The table below shows the concentrations of four different solutes inside a mammalian proximal convoluted tubule (PCT) cell and in the surrounding glomerular filtrate within the tubule lumen:
| Solute | Concentration in lumen (mmol dm−3\text{mmol dm}^{-3}mmol dm−3) | Concentration inside PCT cell (mmol dm−3\text{mmol dm}^{-3}mmol dm−3) |
|---|---|---|
| Sodium ions (Na+\text{Na}^+Na+) | 140 | 15 |
| Glucose | 4.5 | 12.2 |
| Urea | 5.0 | 5.0 |
| Chloride ions (Cl−\text{Cl}^-Cl−) | 115 | 40 |
Which solute requires active transport to be absorbed from the tubule lumen into the PCT cell?
Sodium ions (Na+)\text{Sodium ions } (\text{Na}^+)Sodium ions (Na+)
Glucose\text{Glucose}Glucose
Urea\text{Urea}Urea
Chloride ions (Cl−)\text{Chloride ions } (\text{Cl}^-)Chloride ions (Cl−)
82 exam-style questions on OCR GCSE Biology 2.1 Supplying the cell, covering 2.1.1 Transport across cell membranes, 2.1.2 Mitosis and the cell cycle, 2.1.3 Importance of cell differentiation, and 2.1.4 Stem cells. Each one has a worked solution and a mark scheme showing where the marks go.