2.1 Carbohydrates Sandringham college pete hamilton

Covalent Bonding involves the sharing of electrons This may involve equal sharing or unequal sharing

Carbon atoms can form 4 covalent bonds

All chemical bonds possess energy which can be released when the bonds are broken

Carbohydrates Compounds of : –Carbon C able to form 4 covalent bonds –Hydrogen H able to form 1 covalent bond –Covalent bonds O able to form 2 covalent bonds Fructose

Carbohydrates While often drawn as a linear skeleton, in solution carbohydrates often form hexagonal shaped ring molecules

This can be further abbreviated for your note taking as a simple hexagon

Macromolecules Macro = large Molecules = 2 or more atoms covalently bonded Usually referred to as polymers - chain like Made from several repeating subunits –The repeated subunits are called monomers –Like links in a chain

Monomers & Polymers A monomer is a molecule that is able to bond in long chains. Polymer means many monomers. Polymers are also known as macromolecules or large-sized molecules. Here is a monomer: Here is a polymer: This linking up of monomers is called polymerization.

Saccharides = sugars Monosaccharides = single/simple sugars Disaccharides = double sugar Polysaccharide = many/complex sugars

Making or Breaking Polymers The chemical mechanisms that cells use to make and break polymers are similar for all classes of macromolecules. dehydration synthesis

Making Polymers Monomers are connected by covalent bonds via a condensation reaction or dehydration reaction. –One monomer provides a hydroxyl group and the other provides a hydrogen and together these form water. –This process requires energy and is aided by enzymes.

Breaking Down Polymers The covalent bonds connecting monomers in a polymer are disassembled by hydrolysis. –In hydrolysis as the covalent bond is broken a hydrogen atom and hydroxyl group from a split water molecule attaches where the covalent bond used to be. –Hydrolysis reactions dominate the digestive process, guided by specific enzymes.

Monosaccharides Monosaccharides: generally have molecular formulas containing C : H : O in a 1:2:1 ratio. fructoseC 6 H 12 O 6. glucose C 6 H 12 O 6. nb: most names for sugars end in -ose.

Monosaccharides Monosaccharides are also classified by the number of carbons in the backbone.

Monosaccharides, particularly glucose, are a major fuel for cellular work. They are also building blocks for of other monomers, including those of amino acids (protein) and fatty acids (lipids). While often drawn as a linear skeleton, in aqueous solutions monosaccharides form rings.

Monosaccharides

Disaccharides Sucrose C 12 H 22 O 11.

Examples of Disaccharides Maltose Formed from 2 glucose molecules, formed in germinating seeds from the breakdown of starch, providing energy Sucrose Formed from 1 glucose and 1 fructose molecule and is the form in which carbohydrates are transported in the phloem in plants Lactose Formed from 1 glucose and 1 galactose molecule, it is an energy source found in the milk of nearly all mammals

Polysaccharides of sugars have storage and structural roles Polysaccharides are polymers of hundreds to thousands of monosaccharides joined together One function of polysaccharides is energy storage –it is hydrolyzed as needed. Other polysaccharides serve as building materials for the cell or whole organism.

Starch: is a storage polysaccharide composed entirely of glucose monomers -Long chain of glucose molecules units Used as an energy store in plants. Not soluble. Forms solid grains inside plant cells (often inside chloroplasts). The chains coil up into a basic spiral shape making the molecules compact. Hydrogen bonds hold the polysaccharide chain in the compact spiral shape.

Glycogen The storage polysaccharide in animals (equivalent to starch in plants). Found in liver and muscle cells where a store of energy is needed. Many fungi also store glycogen. Similar in structure to starch - but more branched. Forms tiny granules inside cells which are usually associated with smooth endoplasmic reticulum. Each glycogen molecule contains a upto 30,000 glucose units

Glycogen

Cellulose Most abundant organic molecule ,000 + glucose units It is very slow to decompose % of the plant cell wall. Hydrogen bonding between monosaccharide molecules in the chain gives strength. Hydrogen bonding between cellulose molecules cause bundles called microfibrils to develop. These are held together in fibres. A cell wall will have several layers of fibres running in different directions - gives great strength almost equal to steel. Provides support in plants and stops plant cells bursting. Freely permeable to water and solutes.