Cell Theory and Microscope Basics

Notes

Lecture 1 summary • The invention of the microscope led to the discovery of cells in the 17th century. • The “cell theory” states that (1) all living organisms are made of cells, (2) cells are the basic units of life, (3) cells arise from pre-existing cells, (4) hereditary information passes from cell to cell, (5) all cells have the same basic chemical composition (6) energy flow occurs within cells. • Size scales in cell biology are very important: 1 m = 103 mm = 106 μm = 109 nm. • Cells vary in size, small bacteria are about 1 μm, “typical” vertebrate cells can be about 10 μm and larger. • Many organelles are 1-2 μm, ribosomes are about 25 nm, and a single hydrogen atom about 0.1 nm. • The resolving power (“resolution”) is the ability to distinguish two close objects. • The resolution of the unaided eye is about 0.2 mm, of the light microscope is about 0.2 μm, and much smaller (~nm) for the electron microscope. • Transmission electron microscopy (TEM) allows one to see very fine detail in cells, such as ribosomes and membranes. • Cells are mostly water and therefore transparent, so staining methods are generally needed to see sub-cellular structures. • Fusing proteins to green fl...