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Date November 2016 Marks available 4 Reference code 16N.3.SL.tz0.10
Level Standard Level Paper Paper 3 Time zone time zone 0
Command term Explain Question number 10 Adapted from N/A

Question

Discuss water distribution in trained athletes.

[3]
d.i.

Explain the roles of the medulla and the loop of Henlé in maintaining the water balance of the blood.

[4]
d.ii.

Markscheme

percentage of water distribution depends on body composition ✔

muscle contains 65–75 % water whereas fat mass is 5–20 % water ✔

a trained athlete is likely to have more muscle mass compared to an untrained individual ✔

a trained athlete has greater muscle glycogen stores, which store more water ✔

exercise training increases percentage water distributed within the intracellular compartment ✔

a trained athlete will have greater water content in their body both intra and extracellularly ✔

sweat of a trained athlete is more dilute than an untrained individual which can affect water distribution during exercise ✔

a trained athlete has improved temperature regulatory process ✔

a trained athlete has increased blood plasma volume ✔

Accept answers in the converse.

d.i.

the medulla is a region in the lower/mid-section of the kidney which has an increasing/high salt concentration ✔

«generally» the loop of Henle descends through into the medulla ✔

the high salt concentration/osmolarity in the medulla causes water to «passively» be drawn out of the descending loop of Henle ✔

the ascending loop of Henle actively pumps out salt ✔

the ascending is impermeable to water ✔

the descending is «only» permeable to water ✔

creates a concentration gradient between the medulla ✔

regulates a high concentration of urea near the medulla ✔

 

d.ii.

Examiners report

not always clear and an area for improvement.

d.i.

not always clear and an area for improvement.

d.ii.

Syllabus sections

Option D: Nutrition for sports, exercise and health » D.2. Water and electrolyte balance » D.2.5. Explain the roles of the loop of Henlé, medulla, collecting duct and ADH in maintaining the water balance of the blood.
Option D: Nutrition for sports, exercise and health » D.2. Water and electrolyte balance
Option D: Nutrition for sports, exercise and health

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