Chapter 12 Lecture Notes: Carbohydrates

1 chemistry 108 Chapter 12 Lecture notes Carbohydrates 1 Chapter 12 Lecture notes : Carbohydrates Educational Goals 1. Given a Fischer projection of a monosaccharide, classify it as either aldoses or ketoses. 2. Given a Fischer projection of a monosaccharide, classify it by the number of carbons it contains. 3. Given a Fischer projection of a monosaccharide, identify it as a D-sugar or L-sugar. 4. Given a Fischer projection of a monosaccharide, identify chiral carbons and determine the number of stereoisomers that are possible.

2 5. Identify four common types of monosaccharide derivatives. 6. Predict the products when a monosaccharide reacts with a reducing agent or with Benedict s reagent. 7. Define the term anomer and explain the difference between and anomers. 8. Understand and describe mutarotation. 9. Given its Haworth projection, identify a monosaccharide either a pyranose or a furanose. 10. Identify the anomeric carbon in Haworth structures. 11. Compare and contrast monosaccharides, disaccharides, oligosaccharides, and polysaccharides.

3 12. Given the structure of an oligosaccharide or polysaccharide, identify the glycosidic bond(s) and characterize the glycosidic linkage by the bonding pattern [for example: (1 4)]. 13. Given the Haworth structures of two monosaccharides, be able to draw the disaccharide that is formed when they are connected by a glycosidic bond. 14. Understand the difference between homopolysaccharides and heteropolysaccharides. 15. Compare and contrast the two components of starch. 16. Compare and contrast amylopectin and glycogen.

4 17. Identify acetal and hemiacetal bonding patterns in Carbohydrates . chemistry 108 Chapter 12 Lecture notes Carbohydrates 2 Introduction to Carbohydrates Carbohydrates are also known as_____. Carbohydrates are an abundant biomolecule. More than 50% of the carbon in organic compounds is found in Carbohydrates Plants use photosynthesis to store energy in_____, a simple sugar 6 CO2 + 6 H2O + Energy C6H12O6 + 6 O2 Carbohydrates are a large class of naturally occurring polyhydroxy _____and _____.

5 _____(also known as simple sugars) are the simplest Carbohydrates containing 3-7 carbon atoms. A sugar containing: an aldehyde is known as an _____ a ketone is known as a _____ Classification of Carbohydrates Carbohydrates are grouped into 3 classes: _____ are the simplest sugars and serve as the building blocks of larger molecules Example: Glucose _____ contain 2-10 monosaccharides bonded together (building block = residue) Example: Sucrose _____contain more than 10 residues Example.

6 Complex Carbohydrates chemistry 108 Chapter 12 Lecture notes Carbohydrates 3 Monosaccharides Monosaccharides are _____ ketones or aldehydes with 3 or more carbons. Naming Monosaccharides carbohydrate nomenclature is unique to sugar chemistry we do not name monosaccharides using the IUPAC rules. Monosaccharide names end in ose." Monosaccharides can be classified by: Carbonyl group: _____ or _____ _____ of carbons: triose, tetrose, etc. Both: aldotriose, ketotriose, and so chemistry 108 Chapter 12 Lecture notes Carbohydrates 4 Examples: You try it: Name each of the following monosaccharides as an aldose or ketose & according to its number of C atoms.

7 _____ _____ _____ chemistry 108 Chapter 12 Lecture notes Carbohydrates 5 Stereoisomers in Carbohydrates Carbohydrates are _____molecules since they have carbon atoms carrying four different groups. The simplest three-carbon sugar is glyceraldehyde. This sugar exists as a pair of _____. Enantiomers have the same _____ physical properties except they behave differently in the way they rotate polarized light and the way they are affected by catalysts. Remember: Compounds with n chiral carbon atoms has a maximum of 2n possible stereoisomers and half that many pairs of enantiomers (mirror images).

8 The aldotetrose (below), has 2 chiral carbon atoms and a total of 22 = 4 possible stereoisomers (2 pairs of enantiomers). chemistry 108 Chapter 12 Lecture notes Carbohydrates 6 The D and L Families of Sugars: Drawing Sugar Molecules Fischer Projections represent three-dimensional structures of stereoisomers on a flat page. A chiral carbon atom is represented in the Fisher projection as the _____of two crossed lines. Bonds that point _____ the page are shown as horizontal lines. Bonds that curve _____ _____ _____the page are shown as vertical lines.

9 In a Fischer projection, the aldehyde or ketone carbonyl group of a monosaccharide is always placed toward the top of the page. chemistry 108 Chapter 12 Lecture notes Carbohydrates 7 Example: Glucose Monosaccharides are divided into _____ families: D form and L form sugars. D: the OH group on the chiral C furthest from the C=O comes out of the plane of paper and points to the_____. L: the OH group on the chiral C furthest from the C=O comes out of the plane of paper and points to the _____.

10 chemistry 108 Chapter 12 Lecture notes Carbohydrates 8 Monosaccharides We will briefly survey some important pentoses and hexoses, and their derivatives. D-glucose, also called _____or_____ _____, is the most important monosaccharide in human metabolism. D-fructose, or fruit sugar, is most common natural ketose Honey is 40% fructose Monosaccharide Derivatives In _____ _____ a hydrogen atom replaces one or more of the -OH groups in a monosaccharide. D-ribose and its derivative D-2-deoxyribose (deoxy = minus one oxygen atom) are found in various coenzymes and in DNA.