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Anatomy and Cell Biology
Anatomy and Cell Biology 3309
Kem Rogers

Histology is microscopic anatomy HE staining is the most commonly used stain in histology o It involves formalin fixation Fixation is the first step in the preparation of a tissue or organ sample o This is done by a chemical or a mixture of chemicals o It preserves tissue structure permanently through 4 methods: Terminates cell metabolism Prevents enzymatic degradation of cells and tissues by autolysis (self-digestion) Kills pathogenic bacteria, fungi, viruses (i.e. microorganisms) It hardens the tissue as a result of cross-linking or denaturing protein molecules Formalin is often used as a fixative; it contains formaldehyde o This does not significantly alter the 3D structure of proteins Therefore, proteins are still able to react with antibodies and other reagents o It does not react with lipids and therefore, is a poor fixative for cell membranes The composition of tissue is altered after formalin-fixation; certain substances are lost: o Small nucleic acids o Glycogen o Proteoglycans and GAGs PAS can be used for carbohydrate staining Resolution is the smallest distance between two objects such that you can discriminate between them: o Here are some important limits of resolution: Human eye = 0.2 mm = 200 m = 200 microns Light Microscope = 0.2 = 200 nm TEM = 1-2nm The limits of resolution are important for being able to know what things will be visible under which conditions o For example, the nuclear envelope in a cell is 30 nm thick Therefore, it is not visible under a light microscope o The boundary of the nucleus is visible, however, due to densely packed peripheral heterochromatin, which will be discussed later It is attached to the nuclear envelope and stains basophilic The simplest function of the cell membrane is to act as a barrier o Its composition is that of a phospholipid bilayer, where each phospholipid has a glycerol backbone and a phosphate group attached to two fatty acid chains o The membrane is 10 nm thick (therefore, it cannot be seen under a light microscope) In electron micrographs, it is used to judge size (i.e. act as a ruler) because its size is constant Associated with the plasma membrane are proteins o These can either be integral or peripheral Carbohydrates are also often found on the outside of the plasma membrane o They can be linked to proteins (therefore, glycoproteins) or lipids (therefore, glycolipids) o Together, glycoproteins and glycolipids form the glycocalyx Membrane proteins have various functions: o Ion pumps o Channels (chemical or electrical) o Receptors o Linkers/CAMs o Enzymes o Transducers o Structural Within cells, we can find organelles and inclusions o Membrane-bound organelles: Nucleus Golgi sER, rER Lysosomes Secretory granules Mitochondria o Free organelles: Ribosomes Cytoskeleton o Inclusions (i.e. non-living substances that may or may not be part of a cell; they can be stored nutrients, secretory products, or pigment granules) Stored food (eg. Glycogen, lipid) Pigments (can be endogenous or exogenous) Within a cell, the cytosol refers to the part of the cytoplasm that is left behind when all organelles are removed A polysome is a group of ribosomes that are translating the same mRNA at various locations on the strand The ER cistern refers to the space between the 2 membranes (i.e. the lumen) o In the rER, ribosomes are found on the ER membrane o The rER is important for proteins that are targetted/secreted Proteins can have different destinations: o Cell membrane, secretion, lysosomes o These proteins are made in the rER The signal peptide is present in the cistern from the initial translation It is then cleaved off in the cistern by a signal peptidase The mature protein is then processed in the rER and the golgi (glycosylation begins in the rER) The golgi apparatus is stacks/saccules of cisternae o There can be upto 10 saccules in a stack o It has different faces: The cis/forming face is made from vesicles from the rER, which may or may not be clathrin-coated The trans face is where secretory vesicles get denser and water is removed as they exit the golgi (thus, they decrease in size) o Once proteins enter the golgi lumen, they are sorted and modified Cells can have multiple golgi The cis face is usually convex and the trans face is usually concave In some cells, we see a negative golgi o The staining is excluded because there is no nucleic acid th
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