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A 56- year- old female presents with difficulty opening her eye lids, as well as inability to raise herself from sitting position. She is diagnosed with “myasthenia gravis”, a disease of extreme fatigue, due to decreased concentration of Acetyl choline in her muscles. She has been prescribed physostigmine, a drug that increases the amount of available Acetyl choline, by competitively inhibiting acetylcholinestrase.

myashenia gravis

Figure- Inability to open eyelid in myasthenia gravis

Which of the following statements is not true of competitive inhibitors ?

a) Vmax remains the same

b) Apparent  Km in increased

c) Inhibitor is a structural analogue of the substrate

d) Inhibitor binds covalently to the enzyme

e) Increasing concentration of substrate can reverse the changes

 3- A 55-year-old male presents with difficult breathing and swollen ankles. He is found to have a failing heart, resulting in blood backing up in to his lungs (pulmonary congestion) and making it difficult for him to breathe. He is administered a drug  that inhibits angiotensin converting enzyme (ACE). By inhibiting this enzyme, which of the following will change about the reaction it catalyzes ?

a) Energy of activation

b) Net free energy change

c) Equilibrium concentration of substrate

d) Equilibrium concentration of product

e) Thermodynamics

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