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128 Cards in this Set
- Front
- Back
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What is microscopy? |
Microscopy is a technique that allows examination of small objects with tools that overcome(through sensitivity) the (in)capacity of the human eye. |
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What ithe maximum resolving power and maximum magnification of the light microscope? & What is the principle of the light microscope? |
0.2 μm White light (from the light source) travels through the sample (which is colored, for example with adye) The resulting image is projected and observable through the eyepiece with the human eye. Depending on the dye, the final image will be polychromatic (colored). Its maximum magnification is x 1500. |
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What is the principle of the transmission electron microscope? |
Electrons travel through the sample and are diverted depending on the density of heavy nuclei in thesample’s ultrastructures. For example, ultrastructural elements that bind heavy nuclei will attract electrons and be electron-dense; while elements that do not bind heavy nuclei will allow electrons topass – these are electron-clear areas. The electron-dense areas will appear as dark areas, while the electron-clear parts will be lighter(towards white). The resulting image (seen on a screen, not through an eyepiece) will bemonochromatic (shades of grey). |
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What is the electromagnetic spectrum used for light vs. electron microscope? |
Light microscope: visible light - 760nm-390nm - coloured Electron Microscope: Elctrons - black and white |
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What is the maximum resolving power for light vs. electron microscope? |
Light microscope: 0.2um Electron Microscope: 0.2nm |
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What is the maximum magnification used for light vs. electron microscope? |
Light microscope: x1500 Electron Microscope: x1 000 000 |
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What is the radiation source used for light vs. electron microscope? |
Light microscope: Quartz halogen lamp Electron Microscope: High voltage 50kV tungsten lamp |
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What are the lenses used for light vs. electron microscope? |
Light microscope: Glass lens Electron Microscope: Electro-magnets |
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What is the interior of the light vs. electron microscope? |
Light microscope: Air filled Electron Microscope: Vaccum |
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What is the focusing screen used for light vs. electron microscope? |
Light microscope: Human eye (retina), photographic film Electron Microscope: fluorescent screen, photographic film |
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What is the preparation of specimens used for light vs. electron microscope? |
Light microscope:living or fixed cells Electron Microscope: Dead cells only |
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What is the fixation of cells used for light vs. electron microscope? |
Light microscope: Alcohol Electron Microscope: OsO4 |
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What is the embedding used for light vs. electron microscope? |
Light microscope: wax- paraffin Electron Microscope: resin |
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What is the sectioning used for the light vs. electron microscope? |
Light microscope: slices ~ 5um Electron Microscope: Slices ~ 50nm |
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What are the stains used for light vs. electron microscope? |
Light microscope: Water soluble stains Electron Microscope: Heavy metal stains |
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What is the support used for light vs. electron microscope? |
Light microscope: Glass slide Electron Microscope: Copper Grid |
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What is magnifying power? & What are the maginfications and the names of the objectives? |
Magnification power is the product of the magnification of the objective and the eyepiece 4x - magnifying lens 10x - objective for orientation 20x, 40x - objective for histological diagnosis 60x, 100x - objective for cytological diagnosis |
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What are the different types of light microscopes? |
1. Dark field Microscope 2. Phase Contrast Microscope 3. Interference Microscope 4. Nomarski Microscope 5. Inverted Microscope |
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What is the principle of the dark field microscope? |
A diaphragm in a condenser selects only lateral light. The final image is formed by reflecting rays on sample components. |
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What is the principle of the phase contrast microscope? |
Light passing through the sample is modified in speed and direction These differences are then ‘translated’ by the microscope as differences in contrast |
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What is the principle of the Interference microscope? |
This microscope uses an additional light beam that doesn’t pass through the sample,but rather interferes with the main light beam. Used to analyze density of the sample. |
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What is the principle of the Nomarski type microscope? |
A modified phase-contrast microscope, offering apparent 3D images. |
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What is the principle of the Inverted Microscope? |
As the name implies, this microscope has its components upside-down: the objectiveis under the frame holding the sample, while the light source is above the sample. Used to examine cells in petri dishes or flasks. |
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What happens in the Scanning Electron Microscope and what is it used for? |
It is a elctron microscpe where: electrons from an electron beam that are reflected back off the sample surface are registeredto form a 3D image. It is a good technique to capture 3D images of surfaces of tissue, organs, etc. |
