Lipids Function 5 Types © The Law of Science

Lipid Function Lipids are most commonly referred to as fat, which is slightly inaccurate as you will learn Brainstorm: What use do lipids have?

Lipid Function Long-term energy storage Photos are example of sources of good fats http://cdn.sheknows.com/articles/2013/06/food-sources-for-healthy-fats-collage.jpg

Lipid Function Why are lipids well suited for long term energy storage? Contain many high energy bonds between carbon and hydrogen Contain twice as much energy per gram than carbohydrates (very concentrated) Thus a much more compact form of storage than carbohydrate Animals store fats in adipose cells

Lipid Function Membrane of cells, organelles etc. (phospholipid) http://www.scienceclarified.com/photos/cell-2793.jpg

Lipid Function Insulation http://ih3.redbubble.net/work.6148690.1.flat,550x550,075,f.flop-bull-elephant-seal-sea-lion-island-west-falkland.jpg

Lipid Function Cushioning internal organs http://www.thesecondlunch.com/wp-content/uploads/2012/10/Lamb-Kidneys-fat-on-580x393.jpg

Lipid Function Precursor for several sterol hormones Examples: fat-soluble hormones and hormones responsible for fat metabolism http://woldfitness.com/wp-content/uploads/2011/03/hormones-labelled-on-guy.png

Lipid Function Summary Long-term energy storage (fat) Form cell membrane (phospholipids) Insulation Cushioning of Internal Organs Messaging (hormones)

Types of Lipid Fat: Triglyceride / triacylglycerol Phospholipid Steroid Wax

1. Fat Structure also known as triglyceride or triacylglycerol Fatty acid also known as triglyceride or triacylglycerol Consists of: 1 glycerol backbone 3 fatty acid chains

Glycerol Structure Basic structure: Fatty acid Basic structure: 3 carbon molecule each carbon has a hydroxyl group attached the alcohols are sites for condensation reactions

Fatty acid structure Basic structure: Unbranched chain of carbons A carboxyl group at one end Fatty acid chains can differ from each other in two ways: Length of carbon chain: 4-24 Saturation (number of double bonds) Saturated Monounsaturated polyunsaturated

Properties of Fatty acids Type Saturated Unsaturated Structure Single bonds Double bonds, kink State at r.t. Solid liquid Origin Animals Plants Examples Butter, lard Olive oil, essential FA (omega-3/6 fish oil)

Property of Saturated Fats are solid at room temperature Ex. Butter and lard

Forming a triacylglycerol Condensation reaction between: Hydroxyl on glycerol Carboxyl on fatty acid Results in an ester bond

2. Phospholipid structure Glycerol backbone 2 fatty acids chains phosphate/polar group Phosphate / Polar group Glycerol Fatty acid

2. Phospholipid structure Polar head: negatively charged, hydrophilic Nonpolar tails: fatty acids, hydrophobic tail

Self-assembly of phospholipid Condition: in water (aqueous) Self-assembly = spontaneous aggregate Due to hydrophobic interactions Micelle: single layer of phospholipid with polar head facing out, nonpolar tails facing inward Fig. 5.13 http://www.bio.miami.edu/~cmallery/255/255chem/mcb2.20.micelle.jpg

Self-assembly of phospholipid Phospholipid bilayer have a double layer of phospholipids where the nonpolar tails aggregate forming a hydrophobic core This is the basic structure of the plasma membrane http://www.bio.miami.edu/~cmallery/255/255chem/mcb2.20.micelle.jpg

Plasma Membrane Membranes are made of a bilayer of phospholipids.

Phospholipid Bilayer

3. Steroid Carbon skeleton, 4 interconnected rings Common examples: Cholesterol – a precursor for making steroid hormones such as estrogen and testosterone and vitamin D Good and bad cholesterol. Bad = Low Density Lipoprotein. Good = High Density Liopoprotein

Steroid Cholesterol Testosterone Cortisone Aldoesterone

4. Wax Consists of a long fatty acid chain joined to a long alcohol chain. Waxes are highly waterproof. In plants and animals they provide protective coatings such as on the cuticle of a leaf. Earwax prevents micro-organisms from entering the middle ear.

Properties of Wax Solid at room temperature Becomes liquid when melted has plastic properties: deforms under pressure without application of heat

Natural Wax Natural Animal wax: beeswax, lanolin, shellac Vegetable waxes: soy, jojoba, carnauba Mineral waxes: petroleum (paraffin) from fossil fuels

What is common to all lipids? The 4 forms of lipids studied are not built upon any common monomer. What unified these lipids so that they are all classified under the ‘lipid’ category? In other words, what makes a lipid, a lipid?