protein synthesis

Question 1

what processes constitute protein synthesis?

Answer 1

transcription, translation (activation, initiation, elongation, termination) and post translation

Question 2

What is transcription?

Answer 2

passing the information from DNA to an mRNA to synthesize protein,
DNA -dependent RNA polymerase takes the single strand of DNA and makes the complementary RNA sequence (replacing T with U)
The product will be heterogenous nuclear RNA (hnRNA), that will be processed into mRNA that can leave the nucleus and enter the cytoplasm to serve as a guide for protein synthesis

Question 3

what is translation?

Answer 3

its the synthesis of a polypeptide according to the order of AA in an mRNA

Question 4

what is initiation process?

Answer 4

ribosomal RNA attaches to mRNA and starts assembling the protein with tRNA-Met, which is the first AA in the chain which costs 1 ATP

Question 5

what is the activation and elongation processes?

Answer 5

The AAs must first be recognized according to the respective codon in the mRNA, then activated by aminoacyl tRNA synthetase(activation), and then attached to a tRNA forming aminoacyl tRNA complex that will deliver this AA to the growing peptide chain (elongation) 1 GTP is used to enable the entry of tRNA aminoacyl and one for tRNA to vacate P site.
each step costs 2 ATP

Question 6

what is the termination process?

Answer 6

Starts with one of the 3 non-sense codons that mark the end of translation being recognized by releasing factors that facilitate the hydrolysis of the bond between peptide and the tRNA occupying the P site, releasing the protein and tRNA and the 80S ribosome dissociates into the 40S and 60S subunits.
Costs 1 ATP per protein

Question 7

what is the energetic cost of the translation step in protein synthesis?

Answer 7

4 * number of AA(minus first Met) + 4 (2 initiation and termination + 2 to activate starting Met)

Question 8

what is continuous infusion?

Answer 8

infusion of a tracer at constant rate until the AA specific radioactivity reaches a plateau to calculate fractional synthesis rate. use of intracellular as protein pool leads to overestimation due dilution with aa from protein degradation

Question 9

what is flooding dose?

Answer 9

a large dose of the tracer and unlabeled aa to equilibrate the pool
simple calculation = radioactivity in protein / (Radioactivity of pool * time)
large dose may affect synthesis rate, hormonal response

Question 10

primed continuous infusion?

Answer 10

priming dose that is not as big as flooding followed by constant infusion
simple calculation as well
reduce system disruption