Chemicals of Life - Carbohydrates (PDF)

CHEMICALS OF LIFE FAD1001 : BIOLOGY 1 Hazwani Mat Saad Academic Room (No.23) Level 3, PASUM Complex [email protected] Tel: 03-79675916  Contents ▪ Introduction ✓ Biomolecules definition ✓ Elements, compounds ✓ Important bonds...

CHEMICALS OF LIFE FAD1001 : BIOLOGY 1 Hazwani Mat Saad Academic Room (No.23) Level 3, PASUM Complex [email protected] Tel: 03-79675916  Contents ▪ Introduction ✓ Biomolecules definition ✓ Elements, compounds ✓ Important bonds in biomolecules:- Ionic, covalent, hydrogen, van der Waals ▪ Inorganic compounds : ✓ Structure, properties and functions ✓ Acids, bases and buffers ✓ Mineral salts ▪ Organic compounds: carbohydrates, lipids, proteins, nucleic acids. ✓ Structure, properties and functions Basic principles in studying organic compounds Properties of carbon i. Able to form 4 covalent bonds ii. C has high affinity to other C atoms iii. C forms multiple bonds with C, O and N (strong bonds) Functional groups e.g. OH, NH3+, COOH, CO, PO3-, SH Monomers and polymers  Properties of carbon 1 i) Able to form 4 covalent bonds - Carbon atoms can form diverse molecules by bonding to four other atoms. Carbon valency= 4 Properties of carbon 2ii) C has high affinity to other C atoms Form carbon skeleton (organic molecule skeleton) i.e. long chains or rings other elements e.g. H, N, O, P & S bind to C skeleton Properties of carbon Hydrocarbons – molecules consisting of only carbon and hydrogen – major component of petroleum and fats – hydrophobic compounds because of their many nonpolar carbon-to-hydrogen bonds.  Isomers Properties of carbon – Molecules with the same molecular formula but different structures and properties – Three types of isomers Properties of carbon 3iii) C forms multiple bonds with C, O and N (strong bonds)  Functional groups Atoms or clusters of atoms that are covalently bonded to carbon skeleton Give organic compounds their different properties The parts of molecules involved in chemical reactions Examples and properties Hydroxyl group OH polar Amino group NH3+ charged Carboxyl group COOH charged Carbonyl CO polar Phosphate group PO3- charged Sulfhydryl group SH polar Functional groups Functional groups Functional Groups give organic molecules distinctive chemical properties OH CH3 Estradiol HO Female lion OH CH3 CH3 O Testosterone Male lion  Monomers and Polymers Most macromolecules are polymers. Polymers. carbohydrates, lipids, proteins and nucleic acids. Polymer - long molecule consisting of many similar or identical building blocks called monomers linked by covalent bonds. Monomers Polymers  Synthesis and Breakdown of Polymers Monomers are linked together to form larger molecules by condensation reactions (dehydration) condensation reactions enzymes remove -OH from one molecule and H from another to release H2O e.g. glucoses starch HO 1 2 3 H HO H Short polymer Unlinked monomer Dehydration removes a water H2O molecule, forming a new bond HO 1 2 3 4 H Longer polymer Synthesis & breakdown of polymers Polymers can be broken brokendown down into monomers by into monomers hydrolysis hydrolysis An -OH group and an H atom derived from water are attached at exposed sites e.g. starch glucoses HO 1 2 3 4 H Hydrolysis adds a water H2O molecule, breaking a bond HO 1 2 3 H HO H CARBOHYDRATES  CARBOHYDRATES composed of C, H and O in a 1:2:1 ratio (CH2O)n most are sweet tasting, water soluble and can form crystals know as ‘saccharides’ Functions: energy storage in animal/plants component of structure in cell Three main classes:- monosaccharides disaccharides polysaccharides 1. Monosaccharides Structure simplest carbohydrates (n = 3 - 7), most have 5 or 6-C backbone can be combined into polymers can be converted into other organic molecules (form isomers) may be in linear or ring forms Properties most are sweet tasting, water soluble and can form crystals reducing sugars Monosaccharides Function can be used as source of energy in respiration serve as building blocks for other molecules Classification (based on) size of C skeleton location of carbonyl group  Classification of Monosaccharides Triose sugars Pentose