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WARM UP
With the person next to you complete the table on “Why are cell’s so small?”
When finished with the table complete the questions on the back.
Mr. E. will be checking Passive Transport and Plant Cell Coloring.
Tomorrow: Study Guide Due (w/ Vocab) & Active Transport
Thursday: Exam
LECTURE 13: CELL SHAPE, SIZE & PARTS
Cells come in many different shapes and sizes. With over 200 types they range from flat to branching to round to rectangular.
CELL SIZE: SIZE VARIES WITH FUNCTION Cells vary in size from microscopic to visible
to the naked eye. Ex/ A giraffe’s spinal nerve running to its foot can be up
to 6.5 ft long
WHY IS A CELL SMALL?
Difficulty exchanging materials (such as nutrients, oxygen, and waste products) across the cell
Why is this important to the cell? Small cells can exchange things faster than larger
cells due to surface-to-volume ratio. The higher the ratio the faster the exchange. As the volume of a cell grows there needs to be enough
plasma membrane surface to complete all the necessary transport.
FigureTotal number
of Cubes
Surface area of figure
(=6 x length x width)
Volume of figure
(= length x width x height)
Surface area to Volume
RatioSA / V
Total surface of individual
cubes(6 x # of cubes)
A
1 6 1 6 6
B
8 24 8 3 48
C
27 54 27 2 162
D 64 96 641.5
384
CELL SIZE
Cell size is limited by its surface area-to-volume ratio Larger the cell, the volume increases faster than its
surface area. Surface area to volume ratio decreases with increasing
cell size (EX. 6:1 vs 3:1)
WHAT DOES THIS MEAN FOR THE CELL? The bigger the volume the less surface
area not enough surface area to meet the
needs of the increasing volume distance to center increases as cell
increases Difficulty exchanging materials (such
as nutrients, oxygen, and waste products) across the cell