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Chemistry LibreTexts

Homework 7 (Due 4/22/2016)

  • Page ID
    47379
  • Name: ______________________________

    Section: _____________________________

    Student ID#:__________________________

    Q7.1

    Fill in the blanks.

    Many enzymes require a nonprotein cofactor to assist them in their reaction. In this case, the protein portion of the enzyme, called an _______________ , combines with the cofactor to form the whole enzyme or ____________ . Some cofactors are ions such as Ca++, Mg++, and K+; other cofactors are organic molecules called _____________ which serve as carriers for chemical groups or electrons. Anything that an enzyme normally combines with is called a _____________ .

    Q7.2

    Briefly describe a generalized enzyme-substrate reaction, state the function of an enzyme's active site, and describe how an enzyme is able to speed up chemical reactions.

    Q7.3

    State how the following will affect the rate of an enzyme reaction.

    1. increasing temperature
    2. decreasing temperature
    3. pH
    4. salt concentration

    Q7.4 (steady-state approximation redux)

    The reaction between \(\ce{H2}\) and \(\ce{Br2}\) in the presence of light is consistent with the following chain mechanism: What is the rate of generating \(\mathrm{H}^{\cdot}\)?

    1. \(\ce{Br2} \underset{\Large{k_2}}{\overset{\Large{k_1}}\rightleftharpoons} \mathrm{ 2Br^\cdot}\)
    2. \(\mathrm{Br^\cdot + H_2} \overset{\Large{k_3}}{\underset{\Large{k_4}}\rightleftharpoons} \mathrm{HBr + H^\cdot}\)
    3. \(\mathrm{H^\cdot + Br_2} \xrightarrow{\Large{k_5}} \mathrm{HBr + Br^\cdot}\)

    Options

    • \(k_3\mathrm{[Br ^{\cdot} ][H_2]}\)
    • \(k_5\mathrm{[H ^{\cdot} ][Br_2]}\)
    • \(k_4\mathrm{[HBr][H ^{\cdot} ]}\)

    Q7.5

    The substrate N-acetylglycine ethyl ester can be catalyzed by the enzyme carbonic anhydrase. This enzyme has a turnover rate of 30,000 s-1. Determine how long it will take carbonic anhydrase to cleave the substrate.

    Q7.6

    An solution initially contains a catalytic amount of an enzyme with KM = 1.5 mM, 0.25 M of substrate, and no product. After 45 seconds, the solution contains 25 µM of product. Find Vmax and the concentration of product after 2.0 minutes. Hint: [S] >> KM

    Q7.7

    The data below represents the data recorded after the hydrolysis of a substrate by an enzyme with \([E]_0 = 5.0 \times 10^{-6}\; M\) .
    [S]/10-4 M 2.1 4.2 9.3 14.2
    vo / 10-6 M · min-1 1.2 3.1 6.3 9.1
    Calculate Vmax, Km and K2 for this system using a Lineweaver-Burk plot. Assume Michaelis-Menten kinetics.