sugars Hexose sugars (C3H6O3) (C5H10O5) (C6H12O6) H O H O H O H O C C C C H C OH H C OH H C OH H C OH H C OH H C OH HO C H HO C H Aldoses H H C OH H C OH HO C H H C OH H C OH H C OH Glyceraldehyde H H C OH H C OH Ribose H H Glucose Galactose H H H H C OH H C OH H C OH C O C O C O H C OH H C OH HO C H Ketoses H H C OH H C OH Dihydroxyacetone H C OH H C OH H H C OH Ribulose H Fructose  Monosaccharide Monosaccharides form Isomers Isomers = two different compounds having same molecular formula Two types of isomerism: a) Structural isomers – due to different attachments of atoms or group of atoms in the molecule b) Geometrical isomers – due to different spatial attachments of atoms or group of atoms in the molecule b) Optical isomerism (enantiomers) – a compound which can exist in two forms whose structures are mirror images.  Monosaccharide Monosaccharides - can be linear or ring forms In aqueous solution, pentoses and hexoses form rings (> stable) Pyranose rings (5 C and 1 O) Furanose rings (4 C and 1 O) Glucose can form two interconvertible ring structure i.e α-glucose and β-glucose Linear forms Monosaccharide Ring forms  Monosaccharide Glucose : from linear to ring forms (pyranose)  Monosaccharide α-glucose and β-glucose : interconvertible  Simple drawing α-glucose β-glucose  Monosaccharide Fructose : from linear to ring forms (furanose)  Monosaccharide Reducing sugars Ability of sugars to reduce Copper valency e.g. in Benedict’s or Fehling’s solution Copper (II) sulphate Copper (I) oxide (CuSO4) (Cu2O) Blue solution brick red precipitation Ionic equation: Cu2+ + e- Cu+ Due to the presence of aldehyde or ketone groups (free OH) on the anomeric C of a sugar Linear forms Monosaccharide Anomeric C Ring forms Anomeric C Anomeric C Anomeric C Monosaccharide: Reducing sugars Reducing sugars can react with other parts of the food, like amino acids, to change the color or taste of the food. Monosaccharide and some disaccharide are reducing sugar Application in medicine - diagnosis of glucose’s presence in urine 2. Disaccharides Structure two monosaccharides joined covalently by glycosidic bond involves removal of a water molecule (condensation reaction) Examples: Maltose = glucose + glucose Reducing sugar Lactose = glucose + galactose Sucrose = glucose + fructose Non-reducing sugar Properties Maltose and lactose are reducing sugars  Disaccharide Joining of two monosaccharides and formation of glycosidic bond glucose glucose maltose  Disaccharide (c)  Disaccharide Maltose known as ‘malt sugar’ (created when seeds start to germinate), from hydrolysis of starch composed of two glucose molecules highly soluble in water reducing sugar foods high in maltose include bread products, candies, cereal bars, energy bars, bagels, pies, processed cereals, crackers, sweet potatoes, honey, and pizza.  Disaccharide Lactose also know as ‘milk sugar’ – found primarily in milk (dairy) foods. combination of galactose and glucose reducing sugar foods high in lactose are typically those which contain milk, cheese, butter, or cream. These include infant formula, candies, chocolates, cakes, pies, ice-cream, and macaroni and cheese. Sucrose commonly known as ‘table sugar’ obtained from sugar cane or sugar beets. mainly found in plants (fruits and vegetables) primary component of most granulated sugars use in baking/cooking. combination of glucose and fructose. not a reducing sugar. Why?  Disaccharide Sucrose – non-reducing sugar 3. Polysaccharides Polymers of sugars Serve many roles in organisms Two important biological functions:- i. Energy storage (starch and glycogen) ii. Structural support (cellulose and chitin) i. Starch (energy storage in plants) a polymer consisting entirely of glucose monomers storage polysaccharides in plants plants stored as granules within plastids not soluble in water iodine molecules can become trapped within the 'coils' of amylose chain, causes iodine (in Potassium Iodide solution) to change colour from yellow-brown to blue-black. Polysaccharide: Starch Structure α-glucose units joined by formed from condensation of α-glucose α – 1,4 – glycosidic bonds 2 components of