Lecture 03 BSC2010 Lipids & Carbs - Tagged PDF

3 Lecture Lipids and Chapter 3 Carbohydrates Learning Objectives By the end of this lecture you should be able to: 3.1.1 Define lipids based on their insolubility in water. 3.1.2 Identify triglycerides and phospholipids from...

3 Lecture Lipids and Chapter 3 Carbohydrates Learning Objectives By the end of this lecture you should be able to: 3.1.1 Define lipids based on their insolubility in water. 3.1.2 Identify triglycerides and phospholipids from their chemical structure. 3.1.3 Recognize the difference between saturated and unsaturated fatty acids and explain how saturation affects how closely they can pack together. 3.1.4 List some of functions of lipids. Learning Objectives By the end of this lecture you should be able to: 3.2.1 Draw the ring form of five- and six-carbon carbohydrates. 3.2.3 Define the difference between mono-, di-, oligo-, and polysaccharides. 3.2.4 Describe the functional consequences of linear versus branched polysaccharides, and how branching occurs in terms of the positional carbons involved in the bonding. Concept 3.1 Lipids Are Characterized by Their Insolubility in Water Macromolecules are large molecules formed by covalent linkages of smaller molecules. 4 kinds of macromolecules are typically found in living organisms. 1. Proteins 2. Carbohydrates 3. nucleic acids 4. lipids Concept 3.1 Lipids Are Characterized by Their Insolubility in Water Except for the lipids, the other 3 kinds of biological macromolecules are polymers (“poly”=many; “mer”=unit). Polymers are created by the covalent linkage of smaller molecules called monomers. Polymers are formed and broken apart in reactions involving water. Concept 3.1 Lipids Are Characterized by Their Insolubility in Water Polymers are formed and broken apart in reactions involving water. Condensation — the removal of water creates a covalent bond between monomers. Clicker Question 1 Concept 3.1 Lipids Are Characterized by Their Insolubility in Water Polymers are formed and broken apart in reactions involving water. Hydrolysis—the addition of water breaks a covalent bond between monomers. Concept 3.1 Lipids Are Characterized by Their Insolubility in Water Lipids are hydrocarbons (composed of C and H atoms); they are insoluble in water because of many nonpolar covalent bonds. When close together, weak but additive van der Waals interactions hold them together. Concept 3.1 Lipids Are Characterized by Their Insolubility in Water Lipids Store energy in C—C and C—H bonds Play a structural role in cell membranes Fat in animal bodies serves as thermal insulation Concept 3.1 Lipids Are Characterized by Their Insolubility in Water Triglycerides (simple lipids) Fats—solid at room temperature Oils—liquid at room temperature They have very little polarity and are extremely hydrophobic. Concept 3.1 Lipids Are Characterized by Their Insolubility in Water Triglycerides consist of: Three fatty acids—nonpolar hydrocarbon chain attached to a polar carboxyl group (—COOH) (carboxylic acid) One glycerol—an alcohol with 3 hydroxyl (—OH) groups Synthesis of a triglyceride involves three condensation reactions. Figure 3.2 Synthesis of a Triglyceride Concept 3.1 Lipids Are Characterized by Their Insolubility in Water Fatty acid chains can vary in length and structure. Fatty acids are amphipathic; they have a hydrophilic end and a hydrophobic tail. In saturated fatty acids, all bonds between carbon atoms are single; they are saturated with hydrogens. Concept 3.1 Lipids Are Characterized by Their Insolubility in Water In unsaturated fatty acids, hydrocarbon chains contain one or more double bonds. These acids cause kinks in the chain and prevent molecules from packing together tightly. Concept 3.1 Lipids Are Characterized by Their Insolubility in Water Phospholipid—two fatty acids and a phosphate compound bound to glycerol The phosphate group has a negative charge, making that part of the molecule hydrophilic. Concept 3.1 Lipids Are Characterized by Their Insolubility in Water In an aqueousenvironment, phospholipids form a bilayer. The nonpolar, hydrophobic “tails” pack together and the phosphate-containing “heads” face outward, where they interact with water. Biologicalmembranes have this kind of phospholipid bilayer structure. Clicker Question 2 Carbohydrates and Polysaccharides Concept 3.2 Carbohydrates Are Made from Simple Sugars Biological Roles of Carbohydrates Source of stored energy Transport stored energy within complex organisms Structural molecules that give many organisms their shapes Recognition or signaling molecules that can trigger specific biological responses Concept 3.2 Carbohydrates Are Made from Simple Sugars Carbohydrates are a large group of molecules that have similar composition, but differ in several important properties. composition: Cn(H2O)n’ Concept 3.2 Carbohydrates Are Made from Simple Sugars Some carbohydrates are small and are called simple sugars. Some carbohydrates are large and are polymers of the simple sugars. Concept 3.2 Carbohydrates Are Made from Simple Sugars Simple sugars: carbohydrates with 12 or fewer carbons. Monosaccharides—five or six carbons, usually in a ring (pentoses and hexoses) The 3-D structure of polymers (polysaccharides) depends on the isomers of the simple sugars. Concept 3.2 Carbohydrates Are Made from Simple Sugars Disaccharides—two monosaccharides linked by a glycosidic bond. Concept 3.2 Carbohydrates Are Made from Simple Sugars Oligosaccharides: three to ten monosaccharides joined by glycosidic bonds. Many have additional functional groups. They are often bonded to proteins and lipids on cell surfaces, where they serve as recognition signals. Concept 3.2 Carbohydrates Are Made from Simple Sugars Polysaccharides are large polymers of monosaccharides; the chains can be branching. Starches—a family of polysaccharides of glucose Glycogen—highly branched polymer of glucose; main energy storage molecule in mammals Cellulose—the most abundant carbon-containing (organic) biological compound on Earth; stable; good structural material Clicker Question 3