1 Basic Structure of a Cell

2 A. Main Characteristics of Organisms 1.Made of CELLS 2.Require ENERGY (food) 3.REPRODUCE (species) 4.Maintain HOMEOSTASIS 5.ORGANIZED 6.RESPOND to environment 7.GROW and DEVELOP 8.EXCHANGE materials with surroundings (water, wastes, gases) I. Modern Cell Theory

3 B.CELL THEORY 1.All living things are made of cells 2.Cells are the basic unit of structure and function in an organism (basic unit of life) 3. Cells come from the reproduction of existing cells (cell division)

4 C. Robert Hooke 1. First to view cells 2. Robert Hooke (1665): microscope to examine a slice of cork (dead plant cell walls) 3. Saw small boxes, and called them “CELLS” because they looked like the small rooms that monks lived in called Cells.

5 D. Other Scientists Contributed to the Cell 1.Matthias Schleiden: (1838) plants made of cells; cofounder of cell theory 2.Theodore Schwann: (1839) animals made of cells; cofounded the cell theory 3.Rudolph Virchow: (1855) observed cells dividing using a microscope; all cells come from other pre-existing cells by cell division

6 E. Discoveries Since the Cell Theory 1. 1.Endosymbiotic theory: One organism begins to live within another organism and both organism benefit. Eventually, the two organisms evolve to become one new single organism. 2.Lynn Margulis (1970): evidence that some organelles within cells were at one time free living cells themselves. 3.Examples: Chloroplast and Mitochondria (have their own DNA)

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8 A. Cell Size and Types 1.Cells can only be observed under microscope 2.Cell range: 5 – 50 micrometers (microns; 1 cm = 10,000 microns ) in diameter 3. Three basic types of cells include (Biggest to smallest: plant, animal, bacteria): ii.Animal Celli.Plant Cell iii.Bacterial Cell II. Modern Cell Theory

9 B. Number of Cells 1. Although ALL living things are made of cells, organisms may be: a. Unicellular – composed of one cell b. Multicellular - composed of many cells that may organize into tissues, etc.

C. Prokaryotic or Eukaryotic 1.Prokaryotes include bacteria & lack a nucleus or membrane-bound structures called organelles 2. Eukaryotes include most other cells & have a nucleus and membrane bound organelles (plants, fungi, & animals) 10

11 D. Prokaryotes 1. The first cells 2. Cells that lack a nucleus or membrane-bound organelles 3. Includes bacteria 4. Simplest type of cell 5. Single, circular chromosome

12 D. Prokaryotes 6. Nucleoid region (center) contains the DNA 7. Surrounded by cell membrane & cell wall (peptidoglycan) 8. Contain ribosomes (no membrane) in their cytoplasm to make proteins

13 E. Eukaryotic Cell 1. Contain 3 basic cell structures: a. Nucleus b. Cell Membrane c. Cytoplasm with organelles 2. Two main types of eukaryotic cells a. Plant cells b. Animal cells

14 3. Organelles a. Very small (Microscopic) b. Perform various functions for a cell c. Found in the cytoplasm d. May or may not be membrane-bound e. Examples: i. Golgi Bodies – wrap & export proteins ii. Nucleolus – makes ribosomes iii. Lysosomes – digests & gets rid of wastes iv. Ribosomes – makes proteins E. Eukaryotic Cell