Test 2 - Nucleotides and Nucleic Acids Flashcards
What are the two purines?
Adenine and Guanine
What are the two pyrimidines?
Cytosine, Thymine (DNA) and Uracil (RNA)
When AT is bound what are the molecules?
Thymine (keto) and Adenine (amino)
When CG is bound what are the molecules?
Cytosine (Amino) and Guanine (Keto).
Roles of Nucleotides
>Molecular repository of genetic info >Energy currency of the cell >Essential Chemical links in signal transduction >Structural components of a variety of enzyme factors and metabolic intermediates.
Four levels of Gene Expression Control?
- Transcriptional Control 2. RNA processing control 3. Translation Control 4. Protein activity control.
Localization is used as a control measure at what levels?
mRNA and protein levels.
What is the fifth layer of gene control?
Epigenetics
What is this molecule?
5 - Hydroxymethylcytidine
What is this Molecule?
N6 - Methyladenosine
What is this molecule?
5 - Methylcytidine
What is this molecule?
N2 - Methylguanosine
If thymine loses its 5-Methyl group what molecule does it become?
Why is this bad?
Uracil (RNA)
Uracil causes DNA to become less stable
Define Depurination
Hydrolysis of N-ß-gylcosyl bond between base and pentose
Define Tautomerization
Formal migration of a hydrogen atom or proton
What is this Minor tRNA?
Inosine
Hydrogen bonds in the 2.5 - 3.2 A range are what?
Moderate, mostly electrostatic, like most hydrogen bonds in proteins.
DNA or RNA is more stable?
DNA
Deamination causes the spontaneous conversion of Cytosine to Uracil at a rate of what?
1 : 107 in 24 hours
About 100 spontaneous events per day in a mammalian cell
Spontaneous deamination occurs more often in what pairing?
Cytosine to Uracil
Deamination of Adenine results in?
Hypoxanthine
Deamination of Guanine results in?
Xanthine
What is almost certainly the reason for DNA containing Thymine?
Cytosine readily deaminates to Uracil.
This occuring with both being read for DNA would result in miss match base pairing.
How many hydrogen bonds between Adenine and Thymine?
2
How many hydrogen bonds between Guanine and Cytosine?
3
Depurination creates what?
An abasic site
Depurination happens more often in purines or pyrimidines?
Purines
Depurination is much slower in what molecules?
Ribonucleotides and RNA
Ricin, a naturally occuring lecin, found in the castor oil plant works by?
Depurination of rRNA
Lethal dose of ricin?
LD50 = 22 micrograms/kg
1 mg/kg if ingested orally
Structure of Nucleotides?
Pentose with a purine or pyrimidine base on C1, and with energy (Phosphate group) on C5
C2 has and OH group inRNA
C2 has an H group in DNA
What is the cellular currency of free energy?
ATP
What is the energy that cells can and must use to maintain their order?
Free energy
Where is the energy located in ATP?
Energy is present in the electrostatic repulsion that exists in the four negative charges of ATP.
The actual energy a cell derives from hydrolysis of ATP can be _______ that of free energy?
Twice as much
What molecule acts as a charge insulator for phosphate on ATP?
Mg2+
Energy for Conformational Changes comes from?
ATP
ATP or it’s derivatives provide energy for what systems?
Conformational changes
Regulatory signals
Signal Transduction Cascades
Co-enzymes (They participate in Redox reactions.)
