Download Cells: The Basic Units of Life

What are cells?
EQ: What are the essential components of a cell?
What are cells?
• Cells are the smallest
unit that is capable of
carrying on life
functions
• Most cells are so
small they cannot be
seen by the naked
eye
Cell Discovery
• Because of their size,
cells were not discovered
until the mid-1600’s by
Robert Hooke
• He looked at a thin slice
of cork and noted that
the cork looked like it
was made of little boxes.
• Robert Hooke called
these little boxes “cells”
because they resemble
tiny rooms
Little boxes or “cells”
Hooke also looked at…
• Plants
• Feathers
• Fish scales
• And the eyes of houseflies!
• But he spent most of his time looking at plants and fungi.
• They were easier to see because plant cells have cell walls,
and animal cells do not.
• Since he couldn’t see the animal cells due to the absence of
cell walls, he thought only plants were made of cells!
Cell Discovery
• In 1673, a Dutch merchant named Anton Van Leeuwenhoek,
used a microscope he built himself to look at pond scum
He saw small organisms in the
water (go figure!)
• He named these organisms “animalcules” which means “little
animals”.
• We call these single-celled animals protists
• Leeuwenhoek also looked at…
• Animal blood
• Yeasts
• And was the first person to see bacteria!
Cell Theory
• Different scientists studied both
plants and animal cells during
this time, but in 1839, Theodor
Schwann wrote the first two
parts of what is now known as
cell theory:
• All organisms are made of one or
more cells
• The cell is the basic unit of all
living things
• Later, another scientist added
the third part of cell theory:
• All cells come from existing cells
Types of Cells
• Prokaryotic
• An organism that is
made of a single cell
• No nucleus
• Have a tail called
flagellum
• They have a cell wall
• Bacteria, Archea
Types of Cells
• Eukaryotic
• Have a nucleus, and
other membranebound organelles.
• Anything not
considered bacteria
or archea are
eukaryotic
• Plants, animals, Fungi
Cell Size
• Most cells are too small to be seen without a microscope.
• There is a reason why most cells are so small….
• Cells take in food and get rid of wastes through their outer
surface.
• As a cell gets larger, it needs more food and produces more
waste.
• Therefore, more materials pass through its outer surface.
• As the cell’s volume increases, its surface area grows as well.
• But the cell’s volume grows faster than its surface area.
• If a cell gets too large, the cell’s surface area will not be large
enough to take in enough nutrients or get rid of its wastes
Cell Size
• There are some exceptions…..
• Egg yolk --- one BIG CELL
Cell Composition
• Cells are 90% water
What makes up the other
10%?
• Of that remaining 10%.....
• 50% is proteins (5% of total cell make up )
• DNA
• 15% carbohydrate (1.5% of total cell make up)
• sugars
• 15% nucleic acid (1.5% of total cell make up)
• 10% lipid (1% of total cell make up)
• Fats
• 10% others (1% of total cell make up)
Cell Composition
Water
Protein
Carbohydrates
Nucleic Acid
Lipids
Other