Carbon based life Where is carbon on the periodic table? How many electrons does it have in its outer shell? How many covalent bonds can it form? Being able to form 4 covalent bonds carbon can be the basis of complex molecules – long chains, rings and these can include single, double or triple bonds. This molecular complexity is vital to life.

Lesson objectives: By the end of this session pupils should be able to.... Describe, with the aid of diagrams, the molecular structure of alpha-glucose as an example of a monosaccharide carbohydrate. State the structural differences between alpha and beta glucose. Describe with the aid of diagrams, the structure of glycogen Describe with the aid of diagrams the formation and breakage of glycosidic bonds (maltose and amylose)

Four types to look at Water Carbohydrates Lipids Proteins Revise anything you know about all of these from GCSE!

Elements involved The big three – C, H and O Others that turn up frequently – N, P and S There are small amounts of others too e.g. minerals – Ca, K, Na, Cl, Mg Can you name any instances we have met already where these elements are involved?

Hydrogen atom

Stereoisomers These are molecules that have the same physical and chemical properties except that they are mirror images of each other S NH₂ C H OH This occurs because of the tetrahedral position of the 4 covalent bonds that carbon forms. To create a stereoisomer the carbon must be bonded to 4 different groups Why are stereoisomers significant in biological reactions?

Properties of monosaccharides Soluble in water Sweet tasting Form crystals General formulae: Cn(H2O)n Hydrated carbon!

Classification of Monosaccharides Monosaccharide = a single sugar (MONOMER) Grouped according to number of Carbon atoms in the molecule: 3-carbon monosaccharides = triose sugar 5-carbon monosaccharides = pentose sugars 6-carbon monosaccharides = hexose sugar Which group does glucose belong to?

Glucose Glucose: Alpha (α) beta (β) REMEMBER: beta (β) glucose has the Hydrogen atom at the bottom as you look at the structural diagram

6 5 4 1 3 2

Joining monosaccharides & splitting disaccharides Condensation reactions (join sugars) Hydrolysis reaction (break sugars apart) Glycosidic bond

Properties of Disaccharides Soluble Sweet Crystalline

Types of disaccharide Roles of Disaccharides α glucose + α glucose = maltose α glucose + fructose = sucrose α glucose + galactose = lactose Roles of Disaccharides Maltose: breakdown product of starch, found in malt barley Sucrose: transport of sugars in phloem. Glucose converted to sucrose Lactose: Found in milk. Energy source for babies

Polysaccharides (POLYMER) (long chain carbohydrates) Starch (main storage material in plants) Glycogen (the main storage material in animals) Cellulose (major structural components of cell walls in plants)

Starch (Plants) Made up of alpha glucose Two forms Amylose Amylopectin Unbranched helix Amylopectin Branched structure

Lets try to draw amylose!

Glycogen (animals) Branches much more than amylopectin Made up from alpha glucose subunits. 1-4 linked glucose chains tend to be shorter than for starch. 1: 6 bonds more frequently

Structure and function Insoluble So doesn’t affect osmosis of the cell. H groups and OH groups tucked inside coils, so won’t form H bonds with water. Starch Amylose – coiled structure, compact, good for storage. Amylopectin branched chain of alpha glucose. large surface area Many ends – highly efficient energy store and release Glycogen Highly branched Large surface area Many ends – highly efficient energy store and energy release.

How are we doing? What is the name given to the type of bond that holds sugar molecules together? Name the two different types of molecule which are joined together in a starch molecule. Explain why starch and glycogen are good stores of energy. Stretch and challenge! Draw a diagram to show how a maltose molecule is formed from the end of amylose. Name the enzyme that catalyses the reaction

Lesson objectives: so can we? By the end of this session pupils should be able to.... Describe, with the aid of diagrams, the molecular structure of alpha-glucose as an example of a monosaccharide carbohydrate. State the structural differences between alpha and beta glucose. Describe with the aid of diagrams, the structure of glycogen Describe with the aid of diagrams the formation and breakage of glycosidic bonds (maltose and amylose)

What about cellulose?

Cellulose The most abundant organic molecule on the planet 20-40% of cell walls Polymer of β-glucose straight, unbranched chains Insoluble in water Indigestible by vertebrates (mutualistic microorganisms in herbivores produce cellulase Structural role due to mechanical strength caused by hydrogen bonding 60-70 cellulose molecules become tightly crosslinked to form microfibril bundles Microfibrils held together in bundles called fibres Prevents plant cells bursting.