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cellular and microbiology > the microbial cell part 2 > Flashcards

the microbial cell part 2 Flashcards

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Biology 101 flashcards
1
Q

what are the two main intracellular structures of prokaryotes

A

1) the nuceloid
2) cytoplasm

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2
Q

what is a nucleoid

A

a structure in which compacted DNA within the cytoplasm is kept allowing the prokaryotes to couple transcription and translation

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3
Q

how is DNA organised in prokaryotes

A
  • organised into chromosomes
  • chromosomes are usually circular
    most bacteria have a single chromosomes
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4
Q

outline the structure of prokayotes DNA

A

a double helix in the circular chromosome folded by DNA binding proteins into supercoil loops

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5
Q

what is a negative supercoil

A

when DNA is twisted in opposite directions to the double helix

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6
Q

what is a positive super coil

A

when DNA is twisted in the same direction as the double helix

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7
Q

what are the three challenges faced in DNA replication in prokaryotes

A

1) unwinding the DNA helix
2) replicating each DNA strand at the same time
3) sperating the two daughter chromosomes

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8
Q

outline the process of unwinding the double helix in DNA replication

A

1) after binding of DnaA two strands are seperated
2) DnaB helicase is responsible for seperating two parental strands
3) the strands are kept apart by a ssDNA binding protein
4) seperating and relaxing the two DNA strands tightens the double helix in the unopen region inducing the formation of positve supercoils which can block DNA replication

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9
Q

how is the formation of a positve supercoil relaxed during DNA replication

A

DNA gyrase eases the tension fomred by rapid unwinding of helix carried out by DnaB

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10
Q

outline the process of replicating each DNA strand at the same time

A

1) DNA primase synthesises the RNA primer
2) the leading strand is synthesised continuously
3) the lagging strand is synthesed discontinously and produces okazaki fragments
3) these are ligated and primers are removed

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11
Q

outline how the two daughter chromosomes are seperated

A

1) after DNA replication the two chromosomes are interlocked
2) DNA gyrase decatenates the two daughter chromosomes

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12
Q

what is the role of DNA gyrase in replication

A

1) release the tension of subercoiling
2) decatenates two daughter chromosomes by cutting double helix

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13
Q

where does transcription in prokaryotes occur

A

the nucleoid-cytoplasm interface

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14
Q

outline coupled transcription/translation

A

1) as soon as the prokaryote gene beings being transcribed into mRNA the ribosome lacthes onto the transcript and translates the info into protein
2) many ribosomes can translate the same mRNA transcript
3) this allows proteins to be made faster than in eukaryotes

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15
Q

outline the inititation of transcription

A

1) RNA polyermase has associated with a protein subunit called the sigma factor
2)the sigma subunit of RNA polyermase allows recognition and binding to a specific promoter sequence
3) there are different sigma factors each recognises the consensus sequence

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16
Q

outline elongation of transcription

A

1) once the rNAP clears the promotor region the sigma factor is released
2) NusA protein associated with the RNAP to assist the hairpins in growing RNA strand which can interupt transcription

17
Q

outline termination of transcription

A

1) can be rho-independant
2) can be rho-dependant

18
Q

outline rho-independant termination

A

occurs when RNAP reaches a termination signal a GC rich region followed by a string of A residues which forms a hairpin thereby stalling RNAP

19
Q

outline rho-dependant termination

A

rho factor binds specific sequences within the newly formed mRNA moving towards the 3’
rho catches up with RNAP helping to release mRNA from the DNA template and RNAP

20
Q

what does gene regulation ensure

A

that cells resources are not wasted making proteins which the cell doesnt need

21
Q

what is an operon

A

signle transcriptional unit which corresponds to multiple genes whose expression is also controlled by a single promoter and terminator

22
Q

what is a regulatory region

A

includes the promoter and the region surrounding the promoter to which a regulatory gene will bind

23
Q

what is a regulatory gene

A

a gene which encodes for a protein that controls transcription by binding to a particular site of the DNA aka transcription factors

24
Q

what are cis-acting factors

A

mechanisms that affect gene expression in the vicinity of the gene

25
Q

outline negative regulation of transcription

A

1) the operator is the binding site for a regualtory protein
2) if this protein is a repressor when it binds to the polyermase no transcription is initiated

26
Q

what is positve regulation of transcription

A

when the transcription factor is needed to bind at the promoter to enable RNAP to initiate transcriotion

27
Q

what do antibitoics target

A

1) DNA replication
2) transcription
3) translation

28
Q

outline how antibiotics block DNA replication

A

1) prevent gyrase DNA binding
2) impair DNA religation after cutting
3) inhibit ATPase activity which is needed for gyrase

29
Q

outline how antibiotics target translation

A

1) inhibit formation of functional 70s ribosome
2) impair aminoacyl-tRNA translocation to the A site or peptide bond formation
3) inhibit ribosome recycling

30
Q

what are plasmids

A
  • extrachromosomal dsDNA molecules which can replicate independently and encode important genetic information
31
Q

what is poly-beta- hydroxybutrate

A

produced in organisms in responce to stress from limited nutrients.
it is a carbon polymer used to make biodegradable plastics

32
Q

what are gas vesicles used for

A

to harvest light for photosynthesis or to obtain energy
to keep buoyancy bacteira have gas vescicles allowing photosynthesis in water

33
Q

what are thylakoids

A

membrane bound compartments within chloroplasts and cyanobacteria
- stacks of membranous sacs interconnected to form a common internal space of lumen

34
Q

what are carboxysomes

A

intracellular structures found in many autotrophic bacteria which contain RUBISCO for co2 fixation

35
Q

what are magentosomes

A

presnet in motile aquatic bacteria they are intarcellular sructures surrounded by a membrane containing ion crystals which act like a magent

36
Q

what are transcription factors

A

proteins involved in the process of converting or transcribing DNA into RNA

cellular and microbiology (17 decks)

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