Lipids Fatty Acids Fats Phospholipids Steroids Waxes

Lipids Hydrophobic molecules (don’t dissolve in water) Composed of C, H, and O Fewer polar O-H bonds and more non-polar C-H bonds – Molecule is mostly NON-POLAR Makes them insoluble in water but soluble in other non-polar substances (e.g. grease, etc.) Five main groups: fatty acids, fats, phospholipids, steroids, and waxes

Uses: Store energy (long term) Building material - structural (cell membrane) Chemical signaling Insulation- nerve cell, body Shock absorber Hormones Store about 2x more energy than carbohydrates

1) Fatty Acids A fatty acid consists of a single hydrocarbon chain with a carboxyl functional group (-COOH) at one end

If all the carbons are linked to each other with single bonds, the fatty acid is said to be saturated If there are double bonds, then it is said to be unsaturated. This means that the carbon chain has the potential to form more bonds with hydrogen.

Fatty acids with one double bond are monounsaturated, and those with more than one double bond are polyunsaturated. The presence of a double bond in an unsaturated fatty acid can create a kink in the molecule, which will cause it to bend.

Double Bonds Double bonds do not always create a kink.

2) Fats Triglycerides- most common fat in plants and animals – Can be in the form of an oil – Composed of 3 fatty acids (long C chain with carboxyl group) attached to a glycerol (3 carbon chain with alcohol groups) via a dehydration synthesis reaction – The fatty acid chain can be the same or different

dehydration synthesis H2OH2OH2OH2OH2OH2OH2OH2O enzyme

Triacylglycerol – 3 fatty acids linked to glycerol – ester linkage = between OH & COOH hydroxylcarboxyl Building Fats

Like individual fatty acids, triglycerides generally become less fluid as the length of their fatty acid chain increases. Those with shorter chains remain liquid, as oils, at room temperature. The more saturated fats, such as butter, are solids because their chains are long and straight and can be packed closely together to form a solid at room temperature.

Saturated vs. unsaturated saturatedunsaturated

3) Phospholipids Consist of glycerol + 2 fatty acids + a phosphate group Creates a polar head and a non-polar tail When added to water the hydrophobic regions will group together Cell membranes are made up of 2 layers of phospholipids  phospholipid bilayer

Phospholipid Bilayer (Cell Membrane)

Phospholipids in water Hydrophilic heads “attracted” to H 2 O Hydrophobic tails “hide” from H 2 O – can self-assemble into “bubbles” bubble = “micelle” can also form a phospholipid bilayer early evolutionary stage of cell? bilayer water

Lipids

4) Sterols Four fused hydrocarbon rings  hydrophobic E.g. Cholesterol – Can cause plaque build up in blood vessels - blocks the flow of blood - deprives O 2 – Can be converted into vitamin D (bones and teeth) and bile salts (digestion of fats in the small Intestine) E.g. Sex hormones (testosterone and progesterone)

Cholesterol Important cell component – animal cell membranes – precursor of all other steroids including vertebrate sex hormones – high levels in blood may contribute to cardiovascular disease

Cholesterol helps keep cell membranes fluid & flexible Important component of cell membrane

5) Waxes Waxes are large lipid molecules that are made of long fatty acid chains linked to alcohols or carbon rings. Waxes are hydrophobic, extremely non-polar, and soft solids Used as a flexible waterproof coatings on various plant and animal parts. Without this waxy coating, plants could not survive on land. Birds secrete a waxy material that helps to keep their feathers dry. Bees produce beeswax to make their honeycombs. Earwax protects the middle and inner ear from water and microorganisms

Structure and Function of Lipids Terpenes: long-chain lipids - e.g. the photosynthetic pigments such as chlorophyll in plants and the visual pigments such as retinal in the eye’s retina(pp in text)