BIOCH200 Lecture Notes - Lecture 14: Competitive Inhibition, Dissociation Constant, Allosteric Regulation

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coffeesea-lion820

16 Apr 2018

School

University of Alberta

Department

Biochemistry

Course

BIOCH200

Professor

Adrienne Wright

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Document Summary

01. 03. 18 lec 14 delta g tells us about spontaneity. Its magnitude tells us how spontaneous the reaction is, how much heat will be given off. Transition state is the highest free energy state. More positive the delta g more slow the reaction more activation energy. , more energy put in for collision and for the right orientation of collisions. They just affect activation energy not free energy. Enzymes lower the free energy of transition state. In 1 degree structure residues are far apart. In 3 degree structure residues can come close. Affinity vs specificity (how tightly binds vs a binds, not b) In case of bpg, look for positively charged groups. Any enzyme that uses atp (except those in muscle contraction) does not want water. This is because phosphate will be released which means energy will be released. Advantages of removing water: water hydrolyses, forms h bonds, hydrophobic molecules will have a shell of water around.

Related Questions

26. An enzymatic reaction proceeds with maximal velocity (Vmax) when A. the enzyme is in excess of the substrate. B. allosteric activators are present. the reaction is proportional to substrate concentration. D. the substrate concentration exceeds that of a noncompetitive inhibitor. E. the enzyme is saturated with substrate 27- An enzymatic reaction proceeds with maximal velocity (Vmax) when A. the substrate concentration is equal to that of a competitive inhibitor B. allosteric effectors are present. C. the enzyme substrate complex is maximal. D. the substrate concentration exceeds that of a noncompetitive inhibitor. E. all of the substrate is bound to the enzyme. 28. An enzyme affects the rate of a chemical reaction by A. decreasing the free energy change of the reaction. B. increasing the free energy change of the reaction. C. lowering the energy of activation of the reaction. D. displacing the equilibrium constant. E. raising the energy of activation of the reaction. 29. Which statement is CORRECT? A. Enzymes are small molecules that are heat stable. B. Enzymes affect rates of reactions in the forward and reverse direction. C. Enzymes will determine whether a reaction will take place. D. Enzymes are permanently altered following the conversion of substrate to product. 30. Which of the following statements is TRUE? Enzyme catalysis of a chemical reaction: A. increases the energy of the transition state. B. decreases the change in free energy of the reaction. C. increases the change in free energy of the reaction. D. decreases the change in the free energy of activation. 31. Which of the following statements about enzyme substrate complexes is TRUE? A. At high substrate concentration the rate of the reaction is first order. B. The enzyme concentration is higher than the substrate concentration under physiological conditions. C. Alteration in the conformation of the enzyme may occur when substrate binds. D. Increase in enzyme concentration does not affect the rate of the reaction. 32. All of the following statements about enzymes are correct EXCEPT A. enzymes are usually protein in nature and cause reactions to occur B. enzymes form complexes with substrates and products C. enzymes affect the rate of reactions and are not permanently altered during a reaction D enzymes can undergo structural modification during a reaction E. enzyme specificity requires specific functional groups on the enzyme and substrate

Hydrogen peroxide decomposes into water and oxygen by thefollowing reaction:

2 H2O2(aq) â 2 H2O(l) + O2(g) ÎHrxn = -94.64 kJ/mol

Experimental evidence tells us that this reaction is first orderwith respect to hydrogen peroxide, with an activation energy of75.3 kJ/mol at 300 K.
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a)What is the activation energy for the reverse reaction?

b)Sketch the reaction pathway below. Be sure to label the axes,reactants, products, transition state, and energies.

c)Assuming the forward and reverse reaction have the same frequencyfactor, what is the equilibrium constant for this reaction?(when you answer this question,you will need to write down the value for K, and the temperaturethat you calculated K at.)

d)Catalase is an enzyme found in nearly all living organisms thatcatalyzes the hydrogen peroxide decomposition reaction shown aboveby lowering the activation energy of the forward reaction to 8.8kJ/mol. How many times faster does hydrogen peroxide decompose inthe presence of catalase?

e)What temperature would we need to decompose hydrogen peroxode atto achieve the same rate increase achieved with catalase?

I have the answers for a) and b) Ineed the answers for c), d), & e). I split them up because Ithought it was too long of a question so I can offer more points.Thanks.

Answer for a) and b):

(a) ÎH of reverse reaction = -ÎH offorward reaction

= -(-94.64 kJ/mol) = +94.64kJ/mol

Activation energy of reversereaction

= activation energy of forwardreaction + ÎH of reverse reaction

= 75.3 + 94.64 = 169.94kJ/mol

(b) The forward reaction isexothermic, and the reaction pathway is shown below: