LIPIDSLIPIDS: FRIENDS : FRIENDS OR FOES?OR FOES?

What are lipids?What are lipids?CharacteristicsCharacteristicsWhat are lipids for?What are lipids for?Fats and oilsFats and oilsOther types of lipidsOther types of lipids

WHAT ARE LIPIDS?WHAT ARE LIPIDS?

Lipids are a heterogenous group of Lipids are a heterogenous group of substances formed: substances formed:

by fatty acids and glycerol as in the case by fatty acids and glycerol as in the case of fats and oils,of fats and oils,

by steroids (cholesterol derivatives) as in by steroids (cholesterol derivatives) as in the case of steroid hormones and some the case of steroid hormones and some vitamins, orvitamins, or

by terpenes (another type of complex by terpenes (another type of complex molecules, as in plant pigments and molecules, as in plant pigments and scents.scents.

EXAMPLES OF LIPIDSEXAMPLES OF LIPIDS

FATS AND OILSFATS AND OILS WAXESWAXES STEROID HORMONES SUCH AS STEROID HORMONES SUCH AS

THE SEXUAL HORMONES THE SEXUAL HORMONES (OESTROGEN AND (OESTROGEN AND TESTOSTERONE)TESTOSTERONE)

CERTAIN PLANT PIGMENTS AND CERTAIN PLANT PIGMENTS AND SCENTSSCENTS

PHOSPHOLIPIDS AND PHOSPHOLIPIDS AND SPHYNGOLIPIDSSPHYNGOLIPIDS

CHARACTERISTICS OF CHARACTERISTICS OF LIPIDSLIPIDS

Lipids are Lipids are insoluble in waterinsoluble in water (so they are non- (so they are non-polar).polar).

Lipids are soluble in organic , non-polar Lipids are soluble in organic , non-polar solvents.solvents.

Lipids are large, complex molecules.Lipids are large, complex molecules. Lipids can store and then release a lot of Lipids can store and then release a lot of

energy when broken down (fats store 37 kJ/g energy when broken down (fats store 37 kJ/g compared to 17 kJ/g in carbohydrates). compared to 17 kJ/g in carbohydrates).

Lipids can combine with other types of Lipids can combine with other types of molecules such as sugars and proteins to form molecules such as sugars and proteins to form glycolipids or lipoproteins.glycolipids or lipoproteins.

WHAT ARE LIPIDS FOR?WHAT ARE LIPIDS FOR?

In living organisms lipids are used:In living organisms lipids are used: As a long-term energy source.As a long-term energy source. To help bouying in aquatic large animals.To help bouying in aquatic large animals. As a heat insulator (blubber).As a heat insulator (blubber). As a barrier (as in cell membranes).As a barrier (as in cell membranes). As a waterproof substance or extra As a waterproof substance or extra

protection layer (waxes in plants, skin or protection layer (waxes in plants, skin or feathers).feathers).

Some form sex hormones and vitamins Some form sex hormones and vitamins (D).(D).

THE BAD & GOOD GUYS: THE BAD & GOOD GUYS: FATS AND OILSFATS AND OILS

Fats and oils are made of two types Fats and oils are made of two types of molecules: of molecules: glycerolglycerol and and fatty fatty acidsacids..

glycerolglycerol

FATTY ACIDSFATTY ACIDS Fatty acids are very long chains of carbon Fatty acids are very long chains of carbon

and hydrogen atomsand hydrogen atoms and an acid group and an acid group atone end. They come in two flavours: atone end. They come in two flavours: saturated and unsaturated.saturated and unsaturated.

Saturated fatty acids have single bonds Saturated fatty acids have single bonds between C atoms.between C atoms.

Unsaturated fatty acids have Unsaturated fatty acids have at least oneat least one double bond between C atoms.double bond between C atoms.

Characteristics of saturated and Characteristics of saturated and unsaturated fatty acidsunsaturated fatty acids

Saturated fatty acids Saturated fatty acids are linear, straight and are linear, straight and rigid molecules so they are rigid molecules so they are solid at room solid at room temperaturetemperature (20ºC). (20ºC).

Unsaturated fatty acidsUnsaturated fatty acids bend where the bend where the double bond is, so the molecules are more double bond is, so the molecules are more flexible and flexible and liquid at room temperatureliquid at room temperature (20ºC).(20ºC).

Sources of Sources of saturatedsaturated and and unsaturated unsaturated fatty acids: fatty acids: fats fats

and oilsand oils

Making friends:Making friends:the ester bondthe ester bond

Fats and oils are triglycerides:Fats and oils are triglycerides: 3 fatty acids + glycerol triglyceride + 3 H3 fatty acids + glycerol triglyceride + 3 H22OO

The famous The famous CholesterolCholesterol

Cholesterol is a series of 5 rings and a side hydrocarbon Cholesterol is a series of 5 rings and a side hydrocarbon chain made by all cells as it forms part of the cell chain made by all cells as it forms part of the cell membrane, some hormones and vitamins. Cells membrane, some hormones and vitamins. Cells manufacture almost 1 g/day according to needs.manufacture almost 1 g/day according to needs.

Danger! The trans fatsDanger! The trans fats Trans fats are oils (unsaturated triglycerides) that have been

chemically modified to partially hydrogenate them.

In this way a liquid substance becomes more solid and easily

manageable by the food industry. But in the process, the atoms of H

are in a different position (opposed to each other) when the C-C is

formed. This makes the molecule more sticky and prone to clog

arteries.

Are you sure you want Are you sure you want this?this?