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Lecture 10- Protein Synthesis
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- 1What is an aminoacyl tRNA molecule called?tRNA molecule bound to an amino acid
- 2What is a decylated/uncharged tRNA molecule?A tRNA molecule which has had its amino acid removed
- 3What is a peptidyl tRNA molecule?A tRNA molecule bound to a growing polypeptide chain
- 4Which codon is the start codon?AUG (methionine)
- 5Which codons are stop codons?UAG, UAA, UGA
- 6What can the deletion or insertion of a base cause?A shift in the reading frame which can change the corresponding amino acids and therefore the structure of the protein.
- 7Why does protein synthesis take place outside the nucleus?DNA is too big to leave the nucleus therefore DNA is transcribed in mRNA as it is small and mobile.
- 8What is the 5' cap composed of that is added to pre-mRNA?Phosphorylated 7-methyl guanosine
- 9What adds the 5' cap to the pre-mRNA?Guanyltransferase
- 10Why is a 5' cap added to the pre-mRNA?Ensures mRNA is transported out of the nucleus, blocks degradation of mRNA 5' exonucleases and promotes translation
- 11How is a 3' poly-A-tail added to the pre-mRNA?The pre-mRNA is cleaved by an endonuclease near a signal AUAAAA sequence at the 3' end. 200 adenosine residues are then added at the cleavage site by poly-A-polymerase
- 12Why is a poly-A-tail added?It protects the mRNA from degradation by 3' endonucleases. The tail also aids in the termination of transcription, ensures export from the nucleus and is important in translation.
- 13What is splicing of pre-mRNA?pre-mRNA contains regions which code for proteins known as exons and unused base sequence know as introns which need to be sliced off.
- 14What does alternative splicing mean?That a single gene can code for many different proteins
- 15What does the mRNA do after transcription?Leaves the nucleus and travels to ribosomes for translation
- 16What do ribosomes consist of?40s subunit and 60s subunit
- 17What is initiation?The binding of a ribosome to the 5' end of the mRNA and hydrogen binding of the anticodon of an aminoacylated tRNA carrying methionine on the AUG start codon.
- 18What is elongation?The addition of further amino acids to the growing polypeptide chain brought by corresponding aminoacylated tRNAs. Peptidyl transferase creates covalent peptide bonds between the amino acids
- 19What is termination?When the stop codon is reached and the peptide and ribosomal subunits are released
- 20Where are proteins destined for use in the cytoplasm synthesised?On free ribosomes
- 21Where are proteins destined for secretion out of the cell synthesised?On ribosomes attached to the RER
- 22What is the name given to the cavities of the RER and golgi?Lumen
- 23What mutation occurs in sickle cell anaemia?Glutamine becomes valine
- 24What happens to blood cells in sickle cell anaemia?Haemoglobin crystallises when oxygen levels are low, causing the sickle shape which gets stuck in small vessels
- 25What are the clinical consequences of sickle cell anaemia?Downstream tissue ischemia, causing pain and infarction. Organ damage and ischemic stroke.
- 26Where is sickle cell anaemia common?In sub-Saharan Africa where sickled red blood cells provide protection against malarial parasite, thus giving individuals with the mutation a selective advantage
- 27Where can the nucleotides required for mRNA synthesis be found?The nucleus
- 28Why does alternative splicing mean that more than one protein can be synthesised from a gene?Particular exons will be included and excluded from mRNA which will produce different amino acid sequences
- 29Is the product of translation the finished protein?No because it hasn't been folded yet
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- (Lecture 10- Protein Synthesis ) Biology- Semester 1 Fichas sobre Lecture 10- Protein Synthesis , creado por emma_moran el 02/01/2014.
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