Biological Molecules ‘what you need to know!’

MONOMER – single repeating units that…… ……are joined together to form POLYMER.

MONOMER POLYMERISATION POLYMER

Polymers Monomers Polysaccahrides Proteins Lipids? Glucose Amino acids Glycerol & fatty acids

CARBOHYDRATES

CARBOHYDRATES MONOSACCHARIDES DISACCHARIDES POLYSACCHARIDES

MONOSACCHARIDES A single sugar unit Sweet and soluble Contain carbon, hydrogen & oxygen Classified according to the number of carbons a molecule has.

MONOSACCHARIDES TRIOSE – 3 carbons PENTOSE – 5 carbons HEXOSE – 6 carbons

MONOSACCHARIDES – which is which?

MONOSACCHARIDES – which formula? Molecular formula – C6H12O6 or C3H6O3 or C5H10O5 Structural formula –

Triose or Pentose or Hexose C6H12O6 C3H6O3 C5H10O5 You decide!

Straight chain forms Ring forms Pentose and hexose sugars exist in two forms: Ring forms

Carbon C6 H12 Hydrogen O6 Oxygen

GLUCOSE comes in 2 forms, according how the ring closes. For example, this one: Here this H is above the carbon. This is called  (alpha) glucose.

Here this H is below the carbon. This is called β (beta) glucose. WARNING! A single detail like this one makes all the difference. The position of the OH group on C1 will determine the type of polysaccharide it will form and in turn, the functions it will have in a cell.

Structural Isomers Both these molecules are glucose. Both have a molecular formula of C6H12O6. But they are structurally different and will have different functions in a cell.

Biological role of monosaccharides As an energy source….. A large amount of energy is stored between the C-H bonds This is released to form ATP ATP is the energy currency of the cell As building blocks….. Repeated glucose molecules build up; starch & glycogen Ribose (5C) forms part RNA Deoxyribose (5C) forms part DNA

Forming a disaccharide… …MALTOSE Two  glucose molecules meet. The OH from C1 & H from C4 react. Water is expelled. This is called a condensation reaction. The bond between the two joined glucoses is called glycosidic bond.

Polysaccharides Polymers with subunits of monosaccharides Repeated condensation reactions Normally thousands of monomers long Polysaccharides are not sugars STARCH CELLULOSE GLYCOGEN

Starch Polymer of glucose. Plant storage polysaccharide. Made up of two types of substances; Amylose 2) Amylopectin Amylose Condensation reactions between α glucose (1-4 links). Forms from 1000s of condensation reactions. Coiled springs are formed.

Spiral structure of amylose; part of starch.

Amylopectin Condensation reactions between α glucose (1-4 links). Branches of 1-6 links also exist. Coiled springs with a branched structure are formed.

1-6 links form a branch structure 1-4 links form a helical structure

Amylopectin Mostly 1-4 links. Some 1-6 links.

Starch grains are a mixture of amylose & amylopectin Starch is a polysaccharide Starch it is a insoluble store of glucose Starch is only found in plant cells, the animal equivalent is called GLYCOGEN.

GLYCOGEN is the storage polysaccharide in animals It has 1-4 links and 1-6 links

Cellulose Present in plant cell walls. Has a slow decomposition. It is the most abundant organic molecule on the planet!! It is mechanically very strong. It is a polymer of β glucose

Cellulose C1-4 links make up this polysaccharide. If C1 and C4 are to react, one glucose molecule needs to flip through 180o. It is this subtle difference that make cellulose so strong! This structure has H bonds holding the parallel chains together

70 chains of β glucose combine to form a MICROFIBRIL. Lots of MICROFIBRILS are held together to form FIBRES.