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a. SL12100: Health and disease > L7 - Introduction To Nucleic Acids > Flashcards

L7 - Introduction To Nucleic Acids Flashcards

1
Q

What is DNA?

A

Deoxyribonucleic acids

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2
Q

What are the building blocks of DNA?

A

Nucleotides

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3
Q

What are nucleotides?

A

Phosphate + sugar + base

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4
Q

What are nucleosides?

A

Sugar + base

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5
Q

What are the 4 nucleotides?

A

Deoxy
- adenosine
- guanosine
- thymidine
- cytidine
Phosphate

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6
Q

What are the 4 nucleosides?

A

Deoxy
- adenosine
- guanosine
- thymidine
- cytidine

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7
Q

What are features of the sugars?

A
  • when it points down it’s alpha, when it points up it’s beta
  • pentose sugar
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8
Q

What does deoxyribose exist as?

A

The beta anomer in DNA

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9
Q

What are purines?

A

Nucleic acids with two rings
- adenine
- guanine

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10
Q

What are pyrimidines?

A

Nucleic acis with one ring
- cytosine
- thymine

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11
Q

What is the primary structure of DNA?

A

The sequence of bases, held together by the sugar phsophate backbone
(Contains the genetic information)

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12
Q

What is the secondary structure of DNA?

A

Shape that the primary sequence adopts
- DNA double helix
- due to complimentary base pairings

A = T, G=-C

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13
Q

Features of the secondary structure of DNA

A
  • Directionality: 5’ to 3’, 3’ to 5’, anti parallel
  • There are major grooves and minor grooves
  • there are 10 base pairs per turn
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14
Q

What is the tertiary structure of DNA?

A

How the DNA gets stores into the cell

  • chromosomal packing of DNA onto chromatin
    = compex of histone proteins with DNA/RNA
  • solenoidal supercoililng
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15
Q

What is the primary structure of RNA?

A
  • complimentary code to DNA (transcription)
  • Ribose instead of deoxyribose
  • Uracil instead of thymine
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16
Q

What is the secondary structure of RNA?

A
  • single stranded
  • interacts with itself = helical secondary structure (tRNA)
  • AU, GC
17
Q

What is the tertairy structure of RNA?

A
  • mRNA: relays code for protein from DNA to protein production site
  • tRNA: links triplet code on mRNA to specific a/a
  • rRNA: present in ribosomes, structurally and catalytically important
18
Q

What is the central dogma?

A

Primary sequence of DNA read to code for the primary sequence of mRNA = proteins

19
Q

What are the biosynthesic pathways of nucleic acids?

A

Salvage - recycling pathways, takes less energy
De novo - from the basics

20
Q

What are the key points for the de novo synthesis of purine nucleotides?

A
  • energy provided by dephosphorylation of ATP to ADP
  • additional atoms/groups are added with a loss of another molecule (a/e)
  • when a single C additon is required, tetrahydrofolate
21
Q

How do conversion of nucleotide monophosphates to triphosphates happen?

A

NMP + ATP = NDP + ADP

NDP + ATP = NTP + ADP

22
Q

What is monophosphate kinases?

A

Enzymes specific for each base but not sugar

Adds phosphate to NMP

23
Q

What is diphosphate kinase?

A

Enzyme that is non-specific

Adds phosphate to NDP

24
Q

How are ribonucleotides reduced to deoxyribonucleotides?

A

ribo - NDP + reductant - (SH)2 = deoxyribo - NDP + reductant - (S-S)

25
Q

What are examples of reducing agents?

A
  • thioredoxin (SH)2 = thioredoxin (S-S)
  • glutaredoxin + 2-glutathione -SH = glutaredoxin + (glutathione-S-)2
26
Q

What is thimine the addition of?

A

5-methyl uracil + CH3
takes place at the nucleotide monophosphate stage dUMP

27
Q

What enzyme joines the 5-methyl uracil with the CH3? and what products are formed?

A

thymidilate synthase
= dTMP and dihydrofolate

28
Q

What is the inhibition of thymidilate synthase good for?

A

effective treatment strategy for several cancers
- it prevents the dUMP from converting into dTMP

29
Q

What is the reductive catabolism of pyrimidine bases?

A

reductive breakdown of pyrimidine bases results in small soluble molecules that are easily excreted
- using NADPH + H+
- releases CO2 and NH4+

30
Q

What are the key points for catabolism of pyrimidines?

A
  • can occur through oxidative or reductive pathways
  • products of catabolism are small, water soluble compounds
  • degradation products are readily excreted
31
Q

What is the catabolism of purine nucleotides?

A

it leads to the production of uric acid
- using adenosine deaminase (ADA)
- and xanthine oxidase

32
Q

Why is uric acid bad?

A

It’s excreted in urine as solid (crystallised)
- excess accumulation leads to hyperuricemia (gout) affects joints

33
Q

How are clinical problems of nucleotide catabolism resolved?

A

there is one enzyme to target to reduce uric acid (xanthine oxidase)

Allopurinol: blocks xanthine oxidase as it’s similar to substrate Hypoxanthine/Xanthine

a. SL12100: Health and disease (18 decks)

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