1. 4.1 Introduction to the Cell pp. 69-72
Cells were beyond our limit until the invention of the microscope.
Hooke witnessed dead plant cells in cork (patterns)
Leeuwenhoek witnessed live cells (patterns)
What would these scientists have noticed?

2. 4.1 Introduction to the Cell pp. 69-72
Cell Theory
All living things are composed of cells (1 or more)
Cells are the basic units of structure and function of organisms
Cells come from the reproduction of existing cells: cells make cells
What kind of cells are in you?

3. 4.1 Introduction to the Cell pp. 69-72
Cell diversity
Cells have different sizes and shapes to fit their function
Humans have over 200 kinds of cells
Humans have a total of about 50 trillion cells ( )
Humans have 500 to 1000 different species of bacteria in the gut
There are at least 500 trillion cells in you, that aren’t you
Crazy numbers:

4. 4.1 Introduction to the Cell
Cell shape:
Function determines shape
Shape ↔ Function
Nerve cells are long like telephone lines

5. 4.1 Introduction to the Cell pp. 69-72
Cell size:
Most cells are microscopic (10 μm or 0.01 mm)
Can be larger:
Chicken egg
Nerve cells up to 2 m long
Small size means high surface area to volume ratio so materials can enter fast
Important in physical contact

6. 4.1 Introduction to the Cell pp. 69-72
Cell size matters:
Calculate the surface area to volume ratio of a cube:
Area = (length x width) x6
side = 3mm
Volume= length x width x height
𝑆𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎 𝑣𝑜𝑙𝑢𝑚𝑒 =

7. 4.1 Introduction to the Cell pp. 69-72
Cell size matters:
Calculate the surface area to volume ratio of a cube:
Area = (length x width) x6
side = 3mm
S.A. = 54 mm2
Volume= length x width x height
volume = 27 mm3
𝑆𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎 𝑣𝑜𝑙𝑢𝑚𝑒 = 54 mm2 27 mm3 = 2 1 𝑚𝑚
S.A.= (3mm x 3mm) x6
S.A. = 54 mm2
V=3mm x 3mm x 3mm
V= 27 mm3

8. 4.1 Introduction to the Cell pp. 69-72
OUT :
Calculate the surface area to volume ratio of a cube:
Area = (length x width) x6
side = 8mm
Volume= length x width x height
𝑆𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎 𝑣𝑜𝑙𝑢𝑚𝑒 =
OUT: SHOW YOUR WORK

9. 10 m 1 m 0.1 m 1 cm 1 mm 100 µm 10 µm 1 µm 100 nm 10 nm 1 nm 0.1 nm
Fig. 6-2
10 m
Human height
1 m
Length of some nerve and muscle cells
0.1 m
Unaided eye
Chicken egg
1 cm
Frog egg
1 mm
100 µm
Most plant and animal cells
Light microscope
10 µm
Nucleus
Most bacteria
1 µm
Mitochondrion
100 nm
Smallest bacteria
Electron microscope
Viruses
Ribosomes
10 nm
Proteins
Lipids
1 nm
Small molecules
0.1 nm
Atoms

10. Surface area increases while total volume remains constant
Fig. 6-8
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] 6
150
750
Total volume
[height  width  length 
number of boxes] 1
125
125
Surface-to-volume
(S-to-V) ratio
[surface area ÷ volume] 6
1.2 6