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 The average human being is composed of around 100 trillion individual cells!  On an average day, billion cells die in the human body.  The biggest cell in the world is the ostrich egg, which can be seen with your naked eye! WOW!!!

 In 1673 Leuwenhoek, a Dutch biologist, used a handmade microscope.  He used the microscope to observe pond scum and discovered single-celled organisms. › He called them “animalcules.”

 In 1665 an English Scientist, Robert Hooke, discovered cells while looking at a thin slice of cork.  Observations › Saw that the cork was composed of thousands of tiny chambers. › He called these chambers “cells.”  Significance: opened up the study of cells.

 Very little cell advancements were made after Hooke and Leuwenhook.  This is probably due to belief in spontaneous generation. › Definition: ordinary formation of living organisms without descent from similar organisms. › Mice appearing from dirty clothes/corn husks. › Maggots appearing from rotting meat.

 Much doubt existed around spontaneous generation.  Conclusively disproved by Louis Pasteur. Ummm, I don’t think so!!!

 German Botanist, Matthias Schleiden, concluded that all plant parts are made of cells.  German physiologist, Theodor Schwann, stated that all animal tissues are composed of cells.

 Rudolf Virchow, German physician,, concluded that cells must arise from preexisting cells. › No spontaneous generation!

The 3 Basic Components of the Cell Theory were now complete: 1. All organisms are composed of one or more cells. 2. The cell is the basic unit of life in all living things. 3. All cells are produced by the division of preexisting cells. theory

 Remember….cells are the basic unit of life for ALL living things.  There are two basic types of cells: 1. Prokaryotic cells – found in bacteria. 2. Eukaryotic cells – found in protists, fungi, plants and animals.

 Same basic functions.  Plasma membrane to control what enters and leaves the cell.  “Filled” with cytoplasm.  Contain ribosomes to make protein.  Contain DNA (genetic information).

 Much more complex.  Much larger.  Contain a nucleus to house the genetic material. › Linear DNA packaged into chromatin found inside the nucleus.  Contains organelles - specialized structures in the cytoplasm.

 Much smaller.  Less complex.  No nucleus.  Circular DNA that is found in the cytoplasm.  No organelles found in the cytoplasm.  Surrounded by a cell wall.

 Smaller surface area to volume allows nutrients to easily and quickly reach center of the cell.  Eukaryotic cells are larger and can not pass nutrients as quickly. Specialized organelles: › carry out metabolism. › provide energy. › transport chemicals throughout the cell.

1. Compound Light Microscope › Light passes through lenses to magnify image up to 1000X. › Can observe living cells.

2. Electron microscope › Uses a beam of electrons to magnify image > 1000X. › Kills cells being observed.