Lipids

LIPIDS C, H, O

• More hydrogen than carbohydrates. • Insoluble in water, soluble in organic solvents

(alcohols, acetone, chloroform etc)• http://www.hhmi.org/biointeractive/obesity/obesity_molecular/01.html (structure

of fat)• http://www.hhmi.org/biointeractive/obesity/obesity_processing_fat/01.html (how

body uses fat)• http://www.hhmi.org/biointeractive/media/fate_of_fat-lg.mov (digestion)

Fatty acids: carboxylic acid + long hydrocarbon chain

CO

OHCH3

Carboxylic acid

Hydrocarbon chain

A saturated fatty acid

An unsaturated fatty acid

C

O

OH

CH3

© 2007 Paul Billiet ODWS

Fatty AcidsFatty acids are composed of a chain of carbon attached to a carboxylic acid group. All fatty acids have the same general structure but they have different lengths and some have double bonds.

Saturated vs. Unsaturated Fats

Saturated vs. Unsaturated Fats

Saturated fatty acids Unsaturated fatty acids

no double bonds one or more double bonds

abundant in fats abundant in oils

more reduced less reduced

more energy less energy

high melting point low melting point

© 2007 Paul Billiet ODWS

Formation of a Triglyceride

Glycerol + 3 Fatty Acids Triglyceride

Formation of a Triglyceride

Glycerol Fatty Acid Tails3 H2O

Formation of a Triglyceride

Glycerol Fatty Acid Tails3 H2O

Formation of a Triglyceride

A TriglycerideEster Linkage

Condensation Synthesis of a Triglyceride

Phospholipids

• in lipoprotein membranes (plasma, nuclear, mitochondrial etc.)

© 2007 Paul Billiet ODWS

Phospholipids

Phospholipids in water

Other lipids

Steroids: multiple ring structures (e.g. cholesterol)• Functions: cell membrane structure, digestion (help

to emulsify fats), hormones (testosterone etc), vitamins (e.g. Vitamin D), poisons

Waxes: long chain alcohol + fatty acids• Water proof coating to leaves, fur feathers, insect

exoskeletons. • Used by bees to construct their honey combs.

© 2007 Paul Billiet ODWS

Steroids

Vitamin D• http://ods.od.nih.gov/factsheets/vitamind

• Vitamin D is a steroid vitamin, a group of fat-soluble prohormones, which encourages the absorption and metabolism of calcium and phosphorous.

• Vitamin D for humans is obtained from sun exposure, food and supplements. http://www.medicalnewstoday.com/articles/161618.php

Sunlight and vitamin D requirements

• If you live in the tropics and can expose your unprotected skin to two sessions of 15 minutes of sunlight each week your body will naturally produce adequate amounts of vitamin D. The following factors may reduce your body's vitamin D synthesis:

• If you live far from the equator, your sunlight exposure will be less during many months of the year.

• Cloud cover • Smog • Sunscreens • If your body cannot produce enough vitamin D because of insufficient

sunlight exposure you will need to obtain it from foods and perhaps supplements. Experts say that people with a high risk of vitamin D deficiency should consume 25 μg (1000 IU) of vitamin D each day so that there is a good level of 25-hydroxyvitamin D in the bloodstream. Elderly people, as well as people with dark skin should consume extra vitamin D for good health.

• Most of the food sourced vitamin D in the western diet comes from fortified foods - where vitamin D is artificially added. Most US milk is fortified with 100 IU/cup of vitamin D. In the 1930s milk was fortified in many countries to combat rickets, which was a major health problem then.

• What do we need vitamin D for? • It is crucial for the absorption and metabolism of calcium and phosphorous, which have various functions, especially

the maintenance of healthy bones.

• It is an immune system regulator.

• It may be an important way to arm the immune system against disorders like the common cold, say scientists from the University of Colorado Denver School of Medicine, Massachusetts General Hospital and Children's Hospital Boston.

• It may reduce the risk of developing multiple sclerosis. Multiple sclerosis is much less common the nearer you get to the tropics, where there is much more sunlight, according to Dennis Bourdette, chairman of the Department of Neurology and director of the Multiple Sclerosis and Neuroimmunology Center at Oregon Health and Science University, USA.

• Vitamin D may have a key role in helping the brain to keep working well in later life, according to a study of 3000 European men between the ages of 40 and 79.

• Vitamin D is probably linked to maintaining a healthy body weight, according to research carried out at the Medical College of Georgia, USA.

• It can reduce the severity and frequency of asthma symptoms, and also the likelihood of hospitalizations due to asthma, researchers from Harvard Medical School found after monitoring 616 children in Costa Rica.

• It has been shown to reduce the risk of developing rheumatoid arthritis in women.

• A form of vitamin D could be one of our body's main protections against damage from low levels of radiation, say radiological experts from the New York City Department of Health and Mental Hygiene.

• Various studies have shown that people with adequate levels of vitamin D have a significantly lower risk of developing cancer, compared to people with lower levels. Vitamin D deficiency was found to be prevalent in cancer patients regardless of nutritional status, in a study carried out by Cancer Treatment Centers of America.

• http://www.informationisbeautiful.net/2010/vitamin-d/

LIPID FUNCTIONS IN GENERAL

• STRUCTURAL: biological membranes (phospholipids, steroids, glycolipids), cushioning (fat deposits round the kidneys)

• ELECTRICAL INSULATION: myelin sheath round axons• THERMAL INSULATION: subcutaneous fat deposits.• WATER PROOFING: waxes and oils• ENERGY STORE AND SUBSTRATE: very condensed form of

energy (37 kJ g-1) used by animals and seeds.• HORMONES: steroids• SOLVENT: dissolves some vitamins• VITAMINS: precursor to Vit D• BUOYANCY: oil droplets in plankton

© 2007 Paul Billiet ODWS