L. Noha Soliman Carbohydrates

Objectives  Introduction..  Functions Of Carbohydrates.  Types Of Carbohydrates. Of Carbohydrates.  Classification Of Carbohydrates.  MONOSACCHARIDES Monosaccharide Classification. Some important monosaccharides and their structures. Sugars exhibit various forms of isomerism  DISACCHARIDES  POLYSACCHARIDES

Introduction  Also called saccharides, which means “sugars.” 1:2:1  They composed of carbon, hydrogen, and oxygen in a 1:2:1 empirical ratio. CH 2 O  The general empirical formula for a carbohydrate is CH 2 O.  If a carbohydrate has 5 carbons atoms, what would be its empirical formula?  If a carbohydrate has 12 hydrogen atoms present, what would be its empirical formula?  All carbohydrates have this empirical formula except deoxy sugars, amino sugars. –ose.  Most carbohydrates end with the suffix –ose. C 5 H 10 O 5 C 6 H 12 O 6

 Are produced by photosynthesis in plants.  Such as glucose are synthesized in plants from CO 2, H 2 O, and light energy from the sun.  Are oxidized in living cells (respiration) to produce CO 2, H 2 O, and energy. Introduction

Functions of Carbohydrates  Provide energy source: Living things use carbohydrates as their main source of energy. The breakdown of sugar supplies immediate energy for all cell activities.  Provide energy storage: Plants store energy in a complex carbohydrate form called starch. Animals store energy in a complex carbohydrate in their muscle tissue and liver in the called glycogen.

Functions of Carbohydrates  Structural Building Material: Plants and some animals also use carbohydrates for structural purposes. Plants build their cell walls of a complex carbohydrate called cellulose. Animals such as arthropods build their exoskeletons of a complex carbohydrate called chitin. Chitin is also found in the cell walls of Fungi.

Carbohydrates are chains (polymers) made of monomers. The most common monomer of carbohydrates is…

There are 2 types of carbohydrates Simple Complex

Simple Sugars are carbohydrates made up of 1 or 2 monomers. They taste sweet.

Complex Cabohydrates are polymers made up of many monomers. Most taste starchy.

Classes of Carbohydrates Classifications based on number of sugar units in total chain: Monosaccharides Monosaccharides - single sugar unit Disaccharides Disaccharides - two sugar units Oligosaccharides Oligosaccharides- 3 to 10 sugar units Polysaccharides Polysaccharides- more than 10 units

Classes of Carbohydrates

MONOSACCHARIDESMONOSACCHARIDESMONOSACCHARIDESMONOSACCHARIDES The basic building blocks (monomers) of carbohydrates. (cannot be further hydrolyzed into smaller units). Known as simple sugars. Readily soluble in water. Same no. of C as O atoms. e.g. Glucose is C6H12O6 Have the general formula (CH2O)n They contain: – a carbonyl group (C=O) – either at 1 C atom or at the 2 C atom – multiple hydroxyl groups (-OH) White crystalline solids.

Structural representation of sugars  Fisher projection:  Fisher projection: straight chain form.  Haworth projection:  Haworth projection: simple ring.  Chair form. D-Glucose α- D-Glucose

Monosaccharide Classification MONOSACCHARIDE FUNCTIONAL GROUP FUNCTIONAL GROUP ALDOSEKETOSE NUMBER OF CARBONS IN THE BACKBONE NUMBER OF CARBONS IN THE BACKBONE TRIOSEPENTOSEHEXOSE

Monosaccharide Classification OH H H HO CH 2 OH H H H OH O Glucose H OH HO O H H H Ribose CH 2 OH Glyceraldehyde H H H H OH O C C C Classified by number of carbons: 3C = triose (glyceraldehyde) 5C = pentose (ribose) 6C = hexose (glucose)

TRIOSESPENTOSESHEXOSES contains 3 carbon atomscontains 5 carbon atomscontains 6 carbon atoms C3H6O3C3H6O3 C 5 H 10 O 5 C 6 H 12 O 6 glyceraldehydes dihydroxyacetone ribose deoxyribose glucose immediate source of energy for cellular respiration building blocks to form larger molecules components of nucleic acids galactose sugar found in milk and yogurt fructose sugar found in honey Monosaccharide Classification

