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330 Exam 1

lectures 1+2

QuestionAnswer
What are the 2 concepts of cell theory? • Cells are functional units of life • All living organisms are made of cells
How many types of cells in human body? Over 200
How many species in world? Over 10 million
What are the 5 common threads of all species? growth, reproduction, communicate w enviro, aquire/assimilate energy, homeostasis
What are the 8 common features of all cells? - Highly complex/organized - Have genetic program - Produce more of themselves - Biochemical factories -get/use energy - Engage in mechanical activities - Respond to stimuli - Can self regulate - Evo first happens @mol/cell level
What do model eukaryotes consist of? Sequenced genome, site-directed/tissue specific mutagenesis possible, multiple gene expression tracked simultaneously, developmental sequence is known
What are some examples of model eukaryotes? yeast, arabidopsis (common thale cress), C. elegans (nematode worm), fruitfly (drosophila melanogaster), mouse
Animal cells are (size), (color), and (look) small, colorless, and translucent
Which microscopy type is used to image large-scale cellular structures? Light microscopy
How is the resolution of light microscopy vs electron microscopy? LM has limited resolution but EM allows for very high resolution
If you desire contrast and sensitivity with light microscopy, what can you use? Chemical stains and fluorescent molecules
How does flow cytometry work? Flow cytometry uses fluorescent labels to measure levels of specific biomolecules and ions, and to sort cells based on expression levels.
What 19th century invention allowed visualization of cells? High quality light microscopes
What has happened in the last 200 years in terms of light microscopy developments? Increase in power and sensitivity
Why do cellular structures and most animal cells have to be magnified for study? They are too small to be seen with the naked eye
What are the smallest organelles that can be clearly seen by light microscopy? And how big are they? Mitochondria (~0.5 micrometers)
How long (diameter) is the typical animal cell? 10-20 micrometers
How is light microscopy limited? Limited resolution
What is resolution? The ability to distinguish 2 objects that are close to each other
How is magnification different from resolution? You can zoom in (magnify) an object as much as you want but it may be blurry
What is detection? An item smaller than 0.2 micrometer can be detected if it emits light
What sets the limit of resolution for microscopy? Wavelength of light & Size of lens
How do u get past the problem that animal cells are practically invisible (colorless/translucent) under light microscopy? Use phase contrast or differential-interference-contrast (DIC) microscopy
How do phase contrast and DIC (differential interference contrast) microscopes work? They use the change in phase of light waves as they pass through a cell
What does staining (with chem. dyes) require? Fixation - killing/preserving cells
What do u have to do if you want to visualize a tissue under microscopy? Cut sample into thin sections
How do fluorescent molecules produce color? By absorbing light at one wavelength and emitting light at a longer wavelength
How can fluorescent stains be introduced? chemical dyes, fluorescent molecules attached to antibodies, or intrinsically fluorescent proteins (GFP - green fp + variants) expressed by the cell itself
How is fluorescence microscopy limited? By fluorescence coming from out-of-focus parts of cells
How does confocal microscopy work? A scanning laser and pinhole apertures use focal plane - to get hi-res optical section. The pics from multiple focal planes can be combined to create a 3D reconstruction.
What is FRET microscopy? And how does it work? Fluorescence resonance energy transfer - uses 2 fluorescent proteins where the excitation energy of the 2nd matches the 1st. If proteins very close together, protein 1 can excite protein 2 to fluoresce.
What is TIRF microscopy? And how does it work? Total internal reflection fluorescence - laser light reflected off the cover slip can excite molecules (within 100-200 nm) and provide a narrow band of fluorescence.
How does vital microscopy work? 2 long waves of photons of light excite the fluophone, to allow deep penetration of sample without sectioning
How is electron microscopy different from light microscopy? A beam of electrons is used instead of light
How much more resolution can be achieved with EM compared to LM? 200x more resolution w/ EM
How are cells prepared for use with EM? Must be fixed, desiccated and sliced into thin sections
What chemicals can be used to fix cells for EM? OsO4 (osmium tetroxide) and glutaraldehyde
Since cells are almost transparent to electrons, how can cells be stained? Using electron-dense materials or gold-tagged antibodies (to mark specific proteins/structures)
What is the difference between SEM and TEM? SEM images outside surface of cell (staining, but no sectioning), while TEM images internal structures
Why does an electron beam give more resolution than light? Because the wavelength of an electron is much smaller than the wavelength of a photon
Created by: dominic54