Chapter 6: A Tour of The Cell 1 Flashcards
Light Microscope
Visible light is passed through a specimen. Glass lenses refract light to magnify it.
Magnification
Ratio of image size to real size
Resolution
Clarity. The minimum distance two points can be separated and still be distinguished as two points. Inversely related to wavelength of radiation that microscope uses.
Contrast
accentuates differences in parts of sample
Electron microscope
focuses beam of electrons through specimen. electron beams have very short wavelengths.
Scanning Electron Microscope
Used for topography. The sample is coated with a thin film of gold. The electron beam excites electrons on the surface which are converted to a pattern on the screen.
Transmission Electron Microscope
Used for internal structure of cells. Aims electron beam through thin section of specimen, which is stained with heavy metals that attach to cellular structures and enhance electron density. Electromagnets are used as lenses to focus image of transmitted electrons.
Brightfield
Light passes directly through specimen. sometimes stained with dyes for contrast (needs preserved cells).
Phase-contrast
Variations in density are amplified to enhance contrast in unstained cells (can be living).
Differential-interference-contrast (Nomarski)
Exaggerate differences in density (3D)
Fluorescence
label molecules with fluorescent dyes. reveals locations of molecules
Confocal
uses laser to eliminate out-of-focus light from thick sample. captures sharp images at many different planes to make 3D reconstruction.
Deconvolution
Digitally removes out of focus light and reassigns it to the source.
Super resolution
Lights up individual fluorescent molecules and record position.
Artifacts
structural features seen in micrographs that do not exist in living cell
Cell fractionation
Technique that isolates cell components based on size and density.
Cell fractionation steps
- Centrifuged at 1000g for 10 minutes (pellet rich in nuclei and cellular debris)
- 20,000 g for 10 minutes. Pellet rich in mitochondria (and/or chloroplasts)
- 80,000 g for 60 minutes. Pellet rich in microsomes (pieces of plasma membranes and cells’ internal membranes)
- 150,000 g for 3 hours. Pellet rich in ribosomes
Supernatant
Liquid from centrifuge that is poured into another tube and centrifuged at a higher speed
Cytosol
Semifluid, jelly-like substance inside cells where subcellular components are suspended
Eukaryotic Cell
Most of the DNA is inside the nucleus. Larger than prokaryotic cells. (10-100 um)
Prokaryotic Cell
DNA inside nucleoid. Has ribosomes
Nucleoid
Region where cell’s DNA is located (not enclosed by a membrane)