Lipids

-



Lipids

Lipids are organic compounds that are insoluble in water but soluble in organic solvents such as benzene, chloroform, and ether. Simply, they are defined as esters of fatty acids and alcohol. Examples- fats, oils, waxes, and related compounds.

Classification of Lipids

Lipids are broadly classified into simple, complex, and derived lipids.





1. Simple lipids: They are esters of fatty acids with alcohols. These are mainly of two types

(a) Fats and oils (triacylglycerols): These are esters of fatty acids with glycerol. The difference between fat and oil is only physical. Thus, oil is a liquid while fat is a solid at room temperature.





(b) Waxes:- Waxes are the esters of fatty acids with high molecular weight monohydroxy alcohol. It is the esters of long-chain fatty acids with long-chain alcohols in place of glycerol. Cetyl alcohol is most commonly found in waxes.

CH3-(CH2)28-CH2OH (myricyl alcohol) + CH3-(CH2)14-COOH (palmitic acid) à CH3-(CH2)28-CH2-O-C=O-(CH2)14-CH3 (myricyl palmitate) (Bee’s wax).

2. Complex (or compound) lipids: These are esters of fatty acids with alcohols containing additional groups such as phosphate, nitrogenous base, carbohydrate, protein etc. They are further divided as follows:

Phospholipids: These are lipids containing a phosphate group. Simply, they contain phosphoric acid and frequently a nitrogenous base. This is in addition to alcohol and fatty acids.

a) Glycerophospholipids:- The alcohol is glycerol

b) Sphingophospholipids:- The alcohol is sphingosine.





3. Derived Lipids: These are the derivatives obtained on the hydrolysis of simple and compound lipids, which possess the characteristics of lipids. These include glycerol and other alcohols, fatty acids, mono and diacylglycerols, lipid-soluble vitamins, steroid hormones, hydrocarbons and ketone bodies.


Fatty acids

Fatty acids are building blocks of lipids. Fatty acids are defined as compounds that are composed of long chains of carbon and hydrogen atoms (referred to as hydrocarbon molecules) containing a carboxylic acid moiety at one end (a carboxylic acid is written –COOH). Chemically, it is a carboxylic acid with a long aliphatic chain, which is either saturated or unsaturated.
Fatty acids have many important functions in the body, including energy storage. If glucose (a type of sugar) isn't available for energy, the body uses fatty acids to fuel the cells instead.


Saturated and Unsaturated Fatty Acids

Saturated fatty acids or fats are those in which all the fatty acids have a single bond. E.g., Animal meat – including beef, poultry, pork, Certain plant oils – such as coconut oil, Dairy products – including cheese, butter, and milk

Unsaturated fats are typically liquid at room temperature and diff
er from saturated fats in that their chemical structure contains one or more double bonds. They can be further categorized as:

· Monounsaturated fats – a type of unsaturated fat that contains only one double bond in its structure.

· Polyunsaturated fats – another type of unsaturated fat that contains two or more double bonds in its structure,

E.g., Nuts, Plant oils – such as canola, vegetable, or plant oil, and Certain fish – such as salmon, tuna, and anchovy, which contain omega-3 unsaturated fatty acids


Functions of lipid

The functions of lipids are as follows

· Source of energy- 1 gm of lipid provides us with about 9 kcal of energy.

· Storage form of energy: Lipids are storage compounds; triglycerides serve as the reserve energy of the body.

· Structural component: Lipids are an important component of the cell membrane structure in eukaryotic cells. The cell membrane is made up of phospholipids and cholesterol.

· Heat insulation: Layers of fat in the subcutaneous layer provide insulation and protection from cold. Polar bear, seal, whale, etc, survive in cold surroundings due to an excess fatty layer.

· Transport: Lipoproteins that are complexes of lipids and proteins occur in blood as plasma lipoproteins, enabling the transport of lipids in an aqueous environment and their transport throughout the body.

· Precursors: Cholesterol is the precursor of bile acids, Vitamin D, and steroids.

· Others:

o They serve as a source for fat-soluble vitamins like A, D, E, and K.

o They act as electrical insulators to the nerve fibres, where the myelin sheath contains lipids.

o Lipids are components of some enzyme systems.

o Some lipids, like prostaglandins and steroid hormones, act as cellular metabolic regulators.

o Cholesterol is found in cell membranes, blood, and bile of many organisms.

o As lipids are small molecules and are insoluble in water, they act as signalling molecules.

o Polyunsaturated phospholipids are important constituents of phospholipids; they provide fluidity and flexibility to the cell membranes.

o Cholesterol maintains fluidity of membranes by interacting with lipid complexes.

o Essential fatty acids like linoleic and linolenic acids are precursors of many different types of eicosanoids, including prostaglandins, thromboxanes. These play an important role in pain, fever, inflammation, and blood clotting.



Comments

Post a Comment

Popular posts from this blog

Carbohydrates

-
Image
  Carbohydrates                                                                                                                                       Anup Bajracharya Carbohydrates are organic compounds generally made up of carbon hydrogen and oxygen in the ratio 1:2:1 , which could be represented by the general formula, Cn(H 2 O)n.   It is better defined as polyhydroxy aldehydes or ketones and their derivatives or as substances that yield one of these compounds on hydrolysis. Examples: Glucose (C₆H₁₂O₆). Classification of Carbohydrates Carbohydrates are classified into three...
Read more

BIOCHEMISTRY IN NURSING

-
Image
INTRODUCTION TO BIOCHEMISTRY   1.      What is biochemistry? Biochemistry derives its name from bio= life, chemistry= study of chemicals. So, simply biochemistry is the study of the chemistry of life.   In other words, Biochemistry is the science in which chemistry is applied to the study of living organisms and the atoms and molecules that comprise living organisms. 2.      Who gave the term biochemistry? The term Biochemistry (bios=life) was first coined by a German chemist, Carl Neuberg, in 1903. 3.      What are biomolecules? Biomolecules, also called biological molecules, are substances that are produced by cells  and living organisms, which include carbohydrates, proteins, lipids, nucleic acids, etc. 1.      Explain the importance of biochemistry in Health/ Nursing. Clinical biochemistry is very important in nursing because it helps in understanding, diagnosing, and moni...
Read more

ENZYMES

-
Image
    Enzymes Enzymes are biocatalyst that increases the rate of chemical reactions occurring in the living body. They make a chemical reaction millions of times faster than it would have been without it. They are protein in nature (exception – RNA acting as ribozyme), colloidal and thermolabile in character, and specific in their action. The term enzyme was coined by a German physiologist, Wilhelm Kühne, in 1878. Nomenclature of Enzymes In the early days, the enzymes were given names by their discoverers in an arbitrary manner. For example, the names pepsin, trypsin, and chymotrypsin convey no information about the function of the enzyme or the nature of the substrate on which they act. Some old names indicate the source but not the action, e.g., papain from Papaya, bromelain from Pineapple of the family Bromeliaceae. Sometimes, the suffix-ase was added to the substrate for naming the enzymes, e.g., lipase acts on lipids; nuclease on nucleic acids; lactase on lactose. These ...
Read more