3.1 Cell Theory
LEQ: How do enzymes help cells perform
chemical reactions?
LEQ: What is the cell theory?
Reading: 3.1, 3.3
Activator: Cells carousel
• List one fact about a cell and pass the paper to the
next group member. First letter of the name earliest in
alphabet A-Z goes first!
Key terms – cell, eukaryote, prokaryote
3.1 Cell Theory
UNIT CONCEPT Cells are chemical systems with emergent
properties.
3.1 Cell Theory
The Cell theory has three principles.
– 1) All organisms are made of at least one cell.
– 2) All existing cells are produced by other living cells.
– 3) The cell is the most basic unit of life.
Nothing simpler is considered a living system
3.1 Cell Theory
All cells have a common origin in the history of life.
• All cells share certain characteristics.
– *most are microscopic.
– enclosed by a membrane.
– filled with cytoplasm.
cell membrane
– DNA
– Ribosomes:
Molecular organelle that
makes proteins
cytoplasm
Bacterium
(colored SEM; magnification 8800x)
3.1 Cell Theory
• Cells can be categorized based on the presence of
certain structures.
• Eukaryotic cells have a
nucleus:
nucleus
– (Greek):
– karuon – “kernel”
– eu – “true”
organelles
cell membrane
3.1 Cell Theory
Cells can be categorized based on the presence of
certain structures:
• prokaryotic cell types do not
have a true nucleus.
nucleus
– pro – “before”
• Obsolete term?
organelles
cell membrane
3.1 Cell Theory
Questions:
• How do prokaryotic and eukaryotic cells differ?
3.1 Cell Theory
Answers:
• Eukaryotic cells have a nucleus and membrane-bound
organelles; prokaryotic cells generally do not.