Test 2 - Nucleotides and Nucleic Acids

Question 1

What are the two purines?

Answer 1

Adenine and Guanine

Question 2

What are the two pyrimidines?

Answer 2

Cytosine, Thymine (DNA) and Uracil (RNA)

Question 3

When AT is bound what are the molecules?

Answer 3

Thymine (keto) and Adenine (amino)

Question 4

When CG is bound what are the molecules?

Answer 4

Cytosine (Amino) and Guanine (Keto).

Question 5

Roles of Nucleotides

Answer 5

>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.

Question 6

Four levels of Gene Expression Control?

Answer 6

1. Transcriptional Control 2. RNA processing control 3. Translation Control 4. Protein activity control.

Question 7

Localization is used as a control measure at what levels?

Answer 7

mRNA and protein levels.

Question 8

What is the fifth layer of gene control?

Answer 8

Epigenetics

Question 9

What is this molecule?

Answer 9

5 - Hydroxymethylcytidine

Question 10

What is this Molecule?

Answer 10

N⁶ - Methyladenosine

Question 11

What is this molecule?

Answer 11

5 - Methylcytidine

Question 12

What is this molecule?

Answer 12

N² - Methylguanosine

Question 13

If thymine loses its 5-Methyl group what molecule does it become?

Why is this bad?

Answer 13

Uracil (RNA)

Uracil causes DNA to become less stable

Question 14

Define Depurination

Answer 14

Hydrolysis of N-ß-gylcosyl bond between base and pentose

Question 15

Define Tautomerization

Answer 15

Formal migration of a hydrogen atom or proton

Question 16

What is this Minor tRNA?

Answer 16

Inosine

Question 17

Hydrogen bonds in the 2.5 - 3.2 A range are what?

Answer 17

Moderate, mostly electrostatic, like most hydrogen bonds in proteins.

Question 18

DNA or RNA is more stable?

Answer 18

DNA

Question 19

Deamination causes the spontaneous conversion of Cytosine to Uracil at a rate of what?

Answer 19

1 : 10⁷ in 24 hours

About 100 spontaneous events per day in a mammalian cell

Question 20

Spontaneous deamination occurs more often in what pairing?

Answer 20

Cytosine to Uracil

Question 21

Deamination of Adenine results in?

Answer 21

Hypoxanthine

Question 22

Deamination of Guanine results in?

Answer 22

Xanthine

Question 23

What is almost certainly the reason for DNA containing Thymine?

Answer 23

Cytosine readily deaminates to Uracil.

This occuring with both being read for DNA would result in miss match base pairing.

Question 24

How many hydrogen bonds between Adenine and Thymine?

Answer 24

2

Question 25

How many hydrogen bonds between Guanine and Cytosine?

Answer 25

3

Question 26

Depurination creates what?

Answer 26

An abasic site

Question 27

Depurination happens more often in purines or pyrimidines?

Answer 27

Purines

Question 28

Depurination is much slower in what molecules?

Answer 28

Ribonucleotides and RNA

Question 29

Ricin, a naturally occuring lecin, found in the castor oil plant works by?

Answer 29

Depurination of rRNA

Question 30

Lethal dose of ricin?

Answer 30

LD₅₀ = 22 micrograms/kg

1 mg/kg if ingested orally

Question 31

Structure of Nucleotides?

Answer 31

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

Question 32

What is the cellular currency of free energy?

Answer 32

ATP

Question 33

What is the energy that cells can and must use to maintain their order?

Answer 33

Free energy

Question 34

Where is the energy located in ATP?

Answer 34

Energy is present in the electrostatic repulsion that exists in the four negative charges of ATP.

Question 35

The actual energy a cell derives from hydrolysis of ATP can be _______ that of free energy?

Answer 35

Twice as much

Question 36

What molecule acts as a charge insulator for phosphate on ATP?

Answer 36

Mg²⁺

Question 37

Energy for Conformational Changes comes from?

Answer 37

ATP

Question 39

ATP or it’s derivatives provide energy for what systems?

Answer 39

Conformational changes

Regulatory signals

Signal Transduction Cascades

Co-enzymes (They participate in Redox reactions.)