To evaluate kidney function in a 45-year-old woman with type II diabetes, you ask her to collect her urine over 24 hours. She collects 3600 ml of urine in that period. The clinical laboratory returns the following results after analyzing the patient’s urine and plasma samples: plasma creatinine = 4 mg/dL, urine creatinine = 32 mg/dL, plasma potassium = 5 mmol/L, and urine potassium = 10 mmol/L.

What is the net renal tubular reabsorption rate of potassium in this patient?

#Question id: 625

#Unit 1. Molecules and their Interaction Relevant to Biology

For enzymes in which the slowest (rate-limiting) step is the reaction Km becomes equivalent to:

#Question id: 624

#Unit 1. Molecules and their Interaction Relevant to Biology

The following data were obtained in a study of an enzyme known to follow Michaelis-Menten kinetics: The Km for this enzyme is approximately:

#Question id: 623

#Unit 1. Molecules and their Interaction Relevant to Biology

Which of these statements about enzyme-catalyzed reactions is false?

#Question id: 622

#Unit 1. Molecules and their Interaction Relevant to Biology

An enzyme-catalyzed reaction was carried out with the substrate concentration initially a thousand times greater than the Km for that substrate.  After 9 minutes, 1% of the substrate had been converted to product, and the amount of product formed in the reaction mixture was 12 micromol.  If, in a separate experiment, one-third as much enzyme and twice as much substrate had been combined, how long would it take for the same amount (12 micromol) of product to be formed?

#Question id: 621

#Unit 1. Molecules and their Interaction Relevant to Biology

Michaelis and Menten assumed that the overall reaction for an enzyme-catalyzed reaction could be written as Using this reaction, the rate of breakdown of the enzyme-substrate complex can be described by the expression:

#Question id: 620

#Unit 1. Molecules and their Interaction Relevant to Biology

Which of the following statements about a plot of V0 vs. [S] for an enzyme that follows Michaelis-Menten kinetics is false?