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Biology Exam 2
Terms in this set (16)
Dissecting microscopes or stereoscopes
low magnification of relatively large objects.
used for higher magnification of relatively small objects (usually tissue sections).
Bright field microscopy
uses broad spectrum white light and works best with stained cells, as tissues and cells typically have little inherent contrast.
phase contrast microscopy
allows visualization of differences in refractive index, used for biological tissue
uses filters to direct only specific wavelengths of broad spectrum, high intensity light to a specimen labeled with a fluorescent dye. The fluorescent dye may be attached to an antibody that binds to a specific portion of a particular macromolecule, usually a protein.
requires that a specimen be labeled with a fluorescent dye, but differs from epifluorescence microscopy in that it uses a laser to excite the dye, and it is able to screen out fluorescence emanating from out of focus structures. This results in crisper images.
uses high speed electrons, focused by electromagnets, to image cells and subcellular structures. Allows one to visualize organelles and some large macromolecules.
To determine the molecular conformation of proteins
This technique separates organelles based on size and density.
involves progressive spins at higher speeds to serially pellet structures with decreasing size and density
density gradient centrifugation
Particles centrifuged through this gradient at very high speed will settle in specific sucrose layers based on their densities
also known as actin filaments and are composed of non-covalently bound actin monomers. Actin filaments are the smallest cytoskeletal filament (~ 7 nm) and are generally very dynamic structures: they can polymerize and depolymerize quickly in response to the needs of the cell.
because actin polymerizes head-to-tail, each end of the filament is distinct. The faster growing end is known as the plus end, and the slower growing end is known as the minus end
motor proteins use the energy of ATP hydrolysis to carry organelles (e.g. melanosomes, lysosomes, endosomes, chloroplasts) around the cell. Most myosins travel toward the plus-end of an actin filament
antiparallel heterotetramer; because IFs have no polarity, they do no act as highways for intracellular transport.
Put the steps of the process of signal transduction in the order they occur:
1. A conformational change in the signal-receptor complex activates an enzyme.
2. Protein kinases are activated.
3. A signal molecule binds to a receptor.
4. Target proteins are phosphorylated.
5. Second messenger molecules are released.
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