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Cell Growth. Section 10-1. Limits To Cell Growth. There are two main reasons why cells divide DNA OVERLOAD : The larger a cell becomes the more demands the cell places on its DNA

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Cell growth

Cell Growth

Section 10-1

Limits to cell growth
Limits To Cell Growth

  • There are two main reasons why cells divide

    • DNA OVERLOAD: The larger a cell becomes the more demands the cell places on its DNA

    • EXCHANGE OF MATERIALS: The larger a cell becomes the more trouble it has moving enough nutrients and wastes across the cell membrane

Dna overload
DNA Overload

  • All of the information that controls a cell’s functions is stored in the DNA

    • When a cell is small the information stored in the DNA is able to meet the cell’s needs

    • As a cell increases in size the DNA can not keep up with all of the demands which are placed on it

Dna overload cont
DNA Overload Cont.

  • If a cell were to grow without limit an “information crisis” would occur

Exchanging materials
Exchanging Materials

  • Food, oxygen, and water enter the cell through the cell membrane

  • Waste products leave in the same way

  • The rate at which this exchange of materials takes place depends on the surface area of the cell

    • This is the total area of the cell membrane

Exchanging materials cont
Exchanging Materials Cont.

  • However the rate at which food and oxygen are used up and waste products are produced depends on the volume of the cell

  • Understanding the relationship between a cell’s volume and its surface area is the key to understanding why cells must divide

Surface area to volume ratio
Surface Area To Volume Ratio

  • The volume of a cell increase much more rapidly than the surface area

    • As a result the ratio of surface area to volume ratio decreases

    • Surface area = l x w x 6 sides

    • Volume = l x w x h

  • A cell will have increasing difficulty moving oxygen and nutrients into the cell and moving waste products out as it increases in size.

Cell division
Cell Division

  • A cell will divide into two cells before it reaches the point of DNA overload or the exchange of material becomes a problem

  • The process is called cell division

    • The two cells that result are called “daughter cells” because they are identical to one another

Cell division cont
Cell Division Cont.

  • Before cell division occurs the cell replicates or copies all of its DNA

  • The replication of DNA solves the problem of information storage

    • Each daughter cell gets one complete set of genetic information

Cell division cont1
Cell Division Cont.

  • Cell division also solves the problem of increasing size by reducing the cells volume

  • Each daughter cell has an increased ratio of surface area to volume

    • This allows for efficient exchange of materials with the environment