IB myp 4-5 Biology – Practice Questions- All Topics
Topic :Cells-Systems
Topic :Cells– Weightage : 21 %
All Questions for Topic : Tissues,Organs,System,Structure and Function,Life processes,Factors affecting human health,Vaccination
Investigating amylase
This reaction happens in the mouth:
The amount of amylase in saliva can be assessed by testing how long it takes for a sample of saliva to digest all the starch in a measured quantity of starch solution. You can use the following protocol:
Question:
a) Choose one of these hypotheses:
● There is more amylase in the saliva of girls than boys.
● There is more amylase in the saliva of boys than girls.
● There is no difference between the amount of amylase in the saliva of girls and boys (null hypothesis).
▶️Answer/Explanation
Ans: Most plausible hypothesis is no difference between boys and girls; same amount of starch in the diet; same need for amylase/starch digestion.
Explain the reasons for your choice of hypothesis.
b) Describe how you plan to test your hypothesis, including control of variables.
▶️Answer/Explanation
Ans: Same saliva collection method; same volume of saliva used in testing; same temperature repeats/test saliva from more than one boy and girl.
c) Either using your actual results, or results supplied by your teacher, calculate average rates of starch digestion, showing your working clearly.
▶️Answer/Explanation
Ans: Time taken to digest starch measured in seconds/converted to seconds; amount of starch digested correctly calculated as volume of starch solution (cm3) × starch concentration (mg cm–3) (1% starch is 10 mg cm–3); rate of starch digestion = mass of starch digested (mg)/time taken (seconds); calculate average rates for girls and for boys.
d) Use whatever chart or graph you think is most appropriate to display the rates.
▶️Answer/Explanation
Ans: Mean rate of starch digestion on y axis with scale and legend; boys and girls on X axis; two bars only plotted (not a bar for each saliva sample; range bars to show the highest and lowest rates for boys and for girls).
e) Evaluate your hypothesis using the results of the experiment.
▶️Answer/Explanation
Ans: Difficult to determine whether starch is fully digested; gradual colour change of iodine from blue–black to orange; variability of results; more repeats needed; comment on whether the differences are significant; other valid comment based on actual data obtained/used.