It can be classified based on functional group (According to where the carbonyl group is located): Aldose - polyhydroxyl aldehyde (aldehyde sugar): Aldose - polyhydroxyl aldehyde (aldehyde sugar): with the carbonyl group (C=O) at the first carbon position, which forms an aldehyde group (CHO). Ketose - polyhydroxyl ketone (ketone sugar): Ketose - polyhydroxyl ketone (ketone sugar): Carbonyl group is at C2 position

Monosaccharide Classification Both functional group have reducing properties ~ reducing sugars ALDOSESKETOSES carbonyl group (C=O) at 1 C is the aldehyde group carbonyl group (C=O) at 2 C is the ketone group sugar is known as aldose (aldehyde sugar) sugar is known as ketose (ketone sugar) glucosefructose

Monosaccharide Classification

Learning check Identify each as aldo- or keto- and as tetrose, pentose, or hexose: AldohexoseKetopentose

Some important monosaccharides  Glucose: In plants and fruits. Mild sweet flavor. known as blood sugar. Essential energy source.  Fructose: Sweetest sugar Found in fruits and honey. Added to soft drinks, cereals, deserts.  Galactose: Part of milk sugar. Hardly tastes sweet. Rarely found naturally as a single sugar.

Some important monosaccharides Glyceraldehyde  Glyceraldehyde Simplest sugar Ribose  RiboseFound in RNA Deoxyribose  Deoxyribose Found in DNA Glyceraldehyde

 They are molecules which have the same molecular formula but have different structures.  Glucose and fructose both have the empirical formula C 6 H 12 O 6 but they have different structural formulas or shapes. 1.Aldose – Ketose Isomerism: (Isomers)

Asymmetric carbon: Asymmetric carbon: C l 4 different things are attached to it. | You must have at least one asymmetric I - C - F carbon to have stereoisomers. | Br Chiral center H | C=O | C H-C-OH | CH 2 OH Chiral center Glyceraldehyde

Physical properties Optical activity ability to rotate plane polarized light. Dextrorotatory - rotate to right - use + symbol - usually D isomers Levorotatory - rotate to left - use - symbol - usually L isomers Light is passed through a polarized filter. A solution of an optical isomer will rotate the light one direction.

2. D and L Isomerism: (Enantiomers) 2. D and L Isomerism: (Enantiomers) Pairs of structures that are mirror images of each other and CANNOT be superimposed on each other. Designated by D- or L- at the start of the name.

2. D and L Isomerism: (Enantiomers) 2. D and L Isomerism: (Enantiomers)

3. Epimers: Two sugars that differ in configuration at only one chiral center. The most important epimers of glucose are: MannoseC2 Mannose epimerization at C2 Galactose C4 Galactose epimerization at C4

Hemiacetal & hemiketal formation: An aldehyde can react with an alcohol to form a hemiacetal. A ketone can react with an alcohol to form a hemiketal.

4. Pyranose and Furanose ring structures:  Pentoses and hexoses can cyclize as the ketone or aldehyde reacts with a distal OH.  Glucose  Glucose forms an intra- molecular hemiacetal, as the C 1 aldehyde & C 5 OH react, to form a 6- member pyranose ring.

4. Pyranose and Furanose ring structures: Fructose Fructose forms either A 6-member pyranose ring, by reaction of the C2 keto group with the OH on C6, or A 5-member furanose ring, by reaction of the C2 keto group with the OH on C5.

5. Alpha and beta anomers: Cyclization of glucose produces a new asymmetric center at C1. The 2 stereoisomers are called anomers,  & . GLUCOSE primary source of energy  - glucose  - glucose hydroxyl (-OH) group of the 1C projects the plane of the ring hydroxyl (-OH) group of the 1C projects below the plane of the ring hydroxyl (-OH) group of the 1C projects the plane of the ring hydroxyl (-OH) group of the 1C projects upward the plane of the ring

DISACCHARIDESDISACCHARIDESDISACCHARIDESDISACCHARIDES These are formed when two monosaccharide molecules join together with the elimination of one molecule of water. They have the general formula C12H22O11. Sweet tasting. Water soluble. EXAMPLE: Maltose Sucrose Lactose C 6 H 12 O6 + C 6 H 12 O 6 = C 12 H 22 O 11 + H 2 O Glucose + Glucose = Maltose + Water

CH 2 OH H O H OH OH CH 2 OH H O H HO OH + H20H20 CH 2 OH H O H OH CH 2 OH H O H OH O α- GLUCOSE MALTOSE Disaccharide Formation Disaccharides are formed when two monosaccharides are joined by dehydration synthesis reaction. GLUCOSE + GLUCOSE -> Maltose (malt sugar) GLUCOSE + FRUCTOSE -> Sucrose (cane sugar) GLUCOSE + GALACTOSE -> Lactose (milk sugar)

Dehydration Synthesis Building reaction. H 2 O is removed in order to form a new bond.

