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Levels of Organization
Least complex Most Complex Atoms Molecules Cells Tissue Organ Organ System Organism Population Community Ecosystem Biosphere
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2. The Discovery of the Cell
The invention of the microscope allowed us to make cells visible.
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3. The Discovery of the Cell
Early Microscopes
In 1665, Robert Hooke used an early compound microscope to look at a thin slice of cork, a plant material.
In Holland around the same time, Anton van Leeuwenhoek used a microscope to observe living things.
Cells are the basic units of life.
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4. The Discovery of the Cell
The Cell Theory
: Scientists, such as Schleiden Schwann, and Virchow as well as other biologists observed the cell, developed theories, and summarized their ideas. These discoveries led to the cell theory.
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5. The Discovery of the Cell
The Cell theory states:
All living things are composed (made up of) 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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MICROSCOPES
LIGHT MICROSCOPE (LM) LM - Works by passing visible through a specimen, such as an microorganism or a piece of plant or animal tissue
Micrograph- a photo taken through a microscope
Magnification - the increase in the actual size
Resolving power: a measure of the clarity
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7. Electron Microscopes (EM) - 2 Types
Exploring the Cell
MICROSCOPES
Electron Microscopes (EM) - 2 Types
Electron microscopes reveal details 1000 times smaller than those visible in light microscopes.
Electron microscopy can be used to visualize only nonliving, preserved cells and tissues.
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8. 1. TRANSMISSION ELECTRON MICROSCOPES (TEMS)
Exploring the Cell
1. TRANSMISSION ELECTRON MICROSCOPES (TEMS)
Used to study cell structures and large protein molecules
Used to study the details of the internal cell structure
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9. 2. SCANNING ELECTRON MICROSCOPES (SEMS)
Exploring the Cell
2. SCANNING ELECTRON MICROSCOPES (SEMS)
Produce three-dimensional images of cells
Specimens do not have to be cut into thin slices
Used to study the external cell structure
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10. Scanning Electron Micrograph of Neurons
Exploring the Cell
Scanning Electron Micrograph of Neurons
Photo Credit: © Dr. Dennis Kunkel/Phototake
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11. Prokaryotes and Eukaryotes
CELL TYPES
Prokaryotes and Eukaryotes
Contain small organs called organelles
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12. Prokaryotes & Eukaryotes
All cells, Prokaryotic & eukaryotic have three common features. Nucleus, which contains DNA, the genetic material contained in one or more chromosomes and located in a non-membrane bound nucleoid region in prokaryotes and a membrane-bound nucleus in eukaryotes
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Three main parts
Plasma membrane, a phospholipid bilayer with proteins; separates the cell from the surrounding environment; functions as a selective barrier for the import and export of materials
Cytoplasm, the rest of the material of the cell within the plasma membrane, excluding the nucleoid region or nucleus, that consists of a fluid portion called the cytosol
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Prokaryotes
Prokaryotic cells
Plasma membrane
Cytoplasm
Nucleoid region
DNA
Ribosomes
Pili
Flagellum
Smaller and simpler than eukaryotes
Bacteria are prokaryotes
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Eukaryotic Cells
Eukaryotes
Plant and Animal Cells
More complex - Many cells are highly specialized.Plants, animals, fungi, and protists are eukaryotes
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PLANT CELL
Nucleus
CYTOSKELEYTON: Microtubules, Intermediate filaments, & microfilaments
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Plant Cells
PLANT CELLS contain chloroplasts, a cell wall, & a central vacuole, which are NOT found in animal cells.
Chloroplasts are plant cell organelles that contain chlorophyll and the enzymes required for photosynthesis.
Mitochondria - (singular = mitochondrion) All eukaryotic cells contain mitochondria, often many hundreds per cell. They harvest energy from food during cellular respiration and generate ATP (energy).
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18. CYTOSKELETON: Structural Support
Microfilaments - solid, helical rods composed of globular proteins called actin (shape & movement)
Intermediate filaments - made of fibrous proteins, for reinforcement and anchoring
Microtubules - straight, hollow tubes made up of globular proteins called tubulin ( tubulin pairs)
Together they maintain cell shape, anchor organelles, and cause cell movement.
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19. Cell Movement: Cilia and Flagella
Cilia -short, numerous appendages
On cell lining the human windpipe
Flagella - long, less numerous appendages
sperm
Both are composed of a core of microtubules; a ring of 9 - microtubule doublets that surround a central pair of microtubules; combined called The 9-doublets extend into an anchoring structure called a basal body (identical to centrioles). The basal body has 9 - microtubule triplets.
The microtubule doublets are connected by dynein arms that help them bend and move (H - page 65)
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Endomembrane system
Endomembrane system (4.14) -Transport
Nucleus
nuclear envelope
endoplasmic reticulum (ER)- both
Golgi apparatus
Transport vesicles (develop into lysosomes and vacuoles.
plasma membrane.
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Cell Junctions
Extracellular Matrix
Tight junctions: bind cells together
Anchoring junctions (gap): attach adjacent cells to each other
Communicating junctions : channels that allow water and other small molecules to flow between cells.
Communicating
Anchoring junctions
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