NUTR 3210 Lecture 6: 6 Lipids

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NUTR3210 – Lipids

Facts about Lipids:

• Soluble in organic solvents (ether)

• Insoluble in polar solvents (water)

• Wide variety of structures and functions

• Source of energy and storage

• Building blocks of biological membranes (cellular, nuclear, mitochondrial)

 can disrupt membrane function (lipid rafts)

• Concentrated source of energy (ME=9kcal/g)

• Impact palatability and satiety effects of foods

• Dietary essential fatty acids: alpha-linoleic acid (omega-3) and linoleic acid (omega-6)

• Carrier of fat-soluble vitamins (A, D, E and K)

• Necessary for growth and development

Fatty Acids

• Characteristics

o Chains of 2-24 carbons

o Long linear carbon-hydrogen chain

o Two categories

▪ Saturated – with maximum number of H per C (only single bonds)

• Straight solid shape at room temperature (ex. Margarine)

• Butyric acid and palmitic acid

• Monounsaturated  saturated via hydrogenation

▪ Unsaturated – have missing H per C (with double bonds)

• Monounsaturated (one double bond)

o Straight shape, solid at room temperature

o Oleic acid (cis/trans)

o Saturated  monounsaturated via isomerization

• Polyunsaturated (very kinky)

o Liquid at room temperature

o Linoleic acid and arachidonic acid

o Carboxyl end is hydrophilic; carbon chain in hydrophobic

▪ amphipathic (detergent-like characteristics) *can disrupt cell membranes

• Nomenclature

o Omega System

▪ Numbering starts from the methyl end

▪ Good system: only have to know where 1st double bond is and how many double

bonds there are

▪ Ex. Linoleic acid: 18: 2 n-6 OR 18:2 -6

• 18  number of carbon

• 2  number double bonds

• n=  location of first double bond

o Delta System

▪ Numbering starts from carboxyl end of fatty acid

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▪ Poor system: location of the double bonds change as fast as chains are elongated

as C are added at carboxyl end

▪ Ex. Linoleic acid: 18:2 9,12

• 18 number of C

• 2  number of double bonds

• 9,12  position of double bonds

• Essential Fatty Acids –

o humans lack the enzymes to insert a double bond below C9 (n-9), therefore n3 and n6

precursors must be provided in the diet

o Linoleic Acid (18:2 n-6)  Arachidonic Acid (20:4 n-6)

▪ Plants: vegetable oil (corn, sory)

▪ Dietary sources = animal fat

▪ Required for synthesis of essential eicosanoids (n-6 FA-derived eicosanoids)

o Alpha-Linoleic Acid (18:3 n-3)  Eicosapentaenoic Acid (20:5 n-3) OR

Doscosahexaenoic Acid (22:6 n-3)

▪ Plants: flaxseed, canola, almonds

▪ Dietary sources: fish oil, fatty fish, algae

▪ Required for proper development of retinal and brain tissues

n-6 Deficient

n-3 Deficient

Skin

Dermatitis

Growth

Decreased

Reproductive Maturity

Decreased

CNS development

Decreased IQ in infants and children

Retinal development

Decreased visual acuity in infants

Recommended Intake

2-3% energy in diet

1% of energy in diet

EFA: Desaturation & Elongation pathways

• Desaturation  desaturase enzyme inserts cis double bond (removing 2H)

• Elongation  elongase enzyme adds 2C (from acetyl CoA)

• *Eicosanoids are critical in autocrine, paracrine and endocrine signaling in growth, pregnancy,

inflammation, fever, etc

• 18C n-6 and n-3 precursors are designated as essential since they are primary sources in most

diets

o however in infants, poor conversion of ALA – DHA leads to the recommendation that

EPA or DHA are present in diet

• Steps:

o Linoleic acid  18:3 n-6  20:3 n-6  Arachidonic Acid (20:4 n-6) Essential

Eicosanoid production

o Alpha-linoleic Acid  18:4 n-3  20:4 n-3 Eicospentanoic Acid (20:5 n-3)  22:5 n-

