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Cells
http://www.youtube.com/watch?v=wJyUtbn0O5Y&safe=active
All Cells
Similarities
Cell membrane
Surrounds the cell
Acts as a barrier between the inside of a cell and
its environment
Controls the movement of materials into & out
of the cell
Hereditary Material
DNA controls all the activities of a cell and has
the information to make new cells
Cytoplasm & Organelles
Chemicals and structures that allow a cell
to live, grow & reproduce
All cells have organelles, but they don’t all
have the same kind
Some are surrounded by membranes and
others are not
These structures are surrounded by a fluid.
The fluid and everything in it is called the
cytoplasm
Small size
Almost all cells are too small to be seen without a
microscope
Cells must be small to maintain a large surface area
to volume ratio
As a cell grows larger it requires more food and produces
more waste
Surface area (cell membrane) grows in 2 dimensions and
volume (inside of the cell) grows in 3 dimensions. This
means volume grows faster than surface area
If a cell gets too large it won’t be able to move enough
food and waste through the surface (cell membrane)to
support the needs (inside) of the cell
Two General Types of Cells
https://www.youtube.com/watch?v=ruBAHiij4EA
Prokaryotic Cells:
Also called bacteria
World’s smallest cells
Circular DNA
No membrane covered organelles
Have a cell wall, cell membrane, and ribosomes
First cells on Earth. Oldest fossils date to 3.5
billion years ago.
Eukaryotic Cells:
More complex than Prokaryotic
10x larger than prokaryotic
Appeared ~ 2 billion years ago
DNA is found in a nucleus, linear, there is more
DNA than in a prokaryotic cell
Has membrane covered organelles as well as
ribosomes
Everything that is not a bacteria has this type of
cells
Examples: plants, animals, fungi, protists
Comparing Plant & Animal Cells
few
small
Multicellular vs. Unicellular
Multicellular organisms
Benefits: cells can have specialized functions
Examples: nerve cells, muscle cells
Grow by producing more cells rather than larger
cells
example: you and an elephant have the same size cells,
the elephant just has more
Unicellular organisms
All activities of the organisms must take place
within the single cell
Grow by increasing in size, but are limited by the
S:V ratio
How do cells work together in an organism?
In multicellular organisms, cells are organized into tissues, organs, and organ
systems.
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Cell: basic unit of structure and function in living things
Tissue: group of similar cells that work together to perform a specific function
Organ: different kinds of tissue that function together
Organ system: group of organs that work together to perform a major function
Organism: anything that can live on it’s own