Translation

Question 1

What is the Svedberg unit (s)?

Answer 1

Sedimentation relates to size/shape - Time it takes in centrifugation

Question 2

What are the different parts of a ribosome?

Describe the 3 tRNA binding sites

Answer 2

Small subunit binds to mRNA, Large subunit has peptidyl transferase
3 tRNA binding sites - Aminoacyl (A), Peptidyl (P), Exit (E) sites

Question 3

Describe the primary, secondary and tertiary structures of tRNA

Answer 3

Primary - Nucleotide sequence
Secondary (Cloverleaf) - Formed due to short complementary sequences in tRNA
Tertiary (L shape) - Formed by 3D folding

Question 4

What is an adapter molecule?

Answer 4

RNA with 76 nt long

Question 5

Describe how amino acids bind to 3’ end of tRNA

Answer 5

AA binds to 3’ end of tRNA, Anticodon on base of tRNA - First 2 positions most important compared to 3rd position in terms of mutations occuring

Question 6

Describe how tRNA is loaded with amino acids

Answer 6

At least 1 aminoacyl tRNA synthetase for each AA (Vital for accuracy)
Growing peptide on tRNA in P site, Peptidyl transferase forms p-bond (enzyme activi by rRNA)
Ribosome moves down 3 nucleotides (Translocation)

Question 7

Describe translocation in eukaryotes

Answer 7

Translation occurs at start codon AUG (a specific methionine)
Small subunit of ribosome binds to 5’CAP

Question 8

Describe eukaryotic initiatiin

Answer 8

Met-tRNA bind with 40s subunit, tRNA+Small subunit binds to 5’CAP end of mRNA, Moves along mRNA unit first AUG is in P site, Large subunit joins, Translation begins

Question 9

Describe termination

Answer 9

Stop codons - UGA, UAA, UAG
No tRNA, release factors enter ribosome, release mRNA polypeptide and ribosome subunits.
Transcription+Translation occur at same time in prokaryotes (separate in eukaryotes)

Question 10

Describe some post-translation modifications

Answer 10

Phosphorylation - Adds phosphate to serine/threonine/tyrosine
Lipidation - Attaches lipid to protein chain
Ubiquitination - Adds ubiquitin to lysine residue of target protein for destruction
Disulfide bond - Covalently links S atoms of 2 diff cysteine residues
Acetylation - Adds acetyl group to N-terminus of protein to inc stability
Glycosylation - Attaches sugar to N/O atom in AA side chain
Note: Inhibitors of protein/RNA synthesis are useful as antibiotics

Question 11

What are molecular chaperones?

Answer 11

Proteins which help folding of protein in polypeptide chain (Proteasome)
: If a lot of proteins build up in a cell and are degraded into many pieces, can cause Proteopathy (protein misfolding disease)