lipids

Types of Lipid Molecules Triglycerides Unsaturated fats are liquid at room temperature: e.g. olive oil, canola oil Saturated fats are solids at room temperature: e.g. lard, butter, animal fat Phospholipids Steroids Cholesterol Sex Hormones: testosterone, estrogen, progesterone

Lipid Functions in the Human Body Storage form of energy in humans Key part of cell membranes Hormones that control certain body functions Insulation for heat retention Protection for delicate organs

Glycerol and Fatty Acids

Lipids - Triglycerides Glycerol plus 3 fatty acid chains Triglycerides are biomolecules made from carbon, hydrogen and oxygen atoms joined in long chains. Triglycerides have a backbone of glycerol, attached to three long carbon chains.

Skeletal Shorthand for Big Molecules It is too time consuming to write out all the C’s and H’s in these large molecules, so biochemists developed a shorthand = the skeletal formula. Each vertex represents a carbon atom. It is assumed that you know that each carbon is capable of 4 bonds. In the long chains above, each carbon is bonded to 3 other carbons and the hydrogens (2 in number) are understand to be attached but are not drawn. By using this shorthand, the overall shape of the molecule is clearer.

Lipids – Unsaturated vs Saturated You often hear about saturated and unsaturated fats. Unsaturated fats have double bonds in their long chains while saturated fats do not. The saturated fats can stack quite well, increasing IMF and making them solid at room temperature. The unsaturated fats have kinked chains that do not stack as well, decreasing the IMF and rendering them liquid at room temperature.

Lipids – Unsaturated Skeletal Formula Here is an example of how unsaturated c Notice that the carbons are numbers, starting with the carbon closest to the glycerol backbone.hains are represented using the skeletal formula shorthand.

Lipids – Dehydration Synthesis When triglycerides are created in the cell, faty acids are joined to the glycerol backbone. For this to happen, certain enzymes are present. As the glycerol and the fatty acid chain are moved together, a hydrogen is removed from the glycerol backbone and an hydroxyl group is removed from the carboxylic acid group at the end of the fatty acid chain. The hydrogen and the hydroxyl are joined to form water. Each time a fatty acid chain is attached, a water molecule is removed. A total of 3 water molecules is produced for each triglyceride formed.

Lipids - Phospholipids Basic building block of cell membranes Phospholipids are structured much like triglycerides, except that one fatty acid chain is replaced by a phosphate group. This make the overall phospholipid hydrophilic on one end and hydrophobic on the other.

Lipids - Steroids The general form of a steroid consists of a set of 4 interconnected, carbon based rings with branches. This skeletal formula shows how the carbon atoms are numbered. Each ring is assigned a letter. http://en.wikipedia.org/wiki/Steroid

Lipids - Steroids Testosterone Progesterone On the left is the skeletal formula for testosterone, the main male sex hormone. Testosterone is also an anabolic steroid – that means it’s involved in building muscle and bone mass. On the right is the skeletal formula for progesterone, a main female sex hormone. Progesterone is a key hormone controlling the menstrual cycle, pregnancy and embryogenesis (the development of early embryos). Progesterone is also a precursor for several other important steroid hormones. Testosterone Progesterone