1. Bellwork: 11/19 Put phone up  Week 11/19-11/21
Find the surface area to volume ratio of a cell that is 5cm L x 2cm W x 1cm H
Why is it important that cells maintain a large SA:V ratio?

2. Objective
Students will begin to learn about the importance of cell size to maintain proper function

3. Today:
Bellwork
Finish Part 3 Notes
Cell Size POGIL

4. This Week: Mon/Tues: Cell Size POGIL
Wednesday: Plasma Membrane Notes & Diffusion Demo
Thurs/Fri: THANKSGIVING

5. Materials
Unit book
Cell Size POGIL

6. Homework Cell Size POGIL Quiz Thursday – Organelles & Cell Size
Due Thursday
Quiz Thursday – Organelles & Cell Size

7. Unit III: Cells

8. Part III: Cell Size

9. Intro ?
Could you come across a 2 ton single-celled organism? Why or why not?

10. Cell Size Most cells are quite small in size
Need to maximize surface area to volume ratio

11. Surface Area to Volume Ratio
For a perfect cube:
A cube that is 2cm L x 2cm W x 2cm H. What is its surface area/volume ratio?
Surface area = L x W x # sides
__cm x __cm x __ sides = ___cm2
Volume = L x W x H
__cm x __cm x __cm = ___cm3
Surface Area/Volume Ratio = SA/V
___cm2/___cm3 = ___cm-1

12. With a Partner
What is the surface area to volume ratio of a cube that is 4mm x 4mm x 4mm?

13. Are all cells perfect cubes?

14. Answer! For a perfect cube:
A cube that is 4mm L x 4mm W x 4mm H. What is its surface area/volume ratio?
Surface area = L x W x # sides
4mm x 4mm x 6 sides = 96mm2
Volume = L x W x H
4cm x 4cm x 4cm = 64mm3
Surface Area/Volume Ratio = SA/V
96mm2/64mm3 = 1.5mm-1

15. Surface Area to Volume Ratio
For an imperfect cube:
A cube that is 3mm L x 2mm W x 1mm H. What is its surface area/volume ratio?
Surface area = __ mm2
3mm x 1mm x 2 sides = ___mm2
3mm x 2mm x 2 sides = ___mm2
2mm x 1mm x 2 sides = ___mm2
Volume = L x W x H
___mm x ___mm x ___mm = ___mm3
Surface Area/Volume Ratio = SA/V
___mm2/___mm3 = ____mm-1

16. With a Partner
Calculate the surface/volume ratio of a cell that is 4mm L x 3mm W x 2mm H.

17. Answer For an imperfect cube:
A cube that is 4mm L x 3mm W x 2mm H. What is its surface area/volume ratio?
Surface area = 52mm2
4mm x 2mm x 2 sides = 16mm2
4mm x 3mm x 2 sides = 24mm2
3mm x 2mm x 2 sides = 12mm2
Volume = L x W x H
4mm x 3mm x 2mm = 24mm3
Surface Area/Volume Ratio = SA/V
52mm2/24mm3 = 2.2mm-1

18. Why are Cells Small? Maintain a large surface area to volume ratio
Uptake of oxygen, nutrients, and removal of waste is more efficient
Better for the cell
If the volume becomes too large, surface area to volume ratio becomes small
Therefore, the uptake of nutrients & removal of waste becomes less efficient
Detrimental for the cell

19. Why are Cells Small? In larger cells
Transport of materials from one region of the cytoplasm to another takes longer
Nucleus controls cellular activity
The nucleus communicates with the outer parts of the cell
If the cell becomes too large, it takes longer for chemical signals to reach the outer parts of the cell

20. With a Partner
If the cubes to the right represented a cell, which cube got food, water, or something needed by the cell distributed to all its parts. Why?

21. Answer ?s in Note Guide

22. Cell Size POGIL