3D_Lipids

Fats Come in the form of Properties: Functions Mammals Water repellent properties – waterproof fur and skin. Structural - Cell membranes, phospholipids and polar nature Electrical insulation – myelin, insulates neurones, impulse transmission more rapid. Hormones – steroids e.g. testosterone and oestrogen Physical protection – shock absorb, found round delicate organs e.g. kidneys Thermal insulation – conducts heat poorly, so insulates. Blubber in diving animals. Energy storage: yield twice as much energy compared with carbohydrates Plants Attraction – plant scents contain fatty acids Waterproofing – wax for the cuticle (not glycerol, different alcohol used) Energy storage – Oil droplets in plant cells Other Honey comb– Bees wax Example
 * Oil
 * Wax
 * Fat
 * Insoluble
 * Water- repelling

Lipids
 * Are usually insoluble in water, but soluble in organic solvents.
 * Contain C, H and O. (CH3(CH2)nCOOH)
 * Less oxygen than carbohydrates
 * Identified using the emulsion test.

Lipid molecules consist of 3 elements Lipids are insoluble. They are important dietary constituents as they are full of energy, contain certain vitamins and have a major role in cell membranes. Unlike carbohydrates and proteins, lipids do not form polymers. Two major types of lipids are triglycerides and phospholipids.

Triglycerides (fats & oils)
 * These are NOT made from __monomers__
 * Each contains __1 glycerol__ and __3 fatty acid__ molecules (elements: C, H, O)
 * They are linked by __ester bonds__
 * These form during __condensation reactions__
 * Fats (solid at room temp.) contain __saturated__ fatty acid chains
 * Oils (liquid at room temp.) have __unsaturated__ chains

They are formed from a glycerol molecule linked by ester bonds to three fatty acids.

Ester bond:-This is formed from a condensation reaction where the carboxyl group of a fatty acid and an OH group from the glycerol join and water is lost so they share an oxygen atom.

The formula for fatty acids is R-COOH, where the R, which is the hydrocarbon chain can be saturated or unsaturated.

- Synthesis of Triglycerides - glycerol bonds with 3 fatty acids Triglycerides (fats) are formed using ester bonds



Saturated and unsaturated fats More hydrogen atoms No double bonds No kinks
 * Saturated fatty acid e.g. Stearic acid

less hydrogen atoms Have double bonds Have kinks
 * Unsaturated fatty acid e.g. Oleic acid

A triglyceride with 1 unsaturated and 2 saturated fatty acid chains Fatty Acids (formula R - COOH) Phospolipid

Example of phospholipid - One of the fatty acids has been replaced with a phosphate group


 * Consist of organic group, phosphate group, glycerol and fatty acid.
 * The bonds between the glycerol and fatty acid are broken by hydrolysis.
 * They are a major componant of the plasma membrane, because they have a hydrophilic head and hydrophobic tail (polar molecules), which form a bilayer.
 * Heads outside, tails inside.
 * One fatty acid in triglyceride swapped for phosphate base

- Fatty acid - phosphate
 * Glycerol - Fatty acid
 * The phosphate group is soluble in water, it is water loving, which is termed hydrophillic.
 * The fatty acids are insoluble in water, they repel water, which is known as hydrophobic.
 * Due to these properties phospholipids form cell membranes when in water
 * [[image:webkit-fake-url://42B7994A-B72E-46D4-9BEE-D48ED583D085/pastedGraphic_8.pdf caption="pastedGraphic_8.pdf"]] Simplified structure of a phospholipid molecule used in diagrams of membranes
 * [[image:webkit-fake-url://42B7994A-B72E-46D4-9BEE-D48ED583D085/pastedGraphic_9.pdf caption="pastedGraphic_9.pdf"]][[image:webkit-fake-url://42B7994A-B72E-46D4-9BEE-D48ED583D085/pastedGraphic_10.pdf caption="pastedGraphic_10.pdf"]][[image:webkit-fake-url://42B7994A-B72E-46D4-9BEE-D48ED583D085/pastedGraphic_11.pdf caption="pastedGraphic_11.pdf"]]
 * [[image:webkit-fake-url://42B7994A-B72E-46D4-9BEE-D48ED583D085/pastedGraphic_11.pdf caption="pastedGraphic_11.pdf"]][[image:webkit-fake-url://42B7994A-B72E-46D4-9BEE-D48ED583D085/pastedGraphic_12.pdf caption="pastedGraphic_12.pdf"]][[image:webkit-fake-url://42B7994A-B72E-46D4-9BEE-D48ED583D085/pastedGraphic_13.pdf caption="pastedGraphic_13.pdf"]] Phospholipid Bilayer formed in water
 * [[image:webkit-fake-url://42B7994A-B72E-46D4-9BEE-D48ED583D085/pastedGraphic_14.pdf caption="pastedGraphic_14.pdf"]]
 * [[image:webkit-fake-url://42B7994A-B72E-46D4-9BEE-D48ED583D085/pastedGraphic_15.pdf caption="pastedGraphic_15.pdf"]]
 * This phospholipid has 2 fatty acid chains (hydrophobic). Instead of a third chain, it has a phosphate group (hydrophilic). Cell membranes are made from phospholipids.