DP Biology (last assessment 2024)

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Question 23M.3.SL.TZ2.2

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Date May 2023 Marks available [Maximum mark: 5] Reference code 23M.3.SL.TZ2.2
Level SL Paper 3 Time zone TZ2
Command term Explain, Identify, Outline Question number 2 Adapted from N/A
2.
[Maximum mark: 5]
23M.3.SL.TZ2.2
(a)

Outline the effect of low temperature on enzyme activity.

[1]

Markscheme

slows down/inactivates the enzyme;

Examiners report

Parts (a) of this question on enzymes was well answered.

Guppies (Poecilia reticulata), popular aquarium fish, were used to test the effect of changes in pH on the activity of intestinal protease enzymes in each sex.

[Source: Thongprajukaew, K. and Kovitvadhi, U., 2013. Effects of sex on characteristics and expression
levels of digestive enzymes in the adult guppy Poecilia reticulata. Zoological Studies 52.
https://zoologicalstudies.springeropen.com/articles/10.1186/1810-522X-52-3. Open access.]

(b)

Identify the independent and dependent variables in this study.


Independent variable: 

Dependent variable: 

[2]

Markscheme
  1. Independent variable: pH / sex;
  2. Dependent variable: enzyme/protease activity;
Examiners report

Parts (b) of this question on enzymes was well answered.

(c)

Explain how change in pH affects the protease activity of the females.

[2]

Markscheme
  1. change in acidity/pH changes the charges/shape/denatures/structure of the enzyme;
  2. changes may alter the ability of the enzyme to bind / binding of substrate;
  3. greatest/peak/maximum activity is at optimal pH/pH10;
Examiners report

Part (c) was not well answered with most candidates only describing the shape of the graph when an explanation for the change of shape was required. Many candidates scored 1 mark for stating that the optimum or peak pH was at pH 10.