Cell Growth, Divison, and Reproduction

Cell Growth, Division, and Reproduction

Key Questions

• What difficulties do cells face as they increase in size?

• How do asexual and sexual reproduction compare?

Vocabulary

• Cell division

• Asexual reproduction

• Sexual reproduction

Limits to Cell Size

• Cells grow by increasing in size but eventually divide.

• Two main reasons for cell division:

  • DNA Overload: The larger a cell becomes, the more demands are placed on its DNA.

  • Inefficient Exchange: A larger cell is less efficient in moving nutrients and waste materials across the cell membrane.

Information “Overload”

• Living cells store information in DNA.

• DNA is used to build molecules needed for cell growth.

• As a cell increases in size, its DNA amount does not increase, leading to an "information crisis."

• Analogy: A small town library with limited books versus a growing population; DNA can no longer serve the needs of the growing cell.

Exchanging Materials

• Food, oxygen, and water enter a cell through the cell membrane. Waste products leave in the same way.

• The rate of exchange depends on the surface area of the cell membrane.

• The rate of usage of food and oxygen, and waste production, depends on the cell’s volume.

• Understanding the relationship between surface area and volume is key to understanding why cells must divide rather than continue to grow.

Think About It

• Living things grow by producing more cells rather than increasing the size of each cell.

• Growth requires cells to divide and produce more of themselves.