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Lesson 3 – Lipids. In the Cell membrane. Insoluble in water. Liquid (oils) or solids (fats) at room temperature. Hormones. Uses. Characteristics. Energy Storage. Lipids. Types. t riacylglycerols (triglycerides). phospholipids. steroids. Triacylglycerols.
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In the Cell membrane Insoluble in water Liquid (oils) or solids (fats) at room temperature Hormones Uses Characteristics Energy Storage Lipids Types triacylglycerols (triglycerides) phospholipids steroids
Triacylglycerols Distinguishing features of triacylglycerols: Fatty acids Glycerol Carboxyl group
Glycerol Glycerol is a 3 carbon alcohol.
Fatty Acids Fatty acids can be saturated or unsaturated. An unsaturated fatty acid will contain carbon-carbon double bonds. Fatty acids that are saturated will not have any double bonds – all available bonds are occupied by hydrogens.
Importance of Saturation Unsaturated triglyceride Saturated triglyceride The saturated fatty acids are able to line up neatly and pack together closely. For this reason saturated fats tend to be solids at room temperature. Most saturated fats are animal fats. The unsaturated fatty acids do not fit well together and take up more space. These are oils and tend to be liquids at room temperature.
Formation of Triacylglycerol Ester linkage
Phospholipids On your desk draw a phospholipid including as much detail as you can. A phospholipid is simply a triacylglycerol that has had one fatty acid replaced with a phosphate group – often with another group attached. Choline group Phosphate group Phosphatidylcholine
Phospholipids You can see from the diagram that this phospholipid has one saturated fatty acid and one unsaturated fatty acid. unsaturated saturated
Polarity of Phospholipids Hydrophilic head Both the choline and the phosphate are charged making them attracted to water. - Hydrophobic tail The fatty acids are uncharged and non-polar so they are repelled by water.
Steroids Steroids are totally different from other lipids. They have a four-ring structure of 17 carbons with differing side chains.
Cholesterol OH at the bottom left C8H17 at the top right
Testosterone OH at the top right =O at the bottom left
Steroid - Function Cholesterol is found in cell membranes. It is able to exist in the hydrophobic layer and it reduces phospholipid movement in the membrane. It also helps to prevent solidification of the membrane at low temperatures. Testosterone is a hormone that leads to muscle growth and development in males during puberty.
Your Task Past Paper Questions You will need to access these in the department. Please DO NOT TAKE past papers home – we have limited numbers. 2002 Section c Q1 (ER) 2004 MC Q1,2 2011 MC Q 5