What is the purpose of a buffer in an enzyme pH investigation?
Reveal answer
It keeps the pH at a fixed value throughout the reaction.
Key words: buffer · pH
2(c) BIOLOGICAL MOLECULES · RECALL
2.14B pH and enzyme activity
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What is meant by the term confounding variable?
Reveal answer
An uncontrolled factor that changes with the independent variable and offers an alternative explanation.
Key words: confounding variable
What is meant by the term repeatability?
Reveal answer
Agreement when the same person repeats a method with the same equipment.
Key words: repeatability
What is meant by the term resolution?
Reveal answer
The smallest interval or difference that a method can distinguish.
Key words: resolution
What is meant by the term anomaly?
Reveal answer
A result inconsistent with the pattern and repeats, investigated rather than automatically deleted.
Key words: anomaly
Variables in the pH investigation, Independent. Variable? How it is handled?
Reveal answer
Variable: pH. How it is handled: Use labelled buffers at chosen pH values and equal buffer volumes.
Key words: Independent
Variables in the pH investigation, Dependent. Variable? How it is handled?
Reveal answer
Variable: Amylase activity. How it is handled: Measure starch-disappearance time; calculate rate = 1/time.
Key words: Dependent
Variables in the pH investigation, Controlled (Temperature). How it is handled?
Reveal answer
Use one thermostatically controlled water bath and verify it.
Key words: Controlled
Variables in the pH investigation, Controlled (Concentrations and volumes). How it is handled?
Reveal answer
Use the same stocks and measured volumes each trial.
Key words: Controlled
Variables in the pH investigation, Controlled (Sampling). How it is handled?
Reveal answer
Use equal drops and a fixed interval with the same endpoint rule.
Key words: Controlled
Variables in the pH investigation, Reliability. Variable? How it is handled?
Reveal answer
Variable: Random variation. How it is handled: Repeat each pH at least three times and compare spread.
Key words: Reliability
True or false, and why? “Iodine measures pH.”
Reveal answer
False. The buffer defines pH; iodine reports whether starch remains.
True or false, and why? “Adding more buffer only changes pH.”
Reveal answer
False. It also changes total volume and concentrations, so buffer volume must be controlled.
True or false, and why? “The fastest tested pH is the exact optimum.”
Reveal answer
False. It is the best tested value; the true optimum may lie between tested points.
True or false, and why? “An anomalous result should always be removed.”
Reveal answer
False. It should be checked against repeats and excluded only with a justified reason.