboxyl group)

Isoprenoids

-Compounds derived from 5 carbon isoprene units -Isoprenoids are generally repeating units -Compounds responsible for color, aroma, chemical signaling in plants -Example: carotenoids (lycopene, carotenes, xanthophyll)

Adipose tissue

-Major site for storage of TAG in mammals -When needed, TAG are hydrolyzed and transported to other tissues for use as energy -Also serve as thermal insulators

Eicosanoids

-Oxygenated non-esterified fatty acids principally derived from arachidonic acid (20: 4n-6) -These derivative compounds influence contractility and membrane permeability -Prostaglandins and thromboxanes -Leukotrienes and lipoxins

Sterols and Steroids

-Polycyclic hydrocarbons -Steroids are produced from squalene, a 30-carbon isoprenoid precursor by oxidation and cyclization, to generate the core steroid structure, followed by modification of substituents, degree of saturation and side chain shortening -Characterized by a 4 member ring core structure called the steroid nucleus -Most important animal sterol is cholesterol -Cholesterol modulates membrane features such as -Compressibility -Permeability -Fusibility -Thickness

What happens there is a deficiency in EFAs?

-causes: -- retarded growth -- dermatitis -- kidney lesions -- early death

Two systems of nomenclature for linoleic acid

1. The delta system 2. The omega system

Oleic acid

An omega-9 fatty acid with 18 carbons and one double bond.

Sphingolipids

Ceramides, or lipid material, that are natural part of the intercellular matrix. Glycosphingolipids and phospholipids are also natural lipids found in the barrier layer.

Lipids

Energy-rich organic compounds, such as fats, oils, and waxes, that are made of carbon, hydrogen, and oxygen. - insoluble in water - soluble in non-polar solvents - every cell has characteristic lipids

-Cholesteryl esters are formed when cholesterol is esterified to a fatty acid -stored in adrenal gland and corpus luteum

Free (non-esterified) cholesterol is found in animal cell membranes and increases membrane rigidity and strength. • Cholesterol is stored in lipid droplets and transported in plasma lipoprotein particles in the form of cholesteryl esters. • Attached to some proteins as posttranslational modification (e.g. Hedgehog proteins important in development) • Parent compound for synthesis of steroid hormones • Vitamin D is related to steroids (cleaved B ring) • Parent compound for synthesis of bile acids • Oxysterols are 27-carbon bioactive oxidized metabolites of cholesterol that can have signaling functions.

glycerolipids (triglycerides)

Trihydroxy alcohol (glycerol) to which 3 fatty acids are attached by ester bonds • Maybe simple or mixed • Nomenclature: stereospecific numbering (sn) • Fluidity of TAGs is determined by fatty acyl substituents • Major storage form of fat found predominantly in adipose tissue • Mono and diacylglycerols are important metabolic intermediates

ampipathic

a molecule that have both polar and non polar parts

Triglycerides

an energy-rich compound made up of a single molecule of glycerol and three molecules of fatty acid.

linoleic acid

an essential polyunsaturated fatty acid of the omega-6 family - (ω6, 18:2, Δ9,12) in plant oils - Linoleic acid is an organic compound - Both alkene groups are cis. - It is a fatty acid sometimes denoted 18:2 (n-6) or 18:2 cis-9,12. - A linoleate is a salt or ester of this acid. - is a polyunsaturated omega-6 fatty acid. - It is a colorless or white oil that is virtually insoluble in water but soluble in many organic solvents. - It typically occurs in nature as a triglyceride (ester of glycerin) rather than as a free fatty acid. - It is one of two essential fatty acids for humans, who must obtain it through their diet. - The word "linoleic" derives from the Latin linum "flax" + oleum "oil", reflecting the fact that it was first isolated from linseed oil

Eicosanoids

biologically active compounds that regulate body functions. lipids derived from arachidonic acid. regulatory molecules that can be synthesized from omega-3 and omega-6 fatty acids

Glycerolipids

composed of mostly mono-, di-, and substituted glycerols -glycerol backbone

essential fatty acids (EFAs)

fatty acids that must be consumed in the diet because they cannot be made by our body - when mammals lack the enzymes to introduce double bonds at carbon atoms beyond C-9 in the fatty acid chain

Antithrombotic

inhibits clot formation by reducing the coagulation action of the blood protein thrombin

Erucic acid

is a monounsaturated omega-9 fatty acid, denoted 22:1ω9. It has the chemical formula CH3(CH2)7CH=CH(CH2)11COOH. - It is prevalent in wallflower seed with a reported content of 20 to 54% in high erucic acid rapeseed oil,[1] and 42% in mustard oil. Erucic acid is also known as cis-13-docosenoic acid and the trans isomer is known as brassidic acid.

Glycerophospholipids

phospholipids that contain a glycerol backbone

Glycerophospholipids

phospholipids that contain a glycerol backbone - Derived from parent compound phosphatidic acid (DAG 3- phosphate) - intermediate in TAG synthesis •Structural basis of all membranes •Phosphate group esterified to the sn-3 position •Headgroups (PC, PI, PS, PE) •Headgroups impart amphipathic character •Sn-1 usually saturated and sn-2 usually unsaturated

Glycerophospholipids (phosphoglycerides)

phospholipids that contain a glycerol backbone bonded by ester linkages to two fatty acids and by a phosphodiester linkage to a highly polar head group - Amphipathic nature of phospholipids gives rise to their role in membrane structure • In membrane bilayer, polar head groups face outward in contact with the aqueous phase • Differences in charge and size of various head groups account for different physical properties and biological functions. • Differential and asymmetric distribution in cell membranes • Membrane phospholipids are substrates for synthesis of membrane-bound and soluble signaling molecules. • Second most abundant class of lipids in the diet.

hypolipidemic

reduces blood lipid (cholesterol) levels