This is Just one question not multipple, please help. I always rate. States to r

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This is Just one question not multipple, please help. I always rate. States to remember to write out your calculations and explanations for ALL problems.

18. Protein molecules in the cytosol of a cell have different half-lives t h. The half-life is the time needed for 50% of the molecules to be lost or altered. Half-lives are determined by several factors, one of which is the "marking" ofthe protein by ubiquitin, which signals that the protein is intended for digestion by proteases. Ubiquitin binds differently to proteins due to differences in their amino ends. The following table gives the half-lives t h for some proteins with different amino ends Amino Acid End of Protein MET 20 hrs SER E 20 hrs THR 20 hrs ALLA 20 hrs EVAL 20 hrs BLEU min PHE 33 min ASP min LYS min ARG 2 min Half-life is rclatcd to thc rate K of protcin loss by the following cquation t 0.693 K where 0.693 is the natural logarithm of 2, and K is measured in reciprocal time units. a. What is the rate of protein loss per minute when MET is the amino terminal? (Assume t 24 hr) b. Compare this with the rate when ARG is the amino terminal end. (Assume t 2 min

Explanation / Answer

a) according to the formula, T1/2= 0.693/K

here given T1/2 is 24 hrs= 24x60x50= 86400secs , so 86400 = 0.693/K

K= 0.693/86400= 8x10-6

b)according to the formula, T1/2= 0.693K

here given T1/2 is 2min= 2x60= 120secs , so 120 = 0.693/K

K = 0.693/120 = 5.7 x 10-3

comparing K 2 proteins one having MET aminoacid end, the other is ARG amino acid end. with the values we get we find that k value of arginie is higher ,which indicates its half time in less compared to that of methionine aminoacid end protein

c) % of methionine end protein left after 5 half lives

let us assume initially 100 grams of protein is in the cell

after 24 hrs, 100 reduces to 50g, as the half life is 24hrs

after 48 hrs, 50g reduces to 25g,

after 72hrs 25g reduces to 12.5g

after 96 hrs 12.5g reduces to 6.25g

after 120 hrs ,6.25g is reduced to3.125g

so out of initial 100g, at the end of 5 half lives, 3.125g is left

% for this eft protein is 3.125/100 x 100 = 3.125%

d)the answer for this question is similiar to the 3rd question. irrespective of the halflife period, the amount of protein present after a particular half life is same for two different proteins. but the time taken to achieve this might vary depending on the half life of the protein concerned.

% left is 3.125% but the time taken to attain this is different,which is 10mins

but in the 3rd question the time required to atain 3.125% was 120 hrs

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