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USMLE

Cell Bio/Histo/Path -1

QuestionAnswer
Three cell types with regard to cell cycle Permanent, Stable, Labile
Rough Endoplasmic Reticulum rich cells -Mucus-secreting goblet cells of small intestine -Antibody-secreting plasma cells (ie lost of secretory protein)
Cell cycle: Permanent cells Remain in G0. If they regenerate, they regenerate from stem cells.
Cell cycle: Stable cells Enter G1 from G0 when stimulated
Cell cycle: Labile cells Never go to G0, divide rapidly with a short G1
Smooth Endoplasmic Reticulum: Functions -Steroid synthesis -Detoxification of drugs and poisons
Permanent cells: cell types -Neurons -Skeletal and cardiac muscle -RBCs (regenerate from stem cells)
Stable cells: cell types -Hepatocytes -Lymphocytes
Smooth Endoplasmic Reticulum rich cells -Liver hepatocytes -Steroid hormone-producing cells of the adrenal cortex
Labile cells: cell types -Bone marrow -Gut epithelium -Skin -Hair follicles (think about chemotherapy side effects)
Rough Endoplasmic Reticulum: Functions -Synthesis of secretory (exported) proteins -N-linked oligosaccharide addition to many proteins
Neurons: name of Rough Endoplasmic Reticulum and its function Nissl bodies sytnhesize enzymes (eg ChAT) and peptide neurotransmitters.
6 functions of Golgi apparatus 1. Distribution center --Input: Proteins and lipids from endoplasmic reticulum --Output: Plasma membrane, lysosomes, secretory vesicles 2. Modifies N-oligosaccharides on asparagine 3. Adds O-oligosaccharides to serine and threonine residues (o
I-cell disease: Presentation -coarse facial features -clouded corneas -restricted joint movement -high plasma levels of lysosomal enzymes -fatal in childhood
COPI: Function Retrograde Intracellular transport: cis-Golgi to RER
COPII: Function Anterograde Intracellular transport: RER to cis-Golgi
Clathrin: Function Extracellular/lysosomal transport: -lysosome: trans-Golgi to lysosome -trans-Golgi to plasma membrane to endosomes (for receptor mediated endocytosis)
Microtubules: Diameter 24 nm
Microtubules: Structure 13 dimers of alpha/beta tubulin per circumference (each dimer bound to GTP), repeated in helical configuration
Microtubules: Found in ? -Flagella -Cilia -Mitotic spindles -Slow neuronal axoplasmic transport
Microtubules: Speed of growth and collapse Grows slowly and collapses quickly
Microtubules: Affected by which drugs? -Mebendazole/thiabendazole (antihelminthic) -Taxol (anti-breast cancer) -Griseofulvin (anti-fungal) -Vincristine/Vinblastine (anti-cancer) -Colchicine (anti-gout)
Microtubule polymerization defects: Found in what syndrome Chediak-Higashi syndrome
Chediak-Higashi syndrome Microtubule polymerization defect resulting in decreased phagocytosis
Cilia: Structure -9+2 arrangement of microtubule doublets -The 9 peripheral doublets are linked by dynein atpase
Cilia: Mechanism The 9 peripheral doublets are linked by dynein atpase, which causes bending of cilium by differential sliding of doublets
Molecular motors and direction of transport in cell Dynein: retrograde (DIES back towards nucleus) Kinesin: anterograde (MOVES kinetically forward)
Kartagener's syndrome: Defect Dynein arm defect causing immotile cilia
What is phosphatidylcholine also known as? lecithin
Kartagener's syndrome: Presentation -Male infertility (immotile sperm) -Female infertility (immotile fallopian cilia) -Bronchiectasis and recurrent sinusitis (bacteria and particles not pushed out) -Situs inversus
What syndrome is situs inversus associated with? Kartagener's
Plasma membrane: composition -Cholesterol (~50%) -Phospholipids (~50%) -Sphingolipids -Glycolipids -Proteins
What is lecithin also known as? phosphatidylcholine
Plasma membrane: melting temperature association High cholesterol or long saturated fatty acid content means increased melting temperature
Where is phosphatidylcholine found? Major component of: 1. RBC membranes 2. myelin 3. bile 4. surfactant (DPPC- dipalmitoyl phosphatidylcholine)
Drugs that inhibit the sodium-potassium pump -Ouabain -Cardiac glycosides (digoxin, digitoxin)
Ouabain: Mechanism Inhibits Na-K atpase by binding to K site.
What process uses phosphatidylcholine? Esterification of cholesterol with LCAT (lecithin-cholesterol acyltransferase)
Cardiac glycosides: Mechanism Inhibits Na-K atpase, increasing cardiac contractility
Created by: Asclepius