LIPIDS They are made up of C, H and O atoms. In lipids the number of H atoms is more than the number of O atoms. This is the reason why lipids give more energy. Lipids are found in all cells. They are insoluble in water but soluble in non-polar organic solvents such as ether, chloroform, benzene. Sometimes P and N atoms can join the lipid structure.

LIPIDS NEUTRAL LIPIDS (Triglyceride) PHOSPHOLIPIDS GLYCOLIPIDS STEROIDS The structural units of lipids are glycerol and fatty acids. The type and function of the lipid molecule differs due to the type of fatty acid.

A) Triglycerides (Neutral Lipids) @ 3ATP Glycerol + 3 fatty acids Triglyceride + 3 H2O enzyme G L Y C E R O O G L Y C E R O H HO fatty acids __ O__ fatty acids 3 ATP O H HO +3H2O fatty acids __ O__ fatty acids enzyme O H HO __ O__ fatty acids fatty acids ester linkage

A) Triglycerides (Neutral Lipids) GLYCEROL: is an alcohol that has three –OH (hydroxide groups) FATTY ACIDS: are long chains of H and C atoms. At the end of the chain, there is carboxyl (- COOH) group.

Unsaturated Fatty Acids liquid at room temperature one or more double bonds between C atoms ex: olive oil, peanut oil, corn oil,sunflower oil solid at room temperature only single C-C bonds occur ex: butter, lard

B) Phospholipids The third fatty acid of fat molecule is replaced by phosphate group. Found in the cell membrane structure They have hydrophilic (loves-water) and hydrophobic (hates water) Hydrophilic (polar because of PO4-3) Hydrophobic (non-polar)

B) Phospholipids

B) Phospholipids

B) Glycolipids The third fatty acid of fat molecule is replaced by a glucose or galactose molecule. Found in the cell membrane structure of neurons

B) Steroids They are lipids without fatty acids. They are important in membrane structure and in metabolism. They all have the same backbone made up of carbon rings.

IMPORTANCE OF LIPIDS Lipids are great energy sources. They store twice the energy of carbohydrates because they have more H atoms in their structure. Lipids are used as structural units of cell structure. Lipids are stored in animal body, under the skin and around the organs. This helps protect the body from mechanical effects and is a long-term energy storage. Also this helps in heat isolation.

IMPORTANCE OF LIPIDS Lipids are solvent for A, D, E and K vitamins, so these vitamins can be stored in the body. Because they include more H atoms than carbohydrates, they result in production of more water molecules when used in aerobic respiration. This provides animals living in dry environments with water.

IMPORTANCE OF LIPIDS It is thought that fats (saturated fatty acids) increase the level of cholesterol in the blood. High blood cholesterol levels may be linked to atherosclerosis and other heart diseases.