3.10 Protein Synthesis Flashcards
Where does protein synthesis take place
In ribosomes in the cytoplasm
Why doesn’t protein synthesis happen in the nucleus with the DNA
ribosomes are responsible for synthesising proteins
Why does protein synthesis occur
Because DNA molecules are too large to leave the nuclear envelope so the genes have to be copied first
What is transcription
The process of copying (‘transcribing’) the genes and transporting them to a ribosome
What does transcription produce
shorter molecules of RNA
What has to happen for transcription to happen
- DNA helicase unzips and unwinds the double helix, breaking the hydrogen bonds
2.
What are the sense and antisense strands
Sense: one of the strands in the double helix that contains the code for the protein to be synthesised (runs from 5’ to 3’)
Antisense: the other stand that is complementary to the other strand but doesn’t code for a protein. It acts as a template strand for transcription so that the complementary RNA strand can copy the right bases.
Free RNA nucleotides will pair with the bases on the exposed antisense strand when the DNA unzips.
What enzyme cause phosphodiester bonds to form between the RNA nucleotides
RNA polymerase
What is the completed short strand of RNA called
messenger RNA (mRNA) - it has the same base pair sequence as that on the DNA strand but thymine is switched for uracil.
This detaches from the DNA template and leaves the nucleus through a nuclear pore.
In eukaryotic cells, what 2 things make a ribosome?
Equal parts ribosomal RNA (rRNA) and protein
What is rRNA important for?
It helps maintain the structural stability of the protein synthesis sequence and plays a biochemical role in catalysing the reaction
What is translation
The process of decoding, or translating, the mRNA (that becomes attached to a small subunit on the ribosome, into a sequence of amino acids.
What is Transfer RNA (tRNA)
Another form of RNA which is necessary for translation; it has a strand of RNA folded in such a way that three bases (ANTICODON) are at the end of the molecule
What does the anticodon in the tRNA do?
It will bind to a complementary codon on mRNA, following the normal base pairing rules; the tRNA molecules will carry an amino acid that correspond to that codon.
