BASIC INFORMATION

Most cells are between 1  and 100 um in diameter, too small to be seen by the unaided eye

LIGHT MICROSCOPES

• Visible light is passed through a specimen and through glass lenses 

• Lenses refract (bend) the light, resulting into the image being magnified 

3 IMPORTANT PARAMETERS OF MICROSCOPY

• Magnification | The ratio of objects size to real size 

• Resolution | The measured of clarity of the image or the minimum distance between 2 points

• Contrast | Visible differences in parts of the sample

MORE ON LIGHT MICROSCOPES 

• LMs can magnify effectively 1000 times the size of the specimen 

• Various techniques enhance contrast and enable cell components to be sustained or labeled

• Most subcellular structures, including organelles, are toyo small to be resolved by the light microscopy  

MICROSCOPES USED TO STUDY SUBCELLULAR STRUCTURES

• Scanning electron microscopes (SEMs) focus a beam of electrons onto the surface of a specimen providing images that look 3D

• Transmission electron microscopes (TEMs) focus a beam of electrons through a specimen

• TEMs are mainly used to study the internal structure of cells

RECENT ADVANCES

•  Breaks up cells and separates the components using centrifugation

• Cell components separate based on their relative size

• Fractionation enables scientists to determine functions of organelles

• Biochemistry and cytology help correlate cell function with structure