a. All organisms are made of __.
b. All cells are related by their __
c. Development of __-->advance of science
i. Study of cells progressed with invention of __
1. Robert Hook (1665)
2. Antoni van Leeuwenhoek
cells, which are the simplest collection of matter that can be alive
descent, but have been modified
microscopes in 1590
visualized living cells
Explain light microscopes.
Visible liht is passed throuh the specimen and then through glass lenses, which refract the light in ways that allow image of specimen to be magnified
Threee important parameters of microscopes.
- Magnification: ratio of an object’s
- size to its real size
- Resolution: measure of the clarity
- of the image; minimum distance two points can be separated and still be
- distinguished as two points
- Contrast: accentuates differences
- in parts of the sample
__ are the membrane enclosed structures within eukaryotic cells. Seeing them required the electron microscope
- 1. Focuses beam of electrons through or on specimen surface
- a. Resolution is inversely related to the wavelength of the radiation a microscope uses for iimaging, and electron beans are shorter wavelengths than visible light
- a. Detailed study of the topography of a specimen
- i. Scans surface coated with film of gold, exciting electrons on the surface, and detecting and translating patter
Transmission Electron Microscope
- a. Studies internal structures
- i. Aims through thin section, which has been stained with atoms of heavy metals
Advantages and Disadvantages
- 1. Disadvantage of EM:
- a. Methods used to prepare specimen kills cells
- 2. Advantage of LM:
- a. Labeling molecules or structures with fluorescent markers made it possible to see structures with increasing detail and revealed sharpened images of 3D tissues and cells
__, the study of cell structure, relies on microscopes.
the study of the chemical processes of cells, was integrated.
- i. Takes cells apart and separates major organells and other subcellular structures from one another using a centrifuge
- 1. Spins test tubes holding mixtures of disrupted cells at different speeds, causing a fraction of the cell components to settle on the bottom onf the tube
- a. Lower speeds= larger components
- b. Higher speeds= smaller component
- ii. Allows identification of functions
Explain electron microscopy.
SEM: 3D surface of the topography of a specimen (surface)
TEM: profiles a thin section of a specimen, revealing internal structure