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Biology
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7-1 Life Is Cellular
Photo Credit: © Quest/Science Photo Library/Photo Researchers, Inc.
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3. The Discovery of the Cell
Early Microscopes and Scientists
Robert Hooke – discovered cells – early compound microscope
Cells are the basic units of life
Anton van Leeuwenhoek-discovered living things in pond water – single lens microscope .
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4. The Discovery of the Cell
Hooke’s Drawing of Cork Cells
hoto Credit: © Peter Arnold, Inc.
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5. The Discovery of the Cell
The Cell Theory
In 1838, Matthias Schleiden concluded that all plants were made of cells.
In 1839, Theodor Schwann stated that all animals were made of cells.
In 1855, Rudolph Virchow concluded that new cells were created only from division of existing cells.
These discoveries led to the cell theory.
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6. The Discovery of the Cell
The cell theory states:
All living things are composed of cells.
Cells are the basic units of structure and function in living things.
New cells are produced from existing cells.
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Exploring the Cell
Electron Microscopes
reveal details 1000 times smaller than those visible in light microscopes.
used to visualize only nonliving, preserved cells and tissues.
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Exploring the Cell
Transmission electron microscopes (TEMs)
Used to study cell structures and large protein molecules
Specimens must be cut into ultra-thin slices
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Exploring the Cell
Scanning electron microscopes (SEMs)
Produce three-dimensional images of cells
Specimens do not have to be cut into thin slices
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Exploring the Cell
Scanning Electron Micrograph of Neurons
Photo Credit: © Dr. Dennis Kunkel/Phototake
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Exploring the Cell
Confocal Light Micrograph of HeLa Cells
Photo Credit: © K.G.Murti/Visuals Unlimited
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Exploring the Cell
Scanning Probe Micrograph of DNA
Photo Credit: Dr. Jan Hoh of Johns Hopkins University, School of Medicine
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13. Prokaryotes and Eukaryotes
Cells come in a variety of shapes and sizes.
All cells:
are surrounded by a barrier called a cell membrane.
at some point contain DNA.
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14. Prokaryotes and Eukaryotes
Cells are classified according to the presence or absence of a nucleus
Eukaryotes are cells that contain nuclei.
Prokaryotes are cells that do not contain nuclei.
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15. Prokaryotes and Eukaryotes
Prokaryotic cells have genetic material that is not contained in a nucleus.
do not have membrane-bound organelles.
are generally smaller and simpler than eukaryotic cells.
are Bacteria
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16. Prokaryotes and Eukaryotes
Eukaryotic cells contain a nucleus in which their genetic material is separated from the rest of the cell.
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17. Prokaryotes and Eukaryotes
Eukaryotic cells are
generally larger and more complex than prokaryotic cells.
contain dozens of structures and internal membranes.
are highly specialized.
Plants, animals, fungi, and protists are eukaryotes.
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