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19 Cards in this Set
- Front
- Back
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Name and briefly describe the three types of endocytosis.
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1. Pinocytosis - "cell drinking" non-specific uptake of fluids and solutes.
2. Receptor-mediated endocytosis - occurs when there is a specific binding of a ligand to a receptor. 3. Phagocytosis - "cell eating"; immune thing. |
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During pinocytosis, what are the plasma membrane invaginations called and what protein are they rich in?
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They are called caveolae and are rich in the protein caveolin.
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What is a caveola?
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A caveola is a membrane invagination that happens during pinocytosis.
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Is pinocytosis non-selective or selective?
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Non-selective. That said, it's not completely random either. It is mediated by things like pH and charge.
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What receptors need to be triggered in order for pinocytosis to take place?
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NONE! It's not receptor mediated. Fooled ya!
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Describe how receptor-mediated endocytosis is selective and give an example of what triggers this process.
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Receptor-mediated endocytosis can only be triggered by ligands that specifically bind to the receptors. An example is LDL binding to LDLR and triggering endocytosis.
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Explain the process by which LDL enters the cell.
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When LDL binds to LDLR on the cell surface, this triggers clustering of ligand-receptor complexes in clathrin-coated pits, which will internalize to form vesicles.
The clathrin will quickly fall off for recycling and an ATP-dependent proton pump will acidify the vesicle. The change in pH will cause dissociation of the receptor and ligand. The vesicle will merge with a lysosome, which is necessary for the cholesterol to be retrieved from the LDL. |
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Explain what causes atherosclerosis in hypercholesterolemias.
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An inability of cells to take up LDL results in abnormally high blood LDL levels, resulting in premature atherosclerosis and heart attacks (sometimes by age 2).
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What organelle performs the function of digestion in a cell?
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Lysosome
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What is the difference between a primary and secondary lysosome?
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A primary lysosome has not yet engaged in digestion of materials and a secondary lysosome has.
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From what organelle are lysosomes derived?
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Golgi apparatus
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What feature of proteins embedded in the membranes of lysosomes gives them protection from digestion?
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The proteins are highly glycosylated.
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Describe heterophagy.
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It is the digestion of substances imported into a cell from the external environment. (eg. bacteria and foreign material)
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Describe autophagy.
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Degradation of organelles in an otherwise healthy cell.
The organelle to be degraded is enveloped by the ER, then lysosomal enzymes are released into the compartment and the contents are digested. |
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What are residual bodies and how do they relate to lipofuscin pigment?
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Indigestible residues of lysosomal activity associated with normal wear and tear. They accumulate in the form of lipofuscin.
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What role does mannose-6-phosphate play in digestion of materials?
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It targets lysosomal proteins to the lysosome, so that digestion can occur.
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How are antibodies involved in phagocytosis?
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Antibodies (or other molecules) must bind to the item to be phagocytosed in order for the phagocyte to recognize its target.
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Pompe's disease, Gaucher's disease, Tay-Sachs disease, and Fabry's disease are examples of...
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...lysosomal storage disorders.
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What function do lysosomes containing perforin perform?
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The lysosome is secreted and creates pores in the target cell (that should be destroyed) with perforin.
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