Nucleotide Structure, Function, and Metabolism

Question 1

How many hydrogen bonds are formed between adenine and thymine?

Answer 1

2 Hydrogen Bonds

Question 2

How many hydrogen bonds are formed between guanine and cytosine?

Answer 2

3 Hydrogen Bonds

Question 3

Why are chromosomes typically found as unwound chromatin within the nucleus and not in the typical perceived chromosome form? Also, in what phase of the cell cycle would this be?

Answer 3

So that the DNA is available for transcription of genes.

During Interphase

Question 4

Roughly how many nucleotides make up our genome?

Answer 4

3 Billion

Question 5

What 2 DNA binding proteins are involved in forming chromosomes?

Answer 5

Histones and Non-histone chromosomal proteins

Question 6

How many more times condensed are chromosomes compared to interphase DNA?

Answer 6

Mitotic chromosomes are condensed 500 times compared to interphase DNA.

Question 7

What makes up chromatin?

Answer 7

proteins and nuclear DNA

Question 8

True or False:

Nucleotides are the phosphate ethers of nucleosides.

Answer 8

False - nucleotides are the phosphate esters of nucleosides.

Question 9

What components make up a nucleotide?

Answer 9

Base - Sugar - Phosphate

Question 10

What components make up a nucleoside?

Answer 10

Base - Sugar

Question 11

Which carbon of the sugar is the base attached to in nucleotides, and what type of linkage is this between the nitrogen of the base and carbon of the sugar?

Answer 11

Base is attached to Carbon 1 on the sugar via a Beta-glycosidic linkage.

Question 12

Which bases have a 2 ring structure?

Answer 12

Purines have a 2 ring structure and they’re:

• adenine (A)
• guanine (G)
• hypoxanthine (I)
• xanthine (X)

Question 13

Which bases have a 1 ring structure?

Answer 13

Pyrimidines have a 1 ring structure and they’re:

• cytosine (C)
• Uracil (U)
• Thymine (T)

Question 14

Which carbon is hydrolyzed to make deoxyribose into ribose?

Answer 14

Carbon 2’

Question 15

What type of bond in ATP links the alpha phosphate group to the ribose sugar?

Answer 15

phosphoric acid ester bond

Question 16

How is the structure of DNA written and synthesized in respect to sugar attachment?

Answer 16

Written and Synthesized 5’ -> 3’

Question 17

What type of bond links the beta and gamma phosphate groups to each other and the alpha phosphate group?

Answer 17

phosphoric acid anhydride bonds

Question 18

Of the listed reactions, rank in order of decreasing entropy:

I) ATP -> ADP + Pi
II) ATP -> AMP + PPi
III) PPi -> Pi + Pi

Answer 18

II > I > III

Question 19

How many anstrom is in 1 turn of the DNA helix? Also, how many base pairs are there per turn?

Answer 19

34 A

10 base-pairs/turn

Question 20

Do the bases within the DNA helix point inwards or outwards?

Answer 20

Inwards

Question 21

DNA exists in multiple forms, but which is the most common and is it hydrated or not?

Answer 21

Mostly B form, which is the hydrated form.

Question 22

Is DNA replication conservative, non-conservative, or semiconservative?

Answer 22

Semiconservative

**experiment is in book.

Question 23

Do humans have reverse transcriptase like viruses have?

Answer 23

YES

Question 24

During the joining of the primer strand at the 5’ to 3’ position, how many inorganic phosphates are cleaved (released)?

Answer 24

2 - PPi

Question 25

Note that each phosphodiester linkage in the backbone of both DNA and RNA has a negative charge. This negative charge is important in protecting DNA or RNA from?

Answer 25

Negative charge repels nucleophilic species such as hydroxide ion, which are capable of hydrolytically cleaving the phosphodiester linkages of the nucleic acid backbone. *The absence of the 2' - hydroxyl group in DNA further increases its resistance to hydrolysis.

Question 26

In the digestion of RNA, which enzyme cleaves RNA into short RNA oligomers?

Answer 26

Ribonucleases

Question 27

Which enzyme cleaves the phosphdiester bond of either DNA oligomers or RNA oligomers into nucleoside monophosphates (NMPs) or dexoynucleoside monophosphates (dNMPs)?

Answer 27

Phosphodiesterases

Question 28

Which enzymes convert NMPs and dNMPs in to nucleosides and deoxynucleosides?

Answer 28

Nucleotidases

Question 29

What enzyme removes ribose or deoxyribose from its base, resulting in pyrimidines or purines and ribose or deoxyribose sugars?

Answer 29

Nucleosidases

Question 30

The formation of which molecule in purine synthesis is the committed step of the reaction?

Answer 30

phosphoribosyl amine

Question 31

What are the two salvage enzymes in purine synthesis?

Answer 31

1) hypoxanthine guanine phosphoribosyl transferase | 2) adenine phosphoribosyl transferase

Question 32

What sources provide the ring atoms in purine bases?

Answer 32

``` CO2 Gln Gly Asp N10-formyl THF ```

Question 33

During purine synthesis, which amino acid contributes carbons 4 and 5, along with the 7th nitrogen?

Answer 33

Glycine

Question 34

List the different purine bases.

Answer 34

adenine guanine hypoxanthine xanthine

Question 35

What is phosphoribosyl pyrophosphate (PRPP) synthesized from?

Answer 35

ribose phosphate and ATP

Question 36

What molecule is a central constituent of nucleotide metabolism?

Answer 36

PRPP *phosphoribosyl pyrophosphate