Topic 4 - Protein Synthesis [4]

Question 1

Steps of Translation

Answer 1

once the modified mRNA has left nucleus, it attaches to a ribosome in the cytoplasm.
The ribosome attaches to the start codon.
tRNA molecule aligns opposite the mRNA. It has the complementary anticodon to the start codon. (its held in place by ribosome just like mRNA).
Ribosome moves along the mRNA molecule to enable another complementary tRNA to attach to the next codon on the mRNA. (2 at one time is the max).
The two amino acids that have been delivered by the tRNA are joined by a peptide bond, this is catalysed by an enzyme, requires ATP.
continues until reach a stop codon at the end of mRNA. Stop codon does not code for an amino acids so ribosome detaches.
Polypeptide chain is created and will enter Golgi for modification.

Question 2

Translation, what is it?

Answer 2

the stage in which the polypeptide chain is created using both the mRNA base sequence and the tRNA.

Question 3

After Transcription, mRNA is modified. Expand.

Answer 3

‘Pre-mRNA’ becomes mRNA through splicing of introns.
The Protein ‘spliceosome’ does this.
only Exons, the coding regions. are left.

Question 4

Steps of Transcription

Answer 4

DNA Helix unwinds, exposing the bases.
One chain of DNA acts as a template.
Unwinding and unzipping is catalysed by DNA Helicase
DNA helicase breaks the Hydrogen bonds between bases.
Free mRNA nucleotides in nucleus line up parallel to their complementary DNA bases.
RNA Polymerase bonds together the RNA Nucleotides to create a new RNA polymer chain. One entire gene is copied.
Once copied, the mRNA is modified and leaves nucleus through the pores.

Question 5

Transcription, what is it?

Answer 5

a mRNA copy of one gene on the DNA is created in nucleus.

mRNA fits through the nuclear pores and goes to the cytoplasm and gives the genetic code to ribosome.

Question 6

Two main stages of protein production on ribosomes:

Answer 6

Transcription

Translation