Lecture 10- Protein Synthesis

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Biology- Semester 1 (Lecture 10- Protein Synthesis ) Flashcards on Lecture 10- Protein Synthesis , created by emma_moran on 01/02/2014.

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Question Answer
What is an aminoacyl tRNA molecule called? tRNA molecule bound to an amino acid
What is a decylated/uncharged tRNA molecule? A tRNA molecule which has had its amino acid removed
What is a peptidyl tRNA molecule? A tRNA molecule bound to a growing polypeptide chain
Which codon is the start codon? AUG (methionine)
Which codons are stop codons? UAG, UAA, UGA
What 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.
Why 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.
What is the 5' cap composed of that is added to pre-mRNA? Phosphorylated 7-methyl guanosine
What adds the 5' cap to the pre-mRNA? Guanyltransferase
Why 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
How 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
Why 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.
What 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.
What does alternative splicing mean? That a single gene can code for many different proteins
What does the mRNA do after transcription? Leaves the nucleus and travels to ribosomes for translation
What do ribosomes consist of? 40s subunit and 60s subunit
What 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.
What 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
What is termination? When the stop codon is reached and the peptide and ribosomal subunits are released
Where are proteins destined for use in the cytoplasm synthesised? On free ribosomes
Where are proteins destined for secretion out of the cell synthesised? On ribosomes attached to the RER
What is the name given to the cavities of the RER and golgi? Lumen
What mutation occurs in sickle cell anaemia? Glutamine becomes valine
What 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
What are the clinical consequences of sickle cell anaemia? Downstream tissue ischemia, causing pain and infarction. Organ damage and ischemic stroke.
Where 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
Where can the nucleotides required for mRNA synthesis be found? The nucleus
Why 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
Is the product of translation the finished protein? No because it hasn't been folded yet
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