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Cell Growth and Division. Chapter 10 Notes. What is the difference between an elephant and you?. There are many differences, but an obvious one is size – an elephant is a much larger animal than you But… The elephant is a living thing, so it is made of cells…. So why is the elephant larger?.
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Cell Growth and Division Chapter 10 Notes
What is the difference between an elephant and you? • There are many differences, but an obvious one is size – an elephant is a much larger animal than you • But… • The elephant is a living thing, so it is made of cells…
So why is the elephant larger? • Does it have larger cells? • No, an elephant’s cells are basically the same size as yours • Larger organisms don’t have larger cells, they have MORE cells
Limits to Cell Growth • Growth and Development is one of the 5 characteristics of living organisms • Cells do grow, but their growth is limited by several factors
Limits to Cell Growth • 1st Factor – DNA “overload” - As cells grow in size, they do not make extra copies of DNA and eventually there is not enough DNA to support the cell’s contents
Limits to Cell Growth • 2nd Factor- Surface Area to Volume Ratio: As the surface area of a cell increases, the volume of the cell increases at a faster rate • This means that the cell would now require many more resources, and have a harder time supplying all it’s parts (organelles)
Limits to Cell Growth Surface area to Volume ratio example • The small house requires less resources and is easier to maintain. • The mansion requires more resources and is more difficult to maintain
Limits to Cell Growth • 3rd Factor- Diffusion of Materials: Diffusion of nutrients and wastes constantly occurs between cells and blood vessels, but only over small distances • If cells grow too large, nutrients can not diffuse well because the distance has increased
How do cells solve these problems? • Cell Division- Because of the 3 factors, a cell will divide before it becomes too large into two daughter cells • Cell division solves the problems of DNA overload, surface area to volume ratio, and diffusion of nutrients
Why do cells divide? • To maintain their small size • In single-celled organisms, cell division is how the organisms reproduce (Ex. Bacteria) • In multicellular organisms, cell division is necessary for growth, repairing damaged tissues, and replacing old cells with new ones • After you were conceived, how did your body grow larger? What happens when you get a cut?