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Edexcel iGCSE Biology 4BI1 - Paper 2B -Characteristics of living organisms- Exam Style Questions- New Syllabus

Edexcel International GCSE in Biology Paper 2B - All Chapters
Question

Isotonic drinks are often used to rehydrate athletes after exercise.

(a) Explain why athletes lose water during exercise. 

(b) Isotonic drinks contain salt and sugar solutions that are the same concentration as normal blood plasma.

A scientist uses this method to investigate how well an isotonic drink rehydrates athletes.

  • three athletes exercise for one hour
  • one athlete has no drink
  • the second athlete drinks \(1000\ \text{cm}^3\) of pure water
  • the third athlete drinks \(1000\ \text{cm}^3\) of isotonic drink
  • the volume and colour of urine produced by each athlete are measured one hour later

The table shows the scientist’s results.

Drink consumed by athleteVolume of urine produced in \(\text{cm}^3\)Colour of urine
no drink100very dark yellow
pure water750very light yellow
isotonic drink500yellow

(i) Explain the results shown in the table for the athlete who consumed no drink.
(ii) Explain the differences in urine volume and urine colour produced by the athlete who consumed the isotonic drink and the athlete who consumed pure water. 

Most-appropriate topic codes (Edexcel IGCSE Biology):

• 1(a): Characteristics of living organisms — part (a)
• 2(h): Transport (Humans) — part (a, b)
• 2(i): Excretion (Humans) — parts (b)(i), (b)(ii)
• 2(j): Co-ordination and response (Homeostasis) — parts (b)(i), (b)(ii)
▶️ Answer/Explanation
Solution

(a) An explanation that makes reference to two of the following:

  • Exercise increases body temperature / eq (1)
  • (More) sweat / eq (1)
  • To cool down / lose heat / eq (1)
  • By evaporation (of sweat) (1)

(b)(i) An explanation that makes reference to three of the following:

  • Blood concentration increases / less water in blood / eq (1)
  • (Detected by) hypothalamus / osmoreceptors / pituitary gland (1)
  • Releases ADH (1)
  • Collecting duct becomes more permeable / eq (1)
  • Increased water reabsorption (so less urine produced) (1)

(b)(ii) An explanation that makes reference to two of the following:

  • With (pure water) blood becomes more dilute / less concentrated / has high water concentration / eq (1)
  • Less / no ADH released when drinking water / eq (1)
  • Less water reabsorbed (by kidney) when water drunk / eq (1)
  • Salt / sugar absorbed into blood (in intestine) (from isotonic drink) / eq (1)

Accept converse arguments for the isotonic drink (e.g., more ADH released, more water reabsorbed).

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