Presentation on theme: "Cell Growth and Division"— Presentation transcript:
1 Cell Growth and Division How would you describe the process by which a multicellular organism increases its size?Why do cells stay small?
2 Objectives Explain the problems that growth causes for cells. Describe how cell division solves the problems of cell growth.
3 Limits to Cell GrowthThe larger a cell becomes, the more demands the cell places on its DNA and the more trouble the cell has moving enough nutrients and wastes across the cell membrane.Two reasons why cell size is limited:If a cell were to grow without control, DNA overload would occur.Rate of material exchange is dependent on surface area
4 Exchanging MaterialsFood, oxygen and water enter the cell through the cell membrane. Waste products leave the same way.The rate at which this exchange takes place depends on surface area (the total area of its cell membrane)
5 Ratio of surface area to volume As the length of a cell increases, its volume increases faster than its surface area.The resulting decrease in the cell’s surface-area-to-volume ratio makes it more difficult for the cell to move needed materials in and waste products out.
6 Cell DivisionBefore a cell becomes too large, it divides into two daughter cells by a process called cell division.
7 What are Chromosomes? Chromosomes are made up of DNA DNA carries the cell’s genetic codeThe cells of every organism have a specific number of chromosomes.
10 The structure of a chromosome ChromatinChromatidCentromereChromosomes are not visible in most cells except during cell division.At the beginning of cell division the chromosomes condense into compact, visible structures that can be seen under a light microscope.
11 The ChromosomeChromosome: “X” shaped cell structure that directs cell activities and passes on traits to new cells.Each identical strand of the chromosome is called a chromatid.The strands are held together by a structure called the centromere.Chromatin: Loosely coiled DNA