Cells
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Cells. Discussion Questions. What is a cell? Where do cells come from? What activities are taking place inside a cell ? How do the materials that feed these activities enter and exit the cell? What limits cell size ?. What is a cell?. A cell is the very smallest unit of living matter - PowerPoint PPT Presentation
Transcript of Cells
Cells
Discussion Questions
1. What is a cell?2. Where do cells come from?3. What activities are taking place inside a cell?4. How do the materials that feed these
activities enter and exit the cell?5. What limits cell size?
What is a cell?
• A cell is the very smallest unit of living matter• Cells form the building blocks of living
organisms
Where do cells come from?
All cells come from pre – existing cells.
What activities are taking place inside a cell?
How do the materials that feed these activities enter and exit the cell?
Through the cell membrane
What limits cell size?
Surface Area of a Cube
• Smaller cube (1 cm X 1 cm X 1 cm)• The surface area of one side = length x width• 1 cm X 1 cm = 1 cm2 (1 square centimeter)• A cube has 6 sides… …so the total surface area = 6 X 1cm2 6 cm2
Volume of a Cube
• Volume = length x width x height• 1 cm X 1 cm X 1 cm 1 cm3 (1 cubic centimeter)
Surface Area to Volume Ratio
6 square cm of surface area for each cubic cm of volume
SA/V = 6:1
Surface area [in cm2] Volume [in cm3]
6 1
Cell Volume
The amount of materials required by the cell for chemical activity depends on its volume.
Increasing Cell Volume
As the volume of the cell increases the amount of materials required for chemical activity increases.
Increasing Cell Volume
As the volume of the cell increases, the amount of wastes produced also increases.
Surface Area
The rate at which the materials are taken in and removed from the cell depends on the surface area.
Increasing Surface Area
As the surface area increases, so does the rate at which the materials enter or leave the cell.
How Surface Area to Volume Ratio Limits Cell Size
As the cell increases in size, the surface area does not increase to the same extent as the volume. (The surface area to volume ratio decreases.)
How Surface Area to Volume Ratio Limits Cell Size
Once the ratio reaches a certain point, the materials will not be able to enter the cell fast enough to feed the chemical reactions.
How Surface Area to Volume Ratio Limits Cell Size
Also waste products will build up in the cell because they will not be able to be removed fast enough.
How Surface Area to Volume Ratio Limits Cell Size
As a result of the increased chemical activity, more heat will be produced. The surface area will not be great enough to lose the heat and the cell could overheat.
What limits cell size?
Please write a statement on your handout explaining how the the surface area to volume ratio is a factor in limiting cell size.
How have some cells adapted to increase the surface area to
volume ratio?
• By increasing their surface area
Resources
Surface Area to Volume ratiohttp://www.youtube.com/watch?v=JOTycly_bew
IB Biology 2.1.6 Surface area to volume ratio in cellshttp://www.youtube.com/watch?v=jw0ZHLJGVTY
