DMOZ Directory Web Directory Macromolecules and genetic information - الدكتور

Macromolecules and genetic information

شارك:

Informational macromolecule :


  • means very long molecule 
  • these are DNA,RNA and Protein as they contain biological information in their sequences 
steps in informational flow :

  1. Replication 
  2. Transcription 
  3. Translation
DNA replicate , transcription occur to give RNA and translation occur to form proteins
Macromolecules and genetic information



NUCLEIC ACIDS: 

Macromolecules and genetic information

  • Nucleic acid is a polymer consist of monomers called nucleotides linked together by phosphodiester bond
  • consists of 3 parts :
  1. pentose sugar 
  2. phosphate group 
  3. nitrogenous base 

Nucleic polymer : 



  • Backbone consists of sugar to phosphate bond
  • phosphodiester bond : 
  1.  new base added to sugar at carbon 3 
  2. polymer grows in 1 direction 
  • Nitrogen bases hang off the sugar-phosohate backbone 

Nucleotides:



  • nitrogen base(C-N ring) 
  • pentose sugar (5C) : ribose in RNA and deoxyribose in DNA 
  • phosphate group
why DNA is more stable than RNA ?

  1. The absence of hydroxyl group at carbon 2 in the pentose sugar (presence of oxygen atom in RNA make it more reactive and less chemically stable than DNA 
  2. the hydrogen bond between nitrogen bases in the DNA double strand
Nitrogenous bases :
Macromolecules and genetic information

  1. PURINES: double ring bases , adenine(A) and guanine(G)
  2. PYRIMIDINES: single ring bases , cytosine(C),(thymine(T)in DNA and urascil(U)IN RNA)   

PAIRING OF NITROGENOUS BASES :
Macromolecules and genetic information

  • PURINE WITH PYRIMIDINE 
  1. A with T by 2 H bonds
  2. G with C by 3 H bonds

Chargaff's rules(nucleotide base pairing):



  • States that DNA drom any cell of all organisms should have a 1:1 ratio (base pair rule )of pyrimidine and purine bases,more spesifically, that the amount of guanine is equal to cytosine and the amount of adenine is equal to thymine 

  • phosphate group :

  1. consists of phosphorus atom bonded to 4 oxygen atoms 
  2. always bonded to 5 carbon atom of the sugar 



  • Are nucleic acids are charged molecules?


  • Yes,due to the presence of phosphate,which dissociates at the PH found inside cells,freeing hydrogen ions and leaving the phosphate negatively charged,and thus giving the acidic character of nucleotides 
  • Because the charges attract proteins,most nucleic acids in cells are associated with proteins  

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