Nucleotides Flashcards
what are nucleotides
Biologically ubiquitous substances that participate in nearly all biochemical processes
List 5 functions of nucleotides
> they form the monomeric units of nucleic acids and play a central role in the storage and expression of genetic information
nucleoside triphosphates, such as ATP, are high energy end products of most energy-releasing pathways and they are utilized by most energy-requiring pathways
most metabolic pathways are regulated by the levels of nucleotides, e.g. ATP and ADP
nucleotide derivatives such as, nicotinamide adenine diphosphate, flavin adenine diphosphate and coenzyme A, participate in enzymatic reactions
nucleotides are components of ribozymes(enzyme-like nucleic acids) and nucleotides have their own important catalytic activities
Define a nucleotide
Nucleotides are phosphate esters of a five-carbon sugar residue that is covalently linked to a nitrogenous base at their C1’
What is the difference between a ribonucleotide and a deoxyribonucleotide
A ribonucleotide is a monomer of RNA and the pentose is D-ribose, whereas deoxyribonucleotide is a monomer of DNA and its pentose is 2’- deoxy-D-ribose
What are the components of a nucleotide
A sugar residue, a phosphate group, and a nitrogenous base
What are the components of a nucleoside
A sugar residue and a nitrogenous base
Define a nitrogenous base
A planar, aromatic, heterocyclic molecule that is a derivative of either purine or pyrimidine
Define nucleic acid
Nucleic acids are linear polymers of nucleotides whose phosphate groups bridge the 3’and 5’ posutions of successive sugar residues
Why are nucleic acids polyanions at physiological pHs
The phosphodiester groups are acidic
What does this mean- polynucleotides have directionality
They have a 3’ end and a 5’ end
List Chargaffs rules
> DNA has an equal amount of adenine residues and thymine residues, as well as an equal amount of cytosine and guanine residues. The structural basis of chargaffs rules is that in double-stranded DNA adenine is hydrogen-bonded to thymine and cytosine is hydrogen-bonded to guanine.
Also it was found that the base composition of DNA in a given organism is characteristic of that organism. This means that DNAs base composition differs among different organisms but is constant among species.
Discuss the modification of nucleic acids
Some DNAs contain bases that are chemical derivatives of the standard set. The altered bases are generated by sequence-specific enzymatic modification of normal DNA. The modified DNA obeys chargaffs rules. Many bases in RNA, particularly tRNA, can also be derived.
Is RNA or DNA susceptible to base-catalyzed hydrolysis
RNA is highly susceptible to base-catalyzed hydrolysis, not DNA. DNA is resistant to base-catalyzed hydrolysis because it lacks the 2’-OH group and is, therefore, more chemically stable than RNA. This is probably why DNA and not RNA carries genetic information.
Does double-stranded RNA obey chargaffs rules
Yes
