A sequence question is a set of normal questions that count as one.
<?xml version="1.0" encoding="UTF-8"?> <question type="sequence"> <question type="OPTION"> <text> <p>A sequence question is a series of questions that are regarded as one question.</p> <p>Besides the growth curve in batch of the <span style="color: red;">first organism</span> (red diamonds), the growth curve of a <span style="color: blue;">second organism</span> is drawn (blue boxes) in the graph:<br /> <img src="[attachurl:intro_ld4_17_1.png]" width="378" height="220" /><br /> What is the ratio of <span style="color: red;">μ<sub>max,organism 1</sub></span> / <span style="color: blue;">μ<sub>max,organism 2</sub></span>? </p> </text> <hint mintries="1"> What is the meaning of μ<sub>max</sub>? And what is the meaning of the slope of both growth curves? </hint> <hint mintries="2"> The volumetric growth rate r<sub>x </sub> = dC<sub>x</sub> / dt (kg / m<sup>3</sup> / h). When do the organisms grow at μ<sub>max</sub>? </hint> <hint mintries="3"> When the organisms grow exponentially, they grow at μ<sub>max</sub>. The formula for r<sub>x</sub> yields:<br /> <b>r<sub>x</sub> = μ<sub>max</sub> • C<sub>x</sub></b> (kg / m<sup>3</sup> / h)<br /> So you'll have to compare dC<sub>x,organism1</sub> / dt and dC<sub>x,organism1</sub> / dt in the beginning of the batch. </hint> <hint mintries="4"> The red organisms take 1.25 h to grow to a C<sub>x</sub> of 10 kg / m<sup>3</sup>, the blue need 2 h. So the red organism is faster, &mu will be higher, so the value must be above 1.<br /> μ<sub>max,organism 1</sub> / μ<sub>max,organism 2</sub> = 1.5 </hint> <option correct="0"> <choice>It is impossible to tell on basis of this graph</choice> <feedback>You are wrong. It is possible to tell on basis of this graph</feedback> </option> <option correct="0"> <choice>≈ 0</choice> <feedback>Read the question again, to get an anser of zero, one of the growth rates needs to be zero or infinite, which is obviously not the case.</feedback> </option> <option correct="0"> <choice>≈ 0.4</choice> <feedback>There is no 0.4 X difference in the growth rates.</feedback> </option> <option correct="1"> <choice>≈ 0.6</choice> <feedback>Check again which organism is the first and which is the second.</feedback> </option> <option correct="0"> <choice>≈ 0.8</choice> <feedback>There is no 0.8 X difference in the growth rates.</feedback> </option> <option correct="0"> <choice>≈ 1</choice> <feedback>Assume they grow at the maximum growth rate, the growth rate is definately not the same!</feedback> </option> <option correct="1"> <choice>≈ 1.5</choice> <feedback>That is correct! The slope dC <sub>x</sub> / dt of the growth curve is given by the volumetric growth rate r<sub>x</sub><br /> Because<br /> <b>r<sub>x</sub> = μ<sub>max</sub> • C<sub>x</sub></b> (kg / m<sup>3</sup> / h)<br /> in the beginning of the batch:<br /> <b>r<sub>x,organism1</sub> / r<sub>x,organism2</sub> = μ<sub>max,organism 1</sub> / μ<sub>max,organism 2</sub></b> (-)<br /> Both organisms had the same initial biomass concentration. Organism 1 needed 1.25 h to grow to a C <sub>x</sub> of 10 kg / m <sup>3</sup>, organism needed 2 h for that, so μ <sub>max,organism 1</sub> must be higher then μ <sub>max,organism 2</sub> so the answer will ne higher then 1. <br /> <em>Click continue to go to part 2 of this question.</em> </feedback> </option> </question> <question type="OPTION"> <text> Now the growth curve of a <span style="color: blue;">third organism</span> (blue x-es) is shown together with the <span style="color: red;">first organism</span> (red diamonds):<br /> <img src="[attachurl:intro_ld4_17_2.png]" width="378px" height="220px" /><br /> What is the ratio of <span style="color: red;">μ<sub>max,organism 1</sub></span> / <span style="color: blue;">μ<sub>max,organism 3</sub></span>? </text> <hint mintries="1"> Keep in mind that both growth curves have a different initial biomass concentration C<sub>x</sub> (0) </hint> <hint mintries="2"> The bacteria grow only at their maximum speed in the beginning of a batch </hint> <hint mintries="3"> Organism 1 needs about 1 hour to grow from C<sub>x</sub> = 5 - 10 kg / m<sup>3</sup>. How much does organism 3 need to grow from 5-10 kg / m<sup>3</sup>? </hint> <hint mintries="4"> The answer is that they grow at an identical specific growth rate, the answer is 1! </hint> <option correct="0"> <choice>It is impossible to tell on basis of this graph</choice> <feedback></feedback> </option> <option correct="0"> <choice>≈ 0</choice> <feedback></feedback> </option> <option correct="0"> <choice>≈ 0.4</choice> <feedback></feedback> </option> <option correct="0"> <choice>≈ 0.6</choice> <feedback></feedback> </option> <option correct="0"> <choice>≈ 0.8</choice> <feedback></feedback> </option> <option correct="1"> <choice>≈ 1</choice> <feedback>Yes! On first sight, it may look if organism 3 grows faster than organism 1. Organism 3 does have a higher <i>volumetric</i> growth rate r<sub>x</sub> than organism 1, but both have the same maximal specific growth rate μ<sub>max</sub>. This can be explained using the formula for r<sub>x</sub>:<br /> <b>r<sub>x</sub> = μ • C<sub>x</sub></b> (kg / m<sup>3</sup> / h)<br /> Organism 3 started with a higher initial biomass concentration than organism 1, so with equal μ, it's r<sub>x</sub> became higher. </feedback> </option> <option correct="0"> <choice>≈ 1.5</choice> <feedback></feedback> </option> </question> <question type="PATTERN" duplicates="0"> <text>Select and order the needed steps. This example question contains only one target box.</text> <option identifier="a"> <choice>Step A.</choice> <description name="a"> <b>Step A:</b><br />A description of step A. </description> </option> <option identifier="b"> <choice>Step B.</choice> <description name="b"> <b>Step B:</b><br />A description of step B. </description> </option> <option identifier="c"> <choice>Step C.</choice> <description name="c"> <b>Step C:</b><br />A description of step C. </description> </option> <option identifier="d"> <choice>Step D.</choice> <description name="d"> <b>Step D:</b><br />A description of step D. </description> </option> <option identifier="e"> <choice>Step E.</choice> <description name="e"> <b>Step E:</b><br />A description of step E. </description> </option> <option identifier="f"> <choice>Step F.</choice> <description name="f"> <b>Step F:</b><br />A description of step F. </description> </option> <hint mintries="1">first hint</hint> <sequence correct="1"> <pattern>^bcd$</pattern> <feedback>Correct. You only need steps B, C and D. </feedback> </sequence> <sequence correct="0"> <pattern>^[^b]*c.*$</pattern> <feedback>You can not do step C unless you first do step B.</feedback> </sequence> <sequence correct="0"> <pattern>.*</pattern> <feedback mintries="1">Nope, that't not correct. Try again.</feedback> <feedback mintries="2" maxtries="2">You only need three steps.</feedback> <feedback mintries="3">You need steps BCD.</feedback> </sequence> </question> </question>