Flashcards
DNA VI - Translation and the Ribosome
Cards in this deck (37)
- 1Define a Ribosome -An organelle that provides the interface for translation of the genetic code into the formation of a functional protein
- 2Describe the functions of a ribosomeProvide an interface for mRNA and aminoacyl tRNAs
Ribosomes catalyse the formation of peptide bonds - 3How does a ribosome facilitate tRNA binding?The ribosome has 3 tRNA binding sites:
The (E) exit site
The (P) peptidyl site
The (A) aminoacyl site - 4What are ribosomes composed of?By mass ~35%/40% protein 60%/65% RNA
- 5How is the size of a ribosome measured?Measured in Svedbergs (S) -
Rate of sedimentation during centrifugation -
Bigger the particle, faster it moves down a centrifugation tube - 6What are the subunits of a ribosome?Small 30s subunit, which binds to the mRNA being translated
Large 50s subunit which catalyses peptide bond formation
Size in total is 70s!!! Not 80s! (confusing, right?) - 7Draw a diagram of an E. Coli cell ribosome.20nm high
Large 50s subunit made of rRNA and proteins
Small 30s subunit made of 16s rRNA and 21 proteins
EPA sites - 8Human ribosomeLarge 60s subunit
small 40s subunit
EPA site
overall size is 80s - 9How do mitochondrial ribosomes differ to human ribosomesMitochondria have 55s ribosomes that are more similar to bacterial ribosomes than cytoplasmic ribosomes
- 10Draw a diagram showing the process of translationCoding strand/promoter/coding region/terminator
transcription (RNA polymerase)
translation (tRNAs and ribosomes)
Protein NH3+-COO- - 11Describe very briefly this translationmRNA is read 5'-3'
Protein is synthesised NH3+-COO- - 12What is the first amino acid encoded in prokaryotes?N-formyl-methionine instead of methionine
- 13Describe the process of initiation in E.ColiSmall (30s) subunit assemble and binds to the ribosome binding site on the mRNA strand as a result of complementary base-pairing between it and the 16s rRNA.
- 14What is this sequence known as?The Shine-Dalgarno sequence, exists just before the 1st AUG codon.
- 15Describe the binding of the tRNA molecule to the ribosomeF-met-tRNA^met binds to the initiation codon
The 50s ribosome subunit then binds to generate the complete ribosome - 16Draw a diagram showing this bindingcorfu 06
- 17Describe translation initiation in EukaryotesFirst amino acid is methionine, not N-formyl-methionine
40s and met-tRNA^met combine prior to binding to mRNA - 18How does the ribosome bind to the mRNA molecule?There is no ribosome binding site on mRNA
Instead, the 40s subunit recognises the cap at the 5' end of the mRNA - 19Draw a diagram you cuntwell done you cunt
- 20Draw a diagram translation elogationdo it you prick
- 21What does the elongation cycle consist of?Repeated cycles of:
Binding of aminoacyl-tRNA (needs GTPs)
The peptidyl transferase reaction
Translocation - movement of the ribosome one codon along the mNRA (needs GTP) - 22What is the result of each cycle?Incorporation of one amino acid into the protein
- 23What terminates a cycle?Reaching a stop codon
- 24Why does a stop codon terminate a cycle?As there is no tRNA molecule complementary to a stop codon
- 25What is the energy expenditure during translation?Equivalent of 3 ATP used for each amino acid incorporated
- 26What is each molecule equivalent of ATP used for?One to link the amino acid to its tRNA
One is used when the aminoacyl-tRNA binds to the ribosome
One is used to faciliate translocation - 27Peptidyl transferase diagram. Cunt.Well done. Prick.
- 28What component of the ribosome catalyses the peptidyl-transferase reaction?The 23s rRNA
- 29How do we know this?An E.Coli ribosome that has had ~95% of its proteins removed can still catalyse peptide formation
X-ray crystallography shows that the active site for peptidyl transferase contains 23s rRNA but no proteins - 30What are elongation factors?Accessory proteins that are not part of the ribosome required for translation
- 31Name the elongation factors required for prokaryotic elongation and its eukaryotic equivalentEF-Tu and EF-1α
- 32Describe Step 1 of ElongationDeliver aminoacyl-tRNAs to the ribosome
- 33Describe Step 2 of ElongationEF-G (EF-2 in eu) uses energy provided by the hydrolysis of GTP to move the ribosome along the mRNA during translocation
Look at your notes here in detail to not the EPA site translocation - 34Compare eukaryotic and prokaryotic ribosomesEu ribosomes larger
Initiation is different: Recog of ribosomal binding sites (Pro) or cap (Eu)
Elongation is very similar
Both very sensitive to antibiotics and inhibitors - 35Name and describe the effects of a class of antibiotics that effect ribosomesErythromycin/Clarithromycin
target prokaryotic large ribosomal subunit
Inhibits peptidyl transferase reaction & translocation - 36Name and describe the effects of a class of antibiotics that effect ribosomes cont.Cholramphenicol
targets prokaryotic and mitochondrial large subunit
Inhibits peptidyl transferase reaction - 37Name and describe the effects of a class of antibiotics that effect ribosomes (Cont. cont.)Ricin
Targets Eu 60s subunit
Catalytic action, removes a base fom rRNA, lethal dose in humans is approx 10^-4g
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- User has deleted their subject information Flashcards on DNA VI - Translation and the Ribosome, created by Deleted user on 27/12/2017.
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- Deleted user · Dec 2017
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- Created by J yadonknow · Dec 27, 2017
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