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What is the Freeze-fracture technique and what is it used for? |
The freeze-fracture technique consists of physically breaking apart (fracturing) a frozen biologicalsample (for example, a cell membrane); structural detail exposed by the fracture plane is thenvisualized by molding it in platinum-carbon to make a replica for examination in the transmissionelectron microscope (EM). It is a similar technique to scanning EM, though the images will appear 3Dtextured rather than full 3D in an apparent 3D space, like scanning EM. |
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What are the steps of preparation of tissue for light microscopy? |
1. Harvesting 2. Fixation 3. Embedding 4. Sectioning 5. Staining 6. Mounting |
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What are the steps of preparation of tissue for light microscopy? |
1. Harvesting 2. Fixation 3. Embedding 4. Sectioning 5. Heavy metal contrasting 6. Mounting |
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What is harvesting? |
Harvesting is taking a sample. Biopsy - sampling of tissue from living organisms Necropsy - sampling of tissue from dead organisms |
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What is fixation? |
Sample fixation is a critical step in the preparation of histological sections by whichbiological tissues are preserved from decay, thereby preventing autolysis or putrefaction.Outside of the physiological environment of the organism, isolated tissues will rapidlydegrade: membranes will lose their integrity and enzymes will digest the cell from the inside. Fixation ensures conservation of cellular integrity, but there is one catch: it kills the cells. |
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What are the fixation types for light microscopy? |
Most commonly used fixative in histology is formaldehyde. Formaldehyde fixes tissue by cross-linking proteins together. While this causes deformation in the protein’sstructure, it is excellent for long-term preservation. Another method used for LM is quick freeze (frozen sections). |
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What are the fixation types for electron microscopy? |
For fixing samples for EM, glutaraldehyde can be used. One of the advantages of glutaraldehyde is that it fixes the sample more tightlythan its cousin formaldehyde. It causes rapid and irreversible changes, fixes quickly, and iswell suited for electron microscopy.
Another method for EM is OsO4 (osmium tetroxide) fixation, also known as post-fixation.Osmium tetroxide functions as a secondary fixative by reacting with lipids. It is believed thatthe unsaturated bonds of fatty acids are oxidized by OSO4 and it is reduced to a black metallicosmium which is electron dense and adds contrast to biological tissues (secondary stain). It isoften used in conjunction with gluteraldehyde fixation. |
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What is embedding? |
The fixated tissue sample is put in some sort of solid mass, to make sectioning in fine slices easier. The exception is for frozen sections, since these are already quite solid. Paraffin wax is most widely used for light microscopy, while for electron microscopy epoxy resins are typically used. |
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What is sectioning? |
When sectioning for LM, samples should have a thickness that’s between 5 and 10 µm. For EM, it has to be much thinner: between 40-100 nm. |
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What types of stains do you use for light/electron microscopy and what is concept of using them? |
Staining for LM makes use of dyes to highlight different cell components, while for EM heavy metal contrasting is used. Heavy metals (or rather, heavy metal salts) are used becauseof their high atomic number, and one may use osmium, lead, uranium or gold. The idea behind staining in LM is that the various dyes absorb specific wavelengths of visiblelight. In a similar vein, EM samples of biological tissues can utilize high atomic number stainsto enhance contrast. The heavy metal stain absorbs electrons or scatters part of the electronbeam which otherwise is projected onto the imaging system. |
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What do you mount the tissues on? |
Light microscopy: glass slide - a transparrent cover slip is placed over the sample Electron microscopy: a tiny - usually 3mm diameter grid is used to let electrons pass through. |
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What is a blood smear? |
A smear is the spreading of biological material as a very thin monolayer on a glass slide. Smears are mostly used for peripheral blood tests and Pap tests. |
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What are the steps for a blood smear? |
1. Harvest 2. Spread 3. Dry 4. Stain |
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What are the blood smears usually stained with? |
Blood smears are usually stained with May-Grünwald, Wright's, or Giemsa stain. Thesestains allow for the detection of white blood cell, red blood cell, and platelet abnormalities. |
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What are the colours achieved with M.G.G.? |
Nucleus: purple Cytoplasm of granulocytes: pink Granulations: Neutroplis: red-purple Basophils: dark blue to black Eosinophils: shining red-orange Cytoplasm of lymphocytes and monocytes: blue |
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Where is staining used? |
For light microscopy - in order to achieve permanent microscopic preparation. |
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What is the aim of staining? & What does it depend on? |
To increase contrast between different cell or tissuecomponents. It depends on the tissue we want to examine (and on thenature of the fixing solution). |
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What is a histological dye? |
A histological dye is a colored substance,usually organic, that can enter the cell and attach to the various cellular components, thusenabling optical differentiation to the viewer.
