Answer to Question #198076 in Biochemistry for Paul Hackman

Question

6.Name two key enzymes involved in substrate level phosphorylation reactions of glycolysis

7.Briefly explain how acetyl - CoA used for fatty acid biosynthesis is transported from the mitochondria to the cytosol and indicate the state (fed or fasted ) under which this can occur.

8. Briefly explain how enzymes decrease the activation energy of biochemical reactions

9.write the mechaelis -Menten equation for enzymes catalysis and define the parameters.

10 what are the differences between competitive, non competitive and uncompetitive inhibitions?

Answer 1

Answers:

6. The two key enzymes are :

i) Glyceraldehyde 3-phosphate dehydrogenase; for conversion of 3-phosphoglyceraldehyde and Pi and NAD+ to 1,3-bisphosphoglycerate.

ii) Pyruvate kinase; for dephosphorylating phosphoenolpyruvate,

7. Acetyl-CoA is moved through the mitochondrial membrane, and enters the cytoplasm of the cell, as the molecule citrate. In the cytoplasm, these citrate molecules are once again converted back to Acetyl-CoA bu use of energy derived from the breakdown of an ATP molecule.

Under "fed" state, condition of carbohydrate or glucose excess, this occurs to direct acetyl-CoA away from the mitochondria and back to the cytosol for the synthesis of fatty acids and sterols.

8. Enzymes decreases activation energy through various means, including positioning substrates together in the proper orientation, applying torque on the substrates, providing the proper charge or pH micro-environment, and adding or removing functional groups on the substrates.

9. The Mechaelis -Menten equation is $V_i = \frac{Vmax[S]}{K_m + [S]}$,

Where v_i is the measured initial velocity of an enzymatic reaction, v_max is the maximal velocity of the enzymatic reaction, and K_m is the Michaelis–Menten constant.

10. In competitive inhibition, the inhibitor binds directly to the active site of the enzyme preventing the substrate from binding to the enzyme and forming the enzyme-substrate complex. It is directly competing with the substrate. In non-competitive inhibition, the inhibitor binds to a site on the enzyme that is NOT the active site; this alters the conformation of the active site, such that the substrate can no longer bind to the active site on the enzyme. Uncompetitive inhibition occurs when the uncompetitive inhibitor binds to the enzyme-substrate complex only which increases the availability of substrate as the uncompetitive inhibitor stops the reaction between enzyme and substrate.