Cell Microscopic Functions - Chapter 4.1

Cell Size

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 in the image being magnified.

Magnification

The ratio of the object's size to its real size.

Resolution

The measure of clarity of the image or the minimum distance between two points.

Contrast

Visible differences in parts of the sample.

Effective Magnification of Light Microscopes

Light microscopes can magnify effectively 1000 times the size of the specimen.

Techniques to Enhance Contrast

Various techniques enhance contrast and enable cell components to be stained or labeled.

Limitations of Light Microscopy

Most subcellular structures, including organelles, are too small to be resolved by light microscopy.

Scanning Electron Microscopes (SEMs)

SEMs focus a beam of electrons onto the surface of a specimen, providing images that look 3D.

Transmission Electron Microscopes (TEMs)

TEMs focus a beam of electrons through a specimen and are mainly used to study the internal structure of cells.

Cell Fractionation

Breaks up cells and separates the components using centrifugation.

Organelle Function Determination

Fractionation enables scientists to determine the functions of organelles.

Correlating Cell Function with Structure

Biochemistry and cytology help correlate cell function with structure.