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What are the chemical properties of dyes? |
Dyes have various components that allow them to absorb various wavelengths of visible light and thus impart a certain color. Its main components are chromophores (color carriers) andauxochromes (give the ability to color). Dyes can also be ionized or non-ionized. When ionized, they form electrochemical bonds with the substrate, whereas non-ionized dyes form hydrogen bonds with the substrate. The latterbond increases the interaction stability between dye and susbtrate. |
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What are the natural resources of dyes and what are they? |
Vegetal - hematoxin - safranin - orceina - litmus Animal (insects) - carmine - producing various red, from purple to crimson |
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What are the synthethic dyes? |
- methylene blue - eosin - picric acid -fuchsin |
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What is the classification of dyes after chemical properties ? |
Acids - auxochrome group with negative charge - attaches to a positively charged substrate - stained red or pink Bases - auxochrome group with positive charges - attaches to a negatively charged substrate - stained blue or purple Neutral - basic + acid dyes mixed in certain proportions |
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What are the aims of fixation of staining and how is this done? |
Aims to preserve the shape of the cells or tissue involved as much as possible. - Sometimes heat fixation is used to kill, adhere, and alter the specimen so it accepts stains. - Pieces of tissue may be embedded in paraffin wax to increase their mechanical strength and stability and to make them easier to cut into thin slices. - The paraffin usually has to be removed before staining |
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What is hydration of the stain? |
Involves treatment of cells with (usually) a mild surfactant. This treatment dissolvescell membranes, and allows larger dye molecules into the cell's interior. |
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What are the steps of staining? |
- fixation - hydration - applying mordant (if applicable) - staining proper - washing - dehydration - mounting |
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What is mordant? |
A mordant is a chemical compound that reacts with the stain to form an insoluble, colored precipitate. When excess dye solution is washed away, the mordanted stainremains. |
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What happens during the 'staining proper'? |
Its the actual colouring step - you add the dye. |
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What do you usually use to dehydrate the stain? |
Ethanol |
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What is 'mounting' in the steps of staining? |
Atttaching the samples to a glass microscope slide for observation and analysis. |
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What can the staining methods be classified by? |
- According to the cells’ status at the moment of staining - The number of dyes used - The mechanism itself - The optimal stainingmethod - Relationship of the dye’s color and the obtained staining results. |
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How can staining methods be classified via the status of the tissue? |
Vital stain - Administered while the subject is still alive, or: - In an in vitro cell culture as long as the cells are actually alive Permanent stain - Will stain the tissue permanently |
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How can staining methods be classified via the number of dyes used? |
Simple stains - using a single colour Combined staining (2 or more dyes) - Successive (i.e. H&E: first H is used and then counterstaining with E) - Simultaneous (i.e. Azan) |
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How can staining methods be classified via staining mechanism? |
Direct staining - Simple interaction dye/substrate Indirect staining - Requires the presence of a mordant between dye and substrate. |
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How can staining methods be classified via the method used to obtaing optimal staining? |
Progressive - Successive immersion for achieveing optimal staining time (as in H&E) Regressive - Prolonged dye action until overcoloring is achieved; then decolorizeuntil optimal staining is obtained (like in Nissl staining). |
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How can staining methods be classified via the relationship of the dye colour and obtained stain? |
Orthochromatic - Substrate turns same color as dye (orthos in Greek meaning straight or proper). This is the case for most stains. Metachromatic - By contrast with ortho-, in metachromatism the substrate turns adifferent color than that of the dye (as is the case with toluidine blue). |
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What is janus green B used for? |
For pointing out mitochondria which is coloured green. |
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What is Tryptan Blue used for? |
- vital stain - points out dead cells/tissues by colouring them blue - live cells/tissues are not coloured |
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Masson Stain |
- trichrome (3 colours) - permanent staining method - distinguishes cells from surrounding connective tissue Nucleus - black cytoplasm - light red, pink or purple Collagen fibers - intense blue or greenish blue |
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Giemsa Stain |
- monochromatic method - used in sytogenetics (to stain chromosomes) and in histopathological diagnosis of malaria and other parasites - stains peripheral blood smears and bone marrow specimens Erythrocytes - pink Platelets - pale pink Lymphocytes Cytoplasm - sky blue Monocyte Cytoplasm - pale blue |
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Azan |
Combined staining method using: - azocarmine G - heindenhain blue - orange G Nucleus: reddish pink cytoplasm: reddish Collagen fibers: blue/turquise Striated muscle tissue: red/orange/yellow |
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H&E staining |
