4.2 PROTEIN SYNTHESIS Flashcards
1
Q
What is the proteome?
A
The complete set of proteins produced by an organism at a given time.
2
Q
What is the genome?
A
The complete set of genetic information in an organism.
3
Q
What are the features of mRNA?
A
- Long, single-stranded.
- Has codons to code for polypeptides.
- Made during transcription.
- Used as a template in translation.
- Used as ‘messenger’ RNA.
4
Q
What are the features of tRNA?
A
- Shorter, single-stranded.
- Made of 80 nucleotides.
- A cloverleaf shape, where one end extends past (amino acid attachment site).
- Opposite the amino acid site is the anticodon extension.
- Clover shape is held together by hydrogen bonds.
- Used as ‘transfer’ RNA during translation.
5
Q
How are proteins made?
A
- Transcription
2. Translation
6
Q
Where does transcription occur?
A
In the nucleus of a cell.
7
Q
Outline transcription. (without splicing)
A
- DNA helicase unzips the double helix, forming two strands.
- Free RNA nucleotide line up along the template strand and form hydrogen bonds between complementary base pairs.
- RNA polymerase joins at the promoter region and joins the nucleotides together by phosphodiester bonds.
- This repeats until it reaches a stop codon, where the RNA nucleotide chain leaves the template strand.
- DNA ligase rejoins the template and the other strand of DNA together to reform DNA.
8
Q
What is splicing?
A
The removal of introns from pre-mRNA.
9
Q
Outline splicing.
A
Introns are removed from the pre-mRNA before it is passed out of the nucleus for translation.
10
Q
Where does translation occur?
A
In the cytoplasm of a cell, at the site of ribosomes.
11
Q
Outline translation.
A
- mRNA leaves the nucleus through a nuclear pore to the ribosomes.
- It joins the small subunit of the ribosomes at the start codon.
- tRNA molecules that have complementary anticodons to the mRNA codons moves to the ribosomes and pairs with the mRNA codon. It carries an amino acid that joins the large sub-unit of ribosomes.
- The ribosome moves along the mRNA and another complementary tRNA molecule brings an amino acid.
- The adjacent amino acids form a peptide bond, using enzymes and ATP energy.
- The first tRNA is released and leaves to bring another amino acid. tRNA molecules work in pairs to bring amino acids.
- This process repeats until it reaches the stop codon on mRNA, where the polypeptide leaves the ribosome and is now a protein, and the mRNA dissociates from the ribosomes too.
12
Q
Which way does transcription occur?
A
From the 5’ end to the 3’ end.
