Biochemistry of Proteins Flashcards
What do anticodons of tRNA molecules form base pairs with during translation
codons on mRNA
Why are amino acids degenerate
more than one codon can code for an amino acid
Why are codons unambiguous
1 codon can only code for 1 amino acid (or a stop)
What are the components needed for translation
Amino acids
aminoacyl-tRNA synthetases
protein factors
source of energy
RNA
What is the function of aminoacyl-tRNA syntheses
bind amino acids to their corresponding tRNA molecule
highly specific
What provides the energy for the covalent bond to form between the amino acid and the tRNA molecule
hydrolyses of ATP
What do the subunits of RNA consist of
small subunit for binding to ribosomes
large subunit that catalyses formation of peptide bonds
What are the 3 ribosomal binding points for tRNA
Exit
Peptidyl
Aminoacyl
Where does the energy come from needed for initiation of translation
hydrolysis of GTP
How does translation start
ribosomal subunit finds AUG (Start codon) on mRNA
Initiator tRNA with anticodon base pair with this
How does the ribosomal subunit move along the mRNA strand to find the start codon
ATP provides the energy
Where is the initiator tRNA located after anticodon pairs up
P siten (peptidyl)
What brings the next aminoacyl-tRNA after the start codon to the A site
An elongation factor
What happens after peptide bond is formed
peptide now located in A site
empty tRNA moves to E (exit) site
When does termination occur
when the A site of the ribosome encounters a stop codon
what happens after termination
finished protein is cleaved off tRNA
what is a point mutation
change in a single base in DNA
what does a missense mutation result in
change in amino acid sequence - change in protein function
what is a nonsense mutation
creates a new termination codon which changes the length of the protein
what is a silent mutation
no change to amino acid sequence
no effect on protein function
why do silent mutations occur
degeneracy of the genetic code
what is a frameshift mutation
addition or deletion of a single base (or 2 bases)
What happens when the protein is finished being translated
targeting
modification
degradation
what is targeting of a protein
protein is moved to final cellular destination
dependant on specific AA sequences
Where do proteins go from free ribosomes
cytosol
nucleus
mitochondria
where do proteins go synthesised in bound ribosomes
plasma membrane
endoplasmic reticulum
Golgi apparatus
secreted
What are examples of post translational modifications
disulphide bonds
proteolytic cleavage
folding/assembling of subunits
phosphorylation
