Lesson 6 Lipids - PDF

Lipids What are Lipids? Lipids are categorized into four families Fats Phospholipids Steroids waxes They are used for storing energy and building membranes in the organism Polarity of Lipids...

Lipids What are Lipids? Lipids are categorized into four families Fats Phospholipids Steroids waxes They are used for storing energy and building membranes in the organism Polarity of Lipids Lipids are made up of hydrophobic molecules containing carbon, hydrogen and oxygen They contain fewer polar O-H bonds and more non-polar C-H bonds As a result, they are not soluble in water However, they are soluble in other non-polar solvents  The molecule can contain long hydrocarbon chains or compact rings Energy Consumption Lipids are the most common energy storing molecule in living organisms One gram of fat stores approximately 38kJ of chemical energy per gram This is more than twice the energy stored in either a carbohydrate or protein (approx. 17 kJ)  Excess Carbohydrates When there is excess carbohydrates in the body, animals convert it into fat The fat molecules are stored as droplets in the cells of adipose (fat) tissue The fat often acts as a protective layer under the skin  We use it for insulation to keep us warm Triglycerides (Triacylglycerols ) The most common type of fat are triglycerides They contain; Glycerol 3-carbon alcohol (OH is attached to each carbon) 3 fatty acids Attached to glycerol Long hydrocarbon chains (16-18 carbons long)  Has a carboxyl group on the end of each chain Esterification A triglyceride is formed through a process of esterification This is a type of condensation reaction An ester bond is found between the glycerol molecule and the fatty acids The hydrogen of the glycerol and the hydroxide of the fatty acid is removed to make water  The remaining units form an ester linkage Maximum number of hydrogens attached to carbon Saturated Fat Are solid at room temperature Have only single bonds Creates a kink in the chain Types of Fat Fewer than the maximum number of hydrogens attached Stay liquid at room temperature Unsaturated Fat Have at least one double bond Problems With Saturated Fats The length of a hydrocarbon chain can influence the solubility The longer the chain, more London-dispersion forces form This make it harder to dissolve Likewise, the more compact a chain is (fewer double bonds) it is less fluid  As a result, the molecule is less soluble This makes it harder for it to break down For these reasons, saturated fats can lead to heart disease Saturated Vs Unsaturated Foods  Trans-Fat Trans-fat is a type of unsaturated fat found in foods It is man-made Like unsaturated fats, it contains double bonds However, the double bonds are trans-based This causes the fatty acid chain to become straight This causes reduced solubility Our bodies do not recognize these bonds, making it harder to break down Phospholipids  Phospholipids are the primary lipids of cell membranes It is composed of Glycerol 2 Fatty Acids Non-polar chains 1 phosphate group Charged molecule Typically attached to a polar molecule Phospholipid Structure  Phospholipids are considered to be amphipathic (both polar and non-polar) The phosphate group is polar→ hydrophilic The fatty chains are non-polar→ hydrophobic Due to these properties, the phospholipids organizes itself in a certain structure The tails face inward, so that it doesn’t come into contact with water The phosphate head faces outward towards the water This is known as a micelle (circular structure) Micelle Phospholipid Bilayer  The cells membrane is made up of a phospholipid bilayer This is 2 layers of phospholipids The fatty chains remain on the inside and the phosphate heads are on the outside This helps regulate what goes in and out of the cell Water and polar molecules cannot enter the layer without help Steroids  Steroids are groups of lipids which contain four fused carbon rings Groups attached to these rings, make which steroid unique The most common steroids include the sterols Mostly hydrophobic However, it contains one hydroxyl group, making it slightly polar Examples include testosterone and cholesterol Types of Sterols  Cholesterol High concentrations of cholesterol can lead to atherosclerosis This is where plaque (fatty deposits) form on the inner linings of arteries This blocks oxygen and blood flow Can lead to heart attack Testosterone Control the development of sex traits and gametes Anabolic steroids mimic this steroid, leading to high blood pressure and reduced growth Waxes  Waxes are a type of lipid that contain long fatty acid chains attached to alcohols or carbon rings They are Hydrophobic Non-polar Soft solids Cutin is a type of wax found on plants Act as a water-proof coating Allows plants to conserve water and protects against infections Homework  Complete Questions Pg.38, #4, 6-8