Uses - hematoxylin (alkaline): dark blue/violet stain which is positive. Binds on to DNA/RNA (acidic and negatively charged) - eosin (acid) in succession: binds on to proteins (basic and positively charged due to arginine and lysine amino acid residues) - most used staining method Nucleus: dark blue/ purple Cytoplasm & extracellular fibers: reddish pink |
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Van Gieson's stain |
- mixture of picric acid, ferric hematoxylin and acid fuchsin - simplest method of differential staining of collagen and other connective tissue - used in histopathology Nuclei- black Cytoplasm - yellow Collagen fibers- red |
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Toluidine Blue |
- metachromatism - substrates color different from the original dye colour - granule components: blue'purple |
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Nissl stain |
- used in brain research - dyes neural tissue - (nissl bodies) Nissl bodies: violet Nucleoli: black Nucleus: light blue |
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Mallory Stain |
- used in histology to reveal different macromolecules that make up the cell - trichromatic: aniline blue, acid fuchsin and orange G - reveals collagen. ordinary cytoplasm + red blood cells Nucleus and cytoplasm: red Collagen fibers: light blue Skeletal muscles: red Smooth muscle: violet |
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Orcein Stain |
- used for elastic fibers (aortic wall) - orangey to purplish red |
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Which carbohydrates can you stain? |
Mono- and disaccharide staining is not possible because these sugars dissolve and are lost during preparation. However, carbohydrate structures on proteins and lipids, as well as polysaccharides, can be stained. |
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Periodic acid and Schiff stain (PAS) |
Detects - polysaccharides such as glycogen - mucosubstances such as glycoproteins - glycolipids and mucins in tissues |
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Best's Carmine |
- highlights glycogen |
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Sudan Stains |
- synthetic organic compounds that are used as dyes for sudanophilic biological sample, usually lipids. Sudan III - red-orange Sudan IV - red Sudan B - black Sudan BB - blue |
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Which metals are commonly used to stain materials? |
- silver - gold - osmium - mercury |
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What is the principle of impregnation with metals? |
Specific tissue reduce the metal salts to the elementary metal afterthe salt’s ions bind to the various tissues. The precipitating reduced metal is then easilyobserved. |
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Silver Staining |
- used to study epithelial tissue of nervous system Reticular fibers (collagen): brown/black Neurons: orange/bronze |
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What are cytological stainings? And which ones are they? |
Cytological stainings are stains tha highlight only specific structures of a cell. - cajal da fano method - regaud's hematoxylin |
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Cajal da fano method |
- Use to study golgi apparatus Nucleus: uncoloured Golgi app: black/dark bronze (appears as perinuclear network) Cytoplasm: gold |
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Regaud's Hematoxylin |
- used to study mitochondria - most permanent + simplest is Regaud's modification of iron hematoxylin Nuclei: uncoloured Nucleolus: black Mitochondria: granulations black |
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Smear test |
Smear tests are used for cytopathology – a branch of pathology that studies and diagnosesdiseases on the cellular level. Cytopathology tests are called smear tests because the samplesmay be smeared across a glass microscope slide for subsequent staining and microscopicexamination. A smear test involves cells in a monolayer across a glass slide. It is a good test to examine blood cells, epithelial cells, cellular sediment and parenchymal tissue. A good smear consists of a single, thin layer that is spread evenly across the slide. It occupies about 2/3 of the blade |
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MGG (panoptic pappenheim) |
- topographic staining method - used for staining blood smears - giemsa solution may be used - May grunwald solution may be used (contains eosin, methlene blue solved in a mix of mathanol and neutral glycerine) |
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Which tissues do not stain? |
- Interstitial fluid - other tissue fluid (blood, lymph etc) - lipids or fats (with the one exception being the Sudan method) |
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What are the challenges seen when studying cellular processes? |
- Development of techniques to observe ongoing cellular phenomena (as they happen) - Appropriate experimental modulation of cellular phenomena |
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What are the study methods that exist for live cell study? |
- In vivo - In situ - In vitro |
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What is the in vivo method? What is the advantage of using it? What is the limit of using it? |
Cells or tissue containing the cells we want to study are approached in theintact, living organism (in vivo = live) Advantage - obtained results are a close match with the process in the human organism Limit - Very low measure of control, so the results are tricky tointerpret, due to the influence of many other factors. |
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What is the in situ method? What is the advantage of using it? What is the limit of using it? |
Literally meaning “in its place”, it is a method whereby the tissue is studied in its proper place, but some other factors (endocrine, nervous, etc) are controlled Advantage - Study of living cells in their proper place with some measure ofcontrol over influencing factors Limit - Because we control some external factors, we cannot readily conclude our results to be a match for the ones obtained in vivo. |
