Lecture 1 - Ultrastructure Flashcards
Nucleus - functions, what does it contain, appearance, when its visible, size
-Largest organelle in the cell
-Contains genetic material like euchromatin and heterochromatin (nucleic acids)
Functions: production of RNA (mRNA, rRNA and tRNA), bidirectional RNA and protein transport through nucleus pores
-Is the only consistently visible organelle in LM
-Stains deeply
RER - what does it look like, function
-flattened membrane compartment, has ribosomes which look like little black dots (nucleic acids)
-distinctive staining in LM where there are large aggregates (like in pancreatic acinar cells)
-function: synthesis of secreted proteins and membrane proteins
SER - what does it look like, function, what is it continuous with
-flattened/tubular membrane compartment
-continuous with RER but no ribosomes
-function: synthesis of cell membranes, steroid production, detoxification enzymes, glycogen metabolism, storage and release of calcium
- in LM, cells with a lot of SER have a foamy cytoplasm (like in hepatocytes)
Golgi - what are the parts of it, what does it look like, function, appearance in LM
-there are the cis and trans regions; where material enters the cis and exists the trans regions
-its a stack of flattened membrane sacs
-function: glycosylation of membrane proteins and protein sorting
-in LM, may appear as a clear area in the cytoplasm near the nucleus (like plasma cells)
Lysosomes - what does it look like, what does it contain, function, visibility in LM, accumulation?
- irregular outer membrane with heterogeneous contents/appearance
-contains lysozymes (digestive enzymes) for breakdown of endocytosed material
-involved in recycling of cellular material (autophagy)
-may accumulate with age/genetic defects
-rarely visible in LM
What are lysozymes? what organelle are they in and what do they do?
they are digestive enzymes that are in the lysosomes and they breakdown endocytosed material
mitochondria - appearance, functions, when is it visible
-smooth outer membrane wiht inner folds (cristae) or tubules
-site of ETC and ATP synthesis and other metabolism. Involved in cell survival by sequestering apoptotic proteins
-when numerous, cytoplasm is well stained but it is rarely visible in individual structures in LM
What are the 5 steps for viewing tissue?
fixing, embedding, sectioning, staining, microscopy
staining -what is it used for, general patterns of staining reveal what?
-enhances contrast so different components can be readily viewed
-some special stains also reveal biochemistry/cell activity
-general patterns of staining reveal aspects of cells that inform function, but individuals molecules cannot be seen in LM
why is there variation in staining
- not everything will bind a given dye equally and this leads to staining of different components, which is normal
-pH, osmolarity, other chemicals, integrity of the tissue, etc leading to variable staining of the same components in different regions - this is not normal and is considered artifact
what are the common staining reagents, and what are they commonly used in
- hematoxylin and eosin: most common stain for paraffin section and is the industry standard for pathology
-toluidine blue: most common stain for plastic sections in LM
-heavy metal “stains” (SEM/TEM): they relfect/scatter electrons. TEM = lead, uranium, osmium. SEM = gold, palladium
*heavy metals arent actually staining, but rather binding to the organelles
what binds to H+E, what colour are they, what is the charge
-hematoxylin: stains blue/purple, binds well to basophilic or negatively charged structures such as DNA, RNA, proteoglycans and a few special proteins
-eosin: stains pink/orange, binds well to eosinophilic or acidophilic structures like most proteins and protein rich organelles (mitochondria, cytoskeleton, collagen)
How LM vs TEM vs SEM works
-LM uses a light source to be able to visualize the organelles
-TEM uses an electron gun instead of a light source. the electrons that remain at the end indicate what is there. if it is dark, there are lots of heavy metals bound and negatively charged structures bind it more than positively charged. therefore, deep stain in TEM would indicate things like DNA, RNA, etc
-SEM uses an electron gun as well but here electrons are refracted rather than absorbed. 3D image
