Lipids

TOPIC #10 LIPIDS

INTRODUCTION:

It is a group pf different types of organic compound present in cell protoplasm.

DEFINITION:

Esters of fatty acid with glycerol or alcohol and there derivatives.

COMPOSITION:

It contain carbon,hydrogen and oxygen and other elements such as nitrogen and phosphorous .

FUNCTIONAL GROUP:

Each organic compound has its active chemical part called as functional group.

so Lipids on base of functional group it is ESTER.

SOLUBILITY:

Mostly lipids are non polar and they are insoluble in water means they are hydrophobic but they are easily soluble in organic solvents like acetone,ether,petrol and alcohol etc.

MCQ POINT:

Lipids are more energetic than other compounds because they have more C-H bond than other organic compounds on breaking these bonds they release high amount of energy .

Lipids are classified into various types such as Acylglycerol,phospholipids,waxes,terpenoids,streiods now we will discuss them one by one in detail but first we discuss two important molecules related to lipids:

1-FATTY ACID:

Defined as carboxylic with aliphatic hydrocarbon chain.

A fatty acid is a long hydrocarbon chain with carboxyl group at one end of R-group(alkyl group).

-The R group of fatty acid contain 2-30 carbons(note it contain even number of carbons only).

-But mostly fatty acids have 16-18 carbons.

-simplest fatty acid R group has 2 carbons.

TYPES OF FATTY ACID:

There are two types of fatty acids:

A-SATURATED FATTY ACIDS:

In this type of fatty acids all carbon to carbon bonds are single.

No more hydrogenation (addition of hydrogen) occurs.

At room temprature they present in solid form.

With increase in carbon atoms melting point,solubility in organic solvents and hydrophobic nature increases.

EXAMPLES:

Acetic acid(2C)

Butanoic acid(4 c)

Palmatic acid( 16 C) M.P 63 degree centigrade.

Steric acid (18 C) M.p 70 degree centigrade.

B-UNSATURATED FATTY ACIDS:

The carbon to carbons are mostly multiple bonds.

Hydrogenation occurs.

At room temprature they present in liquid form.

They have low melting point.

EXAMPLES:

Oleic acid (18 C) liquid M.P 4 degree centigrade.

Linolic acid (18 C) M.P -5 degree centigrade.

2-GLYCEROL:

Defined as the trihydroxy alcohol.

A three carbon compound to each carbon a hydroxyl group is attached.

This carbon have hydroxyl group therefore it is easily soluble in water.

In all lipids it is most hydrophilic in nature.

Now we will discuss various types of lipids:

VARIOUS TYPES OF LIPIDS:

1-ACYLGLYCEROL:

It is a type of lipid which is composed of fatty acid and glycerol.

Most abundant type of lipids.

The most common and natural acylglycerol has one glycerol called as triglycerides.

Triglycerides is formed by reaction of acid group of three fatty acids with the hydroxyl group of glycerol and as result Triglycerides is formed with additional product of 3 molecules of water.

3 Fatty acids + 1 glycerol = triglycerides + 3 H2O

This reaction is condensation reaction.

Triglycerides have high caloric value they yield as twice as much energy per gram as that of carbohydrates.

2-PHOSPHOLIPIDS:

It is a type of lipids composed of one glycerol ,2 fatty acids and one phosphoric acid molecule usually linked to some nitrogen group.

It is derivative of phosphtadic acid.

Triglycerides converted to phosphlipids by replacing one molecule of fatty acid with phosphoric acid molecule.

The most common form of phospholipids is lecithin(chemically it is phosphotidatic choline).

Phospholipids molecule have two parts:

HEAD : It is polar and is therefore soluble in water and it is hydrophilic in nature.

TAIL: It has non polar two hydrocarbon tail and are insoluble in water and it is hydrophobic in nature.

Phospholipids arrange themselves in a double layer in a presence of water in the plasma membrane of cells.

3-WAXES:

The type of lipid composed of long chain of fatty acid bonded to long chain of alcohol.

They are solid at normal temprature and have high melting point.

They are hydrophobic.

They are also called as ester of fatty acid of MONOHYDROXYALCOHOL.

They are stable compound resistance to degredation.

They form waterproof layer on the surfaces of some plant parts such as leaves,fruits and in this way reduce the rate of water loss..

4-STEROIDS:

The type of lipid which has no fattyacid and glycerol.

Each steroid is formed of backbone of four fused carbon rings containing 17 carbon atoms.

They different from one another by functional group.

They has important functions in bodies of living organisms.

Examples:

Cholestrol is a steriod play imortant role in animal cell membranes.

Cholestrol is also a precursor of all steriod hormones.

Aldosterone,sexhormones and vitamin D are also steriods.

5-TERPENOIDS:

The type of lipids which have no fatty acid and glycerol.

It is made up of repeating unit of isoprenoid(hydrocarbon compound).

It is lipid soluble and water insoluble substances.

They join by the process of condensation and give rise to different type of compounds such as terpenes,rubber,carotenoids etc.

Carotenoids are terpenoid present in plant cell has role in photosynthesis .

The most important carotene is beta carotene which has orange pigments present in carrots which is break by human body into two molecules of vitamin A.

OVERALL FUNCTION OF LIPIDS:

Lipids are long term energy source molecules in plants and animals.

Plants usually stored lipids in seeds as oils(unsaturated faty acid) .

Animals stored fats as saturated fatty acid.

lipids provide more energy than carbohydrates having more C-H bonds than carbohydrates.

It is building material of cellular membrane called lipoprotein molecules.

Lipids provid various insulation to various organs.

Various plant hormones such as auxins,giberallihns,cytokinins while animal hormones are aldosterone,sex hormones are made up of lipids.

IMPORTANT MCQS IN THIS TOPIC:

1-Esters of fatty acid with glycerol is called:

Answer: LIPIDS

2-Lipids on base of functional group is:

Answer: ESTER

3-Glycerol is _alcohol:

Answer: TriHYDROXY

4-Which fatty acid is in solid from:

Answer: Saturated

5-In R group of fatty acid have_carbons:

Answer: 2-30(EVEN)

6-The most simplest fatty acid have _carbons:

Answer: 2 carbons

7-Palmatic acid have_carbon:

Answer: 16

8-Steric acid have_melting point:

Answer: 70

9-The most common form of phosholipids is:

Answer: LECITHIN

10-_compound is fatty acid of one alcohol:

Answer: WAXES

11-serine is _:

Answer: Aminoacid

12-Cholestrol have _rings:

Answer: FOUR FUSED CARBON

IN SHA ALLAH IN NEXT BLOG WE WILL DISCUSS LIPIDS TOPIC MCQS.

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