 Cells were unknown until the discovery of microscopes in the 1650’s  two scientists working independently built the first microscopes  Anton von Leeuwenhoek in Holland  Robert Hooke in England

 Studied cork - a kind of tree bark  named the structures he saw “cells” because they reminded him of the small rooms monks slept in

 Studied pondwater, sour milk, and semen (magnification 10X greater than Hooke’s)  named moving organisms “animalcules” this scared people who thought:  Human sperm cells contain tiny human beings!  Pond water causes madness  Today we can look back and think “crazy,” but at the time people took these ideas very seriously. (protists)

1. All living things are composed of cells (you, me, plants, bugs, fish, bacteria, yeast,) 2. Cells are the basic units of structure and function in living things (what keeps us upright and helps us live, basically small workers responsible for how we function!) 3. New cells are produced from existing cells (they can’t just appear out of thin air…cells make new cells by dividing!)

1. Schleiden (circa 1838) All plants are made of cells! Onion skin cells

2. Schwann All animals are made of cells! Human red blood cells

3. Virchow All cells come from pre-existing cells!

 Microscopic (mostly)  Measured in microns µm  (micrometers).  A µm is one millionth of a meter =  m = one thousandth of 1 mm.

Form follows function! - a cell’s function influences its physical features - cells vary in shape, size, and internal organization

 Both Have:  Cytoplasm  Ribosomes  Plasma Membrane  With Plants: Cell Wall  With (some) Animals: Flagella  Prokaryotes do not have a nucleus!  Eukaryotes are more complex  Eukaryotes are larger

 From Greek words…  EU means TRUE.  PRO means BEFORE.  KARYON means NUCLEUS. Eukaryote = TRUE NUCLEUS; Prokaryote = BEFORE NUCLEUS.  All cells have DNA, in eukaryotes it is stored in the nucleus.  Prokaryotes don’t have a nucleus, and it floats around in the cytoplasm in an area called the nucleoid.  Only eukaryotes have membrane-bound organelles.

Statement ProkaryoticEukaryotic 1. Have a nucleus 2. Have membrane-bound organelles 3. Contain genetic material (DNA) 4. Can be single or multi-celled 5. Can only be single-celled. 6. Have a plasma membrane and cytoplasm

 Cells make up tissues which make up organs which make up organ systems which make up organisms  We can also take it back to the atomic level..

 Eukaryotic cells Eukaryotic cells  Plant Cells Plant Cells  Bozeman Science – the cell Bozeman Science – the cell