DP Biology (last assessment 2024)

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Question 23M.3.SL.TZ1.16

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Date May 2023 Marks available [Maximum mark: 6] Reference code 23M.3.SL.TZ1.16
Level SL Paper 3 Time zone TZ1
Command term Explain, Identify, Outline Question number 16 Adapted from N/A
16.
[Maximum mark: 6]
23M.3.SL.TZ1.16

Doctors investigated the effect of diets with different protein content on appetite for food in overweight males. One group followed a diet with normal protein (NP group) and a second group followed a diet with high protein (HP group). Participants were asked to record their perceptions of appetite every hour during 15 waking hours.

[Source: Reproduced from Leidy, H.J., Tang, M., Armstrong, C.L., Martin, C.B., Campbell, W.W., 2011. The effects of consuming
frequent, higher protein meals on appetite and satiety during weight loss in overweight/obese men. Obesity, 19(4),
pp. 818–824, with permission from Wiley.]

(a)

Identify the effect on appetite of changing from an NP diet to an HP diet.

[1]

Markscheme

high protein/HP diet decreases appetite;

Accept vice versa but not negative correlation

Examiners report

The majority of candidates answered correctly.

(b)

Outline the control of appetite by the brain.

[2]

Markscheme
  1. control is located in hypothalamus;
  2. reduces or increases desire to eat when stimulated by hormones;
  3. leptin secreted by adipose tissue;
  4. leptin depresses appetite;
  5. other example;

For mpe accept verified examples of other hormones e.g. insulin, glucagon, ghrelin, CCK, PYY3-36

Examiners report

Most knew the hypothalamus controls appetite but some mistakenly thought it produced the controlling hormones. Leptin and ghrelin were most often mentioned.

(c)

Explain the reason that a protein-rich diet would not be recommended to obese adults suffering from phenylketonuria (PKU).

[3]

Markscheme
  1. HP diet will suppress appetite for obese adults;
  2. protein-rich diet may contain (higher levels of) phenylalanine;
  3. people with PKU cannot convert phenylalanine to tyrosine;
  4. (people with PKU) lack phenylalanine hydroxylase;
  5. high levels of phenylalanine build up in blood/body
    OR
    high levels of phenylalanine are harmful to sufferers of PKU;
Examiners report

There was a wide range of knowledge and a lot of misspellings of the amino acids such that awarding with benefit of doubt became difficult. The link from the graph to obese adults was rarely recognised.