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# Homework 7 (Due 4/22/2016)

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.