1. Cellular Level of Organization Prokaryotic vs. Eukaryotic Cells
Cell Structures
Cellular Level of Organization
Prokaryotic vs. Eukaryotic Cells
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2. Important people in Cell Theory
Robert Brown ( ) – discovered the nucleus and its role
Matthias Schleiden (1804 – 1881) – discovered plants are made of cells
Theodore Schwann ( ) – discovered animals are made of cells
Rudolph Virchow ( ) – showed cells self reproduce and come from preexisting cells
Important people in Cell Theory

3. Cell Theory All organisms are composed of cells
Cells are the basic units of structure and function in organisms
Cells come only from preexisting cells because cells are self- reproducing
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4. Structure of Prokaryotes
Prokaryotes are quite small
Three basic shapes are most common
Bacillus – Rod-shaped
Coccus – Spherical shaped bacterium
Long rods that are twisted into spirals
Rigid ones are called Spirilla
Flexible ones are called Spirochetes
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5. Prokaryote Cell Envelope
Envelope consists of the plasma membrane, the cell wall, and the glycocalyx
Plasma membrane – phospholipid bilayer with embedded proteins
Cell wall – maintains the shape of the cell
Glycocalyx – a layer of polysaccharides that lies outside the cell wall
When this layer is well organized, and not easily washed off, it is called a capsule
It helps bacteria resist a host’s immune system
Protects against drying out
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6. Prokaryotic Cells Inside
Cytoplasm - A semifluid solution composed of water and inorganic and organic molecules
Nucleoid – The DNA, found in a single, coiled chromosome is located in the nucleoid
Plasmid – extrachromosomal pieces of circular DNA
Ribosomes – synthesize proteins using RNA
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7. Appendages
Flagella – consists of a filament, a hook, and a body, the hook rotates, propelling the bacteria
Fimbriae – small bristle-like fibers that sprout from the cell surface, that attach bacteria to a surface
Conjugation Pili – rigid tubular structures used to pass DNA from cell to cell
Bacteria reproduce asexually, but can exchange DNA
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8. Two Theories
Evidence from fossil record suggests prokaryotic cells first appeared on Earth between 3 and 3.5 billion years ago
Eukaryotic cells appeared between 1 and 1.5 billion years ago.
What do you think would be a possible explanation for how cells became more complex over time?
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9. Autogenous Theory
According to the autogenic theory, eukaryotes evolved from prokaryotes through the accumulation of changes over time
Gradually, the plasma membrane of the prokaryote folded inward, creating organelles such as the ER and golgi bodies, and the nucleus
Evidence to support this theory are the similarities among the cell membrane and the organelle membranes

10. Endosymbiotic Theory
1960’s Lynn Margulis suggested that mitochondria and chloroplasts have ore in common with prokaryotes than eukaryotes
She suggests that chloroplasts and mitochondria were once prokaryotic cells that evolved into a mutualistic relationship with their eukaryotic cells
Evidence to support this theory, is that mitochondrial DNA is similar to a parasitic endosymbiont bacteria, and chloroplast DNA is similar to photosynthetic bacteria
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11. Eukaryotic cells Are more complex
Contain a nucleus and other membrane bound organelles that perform specific functions that contribute to the overall metabolism and growth of the cell
Metabolism – the process by which cells make, store, and transport chemicals
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12. Structures
Cell wall – surrounds the cell and maintains its shape, in plant, fungi, and protist cells only
Cell Membrane – surrounds the cell and helps move materials into and out of the cell
Cytoplasm – takes up much of the space inside the cell
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13. More Structures Nucleus – organelle that holds DNA
Mitochondria – transforms the energy in food, to a useable form of energy called ATP. ATP is used for growth and cellular reproduction
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More Structures

14. More structures ER – helps transport proteins and produces lipids
Golgi Body – helps package and distribute proteins and lipids within the cell
Ribosomes – are larger in eukaryotic cells and also manufacture proteins
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More structures

15. Structures
Lysosomes – contains enzymes that help break down food, or recycle parts of the cell
Chloroplast – contain the green pigment chlorophyll, which captures energy of sunlight for photosynthesis
Vacuoles – store water, food, and waste, larger in plant cells than in animal
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16. Vocabulary to remember:
Lipid – an organic compound that stores energy – aka fats
Enzyme – a protein in organisms that helps control a chemical reaction
Photosynthesis – the process by which certain organisms use energy from the sun to make food
Protein – a polymer of amino acids
Amino Acid – contains an amino group and an acid group
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