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What is the in vitro method? What is the advantage of using it? What is the limit of using it? |
In this technique, the tissues or cells are separated from the organism andisolated (in vitro meaning “in glass”). Advantage - Detailed control over many factors of the experiment Limit - One cannot guarantee the same results in vivo, of course, because of the rigorous isolation from “real life”. |
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What are the in vitro techniques? |
- organ bath - cell culture |
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Explain the features of an Organ Bath. |
- Takes an organ or part of an organ and maintains its viability - The organ itself is isolated, but the cells within function within the (intact) organ - Constant temperature, oxygenation, bath medium to mimic in vivo - This allows for “closer to life” study and provides functional data and harvesting of biological material |
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What is an organ bath? |
An organ bath is able to accurately model functions of an organ in various states and conditions by the use of the actual in vitro organ itself. |
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What is a cell culture? |
Cell culture is the process by which cells are grown under controlledconditions, generally outside of their natural environment. |
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What are the features of cell culture? |
- It maintains viable cells using special incubators with controlled atmosphere - In appropriate cell culture media |
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What are the steps in order to culture cells? |
1. Harvest cells 2. Isolate cells with the use of appropriate enzymes (enzymatic digestion of tissue- cell suspension) 3. Apply the isolated cells on an appropriate growth medium in a culture (petri dish/ culture flask) (primary culture) 4. culture cell by placing the culture dish in a cell incubator - subculture cells to obtain a pure culture or to bypass some problems (i.e. sumescence) 5. Verify the cultured cells are the cell type of interest (passage/ secondary culture) 6. Cells are ready to be manipulated or modified for experimental procedures |
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Which components does the cell culture medium have ? |
- amino acids - vitamins - salts (ions) - glucose - growth factors - antibiotics *Phenol red, a colouring agent - used to indicate pH values |
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What is flow Cytometry? |
Flow cytometry is a widely used method for analyzing expression of cell surface andintracellular molecules, characterizing and defining different cell types in heterogeneous cellpopulations, assessing the purity of isolated subpopulations, and analyzing cell size andvolume. It allows simultaneous multi-parameter analysis of single cells. |
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What is Flow Cytometry used for? |
Flow cytometry is routinely used in the diagnosis of health disorders, especially bloodcancers. Physical cell parameters may be measured by using this technique. It is also used tomeasure DNA and Ca2+ quantity in cells, as well as intracellular pH. |
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What are trasgenic animals and why are they useful? |
Transgenic animals are animals (most commonly mice) that have had a foreign gene deliberately inserted into their genome. They are useful because you can study the effects the gene has on thehost, and to assess the evolution of certain genetic disorders in order to look for viabletherapies for these disorders. |
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What are knockout animals and what are they used for? |
A knockout animal (again, mostly mice) is a genetically modified animal in which researchers have inactivated, or "knocked out", an existing gene by replacing it or disrupting it with anartificial piece of DNA. The loss of gene activity often causes changes in a animal'sphenotype, which includes appearance, behavior and other observable physical andbiochemical characteristics. In other words, the effect of a gene’s absence can thus be studied. |
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What is videomicroscopy? & What are the advantages? |
Video microscopy uses phase contrast or fluorescence microscopy to monitor cell behavior over time (time lapse). This is done using a so-called biostation. It has many advantages: cells can be monitored for long periods (hours, days etc) in various experimental settings. |
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What is the external surface of the cell membrane? |
Represented like a fuzz-like coat on the external surface of the plasma membranes is theglycocalyx – a glycoprotein/polysaccharide covering. A membrane cytoskeleton (a matrix ofproteins) may also be observed, linked to the cell cytoskeleton. |
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What happens in the freeze fracture technique? |
After rapid freezing, the cells are cleaved along a fracture plane between the leaflets of the lipid bilayer. The external face of the bilayer is called E, while the internal face gets thedesignation P. The two fractured sections are then coated with heavy metal (etched) and a replica is made of their surfaces. This replica is then viewed in an EM. |
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What are cilli? |
A cilium is an organelle found in eukaryotic cells. Cilia are slender protuberances that project from the cell membrane. They are easily recognizable on EM due to the typical 9 microtubuletriplets organized in a circle. |
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What are microvilli? |
Microvilli are cellular membrane protrusions that increase the surface area of cells and areinvolved in a wide variety of functions, including absorption and secretion. Thousands ofmicrovilli form a structure called the brush border that is found on the apical surface of someepithelial cells, such as the small intestines. Their core consists of actin filaments. |
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What are cell junctions?
