Biological Molecules

‘what you need to know!’Mr R Hardy

MONOMER – single repeatingunits that……

……are joined together to formPOLYMER.

POLYMER

MONOMER

POLYMERISATION

PolymersPolysaccahrides

Proteins

Lipids

MonomersGlucose

etc.

Amino acids

Glycerol & fatty acids

CARBOHYDRATES

CARBOHYDRATES

MONOSACCAHRIDES

DISACCAHRIDES

POLYSACCAHRIDES

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

C3H12O6 or C5H10O5

Structural formula –

C6H12O6 C3H12O6 C5H10O5

You decide!

Triose or Pentose or Hexose

Pentose and hexose sugarsexist in two forms:

Straight chain forms

Ring forms

HydrogenCarbon

Oxygen C6H12O6

GLUCOSE comes in 2forms, this one;

Here this H is abovethe carbon.

This is called α (alpha) glucose.

Here this H is belowthe carbon.

This is called β (beta) glucose.

Both these molecules are glucose.

Both have a molecular formula of C6H12O6.

But they are structurally different.

Structural Isomers

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 α glucose molecules C1 & C4 meet.OH (hydroxl grp) from C1 & H from C4 react.Water is expelled.A condensation reaction.This can be reversed by adding water.

Polysaccharides

• Polymers with subunits of monosaccharides• Repeated condensation reactions• Normally 1000’s of monomers • Polysaccharides are not sugars

STARCH CELLULOSE GLYCOGEN

Starch• Polymer of glucose.• Plant storage polysaccharide.• Made up of two types of substances;1)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.

StarchMade up of two types of substances;1)Amylose 2) Amylopectin

Amylopectin• Condensation reactions between α

glucose (1-4 links).

• Branches of 1-6 links also exist.

• Coiled springs with a branched structure are formed.

1-4 links form a helicalstructure

1-6 links form a branchstructure

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 it together

70 chains of β glucose combine to form a MICROFIBRIL.

Lots of MICROFIBRILS are held together to form FIBRES.