CHEM 203                                        Biochemistry
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CHEM 203 Biochemistry. Unit  Nucleic acids. Nucleoproteins : are conjugated proteins formed of: a) basic protein ( histone or protamine ) and b) nucleic acid as prothetic group.

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Unit  Nucleic acids

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Unit nucleic acids

CHEM 203 Biochemistry

Unit 

Nucleic acids

Ola Fouad Talkhan


Unit nucleic acids

Nucleoproteins : are conjugated proteins formed of:

a) basic protein (histone or protamine) and

b) nucleic acid as prothetic group.

They are very complex high molecular weight proteins present in every cell.

Functions of nucleic acids

1-In cell nuclei they form the chromosomes which are responsible for cell division and carries of hereditary factors known as (genes).

2-In cytoplasm are associated with ribosome, the center of protein biosynthesis in every cell.

Ola Fouad Talkhan


Unit nucleic acids

Nucleic acid can be easily separated from nucleoprotein by addition of acids or alkalis .

Nucleoprotein

hydrolysis

Protein

Histone or protamin

(one or more molecules)

Nucleic acids

  • Nucleic acids

  • Nucleic acids is composed of large number of nucleotides,which considered as basal structural component of nucleic acids.

  • There are two types of nucleic acid

  • Deoxyribonucleic acid (DNA)

  • Ribonucleic acid (RNA)

Ola Fouad Talkhan


Unit nucleic acids

Nucleoproteins

Protein

Histone or protamin

Nucleic acid

(Polynucleotide)

Large number of mononucleotides

Nucleoside

Phosphoric acid

Nitrogenous base

Sugar

Ribose Deoxyribose

Purin base Pyrimidine base

Ola Fouad Talkhan


Nucleotides

NUCLEIC ACID STRUCTURE

Nucleotides

• Nucleic acids are polynucleotides

• Their building blocks are nucleotides

  • Nucleic acids consist of nucleotides that have a nitrogen base, Pentose sugar , and phosphate

Ola Fouad Talkhan


Nitrogenous bases

Nitrogenous Bases

The nitrogen bases in nucleic acids are:

  • Pyrimidine bases:

    Cytosine

    Thymine

    Uracil

  • purine bases:

    Adenine

    Guanine

Ola Fouad Talkhan


Pentose sugars

Pentose Sugars

The pentose (five-carbon) sugar:

  • In RNA is ribose.

  • In DNA is deoxyribose.

  • Has carbon atoms numbered with primes to distinguish them from the nitrogen bases.

Ola Fouad Talkhan


Nucleosides

Nucleosides

A nucleoside:

  • Has a nitrogen base linked by a glycosidic bond to C1’ of a ribose or deoxyribose.

  • Is named by changing the the nitrogen base ending to -osine for purines and –idine for pyrimidines

HO

Ola Fouad Talkhan


Nucleotides1

Nucleotides

A nucleotide:

  • Is a nucleoside that forms a phosphate ester with the C5’ OH group of ribose or deoxyribose.

  • Is named using the name of the nucleoside followed

    by 5’-monophosphate.

  • In a nucleoside ,the glycosidic C-1 atom of the pentose bonded to

    N-1 of the pyrimidine

    or N-9 of the purine base

Ola Fouad Talkhan


Nitrogenous bases ribose nucleosides nucleoside phosphate group nuclotides

Nitrogenous bases + ribose = NucleosidesNucleoside + Phosphate group = Nuclotides

Ola Fouad Talkhan


Names of nucleosides and nucleotides

Names of Nucleosides and Nucleotides

Ola Fouad Talkhan


Primary structure of nucleic acids

Primary Structure of Nucleic Acids

In the primary structure of nucleic acids:

  • Nucleotides are joined by phosphodiester bonds.

  • The 3’-OH group of the sugar in one nucleotide forms an ester bond to the phosphate group on the 5’-carbon of the sugar of the next nucleotide.

Ola Fouad Talkhan


Primary structure of nucleic acids1

Primary Structure of Nucleic Acids

Ola Fouad Talkhan


Structure of nucleic acids

Structure of Nucleic Acids

A nucleic acid polymer:

  • Has a free 5’-phosphate group at one end and a free 3’-OH group at the other end.

  • Is read from the free 5’-end using the letters of the bases.

  • This example reads

    5’—A—C—G—T—3’.

Ola Fouad Talkhan


Unit nucleic acids

RNA

  • In RNA, A, C, G, and U are linked by 3’-5’ ester bonds between ribose and phosphate.

Ola Fouad Talkhan


Types of rna

Types of RNA

Ola Fouad Talkhan


Unit nucleic acids

DNA

  • In DNA, A, C, G, and T are linked by 3’-5’ ester bonds between deoxyribose and phosphate.

Ola Fouad Talkhan


Dna double helix a secondary structure

DNA Double Helix: A Secondary Structure

In DNA:

  • There are two strands of nucleotides that wind together in a double helix.

  • Two hydrogen bonds form between the complementary base pairs A-T.

