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330 Exam 1
lectures 1+2
| Question | Answer |
|---|---|
| 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
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