Translation Flashcards
Translation
The synthesis of a polypeptide using information from mRNA
-Occurs at the ribosome
-Nucleotide sequence—>Amino acid sequence
Transfer RNA (tRNA)
Key player in translating mRNA to an amino acid sequence
-Has a anticodon region (complementary and antiparallel to mRNA)
-Carries the amino acid that mRNA codes for
When tRNA carries an amino acid it is “charged”
SEE PHOTO IN CAMERA ROLL
Ribosomes
Where translation occurs
-Has two subunits: small and large
-Prokaryotic and eukaryotic ribosomal subunits differ in size
Large subunit
Has three sites A, P, E
A site: Amino acid site
-Holds the next tRNA carrying an amino acid
P site: Polypeptide site
-Hilds the tRNA carrying the growing polypeptide chain
E site: exit site
Step 1: Initiation
Begins when small ribosomal subunit binds to the mRNA and a charges tRNA binds to the start codon
-The tRNA carries methionine
-The large subunit binds
Step 2: Elongation
Starts when the next tRNA comes into the A site
-mRNA is moved through the ribosomes and its codons are read
Each mRNA codon codes for a specific amino acid
- Codon recognition: the appropriate anticodon of the next tRNA goes to the A site
- Peptide bond formation: peptide bonds are formed that transfer the polypeptide to the A site tRNA
- Translocation: the tRNA in the A site moves to the P site. The tRNA in the P site goes to the E site. The site is open for the next tRNA
Termination
Occurs when a stop codon in the mRNA reaches the A site of the ribosome
Stop codons do not code for amino acids
- The stop codon signals for a release factor
-Hydrolyzes the bond that holds the polypeptide to the P site
-Polypeptide releases
-All translational units disassemble
Protein Folding
As translation takes place the growing polypeptide chain be to coil and fold
-Genes determine the primary structure (primary structure determines the final shape)
-Some poly peptides require chaperone proteins to fold correctly and some require modification before it can be functional in the cell
Four structures of protein folding
1. Primary
2. Secondary
3. Tertiary
4.Quaternary