Chapter 21: Structure/Function of Nucleotides and Nucleosides

Question 1

Nucleotide definition

Answer 1

• A compound formed by nitrogenous base attached by a B-N-glycosydic linkage to a sugar and 1 or more phosphate groups

Question 2

Nucleotides are

Answer 2

• Monomeric subunits of nucleic acids

Question 3

Nucleotides exist as

Answer 3

• Polynucleotides in both DNA and RNA

Question 4

If the phosphate group is lacking, it is considered

Answer 4

• A nucleoside

Question 5

Nucleosides are

Answer 5

• Nitrogenous base plus sugar

- No phosphate groups

Question 6

Since the stable phosphodiester bond links 3’ and 5’ carbons or adjacent monomers,

Answer 6

• Each end of a polymer (DNA polynucleotide segment) is distinct

Question 7

Nucleic acids contain

Answer 7

• 5 major nitrogenous substituted bases

Question 8

Purines

Answer 8

• Adenine

- Guanine

Question 9

Pyrimidines

Answer 9

• Cytosine
• Thymine
• Uracil

Question 10

All nucleic acids contain

Answer 10

• A, G, and C

Question 11

DNA (but not RNA) also contains

Answer 11

• T

Question 12

RNA (but not DNA) also contains

Answer 12

• U

Question 13

Nitrogenous bases absorb

Answer 13

• UV light

Question 14

Purine bases are numbered

Answer 14

• Counter clockwise direction

Question 15

Purine bases include

Answer 15

• Adenine
• Guanine
• Hypoxanthine
• Xanthine

Question 16

Pyrimidine bases are numbered

Answer 16

• Clockwise direction

Question 17

Minor purine bases

Answer 17

• N2-Dimethylguanine
• N2-Dimethyladenine
• 1-Methylguanine

Question 18

Purines or pyrimidines that exist in two or more forms

Answer 18

• Tatomerization

- Depends on pH

Question 19

Ring substituents participate in

Answer 19

• Keto-enol tautomerism

- Amine-imine tautomerism

Question 20

Most predominant forms of tautomerization

Answer 20

• Keto

- Amino

Question 21

Physiologic conditions strongly favor

Answer 21

• The amino and keto forms

Question 22

At near neutral pH present in the cell, these bases are

Answer 22

• Hydrophobic and thus insoluble in water

Question 23

The ability of DNA to absorb UV light is increased following

Answer 23

• Denaturation (hyperchromic shift)

Question 24

Methylated forms of purines from plants

Answer 24

• Caffeine

- Theophylline

Question 25

Caffeine from coffee beans

Answer 25

- Inhibits phosphodiesterase activity

Question 26

Theophylline is found in

Answer 26

- Tea leaves

Question 27

Synthetic analogs of clinical interest

Answer 27

- Anticancer agents - 6-mercaptopurine - 5-fluorouracil - Cytosine arabinoside (ara C)

Question 28

6-mercaptopurine

Answer 28

- Inhibits purine nucleotide biosynthesis | - Used in treatment of childhood leukemia

Question 29

5-fluorouracil

Answer 29

- Thymine analog

Question 30

Cytosine arabinoside (ara C)

Answer 30

- Found in sponges - Inhibits DNA and RNA polymerase activity - Used in treatment of non-Hodgkin lymphoma

Question 31

Ribonucleotides and deoxyribonucleotides differ in

Answer 31

- Sugar component

Question 32

Nucleotides are phopshorylated esters of

Answer 32

- Nucleosides (mostly on C5)

Question 33

Nucleotide functions

Answer 33

- Precursors of DNA and RNA - Group transfer - Transducers of free energy - Portion of coenzymes - Allosteric regulation - Biosynthesis - Second messengers

Question 34

Nucleotides cannot be used as

Answer 34

- Primary sources of energy

Question 35

Adenosine derivatives are important in

Answer 35

- Cellular communication

Question 36

The monomeric building blocks of nucleic acids are

Answer 36

- Nucleotides

Question 37

Nucleotides are compose of three distinct parts

Answer 37

- Substituted nitrogenous base - Five carbon sugar - One or more phosphate groups

Question 38

Nucleosides are composed of

Answer 38

- Sugar and nitrogenous base | - Lack the phosphate group

Question 39

Nucleotides perform a variety of functions in addition to serving as

Answer 39

- The building blocks of nucleic acids

Question 40

Nucleotides are responsible for modulating

Answer 40

- Protein synthesis - Blood flow/coagulation - Provide energy for cellular metabolism

Question 41

Nucleotides also play a role in

Answer 41

- Signal transduction pathways

Question 42

Nucleotides have important biosynthetic roles and modulation of

Answer 42

- Allosteric enzyme activity