Nucleic acid

TOPIC#12        NUCLEIC  ACID

INTRODUCTION:

It is a polymer or polynucleotide chain made up of basic units or monomers Nucleotides.

LOCATION:

It is mostly present in nucleus in eukaryotic cell while in prokaryotic cell it is present in centre of cell cytoplasm because they lack well defined nucleus.

WHAT IS NUCLEOTIDE :

  Nucleotide is a monomer composed of three components;

1-Pentose sugar ribose(5 carbon monosaccaride) 

2-nitrogenous bases like Adenine,thymine,guanine,cytosine and uracil.

3-phosphoric acid

 In typical nucleotide the nitrogenous base is attached to carbon 1 of ribose sugar while phosphoric acid attached to the carbon 5 of pentose ribose sugar.

There are two types of nitrogenous bases pyramidine and purine.

PYRIMIDINE:

    This type of nitrogenous bases are single ring compounds.

Examples:

     Thymine,Uracil,Cytosine.(shortcut TUC)

PURINES:

   This type of nitrogenous base are double ring compound.

Examples:

     Adenine and Guanine.

The nucleotides are monomers they combine to form polymers nucleic acid.

They form two types of bond;

1-When bond is formed between phosphoric acid(H3PO4) and hydroxyl group (OH) of pentose sugar this bond is called ESTER LINKAGE. 

2-When in a polynucleotide chain one phosphoric acid attached to hydroxyl group of carbon 3 of one nucleotide and other phosphoric acid attached to carbon 5 hydroxyl group of another nucleotide tjis bond is called PHOSPHODIESTER LINKAGE.

Now we will study the types of nucleotides:

TYPES OF NUCLEOTIDES:

 There are 3 types of nucleotides:

1-MONONUCLEOTIDES:

  This type of nucleotide has only one nucleotide.

The most common mononucleotide is ATP which has one nucleotide ,adenine(purine) as a base and three phosphate groups.

It is formed when adenine base linked with ribose sugar it form adenosine.

   Adenine + ribose = Adenosine

 After this one phosphate add to adenosine it form adenosine monophosphate.

  Adenosine +  phosphate = AMP

After this another phosphate add to AMP it form Adenosine diphosphate and for this process energy is supplied.

  AMP + phosphate = ADP

After this another phosphate is added + energy it form Adenosine tri phosphate ATP.

  ADP + PHOSPHATE = ATP(Rich energy molecule commonly called as energy currency)

All body function requires which is provided by ATP  when ir breaks into ADP + Pi It produce a lot of energy equals 7.0 K cal which runs the body functions.

ATP molecule form during respiration while break during digestion process.

2-DINUCLEOTIDES:

 When two nucleotides linked this structure is called DINUCLEOTIDES.

 Examples:

Adenine dinucleotides,Guanine dinucleotides etc.

Many dinucleotides are coenzymes in nature like NAD,FAD,NADP these have important function during respiration act as energy molecules.

3-POLYNUCLEOTIDES:

 When many nucleotides linked they form  a structure called as polynucleotides.

DNA and RNA are two examples of poly nucleotides.

Each function in body is controlled by polynucleotides.

These two DNA and RNA are also c alled as type of nucleic acid.

TYPES OF NUCLEIC ACID:

There are two types of nucleic acids:

1-DNA (DEOXYRIBOSE ):

  It is a polynucleotide chain made up of nucleotide which has no oxygen on pentose sugar carbon 3 or in other word it has only 4 oxygen.

It has 4 types of itrogenous bases adenine,guanine,cytosine and thymine.

The physical model of DNA was first given by james watson,francis crick and maurric wilkings in 1953 and they jointly got nobel prize in 1962 for this determination.

According to them DNA has ladder like structure which is coiled they called it double helix structure. p>

Double helix structure can be visualized as a stair case around central axis.

Important point ,In DNA  Nitrogenous base pair always consist of purine point toward pyrimidine keeping molecule diameter constant 2nm.

The base pair are flat has 0.34nm distance between them.

In between nitrogenous bases hydrogen bond is present.

Adenine form double hydrogen bond with thymine.

Guanine form triple hydrogen bond with cytosine.

These bonds between nitrogenous base pairs keep molecule coiled or double helix.

FUNCTION:

It stores genetic information and transfer it from one generation to another generation.

It also controls all function of the body.

2-RNA(RIBONUCLEOTIDE):

 A polynucleotide chain made up of monomers nucleotides having each nucleotide 5 oxygens.

 It also has 4 nitrogenous bases Adenine ,cytosine,Guanine and uracil (instead of thymine).

DNA is double strand molecule while RNA is single polynucleotide strand.

There are three types of RNA:

A-Messenger RNA:

        It carries messages from the DNA to the ribosome for protein synthesis.

B-Transfer RNA:

        It transfer the specific aminoacid from the cytoplasm to the ribosome for orotein synthesis.

C-Ribosomal RNA:

      It combine with proteins form body of ribosome. atOptions = { 'key' : 'fdfe4b4d4f6cd837c982510d17c5d410', 'format' : 'iframe', 'height' : 250, 'width' : 300, 'params' : {} }; type='text/javascript' src='//pl25153006.profitablecpmrate.com/b6/8b/27/b68b277a7fedd02d49bc1f95b007e10c.js'>

IMPORTANT POINTS IN THIS TOPIC:

A nucleotide without phosphate group is called NUCLEOSIDE.

Messenger RNA provides blue print of protein.

80% of RNA is ribosomal RNA .

NAD,FAD,NADP are coenzymes.

Dinucleotides+ vitamins= Coenzymes.

Nicotineamide and riboflavin are vitamins.

IMPORTANT MCQS IN THIS TOPIC:

1-A nucleotide without phosphate group is called:

Answer: Nucleoside

2-Purine is _Ring compound:

Answer: DOUBLE

3-There are_nitrogenous bases:

Answer: 5

4-mRNA comprises _percent of RNA:

Answer: 3-4
5-DNA model was introduced in :

Answer: 1953

6-How many hydrogen bond is present between GUANINE and CYTOSINE:

Answer: 3

7-The width of duplex DNA is:

Answer: 2nm

8-The_state of coenzyme is energy source:

Answer: REDUCED

9-The nicotineamide is _in nature:

Answer: VITAMINS

10-NAD IS _:

Answer: COENZYME

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