There Are Four Enzymes That Can Catalyze the First Step

question 4

Multiple Choice

There are four enzymes that can catalyze the first step of glycolysis.They are hexokinases I,II and III and glucokinase (hexokinase IV) .Hexokinases I,II and III have Km values near 0.1 mM.Glucokinase has a Km range of 2-5 mM.If after a heavy meal the blood glucose level rises to 8 mM which statement will be true?

• A)At this high blood glucose level all four hexokinases are saturated with substrate.
• B)Hexokinases I,II and III are catalyzing at their maximum rate,but glucokinase can still respond to increases in blood glucose levels.
• C)None of the enzymes is saturated.All of them help to increase the rate of glycolysis.
• D)The flux through glucokinase will be extremely low.The only significant catalysis is done by hexokinases I,II and III.