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Basic Structure of a Cell

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A. Main Characteristics of Organisms1. Made of CELLS2. Require ENERGY (food)3. REPRODUCE (species)4. Maintain HOMEOSTASIS5. ORGANIZED6. RESPOND to environment7. GROW and DEVELOP8. EXCHANGE materials with

surroundings (water, wastes, gases)

I. Modern Cell Theory

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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)

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C. Robert Hooke 1. First to view cells2. 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.

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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

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E. Discoveries Since the Cell Theory

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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A. Cell Size and Types1. Cells can only be observed under

microscope2. 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 Celliii.Bacterial

Cell

II. Modern Cell Theory

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B. Number of Cells1. 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

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D. Prokaryotes

1. The first cells2. Cells that lack a nucleus or

membrane-bound organelles3. Includes bacteria4. Simplest type of cell5. Single, circular chromosome

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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

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E. Eukaryotic Cell1. Contain 3 basic cell

structures:a. Nucleusb. Cell Membranec. Cytoplasm with organelles

2. Two main types of eukaryotic cellsa. Plant cellsb. Animal cells

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3. Organellesa. Very small (Microscopic)b. Perform various functions for a cellc. Found in the cytoplasmd. May or may not be membrane-bounde. Examples:

i. Golgi Bodies – wrap & export proteinsii. Nucleolus – makes ribosomesiii. Lysosomes – digests & gets rid of wastesiv. Ribosomes – makes proteins

E. Eukaryotic Cell