STRUCTURE AND FUNCTION OF CELLS

Notes #12

All organisms are made of Cells

• The cell is the basic unit of structure and function

• The cell is the smallest unit that can still carry on life processes

• Unicellular (one-celled) and Multicellular (many celled) organisms are composed of cells

• Before 17th century no one knew cells existed

• Most cells are too small to be seen with the unaided eye

• In the early 17th century, microscopes were invented and cells were seen for the first time

All organisms are made of Cells

Important Contributors• Anton von Leeuwenhoek

– Dutchman– Made the 1st hand held microscope– Viewed microscopic organisms in water and

bacteria from his teeth

Leeuwenhoek's microscope consisted simply of:

A) a screw for adjusting the height of the object being examined B) a metal plate serving as the body C) a skewer to impale the object and rotate it D) the lens itself, which was spherical  

Important Contributors

• Robert Hooke (1665)– Englishman– Made an improved microscope– Viewed thin slices of cork (dead plant cell

walls)– Named what he saw “cells”

Important Contributors• Matthias Schleiden & Theodore Schwann

(1830s)– All living things were made

of cells

• Rudolf Virchow (1855)– Cells only arise from

pre-existing cells– No spontaneous generation

The Cell Theory

• Combined work of Schleiden, Schwann, & Virchow

• Principles of the Cell Theory– All living things are made of one or more cells– Cells are the basic unit of structure and

function in organisms– Cells come only from the reproduction of

existing cells