Cell Theory, Structure,
and Function
Cells
❖ Smallest living unit
❖ Most are microscopic
Discovery of Cells
❖ Robert Hooke (mid-1600s)
➢ Observed sliver of cork
➢ Saw “row of empty boxes”
➢ Coined the term cell
Microscope
❖ Zacharias Janssen is credited
with discovering/creating the
microscope
Discovery of Bacteria
❖ Anton van Leeuwenhoek
➢ Credited with improving the microscope
➢ His microscope could magnify 200x the
human eye! Today’s microscope can
magnify up to 1500x!
➢ He was the first to see bacteria and called
them Animalcules (“little animals”)
Cell Theory
❖ Matthias Schleiden
➢ A German botanist (scientist
who studies plants)
➢ He found that plant parts were
made of cells
➢ He generalized that ALL plants
were made of cells
Cell Theory
❖ Theodor Schwann
➢ Studied animals and
investigations led him to
generalize that all animals
are made of cells
➢ Using Schleiden’s work, he
proposed that all
organisms are made of
cells.
Cell Theory
❖ Rudolf Virchow
➢ German doctor that said new plant cells only
arise from existing plant cells and new animal
cells only arise from existing animal cells.
➢ He built off the work of Francesco Redi (1668)
who disproved the idea of spontaneous
generation in his experiments about rotting
meat.
Cell Theory
❖ (1839) Theodor Schwann &
Matthias Schleiden - “all living
things are made of cells”
❖ (50 years later) Rudolf Virchow “all cells come from cells”
Principles of Cell Theory
❖ All living things are made of cells.
❖ Cells are the smallest unit of life.
❖ All cells come from preexisting cells.
Cell Size
Characteristics of ALL Cells
❖ Membrane: A covering
surrounding the cell.
❖ Cytoplasm: Thick jelly-like fluid.
❖ Ribosomes: Used for protein
synthesis
❖ DNA: Genetic material
Cell Types
❖ Prokaryotic
➢ Pro (before)
➢ Consists of Bacteria and
Archaea.
❖ Eukaryotic
➢ Eu (true)
➢ Consists of Animal and
plant
Prokaryotic Cells
❖ First cell type on earth.
❖ Includes Bacteria and Archaea.
❖ No membrane bound nucleus.
➢ Nucleoid: region of DNA concentration.
❖ No membrane bound organelles.
❖ Have a cell wall.
❖ Generally smaller and simpler than Eukaryotic cells.
❖ Prokaryotes can move using Flagella or Pili.
Prokaryotic Cells
Eukaryotic Cells
❖ Nucleus bound by a membrane.
❖ Include fungi, protists, plant,
and animal cells.
❖ Have many membrane bound
organelles.
Representative Animal Cell
Representative Plant Cell