Fats (Glycerides)

Complex sugars (Polysaccharides)

They are carbohydrates which consist of group of monosaccharides, Complex sugars are also called Polysaccharides

Common properties of simple sugars:-

1- Insoluble in water

2- They have heavy molecular weights

3- They don't have any taste

Examples:-

1- Cellulose

2- Starch

3- Glycogen

(N.B: The polymers of each one of the previous complex sugars consist of glucose molecules bound together)

How to detect starch in substances

Starch changes the colour of iodine solution to blue

à They are biological macromolecules which are composed of carbon, oxygen and hydrogen. They divided into simple lipids (fats, waxes, oil), complex lipids (phospholipids) and derivative lipids (steroids)

à Lipids dissolve in non polar solvents such as carbon tetrachloride and benzene, but don't dissolve in polar solvents such as water

How to detect lipids in substances

à Sudan IV reagent is used to detect lipids, as lipids can dissolve in it changing its colour to red

The molecular structure of lipids

à Lipids are formed from 3 fatty acids bound to a glycerol molecule

à glycerol is an alcohol having 3 hydroxyl OH groups

Fig. (2) the structure of lipids

The importance of lipids

1- A source of energy: The energy released from lipids is more than that released from carbohydrates. Human body begins releasing energy from lipids when it runs out of carbohydrates.

2- The main component of cell membranes.

3- They make up 5% of the organic compounds forming living cells.

4- Some animals (polar bears, penguins, seals) store lipids under their skins to protect them from low temperatures.

5- They work as protective layers in some plants and animals.

6- Some of them (steroids) work as hormones

The classification of lipids

Simple lipids:-

à They are formed from the reaction of fatty acids with alcohols, they are classified according to the saturation of fatty acids into oils, fats and waxes.

Oils (Triglycerides)

à They are liquid lipids formed from the reaction of unsaturated fatty acids with glycerol.

à Some birds' feathers are covered with oils to protect them from water which disable their movement.

Fats (Glycerides)

à They are solid lipids formed from the reaction of saturated fatty acids with glycerol.

Waxes

à They are formed from the reaction of fatty acids with heave molecular weights with monohydroxy alcohols (alcohols having one hydroxyl OH group).

àWax covers the leaves of plants (especially desert plants) to decrease the amount of water they lose by transpiration process.

For Reading only (Enriching informations)

Saturated fatty acids: Fatty acids that contain the greatest possible number of hydrogen atoms without double or triple bonds.

Unsaturated fatty acids: Fatty acids that have carbon-carbon double or triple bonds and don't have the greatest possible no. of hydrogen atoms.

Saturated fats: Fats that contain the greatest amount of unlinked fatty acids molecules.

Unsaturated fats: Fats that contain the greatest amount of fatty acids molecules with double bonds

à Glycerol is used in the industry of soap because of its sweet odour

Complex lipids:-

They are formed from oxygen, hydrogen, carbon, sulphur and phosphorus.

Examples:-

Phospholipids: Lipids which occur in the membranes of plant and animal cells.

Structure: Its structure is like that of fats, but phosphate group PO4 replaces the third fatty acid.

Fig. (3) the structure of phospholipids

Derivative lipids:-

à They are lipids which are derived from complex and simple lipids by Hydrolysis process

Examples:-

1- Cholesterol

2- Hormones

3- Steroids

Biological macromolecules: They are huge organic molecules in living organisms which consist from hydrogen and carbon basically (such as carbohydrates, lipids, proteins and nucleic acids).

Carbohydrates: They are biological macromolecules formed from simple molecules (monosaccharides) which include starches, sugars and fibres. They consist of carbon, hydrogen and oxygen at ratio 1:2:1 respectively.

Benedict reagent: A reagent which is used to detect simple sugars, as these sugars change its colour from blue to orange.

Lipids: They are biological macromolecules formed from carbon, hydrogen and oxygen atoms which include different compounds insoluble in water (but they dissolve in benzene and carbon tetrachloride)

Oils: They are liquid lipids formed from the reaction of unsaturated fatty acids with glycerol and called Triglycerides

Fats: They are solid lipids formed from the reaction of saturated fatty acids with glycerol and called glyceride

Waxes: They are formed from the reaction of fatty acids with heave molecular weights with monohydroxy alcohols (alcohols having one hydroxyl OH group)

Sudan IV reagent: A reagent which is used to detect lipids in substances, as they dissolve in it changing its colour to red.

Дата добавления: 2015-10-23