Lipids 1

* Chapter 15 Lipids

15.1 Lipids

* Lipids

Lipids areBiomolecules that contain fatty acids or a steroid nucleus.Soluble in organic solvents but not in water.Named for the Greek word lipos, which means “fat.”Extracted from cells using organic solvents.

* Types of Lipids

The types of lipids containing fatty acids are Waxes. Fats and oils (triacylglycerols). Glycerophospholipids. Prostaglandins. Not steroids, as they do not contain fatty acids.

* Structures of Lipids

* Fatty Acids
Fatty acids Are long-chain carboxylic acids. Typically contain 12-18 carbon atoms. Are insoluble in water. Can be saturated or unsaturated.

* Fatty Acid Formulas

The formulas for fatty acids are written as Condensed formulas.Line-bond formulas. For example caprylic acid with 8 carbon atoms. CH3—(CH2)6—COOHCH3—CH2—CH2—CH2—CH2—CH2—CH2—COOH


* Saturated fatty acids haveSingle C–C bonds.Molecules that fit closely together in a regular pattern.Strong attractions between fatty acid chains.High melting points that make them solids at room temperature. Saturated Fatty Acids

*
Some Saturated Fatty Acids

* Unsaturated Fatty Acids

Unsaturated fatty acids Have one or more double C=C bond Typically contain cis double bonds.

* Properties of Unsaturated Fatty Acids

Unsaturated fatty acidsHave “kinks” in the fatty acid chains.Do not pack closely. Have few attractions between chains.Have low melting points.Are liquids at room temperature. “kinks” in chain

*
Unsaturated Fatty Acids

* Comparing Melting Points of Some Fatty Acids

* Learning Check
Assign the melting points of –17°C, 13°C, and 69°C to the correct fatty acid. Explain.stearic acid (18 C) saturatedoleic acid (18 C) one double bondlinoleic acid (18 C) two double bonds

* Solution

* Essential F.A.: The essential F.A. could not be synthesized by the liver or by the body, therefore must be supplied from the diet, they are very important for normal growth, each essential F.A. contains more than one double bond. These essential fatty acids are linoleic,linolenic and arachidonic acid. Linoleic acid occurs in high concentration in various edible vegetable oils e.g corn, cottonseed, peanut, soybean, archidonic acid occurs in animals fats although only in rather small amount.

* Prostaglandins

Prostaglandins have 20 carbon atoms in their fatty acid chains. An OH on carbon 11 and 15. A trans double bond at carbon 13.

C 11

C 15
C 13

* Prostaglandins in the Body

Prostaglandins are Produced by injured tissues. Involved in pain, fever, and inflammation. Not produced when anti-inflammatory drugs such as aspirin inhibit their synthesis.

* Omega-6 and Omega 3- Fatty Acids

Fatty acids In vegetable oils are mostly omega-6 with the first C=C at C6. linoleic acid CH3─(CH2)4─CH=CH─CH2─CH=CH─(CH2)7─COOH 6 In fish oils are mostly omega-3 with the first C=C at C3. linolenic acid CH3─CH2─(CH=CH─CH2)3─(CH2)6─COOH 3

* Some Omega-6 and Omega-3 Fatty Acids

* Learning Check
Write a fatty acid with 10 carbon atoms that is: A. saturated B. monounsaturated omega-3 C. monounsaturated omega-6

* Solution

Write a fatty acid with 10 carbon atoms that is:A. saturated CH3—CH2—CH2—CH2—CH2—CH2—CH2—CH2—CH2—COOHB. monounsaturated omega-3CH3—CH2—CH=CH—CH2—CH2—CH2—CH2—CH2—COOHC. monounsaturated omega-6CH3—CH2—CH2—CH2—CH2—CH=CH—CH2—CH2—COOH