Proteins and their synthesis Flashcards
What is translation?
The generation of specific proteins from their mRNA templates
What 2 things does translation involve?
Ribosomal proteins and Functional RNAs
What are the two functional RNAs
tRNAs
rRNAs
What is the the relationship between transcription and translation in Eukaryotes?
It occurs in separate compartments in eukaryotes
What is the relationship between transcription and translation in prokaryotes?
It occurs in the same compartment in prokaryotes
How many amino acids are there in genetic code?
20
What is released each time a peptide bond forms?
Water molecule
What are the ends of a polypeptide chain called?
N-terminal and C-terminal
What are the 3 parts of a ribosome?
Large subunit
Small subunit
decoding center
What are the 4 levels of protein structure?
Primary
Secondary
Tertiary
Quaternary
Secondary structure explanation?
What are the two conformations?
Local structure
Helices
Beta pleated sheet
Tertiary structure explanation?
Composite of all secondary structures
Protein structure is relatred to its function.
Globular-
Linear-
Disordered
Globular - antibodies
Linear - skin
Disordered -
Protein structure is relatred to its function.
Globular-
Linear-
Disordered
Globular - antibodies
Linear - skin
Disordered -
How are amino acids specified?
By nonoverlapping codons containing 3 adjacent nucleotides
What did the experiments of Crick, Brenner and others indicate?
Using the T4 phage, they indicated that the genetic code involved triplets
In the 1960s, Nirenberg, Matthaei, and Khorana
Used synthetic RNAs to crack the genetic code
What is degeneracy?
Multiple sets of codons can code for the same thing
Some mutations wont change what result the codon codes for
What can single nucleotide mutations cause?
They can introduce premature stop codons which break the gene
What do tRNAs do?
They bring amino acids to the ribosome so it can be added to a polypeptide chain
What 2 things do tRNA sceondary structures have?
Anticodons and Amino Acid attachment sites
What does the tRNA anticodon region do?
Binds with a codon for addition to a polypeptide chain
What do aminoacyl-tRNA synthetases do?
Covalently attach appropriate tRNAs and amino acids
tRNAs and AAs dock inside and AAs are bound
What makes it possible for tRNAs to recognize multiple codons
Wobble effect
What is special about Inosine?
Inosine can sometimes replace A and it can pair with A,C, or U
Are prokaryotic or eukaryotic ribosomal subunits larger?
Eukaryotic
What feature of bacterial (prokaryotes) mRNAs helps position the ribosome during translation inition?
Shine-Dalgarno sequence
What are the three key sites that ribosomes have to facilitate interactions with molecules necessary for translation?
Acceptor
Polypeptide
Exit
What role does the start codon play in initiating translation?
It marks the site at which translation into protein sequence begins and facilitates position of ribosome docking
What do the stop codons trigger?
Stop codons recruit release factors which trigger termination of translation and trigger disassembly of ribosome
What are the 3 stages/phases of translation?
Initiation
Elongation
Termination
What proteins are involved in elongation?
Elongation factors, they allow the ribosome to shift during translation extending the polypeptide chain
If prokaryotes have the Shine-Dalgarno sequence, what is the eukaryote version?
5’ cap
How does the ribosome dock in eukaryotes
Docking in eukaryotes is facilitated relative to the start codon and 5’ cap
What allows the large ribosomal subunit to bind to the small unit in prokaryotes?
F-met
What are nonsense supressors?
Secondary mutations that enable translation to proceed through a premature stop
What are post-translational modifications?
Additional levels of modifications to the protein that influence how they function
What are 5 examples of PTMs?
- Addition of chemical groups
- Amino acid modifications
- Cleavage
- Addition of complex molecules
- Addition of polypeptides
