How do you use iodine to time starch digestion by amylase?
Reveal answer
Put drops of iodine on a spotting tile; add a drop of the mixture every 30 s; record when the iodine no longer turns blue-black.
Key words: spotting tile · iodine · interval
2(c) BIOLOGICAL MOLECULES · RECALL
2.12 Temperature and enzyme activity
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What is meant by the term rate?
Reveal answer
Change in a measured quantity per unit time; here estimated as 1/completion time.
Key words: rate
What is meant by the term endpoint?
Reveal answer
The defined observation used to judge that the measured reaction stage has been reached.
Key words: endpoint
What is meant by the term buffer?
Reveal answer
A solution that resists changes in pH.
Key words: buffer
What is meant by the term equilibrate?
Reveal answer
Allow materials to reach the selected temperature before starting.
Key words: equilibrate
What is meant by the term sampling interval?
Reveal answer
The fixed time between successive samples.
Key words: sampling interval
Practical design audit: for Independent variable, give the implementation and the reason.
Reveal answer
Implementation: Water-bath temperature measured with a thermometer. Reason: Tests the intended factor.
Key words: Independent variable
Practical design audit: for Dependent variable, give the implementation and the reason.
Reveal answer
Implementation: Time to starch-negative iodine result; rate = 1/time. Reason: Converts a shorter completion time into a larger rate.
Key words: Dependent variable
Practical design audit: for Control variables, give the implementation and the reason.
Reveal answer
Implementation: pH, concentrations, volumes, sampling interval and mixing. Reason: Prevents alternative causes of rate differences.
Key words: Control variables
Practical design audit: for Reliability, give the implementation and the reason.
Reveal answer
Implementation: At least three repeats and a mean with anomalies justified. Reason: Reduces influence of random error.
Key words: Reliability
Practical design audit: for Resolution, give the implementation and the reason.
Reveal answer
Implementation: Narrower temperature steps near the apparent maximum. Reason: Improves estimate of optimum.
Key words: Resolution
True or false, and why? “Iodine shows how much amylase is present.”
Reveal answer
False. Iodine detects starch; enzyme activity is inferred from how quickly starch disappears.
True or false, and why? “The fastest tube must contain the most enzyme.”
Reveal answer
False. If concentration is controlled, temperature can alter activity without changing enzyme amount.
True or false, and why? “The endpoint time is exact.”
Reveal answer
False. It lies within an interval bounded by consecutive samples.
True or false, and why? “The highest tested rate proves the exact optimum.”
Reveal answer
False. The true optimum may lie between tested temperatures.