Biological Molecules biology unit 1

Biological Molecules

There are 4 important types of organic molecules (compounds containing carbon-carbon bonds) found in living organisms.

These are:

-       Carbohydrates

-       Lipids

-       Proteins

-       Nucleic acid (DNA)

These are mostly polymers

Group name

Elements

Monomers

Polymers

Carbohydrates

CHO

Monosaccharide

Polysaccharides

Lipids

CHOP

Fatty acids and glycerol

Triglycerides

Proteins

CHONS

Amino acids

Polypeptides

Nucleic acid

CHONP

nucleotides

Polynucleotides

Carbohydrates

-       Sugars

o   Monosaccharides

§  (monomers)

§  e.g. glucose, fructose, galactose

o   Disaccharides

§  E.g. sucrose, maltose, lactose

-       Polysaccharides

o   E.g starch, cellulose, glycogen

Monosaccharides

-       Sweet tasting

-       Soluble

-       (CH₂O)n          n=3-7

Most common monosaccharide is glucose

Glucose:

_-               C₆H₁₂O₆

-       Hexose sugar

Pentose sugars

-       Ribose

-       Deoxyribose

Disaccharides

-       Pairs of monomers – formed when 2 monosaccharides are joined

o   Glucose + glucose = maltose

o   Glucose + fructose = sucrose

o   Glucose + galactose = lactose

-       The 2 monosaccharides are joined by glycosidic bonds

-       The reaction forms a bond and a water molecule

-       The reaction is called a ‘condensation reaction’ (it removes water)

 - The breakdown is called hydrolysis

Polysaccharides

-       Chains of many glucose monomers

-       Joined by glycoside bongs

-       Examples:

o   Starch

o   Cellulose

o   Glycogen

-       Formed by condensation reactions

-       Very large

-       Insoluble

-       Suitable for storage

-       Hydrolysised to form monosaccharides or disaccharides

Lipids

-       Contain carbon, hydrogen and oxygen

-       Insoluble in water

-       Soluble in organic solvents (alcohol, acetone)

-       Main groups of lipids:

§  Triglycides

§  Phospholipids

§  Waxes

-       Main role is in plasma membrane

-       Phospholipids contribute to the flexibility of membranes and transfer of lipid-soluble substances

-       Other roles include:

§  Energy source – a lot of energy but slow to release

§  Waterproofing – insoluble in water

§  Insulation

§  Protection – surrounds delicate organs

§   

-       Each fatty acid forms a bond with glycerol in a condensation reaction

-       Hydrolysis produces glycerol and 3 fatty acids

-       Triglycerides are made up of 3 fatty acids and glycerol

-       Fatty acids are long molecule of hydrocarbon chain with a carboxyl acid group at one end

-       The hydrocarbon chain varies so is called the ‘R group’

-       If the fatty acid chain has NO C-C double bonds they are saturated fatty acids

§  High melting point

§  Solid at room temp

§  Often found in warm-blooded animals

-       If the fatty acid does have a C-C double bond they are unsaturated

Fatty acids with more than one C-C double bonds are called polyunsaturated fatty acids  

§  Low melting point

§  Liquid/oil…