3 Docosahexaenoic Acid (22:6 n-3)

• The conversion efficiency from alpha-linoleic acid  eicospentaenoic acid <8%

• Eicospentaenoic acid produces some non-essential eicosanoids which may be anti-inflammatory

o EPA may completely inhibit the conversion of arachindonic acid into essential

eicosanoids

▪ May appear to have anti-inflammatory health benefits with some risks

• Docosahexaenoic Acid is enriched in brain and renal lipids allowing optimal cognitive and visual

development

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Triglycerides

• Three fatty acids (non polar) join to one molecule of glycerol (polar) via condensation reaction

o Process of adding fatty acids onto the glycerol backbone = esterification

o Bonds formed between FA and glycerol = ester bond

o Hydrolysis breaks ester bonds

• Major dietary form – 90% of dietary fats are triglycerides

• Major storage form of lipids in the body (e.g. in adipose tissue)  form lipid droplets

• 3 FA esterified to glycerol backbone = TG

• used in lipogenesis and lipolysis

• Structure:

o Monoacylglycerol/Monoglyceride

o Diacylglycerol/Diglyceride

o Triacylglycerol/Triglyceride

Phospholipids

• Characteristics:

o Structural features similar to TG, modifies at sn-3 position

o Amphipathic Properties

▪ Polar head interacts with cytosol or extracellular fluid

▪ Non-polar FA tails interact with hydrophobic zone of other molecules in core of

membrane bilayer

▪ Amphipathic molecules tend to self-assemble into membrane-like structures

o Predominant components of membrane bilayer

o Source of substrate for eicosanoids

o Anchors membrane proteins

o Involved in intracellular signaling

• Structure:

o Hydrophilic (Polar) Head

▪ Choline (may be replaced with inositol/serine/ethanolamine)

▪ Phosphate

▪ Glycerol (attached to FA via ester bonds)

o Hydrophobic (non-polar) Tail

▪ Fatty Acids are saturated at sn1 and unsaturated at sn2

o Only one FA = lysophospholipid

• Names

o In a phospholipid, there are two FA at the sn-1 and sn-2 positions

▪ When digestive lipase removes sn-1 FA 2-lyso-phospholipid (2-lysoPL) which

is a strong detergents that aids in fat digestion (must be converted back to a PL

once inside cell)

o The sn-3 position bonded to phosphate group + nitrogen containing base

o N base  PL name

▪ Choline  phosphatidyl choline

▪ Ethanolamine  phosphatidyl ethanolamine

▪ Serine  phosphatidyl serine

▪ Inositol  phosphatidyl inositol

• Phospholipid units assemble into forming a cell membrane’s basic structure

o 1. Polar head

2. Non-polar tail (straight tail is FA in sn-1 position and tends to be shorter (16/18C) and

saturated (or MUFA); ex. Palmitic acid and Linoleic acid)

3. Non-polar tail (FA in the sn-2 position tends to be longer (>20C) and PUFA ex.

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Document Summary

Facts about lipids: soluble in organic solvents (ether) Insoluble in polar solvents (water: wide variety of structures and functions, source of energy and storage, building blocks of biological membranes (cellular, nuclear, mitochondrial) Can disrupt membrane function (lipid rafts: concentrated source of energy (me=9kcal/g) Impact palatability and satiety effects of foods: dietary essential fatty acids: alpha-linoleic acid (omega-3) and linoleic acid (omega-6, carrier of fat-soluble vitamins (a, d, e and k, necessary for growth and development. Fatty acids: characteristics, chains of 2-24 carbons, long linear carbon-hydrogen chain, two categories, saturated with maximum number of h per c (only single bonds, straight solid shape at room temperature (ex. Doscosahexaenoic acid (22:6 n-3: plants: flaxseed, canola, almonds, dietary sources: fish oil, fatty fish, algae, required for proper development of retinal and brain tissues n-6 deficient. Epa or dha are present in diet: steps, linoleic acid 18:3 n-6 20:3 n-6 arachidonic acid (20:4 n-6) essential.

