A spherical unicellular alga relies solely on passive diffusion across its cell surface membrane to supply its cytoplasm with dissolved carbon dioxide. During a growth phase, the cell remains spherical but its volume increases by 237.5% (representing a final volume 3.375 times its initial volume).
Which of the following correctly describes the change in the cell's surface-area-to-volume (SA:VSA:VSA:V) ratio and the biological consequence of this scaling?
The SA:VSA:VSA:V ratio decreases by a factor of 3.3753.3753.375 (to approximately 29.6%29.6\%29.6% of its original value), reducing the rate of carbon dioxide supply per unit volume of cytoplasm.
The SA:VSA:VSA:V ratio decreases by a factor of 1.51.51.5 (to approximately 66.7%66.7\%66.7% of its original value), reducing the rate of carbon dioxide supply per unit volume of cytoplasm.
The SA:VSA:VSA:V ratio decreases by a factor of 1.841.841.84 (to approximately 54.3%54.3\%54.3% of its original value), reducing the rate of carbon dioxide supply per unit volume of cytoplasm.
The SA:VSA:VSA:V ratio increases by a factor of 1.51.51.5 (to 150%150\%150% of its original value), increasing the rate of carbon dioxide supply per unit volume of cytoplasm.
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.