Lipids Objective: B2 - Compare the structures & functions of carbohydrates, lipids, proteins, & nucleic acids & their organization into long complex molecules

Function: Consist of: Characteristics: Energy storage Mostly Carbon & Hydrogen with some Oxygen Characteristics: Hate water (hydrophobic) Insoluble (won’t dissolve) in water

Examples of Lipids Fats (helps conserve heat) Oils Waxes (waterproof covering) Butter Phospholipids (part of cell membrane) Steroids (cholesterol, estrogen, testosterone) steroids (not artificial ones, but cholesterol, which is the most common type, estrogen, testosterone, bile salts) Waxes are similar to fats except that waxes are composed of only one long-chain fatty acid bonded to a long-chain alcohol group attached. Because of their long, nonpolar carbon chains, waxes are extremely hydrophobic (meaning they lack an affinity for water). Both plants and animals use this waterproofing characteristic as part of their composition. Plants most noticeably use waxes for a thin protective covering of stems and leaves to prevent water loss. Similarly, animals employ waxes for protective purposes; for instance, earwax in humans prevents foreign material from entering and possibly injuring the ear canal area.

Building Blocks of Lipids (monomers) Glycerol Fatty acids

Fats (triglyceride) Always have 3 fatty acids There are 2 different kinds: Saturated (no double bonds between the carbon atoms) - Solid at room temperature - Examples: butter Unsaturated (have a double bond between two carbon atoms) - Liquid at room temperature - Examples: oil If there is more than one double bond, it is called a polyunsaturated fat. Most vegetable fats are unsaturated (think vegetable oil). Polyunsaturated (have more than one double bond)

Phospholipids Like fats, but only have 2 fatty acids (this causes the glycerol, which now includes a phosphate group to like water, but the tails still hate water) Has a hydrophilic end and a hydrophobic end

Phospholipid Structure Because it has a “split personality,” this forces this lipid to assume an interesting structure when in the presence of water. The hydrophilic (phosphate head side) surrounds the hydrophilic (fatty acid tails) shielding the tails from exposure to water This makes up the phospholipid bilayer (cell membrane) of all cells

Etymology Lipids: (Gk. LIPOS, fat) Hydrophilic: hydro- (water) + -philic or -phile (Gk. PHILOS, loving) Hydrophobic: hydro- (water) + -phobic (Gk. PHOBOS, fear)

Practice: Glycerol Fatty acids

What is the function of lipids? Energy storage

Which side of this molecule likes water? Polar head group

This phospholipid bilayer is also called what? Cell membrane