Related Questions

Question 1 (2.5 points) Question 1 Saved Liquid vegetable oils can be converted to solid fats such as margarine by Question 1 options: 1) hydrogenation. 2) hydrolysis. 3) hydration. 4) oxidation. 5) saponification. Save Question 2 (2.5 points) Question 2 Saved A triacylglycerol that is solid at room temperature is called a(n) Question 2 options: 1) terpene. 2) lecithin. 3) oil. 4) wax. 5) fat. Save Question 3 (2.5 points) Question 3 Saved Unsaturated fatty acids have lower melting points than saturated fatty acids because Question 3 options: 1) they have fewer hydrogen atoms. 2) they have more hydrogen atoms. 3) their molecules fit closely together. 4) the cis double bonds produce a shape that reduces contact between molecules. Save Question 4 (2.5 points) Question 4 Unsaved Cholesterol is a member of the ________ group of lipids. Question 4 options: 1) glycerophospholipid 2) steroid 3) prostaglandin 4) triacylglycerol 5) wax Save Question 5 (2.5 points) Question 5 Unsaved Which of the following is an example of an emulsion? Question 5 options: Paint Milk Jelly Pitch Asphalt Save Question 6 (2.5 points) Question 6 Unsaved _____ are lipids with four fused ring structures. Question 6 options: Sphingolipids Phospholipids Steroids Enzymes Gangliosides Save Question 7 (2.5 points) Question 7 Unsaved The ionic part of a lipid is hydrophobic and the nonpolar part is hydrophilic. Question 7 options: True False Save Question 8 (2.5 points) Question 8 Unsaved The most abundant saturated fatty acid contains 16 carbons and is known as: Question 8 options: lauric acid. myristic acid. palmitic acid. stearic acid. butyric acid. Save Question 9 (2.5 points) Question 9 Unsaved What type of lipid is shown below? lipid Question 9 options: steroid wax fatty acid tryacylgliceride Save Question 10 (2.5 points) Question 10 Unsaved What type of lipid is shown below? lipid Question 10 options: steroid wax fatty acid tryacylgliceride Save

64. Which of these statements about fatty acids are false? A. The physical state of a triglyceride with three unsaturated fatty acid tails would be a clear liquid. B. Complex lipids that contain mainly unsaturated fatty acids are liquids (oils) at room temperature C. Its best to use fats with high melting points in our diet. D. A disadvantage of the ability of saturated fats to pack tightly is that tightly packed, saturated fats clog arteries as atherosclerosis 65. Trans fatty acids A. are formed when vegetable oil is hydrogenated (for solidification). B. are found in fried foods C. have an atypical shape that affects their chemical activity D. are not flexible and can adhere to surfaces E. should be avoided because they are composed of partially hydrogenated (partially hardened) oils F. are all of the above 66 Which of these statements about fatty acids are false? A. When plants and animals build fatty acids they make the trans forms. B. Food manufacturers found that foods like chips with the trans form have a longer "shelf life" C Natural cis fatty acids tend to turn rancid and spoil D Although natural cis fatty acids turn rancid and spoil, it is the cis form that is used by the body. E.The process of hydrogenation, in which hydrogens are added to unsaturated fats, produces a mixture of saturated fatty acids and standard and trans forms of unsaturated fatty acids 67. Good tips for reducing dietary fats are to A. use non-fat or low-fat dairy products and other products B use low-fat cooking methods C bake, roast, steam, broil, stir fry, microwave D. seldom have fried foods E choose lean cuts of meat, trim fat F. do all the above 68. Which of these statements about the properties of fatty acids are true? A. Melting point of all fatty acids increases with increasing hydrocarbon chain length (i.e increasing size) B cis double bonds prevent good alignment of molecules in unsaturated fatty acids leading to C Melting point of unsaturated fatty acid are lower than that of a saturated fatty acid with the D. The melting point of a saturated fatty acid is greater than that of an unsaturated fatty acid of poor packing same number of carbon atoms due to the presence of their double bonds the same chain length, because saturated fatty acid chains tend to be fully extended and to stack in a regular structure, thereby causing increased intermolecular attraction. E. all of the above 69. Freebie 70 Freebie

Nitrogen and phosphorus are in the same column of the periodic table. They have similar properties in bonding with other molecules because they have the same number of:

We cannot answer this question definitively because there is not enough information.

What I choose are wrong.

NUTR 3210 Lecture 6: 6 Lipids

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