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Cell junctions are structures through which the cell membrane establishes connections with neighboring cells or the extracellular matrix. These junctions are only visible with EM.They are as small as 4nm. |
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How are cellular junctions divided? |
Tight junctions - Zonula occludens * Tight junctions appear to be almost fused at the point of contact. Adhesion junctions - Zonula adherens - Macula adherens *DESMOSOME |
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How are adhesion junctions held together? |
The adhesion junctions are held together by various structures (hence adhesion). Of these, the desmosome is a special one: it appears as a disk-shaped structure holding two cells tightlytogether. |
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What type of junctions do secretory epithelial cells have? |
Epithelial cells with secretory or transport functions, such as the one pictured above, oftencome with a junction complex: a mix of all types of junctions. |
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What are Gap junctions? |
These are communication junctions. So-called connexons on the membranes of each cell connect with one another andform a means of communication. They directly connect the cytoplasm of two cells, whichallows various molecules, ions and electrical impulses to directly pass through a regulatedgate between cells. |
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Why do some organelles need an endomembrane? |
To create the proper medium for their activities, separate them from cytoplasm and to increase the surface where metabolicprocesses take place. |
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What are the membrane bounded organelles? |
Endoplasmic reticulum Golgi complex Lisosomes Peroxisomes Mitochondria Nucleus |
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What is ER and what type of ER is there? |
ER comes in two forms: - smooth - rough Er is a system of membranous channels and saccule. |
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rER |
The rough ER is continuous with the outer layer of the nuclear envelope. It is the place of protein synthesis, and as such a multitude of ribosomes will be found here. Because of thesetwo features, it is typically easily recognizable on EM. |
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What is the smooth ER used for? |
The smooth endoplasmic reticulum is the place of lipid synthesis, calcium deposit and cellular detox. |
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What are the faces of the Golgi apparatus? |
- cis (convex) - trans (transverse) *the cis region is typically pointing in the general direction of the nucleus. |
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What are Lysosomes and what do they do? |
Lysosomes are organelles involved in intracellular digestion. They engulf macromolecules(phagocytosis) and use their hydrolytic enzymes to break the macromolecules into monomersthat the cell can use for different purposes. |
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What are perixisomes? |
Peroxisomes, small spherical organelles, are more difficult to identify. |
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What are marker enzymes? |
Marker enzymes are enzymes specfic to organelles and they mark various structures. |
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What is the marker enzymer for ER? |
Glucose 6- phosphate |
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What is the marker for the Golgi complex? |
Tyamin pyrophosphatase (cis face) - endomembranes of the cis face also contain G6P - endomembranes of the trans face also contain AP |
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What is the marker for Lysosomes? |
Acid Phosphatase |
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What is the marker for mitochondria? |
external membrane: monoaminoxydase internal membrane: succinate dehydrogenase |
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What are the exceptions for the rule 'one cell, one nucleus'? |
- mature red blood cells don't have a nucleus |
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What is the nature of the nucleus and what will it attract? |
By its (acidic) nature, the nucleus is basophilic, so will attract basic stains (hemalaun). |
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What does the nucleus contain? |
The nucleus contains chromatin (DNA) in two forms: - Heterochromatin is tightly packed, “inactive” DNA, and is electron-dense, so will appear darkon EM. - Euchromatin, by contrast, is unpacked DNA that will appear light on EM. *a nucleus that is very lightly stained (so has lots of euchromatin) is a very active cell. *Heterocromatin tends to stick to the inner membrane of the nuclear envelope. Where there arenuclear pores, there will be no heterochromatin, so as to not block the way. The nucleus also contains another (non-membrane bounded) organelle: the nucleolus. Thisusually appears dark on EM. |
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What are the non-membrane bounded organelles? |
Ribosomes Proteasomes Cytoskeleton Centrioles Cytoplasmic inclusions |
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What are proteasomes? |
Proteasomes are involved in the digestion of cytosomal proteins. They appear as cylindrical configurations composed of overlapping ring structures |
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What is the cytoskeleton composed of and what do you use to study it? |
The cytoskeleton, composed of complex actin filament structures, can be studied usingfluorescence in EM (phalloidin‐fluorochrome antibody‐fluorochrome). |
