Lipids By Umair, Manjit, and Rajat

 Lipids are a biological macromolecule composed of hydrogen, carbon and oxygen atoms  However the ratio of oxygen to carbon and hydrogen is very low which gives lipids its hydrophobic nature  Lipids yield longer term energy in their carbon to hydrogen bonds than carbohydrates and accessed after carbohydrates have been used up  Lipids are essential for life because they insulate the body, they form a protective cushion around major organs and are important part of cell membranes Example of a lipid: Triglyceride 

 Triglycerides are a type of lipid composed of a glycerol and 3 fatty acids linked by ester bonds  A fatty acid is a hydrocarbon chain ending in a carboxyl group (-COOH)  The bond between the hydroxyl group on the glycerol and the carboxyl group on the fatty acid is called ester linkage because it forms an ester  There are 2 types of fatty acids: saturated and unsaturated  Saturated fatty acids do not have double bonds between the carbon atoms  Unsaturated fatty acids have 1 or more double bonds between the carbon atoms  There are also 2 types of unsaturated fatty acids  Monounsaturated fatty acids have only 1 double bond  Polyunsaturated fatty acids have 2 or more double bonds

 The presence of a double bond affects the properties of the triglyceride  A double bond in an unsaturated fatty acid causes a bend in the hydrocarbon chain which is called a cis  This is why unsaturated fatty acids such as olive oil are liquid at room temperature and saturated fatty acids like butter are solid at room temperature  A chemical process called hydrogenation causes unsaturated fats to transform into saturated fats and changes cis fats into trans fats and cause an increase risk to heart disease

Glycerol Molecule in green  3 saturated fatty acids in red (no double bond)  Glycerol in blue  3 unsaturated fatty acids in black (double bond in green a.k.a. cis) 

Is a lipid composed of a glycerol molecule which is bonded to two fatty acids Are called the main components of the Cell membrane Phospholipids and triglycerides have a very similar structure The difference that can be found in the structures of these two macromolecules is that triglycerides have an extra fatty acid, as in phospholipids the extra fatty is replaced by the phosphate head

 A Phospholipid molecule consists of a Phosphate head and 2 fatty acids  The head of a Phospholipid is polar meaning it is hydrophilic  The tail portion only consists of C-C & C-H bonds meaning it is non- polar and hydrophobic

 In aqueous environments phospholipids tend to form a lipid bilayer  In a lipid bilayer the hydrophilic heads face the aqueous solutions on either side of the bilayer  The hydrophobic tails tend to get tucked in away from the water form a hydrophobic interior

Steroids  Groups of lipids that are composed of four carbon-based rings attached to each other  Cholesterol: component of cell membranes and precursor of several other compounds such as testosterone and estrogen

Advantage of Steriods  In medicine, steriods are used to reduce inflammation.  Example: steroid ointments to treat skin conditions or inhalers to treat asthma

Disadvantages of Steriods  High Levels of Cholesterol in blood can cause fatty material to accumulate inside the lining of blood vessels causing heart disease

Waxes  Have a diversity of chemical structures, often with long carbon-based chains and are solid at room temperature  Plants: Waxes coat the surfaces of leaves, preventing water and solutes from escaping and helping to repel insects  Animals: Present on skin, fur, and feathers of many animal species and on the exoskeletons of insects

Example: Plants and Animals