How does the internal organization of eukaryotic cells allow them to perform the
functions of life?
Concept 6.1
Light Microscope (LM) - visible light is passed through the specimen and then through
glass lenses; the lenses refract (bend) the light in such a way that the image of the
specimen is magnified as it is projected into the eye or into a camera
Brightfield - light passes directly through the specimen
Phase-contrast - variations in density within the specimen are amplified to
enhance contrast
Differential interference contrast (Nomarski) - optical modifications are used
to exaggerate differences in density
Fluorescence - location of specific molecules are revealed by labeling the
molecules with fluorescent dyes or antibodies
Confocal - a laser is used to create a single plane of fluorescence
Super-resolution - individual fluorescent molecules are excited by UV light and
their positions are recorded
Magnification - increasing the apparent size of an object
,Resolution - a measure of the clarity of the image
- Inversely related to the wavelength of the light (or electrons a microscope uses
for imaging
Contrast - visible differences in brightness between parts of the sample
- staining samples can make things that were invisible or hard to see before,
visible
Electron Microscope (EM) - focuses a beam of electrons through the specimen or onto
its surface
- Electron beams have much shorter wavelengths than visible light
Scanning Electron Microscope (SEM) - electron beam scans the surface of the
sample, usually coated with a thin film of gold; the beam excites electron on the surface,
which are detected by a device that translates the pattern of electrons into an electronic
signal sent to a video screen
Transmission Electron Microscope (TEM) - used to study the internal structure of
cells; aims an electron beam through a very thin section of the specimen
- Specimen has been stained with atoms of heavy metals, which attach to certain
cellular structures, thus enhancing the electron density of some parts of the cell
more than others
- The image displays the pattern of transmitted electrons
- Both SEM and TEM use electromagnets as lenses to bend the paths of the
electrons, ultimately focusing the image onto a monitor for viewing
, - A disadvantage of electron microscopy is that the methods customarily used to
prepare the specimen to kill the cells and can introduce artifacts, structural
features seen in micrographs that do not exist in the living cell
Cell fractionation - takes cells apart and separates major organelles and other
subcellular structures from one another
- Differential centrifugation - a process where the centrifuge spins test tubes
holding mixtures of disrupts cells at a series of increasing speeds
- This causes a subset of the cell components to settle to the bottom of the
tube, forming a pellet
- At lower speeds, the pellet consists of larger components
- At higher speeds, the pellet consists of smaller components
- The goal of cell fractionation is to release the contents of the cell by breaking
apart the plasma membrane
- Creates a homogenate (cell fragments and tissues)
- Our ability to isolate different components in differential centrifugation will be
linked to the force and duration of our centrifugation
- This particular type of experiment is a way to fraction out of isolate out
pellets that we are interested in learning more about
, Concept 6.2
- All cells share certain basic features:
- They are all bounded by the plasma membrane (or cell membrane)
- They all have cytosol inside
- semifluid, jelly like substance in which subcellular components are
suspended
- They all contain chromosomes
- Carry genes (genetic information) in the form of DNA
- They all have ribosomes
- Tiny complexes that make proteins according to instructions from
the genes
Organelles - the membrane-enclosed structures within eukaryotic cells
Eukaryotic cell - cells in animals, fungi, plants, and protists; most of the DNA is in the
nucleus
- Generally larger than prokaryotic cells
Prokaryotic cell - cells in bacteria and archaea; DNA is concentrated in the nucleoid,
which is not membrane-enclosed
- Organelles (membrane-bounded structures) are absent in almost all prokaryotic
cells
functions of life?
Concept 6.1
Light Microscope (LM) - visible light is passed through the specimen and then through
glass lenses; the lenses refract (bend) the light in such a way that the image of the
specimen is magnified as it is projected into the eye or into a camera
Brightfield - light passes directly through the specimen
Phase-contrast - variations in density within the specimen are amplified to
enhance contrast
Differential interference contrast (Nomarski) - optical modifications are used
to exaggerate differences in density
Fluorescence - location of specific molecules are revealed by labeling the
molecules with fluorescent dyes or antibodies
Confocal - a laser is used to create a single plane of fluorescence
Super-resolution - individual fluorescent molecules are excited by UV light and
their positions are recorded
Magnification - increasing the apparent size of an object
,Resolution - a measure of the clarity of the image
- Inversely related to the wavelength of the light (or electrons a microscope uses
for imaging
Contrast - visible differences in brightness between parts of the sample
- staining samples can make things that were invisible or hard to see before,
visible
Electron Microscope (EM) - focuses a beam of electrons through the specimen or onto
its surface
- Electron beams have much shorter wavelengths than visible light
Scanning Electron Microscope (SEM) - electron beam scans the surface of the
sample, usually coated with a thin film of gold; the beam excites electron on the surface,
which are detected by a device that translates the pattern of electrons into an electronic
signal sent to a video screen
Transmission Electron Microscope (TEM) - used to study the internal structure of
cells; aims an electron beam through a very thin section of the specimen
- Specimen has been stained with atoms of heavy metals, which attach to certain
cellular structures, thus enhancing the electron density of some parts of the cell
more than others
- The image displays the pattern of transmitted electrons
- Both SEM and TEM use electromagnets as lenses to bend the paths of the
electrons, ultimately focusing the image onto a monitor for viewing
, - A disadvantage of electron microscopy is that the methods customarily used to
prepare the specimen to kill the cells and can introduce artifacts, structural
features seen in micrographs that do not exist in the living cell
Cell fractionation - takes cells apart and separates major organelles and other
subcellular structures from one another
- Differential centrifugation - a process where the centrifuge spins test tubes
holding mixtures of disrupts cells at a series of increasing speeds
- This causes a subset of the cell components to settle to the bottom of the
tube, forming a pellet
- At lower speeds, the pellet consists of larger components
- At higher speeds, the pellet consists of smaller components
- The goal of cell fractionation is to release the contents of the cell by breaking
apart the plasma membrane
- Creates a homogenate (cell fragments and tissues)
- Our ability to isolate different components in differential centrifugation will be
linked to the force and duration of our centrifugation
- This particular type of experiment is a way to fraction out of isolate out
pellets that we are interested in learning more about
, Concept 6.2
- All cells share certain basic features:
- They are all bounded by the plasma membrane (or cell membrane)
- They all have cytosol inside
- semifluid, jelly like substance in which subcellular components are
suspended
- They all contain chromosomes
- Carry genes (genetic information) in the form of DNA
- They all have ribosomes
- Tiny complexes that make proteins according to instructions from
the genes
Organelles - the membrane-enclosed structures within eukaryotic cells
Eukaryotic cell - cells in animals, fungi, plants, and protists; most of the DNA is in the
nucleus
- Generally larger than prokaryotic cells
Prokaryotic cell - cells in bacteria and archaea; DNA is concentrated in the nucleoid,
which is not membrane-enclosed
- Organelles (membrane-bounded structures) are absent in almost all prokaryotic
cells
