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 whiletotal volume remains constant

5

11

6 150 750

125 1251

6 61.2

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]

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?