What limits cell size?
What will be an ideal response?
A living cell must exchange substances with its environment at a rate that keeps pace with its metabolism. These exchanges occur across the plasma membrane, which can handle only so many exchanges at a time. The rate of exchange across a plasma membrane depends on its surface area: the bigger it is, the more substances can cross it during a given interval.
Cell size is limited by a physical relationship called the surface-to-volume ratio. By this ratio, an object's volume increases with the cube of its diameter, but its surface area increases only with the square. As a cell expands in diameter, its volume increases faster than its surface area does. Therefore, the exchange required for a larger cell volume would not be met with the smaller plasma membrane.
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An increase in diameter in a plant is called:
A. primary growth. B. secondary growth. C. longitudinal growth. D. apical growth. E. herbaceous growth.
The primary function of the large intestine is
a. storage of feces. b. retention of water. c. manufacture of vitamin K. d. digestion of fats. e. absorption of water.
The highest rates of reproduction would be expected in which of the following countries?
a. United States b. Germany c. Nigeria d. Argentina e. Russia
Which of the following domains contains the common advanced plants and animals and fungi?
A) Archaea B) Bacteria C) Plantae D) Fungi E) Eukarya