Carbohydrates - Lecture Slides PDF

# Chapter 18: Carbohydrates - Structure and Function ## Table of Contents - **18.1 Occurrence and Functions of Carbohydrates** - **18.3 Classification of Carbohydrates** - Simpler Formula: $C_nH_{2n}O_n$ or $C_n(H_2O)_n$ (hydrates of C) - Polyhydroxy aldehydes or Polyhydroxy ketones, or co...

# Chapter 18: Carbohydrates - Structure and Function ## Table of Contents - **18.1 Occurrence and Functions of Carbohydrates** - **18.3 Classification of Carbohydrates** - Simpler Formula: $C_nH_{2n}O_n$ or $C_n(H_2O)_n$ (hydrates of C) - Polyhydroxy aldehydes or Polyhydroxy ketones, or compounds that produce such substances upon hydrolysis - **18.4 Classification of Monosaccharides** - The Simple Sugars - Cannot be degraded into simpler products - Pure monosaccharides are water-soluble, white, crystalline solids - **18.5 Biochemically Important Monosaccharides** - **18.6 Cyclic Forms of Monosaccharides** - Haworth Projection Formulas - **18.7 Reactions of Monosaccharides** - **18.8 Classification of Monosaccharides** - Carbohydrates that have the general formula $C_nH_{2n}O_n$ - Grouped together according to the number of carbons they contain - **Trioses** - Glyceraldehyde - Dihydroxyacetone - **Pentoses** - Aldopentoses - D-(-)-Lyxose - D-(-)-Ribose - Ketopentoses - D-Ribulose - D-Xylulose - **Hexoses** - Aldohexoses - D-(+)-Mannose - D-(+)-Glucose - A 5% (m/v) Glucose solution is often in hospitals - D-(+)-Galactose - Ketohexose - D-(-)-Fructose - D-Mannose - **18.9 Biochemically Important Monosaccharides** - **Glucose and Fructose** - Most abundant in nature - Nutritionally most important - Grape fruit good source of glucose - Six membered cyclic form - **Galactose and Ribose** - A component of milk sugar - Synthesized in human - Also called brain sugar - Six membered cyclic form - Galactosemia - Result of genetic deficiency in the infant - Five membered cyclic form - **18.10 Cyclic Forms of Monosaccharides** - Hemiacetals and Hemiketals - May take place either intermolecularly or intramolecularly - Cyclic Hemiacetal forms of D-Glucose - In the cyclic hemiacetals of glucose - **18.11 Haworth Projection Formulas** - Practice Exercise - Answers: - a. Ribose - b. Fructose - c. Glucose, galactose - d. Fructose - **18.12 Reactions of Monosaccharides** - Five important reactions - Oxidation to acidic sugars - Reduction to sugar alcohols - Phosphate ester formation - Amino sugar formation - Glycoside formation - Redox Reactions - Under prescribed conditions, some sugars reduce silver ions - A reducing sugar will have one of the following groups - The Benedict, Barfoed - Redox Tests for Carbohydrates - Reducing Sugars - Sugars with the hemiacetal structure - Many clinical tests - Phosphate Ester Formation - The hydroxyl groups of a monosaccharide - Phosphate esters are stable - Amino Sugar Formation - One of the hydroxyl groups - Amino sugars and their N-acetyl derivatives - Glycoside Formation - The cyclic forms of monosaccharides - A glycoside is an acetal formed - A glycoside produced from - **18.13 Disaccharides** - Maltose - Malt sugar, found in corn syrup - a-1,4-glycosidic bond - Cellobiose - One of the major fragments - The 2 glucose units are joined - Maltose is digested easily - Lactose - Milk sugar - Consists of ẞ-galactose - Lactose intolerance: a condition in - Sucrose - The common table sugar - Produced commercially from - The a-anomeric carbon 1 of glucose - Invert Sugar - Optical activities: - Invert sugar has a much greater - In the manufacture of jelly - Honeybees and many other insects - Practice Exercise - Answers - a. Lactose, sucrose - b. Maltose, cellobiose, lactose, sucrose - c. Sucrose - d. Sucrose - Artificial sweeteners - Table 27.1 - **18.14 Oligosaccharides** - Commonly found in onions - In humans, intestinal bacteria - Solanin - Bitter taste of potatoes is due to - **18.15 General Characteristics of Polysaccharides** - The Polymer Chain - Many monosaccharide units - Homopolysaccharides: - Starch - Glycogen - Cellulose - Chitin - Carageenan - Heteropolysaccharides - Hyaluronic acid - Heparin - Chondroitin sulfate - Alginic acid - **18.16 Storage Polysaccharides** - Starch - The chef caloric distributor in the diet - Amylopectin - Branched chain polymer - 80-85% of the starch - Glycogen - The animal starch - Glucose storage molecule of - Stored in granules in liver - Like amylopectin, is a non linear - **18.17 Structural Polysaccharides** - Cellulose - A fibrous carbohydrate - It serves as dietary fiber - A linear polymer of glucose units - Cotton - Chitin - Similar to cellulose in both - Polymer of N-acetyl-D-glucosamine - Function is to give rigidity - Carageenan - Occurs as hydrocolloid - Widely used in food industry - **18.18 Acidic Polysaccharides** - Hyaluronic acid - Repeating unit is a disaccharide - Each disaccharide is attached to - Alternating - Heparin - Consists of repeating units - An anticoagulant in blood - Used in open heart surgery - Alginic acid - Locally extracted from Sargassum - **18.19 Dietary Considerations and Carbohydrates** - Glycemic Foods - A developing consent about intake - Unavailable carbohydrates - Those not hydrolyzed by digestive - They constitute - Dietary fiber - Lack of dietary fiber may also lead to - Fiber - What Can Fiber Do For Your Heart? - **18.20 Glycolipids and Glycoproteins: Cell Recognition** - A glycolipid is a lipid molecule - A glycoprotein is a protein molecule - Such carbohydrate complexes are very important