1. 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.

2. 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)

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

4. 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?

5. Hydrogen atom

6. 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?

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

8. 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?

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

10. 6 5 4 1 3 2

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

12. Properties of Disaccharides
Soluble
Sweet
Crystalline

13. 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

14. 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)

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

16. Lets try to draw amylose!

17. 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

18. 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.

19. 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

20. 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)

21. What about cellulose?

22. Cellulose
The most abundant organic molecule on the planet % 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.