Download surface area ÷ volume

5.1 The Cell Cycle
LEQ: Why are most cells microscopic?
• Reading: 5.1, 5.5
• Activator – identify small everyday objects in your life.
What are the advantages to being small? Why are these
things small? Record the thoughts of your group in your
journal.
• Key terms: surface area, volume
5.1 The Cell Cycle
UNIT CONCEPT
Cells have distinct phases of growth, reproduction,
and the potential for specialization in multicellular
organisms.
5.1 The Cell Cycle
Cells need surface area to acquire resources for
chemical reactions
• Diffusion depends on surface area and volume
– How do cells acquire more surface area?
– compartments (volume) for chemical reactions?
• ,
5.1 The Cell Cycle
Volume increases faster than surface area.
Limitations:
– concentration is inversely related to volume
– Surface area to volume ratio
5.1 The Cell Cycle
Surface area increases while
total volume remains constant
5
1
1
Total surface area
[Sum of the surface areas
(height  width) of all boxes
sides  number of boxes]
Total volume
[height  width  length 
number of boxes]
Surface-to-volume
(S-to-V) ratio
[surface area ÷ volume]
6
150
750
1
125
125
6
1.2
6
5.1 The Cell Cycle
Simple cells can only perform so many different reactions
efficiently
5.1 The Cell Cycle
Summary:
• Which has a larger surface are to volume ratio – a tennis
ball or a soccer ball? Explain your answer.
• What limits the maximum size of a cell? Some single
celled organisms have been found to consist of cells over
4 mm long. Speculate – what sorts of adaptations should
biologists look for to explain how they maintain
homeostasis?