I. Cell Theory A. Three part theory about cells

I. Cell Theory
A. Three part theory about cells
1. All living things are made of cells
2. All cells arise from existing cells
3. All cells come from pre-existing cells
Red Blood Cells
Onion Skin Cells
B. Who came up with this theory circa 1838?
(all plants are made of cells)
(all animals are made of cells)
(all cells come from pre-existing cells)
II. How do we study cells?
A. Light Microscopes
1. Light passes through lenses to magnify image up to 1000X
2. Can observe living cells
B. Electron Microscopes
1. Uses a beam of electrons to magnify image > 1000X
2. Kills cells being observed
III. Common features of all cells
A. Small size – allows materials to move via diffusion
Diffusion = process by which molecules move from
levels of high concentration to levels of low
concentration until equilibrium is reached
B. Cell Membrane – selectively/differentially permeable (lets some
things in and out)
C. Cytoplasm – semi-fluid material in which cell organelles float
D. Cytoskeleton – proteins that support the cell
E. Ribosomes – make proteins