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Biochemistry I > Chapter 21: Structure/Function of Nucleotides and Nucleosides > Flashcards

Chapter 21: Structure/Function of Nucleotides and Nucleosides Flashcards

1
Q

Nucleotide definition

A
  • A compound formed by nitrogenous base attached by a B-N-glycosydic linkage to a sugar and 1 or more phosphate groups
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2
Q

Nucleotides are

A
  • Monomeric subunits of nucleic acids
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3
Q

Nucleotides exist as

A
  • Polynucleotides in both DNA and RNA
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4
Q

If the phosphate group is lacking, it is considered

A
  • A nucleoside
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5
Q

Nucleosides are

A
  • Nitrogenous base plus sugar

- No phosphate groups

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6
Q

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

A
  • Each end of a polymer (DNA polynucleotide segment) is distinct
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7
Q

Nucleic acids contain

A
  • 5 major nitrogenous substituted bases
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8
Q

Purines

A
  • Adenine

- Guanine

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9
Q

Pyrimidines

A
  • Cytosine
  • Thymine
  • Uracil
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10
Q

All nucleic acids contain

A
  • A, G, and C
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11
Q

DNA (but not RNA) also contains

A
  • T
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12
Q

RNA (but not DNA) also contains

A
  • U
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13
Q

Nitrogenous bases absorb

A
  • UV light
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14
Q

Purine bases are numbered

A
  • Counter clockwise direction
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15
Q

Purine bases include

A
  • Adenine
  • Guanine
  • Hypoxanthine
  • Xanthine
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16
Q

Pyrimidine bases are numbered

A
  • Clockwise direction
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17
Q

Minor purine bases

A
  • N2-Dimethylguanine
  • N2-Dimethyladenine
  • 1-Methylguanine
18
Q

Purines or pyrimidines that exist in two or more forms

A
  • Tatomerization

- Depends on pH

19
Q

Ring substituents participate in

A
  • Keto-enol tautomerism

- Amine-imine tautomerism

20
Q

Most predominant forms of tautomerization

A
  • Keto

- Amino

21
Q

Physiologic conditions strongly favor

A
  • The amino and keto forms
22
Q

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

A
  • Hydrophobic and thus insoluble in water
23
Q

The ability of DNA to absorb UV light is increased following

A
  • Denaturation (hyperchromic shift)
24
Q

Methylated forms of purines from plants

A
  • Caffeine

- Theophylline

25
Q

Caffeine from coffee beans

A
  • Inhibits phosphodiesterase activity
26
Q

Theophylline is found in

A
  • Tea leaves
27
Q

Synthetic analogs of clinical interest

A
  • Anticancer agents
  • 6-mercaptopurine
  • 5-fluorouracil
  • Cytosine arabinoside (ara C)
28
Q

6-mercaptopurine

A
  • Inhibits purine nucleotide biosynthesis

- Used in treatment of childhood leukemia

29
Q

5-fluorouracil

A
  • Thymine analog
30
Q

Cytosine arabinoside (ara C)

A
  • Found in sponges
  • Inhibits DNA and RNA polymerase activity
  • Used in treatment of non-Hodgkin lymphoma
31
Q

Ribonucleotides and deoxyribonucleotides differ in

A
  • Sugar component
32
Q

Nucleotides are phopshorylated esters of

A
  • Nucleosides (mostly on C5)
33
Q

Nucleotide functions

A
  • Precursors of DNA and RNA
  • Group transfer
  • Transducers of free energy
  • Portion of coenzymes
  • Allosteric regulation
  • Biosynthesis
  • Second messengers
34
Q

Nucleotides cannot be used as

A
  • Primary sources of energy
35
Q

Adenosine derivatives are important in

A
  • Cellular communication
36
Q

The monomeric building blocks of nucleic acids are

A
  • Nucleotides
37
Q

Nucleotides are compose of three distinct parts

A
  • Substituted nitrogenous base
  • Five carbon sugar
  • One or more phosphate groups
38
Q

Nucleosides are composed of

A
  • Sugar and nitrogenous base

- Lack the phosphate group

39
Q

Nucleotides perform a variety of functions in addition to serving as

A
  • The building blocks of nucleic acids
40
Q

Nucleotides are responsible for modulating

A
  • Protein synthesis
  • Blood flow/coagulation
  • Provide energy for cellular metabolism
41
Q

Nucleotides also play a role in

A
  • Signal transduction pathways
42
Q

Nucleotides have important biosynthetic roles and modulation of

A
  • Allosteric enzyme activity

Biochemistry I (34 decks)

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