Transcript Cell Size Limitations

Cell Size
Limitations
• Why are living organisms
the sizes that they are?
• Are there advantages to
being large or small?
• What are the advantages
to being a certain size?
1–
limits cell size:
• Diffusion is ______ and efficient
over _______ distances and
becomes ______ and inefficient
as distances become larger
2–
limits cell size:
• The nucleus has DNA which
contains instructions for making
_________. Proteins are used by
all organelles in the cell.
Imagine a 20cm cell
with a speck of DNA
inside the nucleus.
The cell won’t survive
if there isn’t enough
DNA to build all the
protein cell needs.
3–
limits
cell size:
Surface Area to Volume Ratio
First, calculate Surface Area
of this box
• Area of one square = Length x Width = __ in2
3–
limits
cell size:
Surface Area to Volume Ratio
• A cube has 6 sides (multiply the
area of one side by six)
• Total Surface Area = ____ in2
Volume
Second, calculate Volume for this box
• Volume = Length x Width x Height =
__ inches3
3–
limits
cell size:
• We now have _____ in2 of surface area and
____ in3 of volume.
• Reduce the ratio. ___ to ___
Is the surface
always a larger
number?
No. Let's
look at some
more cubes.
Length x
height x Volume
width
Ratio of
Surface
Area to
Volume
Side of
cube
Area of 1
Area x 6
Side
Surface
area of
Cube
2
4
4x6
24
2x2x2
8
3 to 1
4
16
16 x 6
96
4x4x4
64
3 to 2
6
36
36 x 6
216
6x6x6
216
3 to 3
8
64
64 x 6
384
8x8x8
512
3 to 4
12
144
144 x 6
864
12 x12 x
12
1728
3 to 6
20
400
400 x 6
2400
20 x 20 x
20
8000
3 to 10
What does
this mean?
What does this mean?
• It means that small
animals, like mice,
have a lot of skin on the
outside compared to a
small volume of bones,
blood, and internal
organs on the inside.
So a mouse or a baby
bird loses ______
rapidly.
• When an animal has a large volume (big
bones, muscles, lungs, digestive
system) the skin on the outside (the
surface area) gets progressively smaller
when it is compared to the volume
inside. This means that large animals
tend to maintain their temperatures and to
get cooler or warmer _______. It is also
difficult for them to get rid of excess
body heat, for example, if they have
been running.
What is Surface Area to Volume
ratio? Why is it Important?
• Surface area to volume ratio is just the
surface area of a cell divided by its
volume.
What is Surface Area to Volume
ratio? Why is it Important?
• In biology, the larger this number the better
for cells because that would mean that the
cell has a relatively large surface area
compared with its volume.
• This is important because it is one of the
factors that determines how _________
substances can diffuse into and out of the
cell.
• Generally the smaller the
cell, the larger the SA to
V ratio and the ______
the rate of diffusion.
• This is also why larger organisms
need more specialized transport
systems to carry substances to
certain parts- diffusion would be
too slow.
• In the end, cell size can have dramatic and
negative effects on a cell. If it is too
it might
large,
not function properly.
Since everything wants to reach
equilibrium, there is some ________ size
where a cell (or an organism) performs
best.