Transcript LAB: CELL SIZE & DIFFUSION

LAB: CELL SIZE & DIFFUSION
1cm
1-cut 3 cubes in agar—
2cm
3cm
calculate SA & vol for each cube
2-place 3 cubes in beaker w/NAOH
DO NOT touch NAOH—MUST wear goggles!!
3-stir gently—turn cubes gently—10 minutes
4-remove cubes—place on paper towel—blot dry
5-dry for 5 minutes—cut each cube in ½ w/ruler
6-look at pink—measure on each cube
7-record--DRAW each cube
PROBLEM
-Why are cells so small?
-Why do cells stop growing after reaching a certain size?
-What causes cells to stop growing and divide?
RESULTS
L x W x #sides
LxWxH
SA:VOL
54
27
2:1
3
24
8
3:1
3
6
1
6:1
3
.0006
.000001
600:1
na
QUALITATIVE DATA
SHADE in the cross section of each of the 3 cubes showing
the relative amount of material diffused into each cube.
1cm
2cm
3cm
SCIENTIFIC METHOD
INDEPENDENT VARIABLE:
-size of cell (SA:vol)
DEPENDENT VARIABLE:
-% of cell diffused
CONSTANTS:
-time, type of cell, NaOH solution
CONCLUSION: summarization
-As cube size increases the SA:VOL decreases
-Diffusion rate is the same regardless of cube size
-Smaller cells have a higher % of the cell “diffused”
QUESTIONS
1-What evidence is there that NaOH diffused into the cube?
-dark pink border
2-What evidence is there that the RATE of diffusion is about
the same for each cube?
-WIDTH of dark pink is SAME for all cubes
-distance diffused
QUESTIONS
4- Which cube has the greatest surface area……the 3 cm
cube or the 1 cm cube?
-3cm cube
5- Which has the greater surface area in proportion to its
volume?
-1cm cube 6:1
QUESTIONS
6-What predictions can you make about the efficiency of
each cube/cell model based on the information above?
-smaller cube is more efficient
-nutrients/waste don’t need to diffuse as far
7-What happens to the surface area-to-volume ratio of cubes
as they increase in size?
-SA:VOL decreases as cube size increases
QUESTIONS
8-Most cells and microorganisms measure less than .01 cm on a
side. What is the relationship between RATE of diffusion and cell
size?
-RATE: how long it takes to diffuse
-is SAME for all cells
-greater % of cell is diffused if smaller
9-Explain why large organisms (like yourself) have developed from
MORE cells rather than LARGER cells.
-smaller cells are more efficient
-gain nutrients and remove waste more easily through entire cell
-cells have different functions (nerve, skin, heart…)
CHALLENGE QUESTION
How could you increase the surface area of a cell
without changing the size of the cell?
-change the shape
-poke holes with straw
-make scallops on edges w/straw
Esophagus cells