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Transcript
Cells Chapter 6 Notes What does the word ‘Cell’ Mean? The word cell is derived from the Latin word 'cellula' which means small compartment. A Famous Man in Science – Robert Hooke In 1663 an English scientist, Robert Hooke, discovered cells in a piece of cork, which he examined under his primitive microscope. Hooke only observed cell walls because cork cells are dead and without cytoplasmic contents. Hooke drew the cells he saw and also coined the word CELL. Anton van Leeuwenhoek Today, he is known as the “Father of Microbiology” and discovered bacteria Used his own (single lens) monocular microscopes and was the first person to observe bacteria and protozoa Anton van Leeuwenhoek Built microscopes that magnified over 200 times, with clearer and brighter images than any of his colleagues at that time. Cell Theory The CELL THEORY, or cell doctrine, states that all organisms are composed of similar units of organization, called cells. The concept was formally articulated in 1839 by Schleiden & Schwann and has remained as the foundation of modern biology. Cell Theory Components 1. 2. 3. 4. 5. 6. There are 6 Components to Cell Theory: All known living things are made up of cells. The cell is structural & functional unit of all living things. All cells come from pre-existing cells by division. (Spontaneous Generation does not occur). Cells contain hereditary information which is passed from cell to cell during cell division. All cells are basically the same in chemical composition. All energy flow (metabolism & biochemistry) of life occurs within cells. Two Major Classes of Cells 1. 2. Prokaryotic Cell Lacks a nucleus and most other organelles. Bacteria and another group of organisms called the archaea are prokaryotic cells. Prokaryotic organisms appear earliest in Earth's fossil record. Eukaryotic Cell Has a nucleus surrounded by its own membrane, and has other internal organelles bounded by membranes. Protists, fungi, plants, and animals consist of eukaryotic cells. Organisms with eukaryotic cells appeared later in Earth's history. Prokaryotic Cells A bacterium is an example of a prokaryotic cell (pro means "earlier than"). Prokaryotic cells are much simpler in structure They do not have a true nucleus or membrane bound organelles that a eukaryotic cell would have. The DNA in a prokaryotic cell is concentrated in an area called the nucleoid region: This is not separated from the rest of the cell by a membrane. ONLY EUKARYOTIC CELLS HAVE MEMBRANE BOUND ORGANELLES Prokaryotic Cells Notice how everything is floating around together – not bound separately from one another! Example: The DNA is not bound separately from the ribosomes Eukaryotic Cells Protists, fungi, plants, and animals consist of eukaryotic cells. Eukaryotic cells are much more complex in structure They do have a true nucleus and membrane bound organelles The DNA in a eukaryotic cell is concentrated in an area called the nucleus Eukaryotic Cells Notice how everything is bound in a membrane separate from one another. Example: The DNA is seen inside the nucleus which has a nuclear membrane separate it from everything else! Compare, Compare! Prokaryotic Cell Eukaryotic Cell o What are some similarities? o What are some differences?