Tube 1 of a row of ten tubes has 512 mg of an antibiotic in each litre…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Tube 1 of a row of ten tubes has mg of an antibiotic in each litre. Each next tube has half the dose of the one before it. Bacterium X is stopped by a dose of mg per litre or more. Bacterium Y is stopped by a dose of mg per litre or more.
- What is the lowest dose in a clear tube for bacterium X?
- What is the lowest dose in a clear tube for bacterium Y?
- How many tubes are clear for bacterium Y?
Need a reminder? The key ideaShow
Penicillin was seen by Fleming in 1928 and made a medicine by Chain and Florey. Lipases are used in detergents, pectinases and proteases to clear juices, and streptokinase from Streptococcus as a clot buster. Cyclosporin A (Trichoderma polysporum) suppresses the immune response. Statins (Monascus purpureus) are competitive inhibitors of the enzyme that makes cholesterol. In a row of tubes, each tube has half the dose of the one before. The lowest clear tube is the last one whose dose is at least the least dose that stops the bacterium.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. Doses in mg per litre: .
Plan. Keep the tubes whose dose is at least the dose that stops the bacterium.
Step 1. Bacterium X. The doses of or more are and . The lowest is mg per litre. The next tube, mg per litre, is below , so it is cloudy.
Step 2. Bacterium Y. The doses of or more run down to mg per litre. The next dose, , is below .
Step 3. Count. The clear tubes for Y are and , which is tubes.
Answer: mg per litre; mg per litre; tubes.
Check. The reading for X is , above its true value of . The row can only show the doses that are in it.
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