Nucleotides Flashcards
Central dogma?
How genetic info flows in one direction from DNA - RNA - Protein
When you stretch out a chromosome, what d’you get
Chromosome - chromatid - solenoid - nucleosome - histones - DNA (which collectively form genes)
What serves as the building block of DNA
Nucleotides
What is the nucleotide made of
Sugar (deoxyribose/ribose), nitrogenous base, Phosphate group
nucleoside consists of ……?
hence nucleoside + ……. = nucleotide
nucleoside consists of ‘sugar + base’
hence nucleoside + phosphate = nucleotide
What bond exists between a sugar and another group? (eg: base)
Glycosidic bond (covalent bond between a carb and another compound)
What bond exists between the Phosphate and sugar in a nucleotide
Ester bond (a covalent bond).
Two bonds in a chain - phosphodiester bond
what are pentoses?
5-C sugars or carbohydrates.
(NB: their numbering is primed)
Why are 5’ and 3’ the most important carbons in the ribose and deoxyribose sugars
These two carbons are involved directly in the formation of the nucleic acid (chain of nucleotides). They are the carbons that bond to the phosphates
NB: draw structure for revision
Why are deoxyribose sugars sometimes called 2’ - deoxyribose
Because in it’s structure, there’s a lacking oxygen on the 2’ - C
In purines and pyrmidines, which ‘N’ atoms form the glycosidic bond with the sugar
Purines = N-9
Pyrimidines = N-1
(Refer to notes for diagram)
mention the purines and pyrimidines
Purines = A G
Pyrymidines = T U C
{Adenine, guanine, thymine, uracil, cytosine)
Which bases occur in deoxynucleotides only? and which ones in ribonucleotides only?
Thymine = deoxynucleotide only
Uracil= ribonucleotide only
{A,G, C} occur in both
Explain “ Adenosine triphosphate” (ATP)
“Adenosine” means the the base in this ribonucleoside is adenine and because it is a purine, it ends in ‘sine’.
Triphosphate shows that the ribonucleoside is bonded to three phosphates.
[if this was a deoxynucleotide, ‘adenosine’ would have been ‘deoxyadenosine’. This applies to Guanosine too]
Explain “Uridine monophosphate” (UMP)
The base in this ribonucleotide is Uracil, and since it’s a pyrimidine, it ends in “-dine”
monophosphate means the ribonucleoside bonds to one phophate.
[uridine can not exist in deoxynucleoside as deoxyuridine, because it is found in ribonucleotides only.]
[vice versa applies to deoxythymidine. Cytosine however occurs in both]
Difference between bonds of A-T and G-C?
A-T is a double bond
G-C is a triple bond (the stability of DNA depends on it)
What does the stability of a dsDNA depend on
G-C bond,
sequence (how the molecules are stacked),
length of the molecule.
What are the common forms of DNA
B, A, Z (in that order)
C and D are not common
what specialized portion of DNA at the ends of linear chromosomes aids in replication
telomere (single stranded)
Which two adenosine derivatives perform a similar function in carrying hydrogen and high power electrons for the synthesis of ATP?
Nicotinamide Adenine Dinucleotide (NAD)
Flavin Adenine Dinucleotide (FAD)
Function of Cyclic Adenosine Monophosphate (cAMP)?
= Regulates metabolism (facilitates the mobilization of glucose and fatty acid reserves / glycogen and lipids)
= Second messenger in signal transduction
What are analogues?
Analogues are organic compounds related to another by substition of an atom with other groups
OR chemically synthesised nucleotides used as drugs in clinical therapy.
In nucleotides, analogues are prepared by altering the base ring or sugar moiety.
hat disease does the analogue “allopurinol” treat?
gout
