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21 Carboxylic Acid Derivatives -- Part 10
The presence of uracil inRNA is different to the presence of thymine in DNA.
It is simply uracil with an additional group.
There are four common bases of DNA.
The bases in ribonucleosides and ribonucleotides are similar to these four bases.
The structures show the common nucleosides.
The same structures with different groups are found at the 5' positions.
There are no hydroxy groups on the 2' carbon atoms of the ribose rings in the structure of the DNA.
The bases attached to the deoxyribose units carry the genetic information.
We now consider how the nucleotide sequence is reproduced or transcribed into another molecule.
The hydrogen-bonding interaction between specific pairs of bases is what transfers this information.
Each pyrimidine base forms a stable hydrogen-bonded pair with only one of the two purine bases.
Each purine base has a hydrogen-bonded pair with a specific pyrimidine base.
The maps show that hydrogen bonding takes place between nitrogen and oxygen atoms.
Two hydrogen bonds are joined by a base pair of uracil and adenine.
The lengths of hydrogen bonds have to be the same in order to form a structure.
In 1950, it was suspected that various DNAs, taken from a wide variety of species, had about equal amounts of adenine and thymine and guanine and cytosine.
The rings of the four bases are aromatic.
James D. Watson and Francis C. Crick were the first to use X-ray diffraction patterns to determine the structure of DNA.
They found that there are two hydrogen bonds between the pairs of bases.
One strand runs from the left to the right while the other runs from the left to the right.
There are two strands of DNA with all the base pairs hydrogen bonding together.
The strands are running in opposite directions.
The two strands of DNA are coiled around the same axis and have a 20 A in diameter.
The helix makes a complete turn for every tenth of a second.
The two sugar-phosphate backbones form the vertical double helix in this drawing.
The attractive stacking forces between the pi clouds of the aromatic pyrimidine and purine bases help to stable the arrangement.
Two strands are joined by another.
C. G A.
A strand is assembled.
A double electron micrograph.
There is a lot of knowledge about the translation of the DNA/RNA sequence of bases into proteins.
The versatile biomolecules serve a variety of additional functions, even though we generally think of them as the monomers that form DNA and RNA.
There are a few additional uses of nucleotides.
The 3'@ and 5'@hydroxy groups are both esterified by the samephosphate group.
One of the main oxidation-reduction reagents in biological systems is nicotine adenine dinucleotide.
One ribose has nicotinamide and the other has adenine.
It is possible that adenosine acts as a neurotransmitter that causes sleep.
The wakefulness cal oxidation of an alcohol is caused by the oxidizing agent in the biologi receptor being NAD+.
The nicotinamide portion of NAD is shown in the picture.
The alcohol dehydrogenase is the catalyst for this reaction.
Most anhydrides are exothermic.
The products that are used in the process are adenosine diphosphate.
The heat of hydration explains the exothermic nature of the products.
The heat of hydration is different between the two, with the former being hydrated about as well as the latter.
The three negatively charged groups in ATP are reduced by hydrolysis.
31 kJ of energy per mole ofATP is freed by hydrolysis.
The energy that muscle cells use to contract is the same energy that all cells use to drive their chemical processes.
The acetal form of a sugar is the anomeric carbon of a glycoside.
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