Hydrolysis Reaction Breaking reaction. H 2 O is required to break a bond.

Glycosidic linkage The bond between monosaccharides. What type of reaction would form this bond? – Dehydration synthesis reaction. What kind of bond is a glycosidic linkage? – Polar covalent bond.

Disaccharide Formation

Some important disaccharides Sucrose: Saccharose or table sugar Sucrose: Saccharose or table sugar It is fructose and glucose combined. Source of sucrose is sugar beets and sugar cane. Tastes sweet, and is readily available. brown, white, powdered.

Some important disaccharides Maltose: Malt sugar Maltose: Malt sugar Consists of two glucose units. Produced when starch breaks down. Not abundant. Present in germinating seeds. Lactose: milk sugar Glucose and galactose. Main carbohydrate in milk.

Some important disaccharides

OLIGOSACCHARIDESOLIGOSACCHARIDESOLIGOSACCHARIDESOLIGOSACCHARIDES Oligosaccharide is a few linked monosaccharides and are at time associated with proteins (glycoproteins) or lipids (glycolipids).

POLYSACCHARIDESPOLYSACCHARIDESPOLYSACCHARIDESPOLYSACCHARIDES Polysaccharides are chains of monosaccharides that have been joined by many dehydration synthesis reactions. Do not taste sweet and do not crystallize. Insoluble in water. Form colloidal solutions when Form colloidal solutions when added to water. added to water.

Polysaccharide diversity  Molecular structure determines function.  The function of the polysaccharide depends on what type of isomer of glucose the polysaccharide is made.  Storage Polysaccharides Energy storage - starch and glycogen.  Structural Polysaccharides Used to provide protective walls to cells – cellulose and chitin. In starch In cellulose

Some important polysaccharides

Starch  Energy storage used by plants. – Storage form of glucose in plants. – Found in grains, tubers, and legumes.  Body hydrolyzes plant starch to glucose.  Long repeating chain of α-D-glucose.  Chains up to 4000 units.

Starch   Starch consists of two compounds: – – Amylose: straight chain of α-D- glucose, major form of starch. – – Amylopectin: branched chains of α-D-glucose.

Glycogen  Energy storage of animals: – Storage form of glucose in the body. – Provides a rapid release of energy when needed.  Structure is similar to amylopectin but more branches.  Made from α-glucose.

Glycogen  Found mainly in liver and muscle cells.  When the level of glucose in your blood runs low, glycogen is released from your liver.  The glycogen stored in your muscles supplies the energy for muscle contraction and thus, for movement.

more branching carbon and energy (glucose) storage molecules

Some important polysaccharides

Cellulose  Most abundant organic compound on Earth.  It forms the main part of the cell wall in plants cells.  Cellulose is the major component of cotton, wood and paper.

Cellulose  It is a polysaccharide of β glucose units in unbranched chains.  Linked by β-1,4 glycosidic bonds.  Each β-glucose related to the next by a rotation of 180°

Cellulose  Every other glucose is flipped over, due to β linkages.  This promotes intra-chain and inter-chain H-bonds and van der Waals interactions, that cause cellulose chains to be straight & rigid, and pack with a crystalline arrangement in thick bundles - microfibrils.

Digesting starch vs. cellulose starch easy to digest enzyme cellulose hard to digest

Cow can digest cellulose well; no need to eat other sugars Gorilla can’t digest cellulose well; must add another sugar source, like fruit to diet Digesting starch vs. cellulose

Amino derivatives  The replacement of a hydroxyl group on a carbohydrate results in an amino sugar. Uses for amino sugars. Uses for amino sugars. Structural components of bacterial cell walls. As a component of chitin. A major structural unit of chondroitin sulfate - a component of cartilage. Component of glycoprotein and glycolipids.  -D-glucose  -D-2-aminoglucose (glucosamine)

Chitin  It is the “plastic-like” material that composes the exoskeletons of arthropods (insects, arachnids, and crustaceans).  Most fungi (mushrooms) have chitin present within their cell walls.

Chitin  Similar to cellulose but the hydroxyl group on each monomer substituted with an acetyl amine group.  Cellulose strands are parallel, chitins can be parallel or antiparallel. Above is a structural monomer of chitin.