An athlete's body must regulate water, salts, and glucose during exercise.
In which specific part of the nephron does the selective reabsorption of glucose normally take place?
During a long-distance run, an athlete loses a large volume of water through sweat.
State how the concentration of ADH in the blood changes in response to this dehydration.
Describe the effect of this change on the kidneys and the resulting urine.
The table below shows information about three types of sports drinks:
| Sports drink | Solute concentration relative to blood | Carbohydrate mass per 100textmL100\\text{ mL}100textmL (g) | Speed of absorption |
|---|---|---|---|
| Hypotonic | Lower | <3<3<3 | Very fast |
| Isotonic | Same | 4−84-84−8 | Fast |
| Hypertonic | Higher | >8>8>8 | Slow |
An athlete drinks a hypertonic sports drink 45 minutes before starting a long-distance race. After completing the race, the athlete drinks an isotonic sports drink.
Explain the biological reasons behind the athlete's choice and timing of these drinks.
22 exam-style questions on OCR GCSE Biology 3.3 Maintaining internal environments, covering 3.3.1 Importance of a constant internal environment, 3.3.2 The skin and body temperature, 3.3.3 Insulin and blood sugar, 3.3.4 Glucagon and blood sugar, 3.3.5 Type 1 and type 2 diabetes, 3.3.6 Osmotic changes in body fluids, 3.3.7 Kidneys and water balance, 3.3.8 Structure of the kidney and tubule, 3.3.9 ADH and kidney tubule permeability, and 3.3.10 Responses to temperature and osmotic challenges. Each one has a worked solution and a mark scheme showing where the marks go.