Campbell Biology Third Canadian Edition Chapter 5 PDF

Campbell Biology Third Canadian Edition Chapter 5 The Structure and Function of Large Biological Molecules Copyright © 2021 Pearson Canada, Inc. 5-1 Concept 5.3: Lipids are a Diverse Group of Hydrophobic Molecules Lipids are the one class of large biological molecules that does not form polymers Uni...

Campbell Biology Third Canadian Edition Chapter 5 The Structure and Function of Large Biological Molecules Copyright © 2021 Pearson Canada, Inc. 5-1 Concept 5.3: Lipids are a Diverse Group of Hydrophobic Molecules Lipids are the one class of large biological molecules that does not form polymers Unifying feature of lipids is little or no affinity for water Lipids are hydrophobic because they consist mostly of hydrocarbons which are nonpolar Biologically important lipids include fats, phospholipids, and steroids Copyright © 2021 Pearson Canada, Inc. 5-2 Fats (1 of 5) Fats are constructed from glycerol and fatty acids – Glycerol is a three-carbon alcohol with a hydroxyl attached to each carbon – Fatty acids consist of a carboxyl group linked to a long hydrocarbon chain Figure 5.9a The synthesis and structure of a fat, or triacylglycerol. Copyright © 2021 Pearson Canada, Inc. 5-3 Fats (2 of 5) In a fat, three fatty acids are joined to glycerol by ester linkages, to form a triacylglycerol, or triglyceride The fatty acids can all be the same, or of two or three different kinds Fats separate from water because water molecules hydrogenbond to each other, but exclude the non-polar fats Figure 5.9b The synthesis and structure of a fat, or triacylglycerol. Copyright © 2021 Pearson Canada, Inc. 5-4 Fats (3 of 5) Fatty acids vary in length (number of carbons), number and location of double bonds Figure 5.10a Saturated and unsaturated fats and fatty acids. Saturated fatty acids do not have double bonds Solid at room temperature Most animal fats are saturated Copyright © 2021 Pearson Canada, Inc. 5-5 Fats (4 of 5) Unsaturated fatty acids have one or more double bonds Figure 5.10b Saturated and unsaturated fats and fatty acids. Liquid at room temperature Plant fats and fish fats are usually unsaturated Copyright © 2021 Pearson Canada, Inc. 5-6 Fats (5 of 5) Animation: Fats Right-click slide / select “Play” Copyright © 2021 Pearson Canada, Inc. 5-7 The Structure and Function of Large Biological Molecules (1 of 4) THINK PAIR SHARE Why are unsaturated fats liquid at room temperature? Which membrane will be more fluid at room temperature? 1. 20%saturated 80%unsaturated 2. 80%saturated 20%unsaturated 3. 50%saturated 50%unsaturated What affect does saturation have on melting point? Copyright © 2021 Pearson Canada, Inc. 5-8 Fats (1 of 3) A diet rich in saturated fats may contribute to cardiovascular disease Hydrogenation is the process of synthetically converting unsaturated fats to saturated fats, By adding hydrogen Hydrogenation also creates unsaturated fats with trans double bonds – These trans fats may contribute more than saturated fats to cardiovascular disease Copyright © 2021 Pearson Canada, Inc. 5-9 Fats (2 of 3) Certain unsaturated fatty acids are not synthesized in the human body, must therefore be supplied through the diet – Called essential fatty acids Essential fatty acids include omega-3 fatty acids, which are required for normal growth Thought to also provide protection against cardiovascular disease Copyright © 2021 Pearson Canada, Inc. 5 - 10 Fats (3 of 3) Major function of fat is energy storage Humans and other mammals store their fat in adipose cells Adipose tissue also cushions vital organs and insulates the body Copyright © 2021 Pearson Canada, Inc. 5 - 11 Phospholipids (1 of 2) In phospholipids, two fatty acids and a phosphate group are attached to glycerol – The two fatty acid tails are hydrophobic – The phosphate head group is hydrophilic Figure 5.11a and b The structure of a phospholipid. Copyright © 2021 Pearson Canada, Inc. 5 - 12 Phospholipids (2 of 2) Phospholipids are the major component of cell membranes When phospholipids are added to water, they spontaneously self-assemble into a bilayer – The structure of phospholipids results in the bilayer arrangement of membranes Figure 5.11c and d The structure of a phospholipid. Copyright © 2021 Pearson Canada, Inc. 5 - 13 Steroids Steroids are lipids with a carbon skeleton consisting of four fused rings Cholesterol is a component in animal cell membranes Although cholesterol is an essential component of animal cell membranes, high levels in blood may contribute to cardiovascular disease Figure 5.12 Cholesterol, a steroid. Copyright © 2021 Pearson Canada, Inc. 5 - 14