  • Three hydrogen bonds form between the complementary base pairs G-C.

Ola Fouad Talkhan


Unit nucleic acids

The negatively charged phosphate group and the sugar units expose themselves to the outside of the chain.

Ola Fouad Talkhan


Dna double helix structure

DNA Double Helix Structure

Ola Fouad Talkhan


Unit nucleic acids

The antiparallel nature of the DNA double helix.

Ola Fouad Talkhan


Unit nucleic acids

The DNA Double Helix

Watson and Crick were Proposed a structure of DNA double helix

The double helix is stabilized by hydrogen bonds and hydrophobic interactions

Ola Fouad Talkhan


Unit nucleic acids

1.Two helical polynucleotide chains are coiled around a common axis. The chains run in opposite directions, (anti parallel).2. The two antiparallel polynucleotide chains are not identical, but they are complimentary.3.The purine, pyrimidine bases are on the inside of the helix, the phosphate and deoxyribose groups are on the outside.4. The two chains are held together by hydrogen bonds between pairs of bases. Adenine is two hydrogen bonds (A= T), Guanine is bonded to cytosine by three hydrogen bonds (G=C)

Ola Fouad Talkhan


Comparison between dna and rna

Comparison between DNA and RNA

  • DNA - one type, one purpose .

  • RNA - Several types, several purposes:

    • ribosomal RNA - the basis of structure and function of ribosomes (largest amount).

    • messenger RNA - carries the message for protein synthesis (fewest and unique).

    • transfer RNA - carries the amino acids for protein synthesis (smallest molecules).

Ola Fouad Talkhan


Dna replication

DNA Replication

The duplication of DNA to give two DNA molecules identical to the original one.

DNA in the chromosomes replicates itself every cell division

•Maintains correct genetic information

DNA replication involves:

  • Unwinding the DNA

  • Pairing the bases in each strand with new bases to form new complementary strands.

  • Producing two new DNA strands that exactly duplicate the original DNA.

Ola Fouad Talkhan


Unit nucleic acids

  • Before new DNA strands can form, there must be RNA primers present to start the addition of new nucleotides.

  • Primase is the enzyme that synthesizes the RNA Primer.

  • DNA polymerase can then add the new nucleotides

DNA polymerase can only add nucleotides to the 3’ end of the DNA.

•This causes the NEW strand to be built in a 5’ to 3’ direction

Ola Fouad Talkhan


Unit nucleic acids

DNA Replication - General considerations

Replicating DNA

A. Function of replication.

  • Proteins must have the correct shape.

  • The shape is determined by the primary structure (amino acid sequence.

Base Pairing & Double Helix

  • The amino acid sequence is determined by the gene (the sequence of bases in the DNA).

Ola Fouad Talkhan


Unit nucleic acids

Information Transfer in Cells

Figure 10.1

The fundamental process of information transfer in cells.

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Transcription

Transcription

  • Process of copying DNA to mRNA

  • Differs from DNA synthesis in that only one strand of DNA, the template strand, is used to make mRNA

  • Does not need a primer to start as RNA polymerases have ability to initiate synthesis de novo

  • Can involve multiple RNA polymerases

  • Divided into 3 stages

  • Initiation

  • Elongation

  • Termination

Ola Fouad Talkhan


Transcription synthesis of mrna

Transcription: Synthesis of mRNA

Intranscription:

  • A section of DNA containing the gene unwinds.

  • One strand of DNA is copied starting at the initiation point, which has the sequence TATAAA.

  • An mRNA is synthesized using complementary base pairing with uracil (U) replacing thymine (T).

  • The newly formed mRNA moves out of the nucleus to ribosomes in the cytoplasm.

Ola Fouad Talkhan


Rna polymerase

RNA Polymerase

  • During transcription, RNA polymerase moves along the DNA template in the 3’-5’direction to synthesize the corresponding mRNA.

  • The mRNA is released at the termination point.

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Unit nucleic acids

Translation

  • Interpreting the information coded in the mRNA into proteins

  • The nucleotides are read in triplets (set of three) called codons

  • Each triplet code for a specific amino acid, and sometimes more than one codon exist for an amino acid

  • mRNA are read by the translational machinery including ribosomes, tRNAs and rRNAs

  • Like transcription, it also includes initiation, elongation and termination

Ola Fouad Talkhan


Translation

Translation

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Unit nucleic acids

DNA Replication - General considerations

The flow of genetic information in the cell.

A. Function of replication.

  • Proteins must have the correct shape.

  • The shape is determined by the primary structure (amino acid sequence.

  • The amino acid sequence is determined by the gene (the sequence of bases in the DNA).

DNA  RNA  protein

Ola Fouad Talkhan


Unit nucleic acids

Mutation

  • A change or alteration that occurs in the DNA. Mutations can be caused by the environment (sun, radiation, or chemicals), aging, or chance. Some mutations do not affect the information contained in the DNA. Other mutations have serious consequences on how that gene functions.

Ola Fouad Talkhan


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