- #Dna molecule sugar phosphate backbone and nucleotides code
- #Dna molecule sugar phosphate backbone and nucleotides free
( dAMP, dCMP, dGMP, dTMP, for the DNA versions - deoxyribonucleotides)īut some have more than one phosphate group:ĪTP, ADP - adenosine triphosphate and diphosphate (and also GTP and GDP) are well known for their role in energy transfer in respiration and metabolic reactions in general, and UTP in glycogen synthesis These are given slightly different names:Īnd a nucleotide consists of a nucleoside attached to a (single) phosphate group.ĪMP, CMP, GMP, UMP for the RNA versions - ribonucleotides The names of, or abbreviations for, the 5 (nitrogenous organic) bases in nucleic acids are generally quite well known.Ī nucleoside normally consists of a nitrogenous base section bonded to a pentose sugar. Of course DNA has deoxyribose, and thymine not uracil.ĭo not confuse the base thymine with thiamine - the vitamin (B1) The diagram at the right could be a short section of RNA, or a single strand of DNA. In fact the 3' ends of DNA and RNA molecules have hydroxyl groups (-OH), whereas all the other nucleotides have phosphate groups attached at the 3' position. This process only works in one direction, adding nucleotides to the 3' end of the developing polynucleotide chain. The 3' and 5' labels are important in identifying the ends of nucleic acid strands, and showing the direction of propagation. This is then called a phosphodiester bond, and it is quite a strong linkage but it is flexible and can rotate somewhat so the strand can become curved.Ī polynucleotide is formed when this process is repeated many times.Īs a result, the backbone of DNA and RNA is made up from alternating sugar and phosphate groups which are not easily broken apart. Two nucleotides can join together by forming another covalent bond between a phosphate group and carbon 3' on the next pentose sugar. Interestingly, the bases form a flat section across the middle of the DNA molecule, but thymine's methyl group is the only section that projects somewhat from this.Ī trinucleotide Phosphodiester bonds are shown within green boxes. This would result in a uracil which would cause problems in DNA. In particular, cytosine could become deaminated (and pick up a >O group). It has been suggested that this modification is more suited to DNA's role as a long-term store of information in that error-checking enzymes have evolved to bypass this base (thymine) as they screen for bases which might result from chemical changes which could result in mutations. Thymine is the same as uracil, but with a methyl group off to one side. The O shown in red spans between C1 and C4, forming an ether linkage. ( -OH can make the C3 phosphate bond susceptible to alkaline hydrolysis) Hydroxyl (-OH) groups are the basis for bonds with other groups, formed by condensation reactions:Ĭ1 to the organic base, C5 to the phosphate group.Īnd C3 bonds with phosphate on the next nucleotide ( see below).ĭNA does not have an -OH group at C2, which increases its long-term chemical stability
#Dna molecule sugar phosphate backbone and nucleotides code
The order of bases contains the information needed to code for amino acids in proteins during translation.Ribose and deoxyribose - possible bonding sitesĬarbon numbers are shown without ' - prime.Hydrogen bonds stabilize the double helix, but can be broken when DNA needs to be accessed.A complementary strand can always be synthesized from a single strand, due to the arrangement of hydrogen bonds between GC and AT bases.Important properties that are derived from the DNA structure are: (OpenStax-CNX)Īs for most biological molecules, the structure is important to the function, and the function of DNA is to contain information.
#Dna molecule sugar phosphate backbone and nucleotides free
The 5ʹ end is the one where carbon #5 is not bound to another nucleotide the 3ʹ end is the one where carbon #3 is not bound to another nucleotide and has a free hydroxyl group. (c) The direction of each strand is identified by numbering the carbons (1 through 5) in each sugar molecule. (b) The two DNA strands are antiparallel to each other. (a) The sugar-phosphate backbones are on the outside of the double helix and purines and pyrimidines form the “rungs” of the DNA helix ladder. \):Watson and Crick proposed the double helix model for DNA.
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