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THE CELL:
Seeing is Believing!
“Seeing is Believing”
Cell - The basic unit of life. Cells remained “Out of sight out of
mind” until… Microscopes! Micro- very small Scope- to look at
Discovery of the Cell
Robert Hooke Anton van Leeuwenhoek Matthias Schleiden Theodor Schwann Randolph Virchow
Robert Hooke
1665 Published a book:
Micrographia Viewed cork cells
through the first microscope
Anton van Leeuwenhoek
9 years later 1674 Observes tiny living
organisms in drops of pond water.
Used a simple microscope = magnified 200X
Matthias Schleiden
164 years later1838 German Botanist =
studies plants Concludes that all
plants are made up of cells.
Theodor Schwann
1 year later1839 German zoologist =
studies animals Concludes that all
animals are made up of cells.
Rudolph Virchow
16 years later1855 German doctor Proposes that all cells
come from other cells.
The Cell Theory
1. All living things are made up of one or more cells. 2. Cells are the basic units of
structure and function in organisms. 3. All cells come from other cells
that already exist.
Cell Size
Small size= efficient 100 trillion cells in the human body 5 µm - 20 µm in diameter 1 m = 1 million µm Why do we have so many tiny cells
instead of a few large cells?
Cell Size Substances that go into the cell have
to move across very quickly. Why? Cells need to work at high speeds. They are able to do this because
their surface area is large compared to their volume = high surface area-to-volume ratio. What is this?
Surface Area
Cell Size
Surface area of a cube with sides measuring 2 cm =
SA = (Length x
width) x 6 sides (2x2) x6 = 24 cm2
Volume of a cube with sides measuring 2 cm=
V = Length x width
x height 2 x 2 x 2 = 8 cm3
Surface Area-to-Volume Ratio
If a cube has sides measuring 2 cm… Surface area-to-volume ratio = Surface area/volume =24/8 = 3:1
CURIOUS FACT: The largest cell on Earth is about the size of a baseball!
Largest Cell on Earth
The yolk of an Ostrich’s egg.
One ostrich egg can feed about 15 people!
Two Main Types of Cells
Prokaryotes DNA is not
contained in a nucleus
Eukaryotes Contain a nucleus
that separates DNA from rest of the cell
3 Main Cell Parts
Nucleus Cytoplasm Cell Membrane
Movement Prokaryotes have flagella = long
threadlike structures for movement. Eukaryotes have flagella or cilia =
short hair-like structures for movement.
Different Shapes
REVIEW Name the 3 parts of the Cell Theory. What is the main difference between
prokaryotes and eukaryotes? Why do smaller pieces of food cook
faster than larger pieces? Why is it good for cells to be
microscopic (very small)?