starch: Amylose simple, linear unbranched helix 200 to 1500 α-glucose units Amylopectin linear, branched helix branched at α – 1,6 – glycosidic bond can be hydrolysed by amylase enzyme to break α – 1,4 – glycosidic bond (in most animals) Components of starch: amylose and amylopectin ii. Glycogen (energy storage in animals) Storage polysaccharides in animals animals Present in liver and muscle cells (high metabolic activity) Large αα–– glucose more branched glucose polymer, more branched than amylopectin - allows for the fast breakdown of the molecule during respiration (more ends which enzymes can start the process of hydrolysis) insoluble in water iii. Cellulose (structural support in plants) major structural component of plant cell wall long unbranched polymer of β-glucose β-glucose units linked by β –β 1,4 – 1,4––glycosidic bonds glycosidic bonds linear Linear chains arranged in parallel parallel , stick together due to hydrogen bonds formed between hydroxyl hydrogen bonds groups on adjacent chains chains group together to form microfibrils microfibrils microfibrils - high tensile strength that give rigidity to plant cells. Polysaccharide: Cellulose in plant cell walls, they criss-cross criss-cross forming a strong structure held by Hydrogen hydrogen bonds. bonds this also allows water to move through and along the cell wall. strength of the cell walls prevent cell form bursting when water passes into the cell. pressure cause by the water makes the cell turgid, supporting the plant through turgor pressure. Polysaccharide: Cellulose Most organisms cannot digest cellulose due to absence of cellulase enzyme (hydrolize β – 1,4 – glycosidic bond) except in symbiotic bacteria, other microorganisms and fungi Ruminants such as cows have microbes in their stomachs to facilitate this process Important in human diet (aid in smooth passage of food thru the digestive tract) Sources: fresh fruits, vegetables & grains  Cellulose has different glycosidic linkages than starch H O C CH2OH CH2OH O H C OH H O OH H H H H 4 OH HO C H 4 1 H OH H HO OH HO H H C OH H OH H OH H C OH  glucose H C OH  glucose (a)  and  glucose ring structures CH2OH CH2OH CH2OH CH2OH O O O O 1 4 1 4 1 4 1 OH OH O OH O OH HO O O OH OH OH OH Spot the (b) Starch: 1– 4 linkage of  glucose monomers differences CH2OH OH CH2OH OH O O O OH O OH OH 1 4 O OH HO OH O O OH CH2OH OH CH2OH (c) Cellulose: 1– 4 linkage of  glucose monomers Polysaccharide: Cellulose Structure of cellulose  Starch Cellulose  a major component of the tough walls that enclose Cellulose plant cells About 80 cellulose Cellulose microfibrils molecules associate in a plant cell wall Microfibril to form a microfibril, the Cell walls main architectural unit of the plant cell wall. 0.5 m Plant cells CH2OH OH CH2OH OH O O O O OH OH OH OH O O O O O O CH OH OH CH2OH H 2 Cellulose CH2OH OH CH2OH OH molecules O O O O OH OH OH OH Parallel cellulose molecules are O O O O O O CH OH OH CH2OH held together by hydrogen H 2 bonds between hydroxyl CH2OH OH CH2OH OH groups attached to carbon O O O O OH OH O OH O O OH O atoms 3 and 6. O CH OH O A cellulose molecule OH H 2 CH2OH is an unbranched  Figure 5.8  Glucose glucose polymer. monomer iv. Chitin Polymer of amino sugar Forms the exoskeleton (nitrogen-containing of arthropods, cell groups attached to walls of many fungi glucose monomers). CH2O H H O OH H OH H OH H H NH C O CH3 (a) The structure of the (b) Chitin forms the exoskeleton (c) Chitin is used to make a chitin monomer. of arthropods. This cicada strong and flexible surgical is molting, shedding its old thread that decomposes after exoskeleton and emerging the wound or incision heals. in adult form.  Activity Draw a simple diagram of α-glucose and β-glucose Where can we find α-glucose and β-glucose? Exercise  Contents ▪ Introduction ✓ Biomolecules definition ✓ Elements, compounds ✓ Important bonds in biomolecules:- Ionic, covalent, hydrogen, van der Waals ▪ Inorganic compounds : ✓ Structure, properties and functions ✓ Acids, bases and buffers ✓ Mineral salts ▪ Organic compounds: carbohydrates, lipids, proteins, nucleic acids. ✓ Structure, properties and functions