16 2pts The enzyme argininetRNA synthetase requires three su

16. (2pts) The enzyme arginine-tRNA synthetase requires three substrates-ATP, tRNA, and the amino acid arginine.The Km values for these substrates are 300 uM, 0.4 uM and 3uM, respectively. Which of these has the lowest affinity for this synthetase? O arginine O the affinity depends on the enzyme concentration O ATP O the affinity depends on the substrate concentration O tRNA 17. (2pt) Enzymes speed up reactions by O stabilizing the transition state O binding substrates tightly O shifting the equilibrium constant to favor the products O forming very stable products O all of the above

Solution

16. The correct answer is ATP. ATP has the lowest affinity to the enzyme arginine-tRNA synthetase. This is because as K_m increases, it shows that the affinity for that compound to the enzyme is low. Higher K_m means higher substrate concentration must be present to saturate the enzyme, whereas low K_m means that the enzyme becomes saturated even at a lower substrate concentration. If an enzyme is being saturated with a low substrate concentration, then it means that the affinity of that substrate is high. Since ATP has the highest K_m among the three substrates, it has the lowest affinity. Also, the affinity does not depend upon the substrate concentration or the enzyme concentration.

17. Enzyme speed up the reaction by Stabilizing The Transition State.

Enzyme plays the role of carrying out the reaction through an alternate path instead of the usual.In this path enzyme decrease the Activation Energy(Minimum energy required to reach the Transtition State ), while all other parameter such as energy of product , Equilibrium Equation etc remain unaffected.

As the Activation Energy decrease, it ultimately indicates that Enzyme stabilize the Transition state.