Protein synthesis

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How many of the DNA strands code for a protein to be synthesised?
1 of the 2 strands, this is the sense strand
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What is the antisense strand?
The other strand, complimentary to the sense strand so it acts as a template during transcription
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Describe transcription
The DNA unzips, free RNA nucleotides base pair with the complimentary bases on the anitsense strand, then phosphodiester bonds are formed due to the enzyme RNA polymerase. At the end of a gene, transcription stops, the completed molecule is the mRNA.
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In terms of bases, describe the structure of the mRNA
It has the same bases as the sense strand (apart from the thymine is replaced by uracil)
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What happens to the mRNA after transcription?
It detaches itself from the DNA and leaves the nucleus (the DNA double helix reforms) and it goes towards the ribosome
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What is a ribosome and what protein does it consist of?
It is an organelle which has 2 subunits (one big and one small) and it contains lots of ribosomal RNA
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What does rRNA do?
Maintains structural stability of the ribosome during protein synthesis and also catalyses the reaction
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Briefly describe translation
When the mRNA binds to the small subunit of the ribosome where it is then decoded into a sequence of amino acids
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What is transfer (t)RNA?
A type of RNA where 3 bases (the anticodon) are at one end of the molecule and an amino acid is on the other end. The codon binds to the complimentary bases on the mRNA on the ribosome and the amino acid corresponds with the 3 bases on the mRNA
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What happens after the first tRNA binds with the mRNA?
More tRNA's bind to the corresponding to the bases on the mRNA, only 2 tRNA molecules can be joined to the mRNA at the same time, so as more tRNA's join, the tRNA's leave the ribosome
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What happens to the amino acids after the tRNA leaves the ribosome?
The amino acids interact and form a polypeptide chain as they join by peptide bonds. This forms the primary structure of the protein.
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What happens when the ribosome reaches the end of the mRNA?
The ribosome reaches the stop codon and then releases the polypeptide
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What happens to the polypeptide after it has been released?
It folds into its secondary and tertiary structures determined by the primary structure. Sometimes it can undergo further modifications in the Golgi apparatus
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Other cards in this set

Card 2

Front

What is the antisense strand?

Back

The other strand, complimentary to the sense strand so it acts as a template during transcription

Card 3

Front

Describe transcription

Back

Preview of the front of card 3

Card 4

Front

In terms of bases, describe the structure of the mRNA

Back

Preview of the front of card 4

Card 5

Front

What happens to the mRNA after transcription?

Back

Preview of the front of card 5
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