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17 Cards in this Set
- Front
- Back
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Regulators of cell cycle checkpoints |
cyclins, cyclin-dependent kinases (CDKs) & tumor suppressors |
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CDKs |
constitutive & inactive |
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Cyclins |
regulatory proteins that control cell cycle events; phase specific; activate CDKs |
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Cyclin-CDK complexes |
must be both activated & inactivated for cell cycle to progress |
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Tumor suppressors |
p53 & hypophosphorylated Rb normally inhibit G1 to S (synthesis) progression; -mutations result in unrestrained cell division (e.g. Li-Fraumeni syndrome) |
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Permanent cell types |
remain in G0, regenerate from stem cells (neurons, skeletal & cardiac muscle, RBCs) |
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Stable (quiescent) cell types |
enter G1 from Go when stimulated (hepatocytes, lymphocytes) |
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Labile cell types |
never go to G0, divide rapidly with a short G1 *most affected by chemotherapy (BM, gut epithelium, skin, hair follicles, germ cells) |
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Rough endoplasmic reticulum |
site of synthesis of secretory (exported) proteins & of N-linked oligosaccharide addition to many proteins -Nissel bodies (RER in neurons) synthesize peptide NTs for secretions -Free ribosomes: unattached to any membrane (site of synthesis of cytosolic & organellar proteins) |
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Smooth endoplasmic reticulum |
site of steroid synthesis & detox of drugs/poisons -lacks surface ribosomes |
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Golgi trafficking |
golgi is the distribution center for proteins & lipids from ER to vesicles & plasma membrane -modifies N-oligosaccharides on asparagine -adds O-oligosaccharides on serine & threonine -adds mannose-6-phosphate to proteins |
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Endosomes |
sorting centers |
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I-cell disease (inclusion cell disease) |
inherited lysosomal storage disorder -defect in phosphotransferase > failure of golgi to phosphorylate mannose residues (e.g. decrease mannose-6-phosphate) on glycoproteins > proteins are secreted extracellularly rather than delivered to lysosomes *Sx: coarse facial features, clouded corneas, restricted joint movement, & high plasma levels of lysosomal enzymes (often fatal in childhood) |
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Signal recognition particle (SRP) |
abundant, cytosolic ribonucleoprotein that traffics proteins from the ribosome to the RER. -absent or dysfunctional SRP > proteins accumulate in cytosol |
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Vesicular trafficking proteins |
COPI: golgi > golgi (retrograde); Golgi > ER COPII: Golgi > golgi (anterograde); ER > golgi Clathrin: trans-Golgi > lysosomes; plasma membrane > endosomes (receptor-mediated endocytosis [e.g. LDL receptor activity]) |
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Peroxisome |
membrane-enclosed organelle involved in catabolism of very-long-chain fatty acids, branched-chain fatty acids & amino acids |
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Proteasome |
barrel-shaped protein complex that degrades damaged or ubiquitin-tagged proteins. Defects in the ubiquitin-proteasome system have been implicated in some cases of Parkinson disease. |
