Cell Size Limitations

Why cells can't be infinitely large! Learn about diffusion, DNA limits, and the surface area to volume ratio.

Watch the video below to learn how surface area and volume affect organisms. Then answer the questions that follow. Diffusion is the tendency of molecules to spread from areas of high concentration to low concentration. Cells depend on diffusion through the cell wall and cell membrane to obtain water, oxygen, and food, and to get rid of carbon dioxide and waste products. Why would diffusion limit cell size? Because diffusion stops working completely if the cell is too big Because diffusion works too quickly in large cells Because diffusion becomes slow and inefficient in large cells Every cell needs DNA in order to make proteins through protein synthesis. Protein synthesis has a maximum rate, meaning that at some point the cell is making as many proteins as possible. Why would DNA limit the size of a cell? The DNA is gets lost when the cell is too large. Protein synthesis cannot keep up with a cell's need for protein when the cell is too large. Protein synthesis stops working when the cell is too large. The surface area to volume ratio compares the physical surface area of a 3D object (like a cell) to the volume of the object. As a cell's size increases, the cell's volume increases much faster than the surface area.If a cell doubles in size, the cell would need 8 times more nutrients and create 8 times as much waste, but the surface area will only increase by a factor of 4. That means that the nutrients and waste have much farther to travel to get in or out of the cell.What would be the end result of the cell's surface area to volume ratio becoming too low (by the cell becoming too large)? The cell would either starve to death or be poisoned from the buildup of waste products. The cell would gain special powers that mutate the membranes. The cell would explode. When a cell grows too large, and the surface area is no longer to keep up with the cell's demands, the cell will stop growing. At that point, there are a number of choices. If you were a single-cell, what would you choose? Die from starvation or waste build-up Change shape to become long and thin Divide into smaller cells