36. The diagram to the right depicts one of the most important metabolic pathway

Question

36. The diagram to the right depicts one of the most important metabolic pathways in biology. Use the diagram to answer the following questions. f. What enzyme catalyzes the reaction: Glucose ATPhe xokinase ADP glucokinase Glucose-6+phosphate Fructose-6-phosphate + ATP Fructose-1,6- bisphosphate +ADP Phosphofructokinase-1 What reaction does triosphosphate isomerase catalyze? Suppose the enzyme hexokinase is inhibited by dihydroxyacetone phosphate. What would this be an example of? phosphohexose isomerase g. Fructose-f-phosphate phospho- fructokinase-1 h. ADP Fructose-1,6-bisphosphate aldolase Glyceraldehyde-3-phosphate Dihydroxyacetone triosephosphate phosphate isomerase

Explanation / Answer

Answer 36

f) This is a second phosphorylation step in glycolysis. This reaction is catalyzed by an allosteric enzyme, phosphofructokinase (PFK). In this reaction , Fructose-6-Phosphate is phosphorylated by ATP to form Fructose 1,6-bisphosphate. Here the prefix bis-indicates the presence of two seperate monophosphoryl groups.

g) Step 5 in glycolysis is isomerization which is catalyzed by triose phosphate isomerase (TPI). A three carbon compound, Dihydroxyacetone phosphate (a ketose) is isomerized to another three carbon compound, Glyceraldehyde 3-Phosphate (an aldose). This isomerization of a ketose into an aldose occurs by intermolecular oxidation and reduction by the transfer of a hydrogen atom from carbon 1 to carbon 2.

h) This is an example of inhibition of regulation of glycolysis in very first step of glycolysis pathway. Hexokinase is inhibited by Glucose-6-Phosphate, which accumulates when Phosphofructokinase is inactive.

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