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MBBS - Year 1 > Intro to biochem > Flashcards

Intro to biochem Flashcards

1
Q

Classes of nucleic acids found in cells

A

Ribonucleic - 90%

Deoxyribonhuycleic - 10%

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2
Q

Classes of RNA

A

rRNA - 80%
tRNA - 15%
mRNA - 5%

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3
Q

Functions of DNA

A

Repositiry of genetic info
Directs its own replication
Directs transcription of complimentary molecules of mRNA

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4
Q

Function of mRNA

A

Carriers of genetic info

Directs translation of genetic info into proteins

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5
Q

Function of tRNA

A

Translator of genetic info

Delivers AA during protein synthesis

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6
Q

Function of rRNA

A

Components of ribosomes

Have structural and functional roles

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7
Q

Purine bases

A

Adenine

Guanine

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8
Q

Pyrimidine bases

A

Cytosine
Thymine
Uracil

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9
Q

Nucleoside of adenine

A

Adenosine

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10
Q

Nuceloside of guanine

A

Guanosine

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11
Q

Nucleoside of cytosine

A

Cytidine

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12
Q

Nucleoside of thymine

A

Thymidine

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13
Q

Nucleoside of uracil

A

Uridine

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14
Q

How to read nucleic acids

A

5’ to 3’

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15
Q

Watson - Crick base pairing

A

A and T form 2 hydrogen bonds

G & C form 3 hydrogen bonds and are more stable

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16
Q

Structure of B-DNA

A 
Double stranded alpha-helix 
One full turn contains 10 base pairs 
Width of molecule is 2nm
Contains major and minor groove 
Distance between 2 base plates - 0.34 nm
Base pairs are orientated to the right angle of the helix
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17
Q

DNA replication process

A

DNA Helicase separates parental strand into leading strand and lagging strand
DNA primase and RNA primers re used by DNA polymerase as starting points for replication
Leading strand (5’ to 3’) is replicated in a continuous fashion but the lagging strand is unable to - Okazaki fragnments
RNA primers are removed by exonuclease activity of DNA polymerase and are replaced w/ DNA
DNA Ligase seals fragments to complete synthesis of lagging strand

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18
Q

Length of Okazaki fragments

A

1,000 to 5,000 bases

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19
Q

Antiviral chemotherapeutic agents

A

Analogue nucleosides are phosphorylated at 5’ carbon –> triphosphate analogue. Reverse transcriptase then incorporates these into the viral genome and this blocks DNA synthesis –> no more chain elongation

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20
Q

Why is DNA synthesis is blocked in antiviral chemotherapeutic agents

A

Analogues don’t have hydroxyl groups at 3’ and other atoms/ groups instead

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21
Q

Structure of RNA molecules

A

Single stranded molecules
Nucleotides joined by phosphodiester bonds
Starts at 5’ end and terminates at 3’ end
Extensive 2’ structures e.g hairpin loop due to intramolecular double stranded regions

22
Q

RNA polymerases

A 
Synthesis RNA 
Types are distinguished by the class of which they direct the synthesis
23
Q

RNA polymerase I

A

Direct the synthesis of rRNA’s

24
Q

RNA polymerase II

A

Direct synthesis of mRNAs

Sensitive to inhibition by alpha-amanitin, found in Amanita phalloides (mushroom)

25
Q

RNA polymerase III

A

Direct synthesis of tRNA

26
Q

Transcription - initiation

A

Interaction w/ RNA polymerase w/ spp sites on the DNA (promoters)

27
Q

Promoters

A

Charcteristic sequences of DNA in front of or upstream of the genes that is to be transcribed

28
Q

Transcription - elongation

A

RNA polymerase selects appropriate ribonucleotides and forms phosphodiester bridges between them
Rapid process - 40 nt/ second
Requires double stranded DNA to unwound

29
Q

How is double stranded DNA unwound in transcription

A

Topoisomerases I and II

These enzymes are associated w/ the transcription complex and are targets for anti-cancer drugs in chemo

30
Q

Transcription - termination

A

Diff types employ diff mechanisms to terminate transcription

31
Q

RNA polymerase I to terminate transcription

A

Uses spp protein

32
Q

RNA polymerase II to terminate transcription

A

Uses spp termination sequences & protein factors

33
Q

RNA polymerase III to terminate transcription

A

Uses spp termination sequences

34
Q

Features of prokaryotic mRNA’s

A

Polycistronic
No chemical modification
No splicing

35
Q

Features of eukaryotic mRNA’s

A

Monocistronic
Chemical modifications
Splicing - contains introns and axons

36
Q

Chemical modifications of eukaryotic mRNA

A

5’: methylated guanine nucleotide cap added

3’: polyA tail added

37
Q

Monocistronic

A

Encode for only one protein

38
Q

Polycistronic

A

Encodes for multiple proteins

39
Q

When does transcription and translation occur in prokaryotes

A

Simultaneously -meaning that transcripts may already be partially transcribed into proteins even before transcription is completed

40
Q

Why can’t simultaneous transcription and translation occur in eukaryotes

A

Nuclear envelope acts as a barrier between process of transcription and translation

41
Q

Structure of tRNA

A 
Acceptor stem 
T Psi C loop 
Variable loop 
Anticodon loop 
Trinucleotide anticodon 
D loop
42
Q

Acceptor stem

A

Last 3 bases unpaired and form acceptor stem

AA is joined to 3’ end by an ester bond between hydroxy group on adenosine nucleotide and carboxyl group on AA

43
Q

Trinucleotide anticodon

A

Trinucleotide codon directs a spp interaction w/ the corresponding don in the mRNA

44
Q

Secondary structure of tRNA

A

Cloverleaf

45
Q

Ribosome-inhibiting antibiotics

A

As ribosomes in prokaryotes and eukaryotes are different compounds can preferentially target bacteria ribosome

46
Q

Antibiotics targeting 30S subunit

A

Streptomycin

Tetracycline

47
Q

Antibiotics targeting 50S subunits

A

Erythromycin

Chloramphenol

48
Q

Nucleotide triphosphates

A

Substrates for nucleic acid synthesis

49
Q

When is PPi released

A

During the incorporation of nucleotide triphosphates into the nascent acid chain

50
Q

PPi

A

Pyrophosphate

51
Q

Tertiary structure of DNA

A

Chromatin and nucleosomes
DNA is wrapped around histones found in core of nucleosomes, found in chromatin
Each nucleosome has a pice of linker DNA in between which allows extra folding of nucleosome string –> supercoiled structure

MBBS - Year 1 (93 decks)

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