biological molecules t h e m e o n e : p r i n c i p l e s o f b i o l o g y c h a p t e r 3 define...

Biological MoleculesBiological Molecules

T H E M E O N E : P R I N C I P L E S O F B I O L O G Y

C h a p t e r 3

• Define the structure of carbohydrates, fats and proteins.

• Carry out tests to identify starch, reducing sugars, fats and proteins.

• State the role of water in living organisms

Learning Outcomes



C h a p t e r 3

• 2 hydrogen atoms attached to the oxygen atoms

• V-shaped molecule• Stronger pull of O atom result

in H2O becoming slightly polar

• O atom is more negative, H atoms are more positive

Water

3.1 The Building Materials of Life



C h a p t e r 3

• Water has a high heat capacity due to the many bonds between water molecules.

Water has a high heat capacity




C h a p t e r 3

• As water loses heat, the molecules slow down.• More bonds are formed between the molecules.

• Ice is formed and it is less dense than water since its molecules are further apart than in liquid state.

Ice is Less Dense than Water




C h a p t e r 3

• Cohesive force – ease with which hydrogen bonds are formed between water molecules.

• Adhesive force – attraction between two different kinds of molecules.

Cohesive and Adhesive Forces




C h a p t e r 3

• Also a very good solvent – due to it being slightly polar.

Water as a Solvent




C h a p t e r 3

• Absorbs and removes heat produced by metabolic activities.

• Removes heat by evaporation of sweat.• Its unique density as ice results in ice floating

over slightly warmer water.– Insulates water from further loss of heat.– Ensures survival of aquatic organisms.

• Forms a large part of the cytoplasm of the cell, tissue fluid and transporting medium.

• In plants, it helps the cells to maintain turgor pressure and keep their shape. Also essential in photosynthesis.

Role of Water in Living Organisms3.1 The Building Materials of Life



C h a p t e r 33.1 The Building Materials of Life

• Contain carbon, hydrogen and oxygen.• Hydrogen : Oxygen 2 : 1

• Chemical formula: Cm(H2O)n

Carbohydrates



C h a p t e r 3

• Monosacharides (single sugars) are carbohydrates which cannot be broken down into simpler form.

• E.g. glucose, fructose, galactose.

• Sweet and soluble

Carbohydrates




C h a p t e r 3

• Disaccharides (double sugars) are created when two mono-saccharides become linked.

• Sweet and soluble

Carbohydrates




C h a p t e r 3

• Sugars may be classified as reducing or non-reducing sugars

• Eg. glucose, fructose, maltose, lactose are reducing sugars

Carbohydrates




C h a p t e r 3Test for Reducing sugars

• Add 2ml of Benedict’s Solution to 2ml of test solution in a test-tube.

• Shake well to mix.• Place test-tube in boiling water bath for 5 min.• Solution turns green =• Solution forms yellow ppt =• Solution forms ornage-red ppt =• Solution remains blue =



C h a p t e r 3

• Polysaccharides are long chains or polymers of monosaccharides.

• The chains produced can be branched or unbranched. The chains may also be folded, thus making them compact and ideal for storage.

• The large size of the molecules makes them insoluble so do not affect water potential and they cannot easily diffuse out of the cell.

• Functions: mainly for storage and provide structural support.

Carbohydrates




C h a p t e r 3

• Storage polysaccharides:– Starch is a polymer of glucose molecules.– Stored as starch granules in plastids in plant cells or

tissue.

Carbohydrates




C h a p t e r 3

• Storage polysaccharides:– Glycogen is also a polymer of glucose.– Primary store of carbohydrates in animals.– Stored in liver and skeletal muscles of vertebrate

animals.

Carbohydrates




C h a p t e r 3

Carbohydrates• Structural polysaccharides:

– Cellulose is the most abundant organic compound on the Earth.

– Long cable-like bundles of fibrils in the cell walls of all plant cells.




C h a p t e r 3

Carbohydrates• Structural polysaccharides:

– Most animals do not have the enzymes to break the molecular linkages.

– However, it aids peristalsis.– For herbivores, cellulose is digested by micro-

organisms present in the gut of those animals.




C h a p t e r 3Why Glycogen and Starch are suitable storage materials?

• Insoluble so

• Large molecules so

• Easily broken down (hydrolysed) so

• Molecules have compact shapes, folded so



C h a p t e r 3Test for starch

• Add 2ml of Iodine solution to 2ml of test solution.

• Shake well to mix.

• Solution turns blue-black =

• If solid, its stained blue-black =

• Solution remains yellowish brown =

biological molecules t h e m e o n e : p r i n c i p l e s o f b i o l o g y c h a p t e r 3 define...

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