AP
Bio
Lab
3
Part
A
Name:
Big
Idea
2
–
Cell
Processes
Materials:
Ruler
(small)
Scalpel
Paper
Towel
Iodine
Solution/small
beaker
Calculator
Potato
pieces
Gloves
Tweezers
Water/large
beaker
In
your
notebook
on
page
______
do
the
following.
(10
min)
1. Set
up
a
table
to
calculate
the
following
for
each
potato
size
(5
mm,
10
mm,
and
20
mm):
a. Cube
Size
(mm)
b. Surface
Area
(mm2)
c. Volume
(mm3)
d. Surface
Area
to
Volume
Ratio
2. Set
up
a
second
table
for
the
following
a. Cube
size
(mm)
b. Depth
of
iodine
movement
(mm)
c. Time
(min)
d. Rate
of
movement
(mm/min)
3. Set
up
a
third
table
for
the
following
a. Total
Volume
of
Cube
(mm3)
b. Unchanged
Cube
Side
Length
(Subtract
depth
of
diffusion
(both
sides)
from
original
cube
dimensions)
mm
c. Volume
of
unchanged
cube
(hasn’t
changed
color)
mm3
d. Percent
total
volume
of
cube
that
received
iodine
(equation
in
formulas
below)
4. Create
a
Hypothesis:
Make
a
statement
as
to
which
potato
(representing
different
sized
cells)
will
have
the
nutrients
diffuse
the
farthest
into
the
cell
in
20
minutes
and
the
reasoning
behind
your
idea.
Math
Formulas
Surface
Area
=
Length
x
Width
x
#
of
sides
Volume
=
Length
x
Width
x
Height
Surface
Area
to
Volume
Ratio
=
Surface
Area/Volume
Percent Volume of Cube
That Received Iodine
=
(total cube volume) – (volume of cube that has not changed color)
(total cube volume)
X 100%
Procedure
(25
min)
1.
2.
3.
4.
5.
6.
7.
8.
Obtain
one
of
each
size
potato
cell.
Submerge
the
potato
cells
into
iodine
solution
for
15
min.
Work
your
calculations
while
you
wait.
Remove
the
potato
cells
from
the
iodine
solution
and
place
them
in
the
beaker
with
water.
Swirl
the
cells
in
the
water
to
rinse
off
excess
Iodine
and
place
the
potatoes
on
paper
towel.
IMMEDIATELY
cut
each
cell
in
half
and
measure
how
far
the
color
has
moved
into
the
cell
(in
mm!).
Record
measurement
and
add
a
drawing
into
your
table.
Clean
up
materials.
Finish
calculations
and
begin
working
on
analysis
questions.
Analysis
Questions
–
answer
on
left
page
next
to
data.
1.
2.
3.
4.
As
your
cell
size
increases,
which
increases
faster:
cell
surface
area
or
cell
volume?
What
trend
do
we
see
in
the
surface
area
to
volume
ration
as
cell
size
increases?
If
iodine
was
a
substance
needed
within
the
cell,
what
problem(s)
would
the
largest
cell
have?
According
to
your
data,
which
cell
is
most
successful
at
receiving
the
needed
nutrient
in
the
allowed
time?
What
can
you
say
about
the
surface
to
volume
ratio
that
will
best
meet
the
needs
of
living
cells?
How
could
the
potato’s
(cell’s)
shape
affect
the
rate
of
the
movement
of
iodine?
Based
on
your
observations,
why
are
cells
microscopic?
Reevaluate
your
hypothesis.
Change
it
as
needed.
5.
6.
7.
8.
Graph:
Graph
the
percent
volume
of
cube
changed
by
cell
size
(5,
10,
20mm).
Title:
Predict:
What
would
the
Percent
Volume
of
Cube
Changed
for
the
following
cubes:
a. 2.5
mm
b. 40
mm
c. 15
mm