From the Edexcel GCSE additional science specification for biology. Talks about - Background knowledge of genes - What proteins are - Amino acids - Transcription and translation processes - Full process of protein synthesis - DNA, tRNA, mRNA, polypeptides, codons, triplets of bases, ribosomes. In parallel with the CGP revision books - Everything you need to know for A*.

1. PROTEIN
SYNTHESIS
What it is, genes, ribosomes and amino acids and
proteins (polypeptides)
Edexcell GCSE
gcsepresentations

2. *FOUNDATIONS*
!
A gene is a short section of DNA, that codes for a specific protein.
!
There are codons of bases (triplets) that code for a particular amino
acid, such as AGT or CCA - there are 20 of them.
!
Proteins are simply a long chain of these amino acids called a
‘polypeptide’ chain.
!
For example:
!
If the order of the genes was…
TATGCATAT
!
Then the protein will be…
Tyrosine-alanine-tyrosine.

3. *PROTEINS*
!
DNA determines which genes are switched on or off.
!
This in turn determines which proteins are made, which in turn
determines what kind of cell it is.
!
Proteins can produce things like haemoglobin and they are vital for
the growth of an organism.

4. *PROCESSES*
There are two main stages in protein synthesis.
!
*TRANSCRIPTION*
The Strands of double helix DNA unzip, exposing the bases.
The mRNA enters the nucleus and makes a complimentary copy of the
bases from the gene that are needed to code for the certain amino acids.
!
The mRNA molecules move out of the nucleus via the nuclear pore and travel
to the ribosome, where they join to it.
Amino acids that match the code are bought to the ribosome by molecules
called tRNA.
!
*TRANSLATION*
During translation, the Ribosome joins the amino acids together in a long
chain called a polypeptide, known as a protein that follows the order of
codons in the mRNA.

5. PROTEIN
SYNTHESIS