Biology Class 4

“Cells, Units of Life”

Biology 4th Class

A. The Early Years 1. Robert Hooke (1660) • first person to see outline of cells 2. Antonie von Leeuwenhoek (1673) • developed high magnification lenses • first record of microorganisms 3. Matthias Schleiden and Theodore Schwann (1839) and Rudolph Virchow (1855)

Cell Theory: 1. All living things are composed of cells. (Schleiden and Schwann) 2. All things come from preexisting cells. (Virchow, in opposition to spontaneous generation) B. Cell Size 1. Most are 1-100 pm in diameter 2. Smallest cells are bacteria 3. Ostrich eggs are the largest cells 4. There is a limit to the size of cells • surface area / volume ratio • as cell grows, its volume increases more rapidly than its surface area C. Types of Cells (three basic types) • Bacterial • Archaean • Eukaryotic a. bacterial cells 1. 1-10 um in diameter 2. No membrane bound organelles 3. 1 circular DNA molecule located in nucleoid region 4. most have a cell wall (peptidoglycan) ex. Bacteria and cyanobacteria b. archaeon cells 1. 1-10 um in diameter 2. No membrane bound organelles 3. Cell walls lack peptidoglycan

4. have characteristics of both bacteria and eukaryotic cells c. eukaryotic cells 1. 10-100 um un diameter 2. membrane bound organelles 3. linear DNA molecules 4. some have a cell wall (cellulose or chitin) (plants, animals, fungi, protista) D. Organelles of Eukaryotic Cells • Compartmentalize a Cell’s activities • Keep reactions isolated from one another • Increase efficiency in the cell a. nucleus 1. surrounded by a nuclear envelope perforated with nuclear pores 2. contains DNA and nucleolus (stores RNA and nucleotides) 3. functions to separate the DNA from the rest of the cell E. The Endomembrane System • a series of compartments made from folded membrane and connected via vesicles • Endoplasmic Reticulum a. Rough b. Smooth • Golgi apparatus • Lysosomes 1. Endoplasmic Reticulum\ * interconnected network of membranes extending from the nucleus to plasma membrane a. Rough ER – studded with ribosomes (site of protein synthesis) b. Smooth ER – lacks ribosomes (site of lipid synthesis) 2. Golgi Apparatus • shipping and processing center • receives materials from ER and ships them out 3. Lysosomes (suicide sacs) * vesicles containing >40 types of digestive enzymes

* function to recycle damaged organelles, break down cellular byproducts and destroy invading microbes 4. Mitochondria (Power House of the Cell) * double membrane * #/cell varies * contain DNA * inherited from female parent * site of cellular respiration (production of ATP) 5. Chloroplasts (plant version of mitochondria) * possess 3 membranes * #/cell varies * contain DNA * found in plants and protests * function in photosynthesis F. The Endosymbiont Theory Proposes that chloroplasts and mitochondria evolved from once free-living bacteria engulfed by archaea. Based on the fact that mitochondria and chloroplasts resemble certain bacteria. (size, shape, membrane, structure, and method of making proteins)