Histology NBME exam questions with correct answers

Histology NBME exam questions with |\ |\ |\ |\ |\




correct answers |\




Cell membrane - CORRECT ANSWERS ✔✔Phosphatidylcholine and
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sphingomyelin on EC side
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Phosphatidylethanolamine and phosphatidylserine on inside |\ |\ |\ |\




Increase in cholesterol => decrease in fluidity/permeability
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In some cells, covered by carb-rich glycocalyx
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Receptor-mediated endocytosis => both receptor and ligand get |\ |\ |\ |\ |\ |\ |\ |\


ingested by clathrin-coated vesicle
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Disorders of transport - CORRECT ANSWERS ✔✔CF: defect in
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CTFR => salty sweat and thick mucus
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Cystinuria: inability to reabsorb cys in kidneys => kidney stones
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Hereditary hypercholesterolemia: no LDL receptors on cells
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Textrodotoxin (puffer fish) blocks Na channels => death |\ |\ |\ |\ |\ |\ |\




Disorders of cell signalling - CORRECT ANSWERS ✔✔Ras:
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mutation => even on w/o ligand => neoplastic transform
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Cholera: active GPCR w/o ligand => more cAMP => diarrhea
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Curare: nACHr antagonist => paralysis
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Graves: autoimmune stim of TSH receptor => hyperthyroidism
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and decreased TSH levels
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,Junctions - CORRECT ANSWERS ✔✔ZO: tight junctions fuse ECM
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sides of adjacent cell PMs
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ZO acts a diffusion barrier
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MA: spot desmosome that has proteins anchored in plaques
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MA held together by cadherins and leave wide gap b/t cells
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GJ: connexon channels assoc to form passage b/t cells
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Mitochrondria - CORRECT ANSWERS ✔✔Outer membrane is |\ |\ |\ |\ |\ |\ |\


relatively permeable and inner opposite
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Proteins made from nuclear DNA made in cytosol then imported
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Lysosomes - CORRECT ANSWERS ✔✔ATP-powered H pump
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maintains acidic environment |\ |\




Primary lysosomes bud from Golgi and can't digest
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Secondary digest and form heterophagic or autophagic vacuole
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Residual bodies are postdigestive lysosomes with leftover stuff,
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such as lipofuscin, which increases w/ age
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Peroxisome - CORRECT ANSWERS ✔✔Oxidases break down toxic
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metabolites, releasing H2O2 |\ |\




Catalases break down H2O2 |\ |\ |\




Zellweger => PCKD, jaundice, hypotonia, hepatomegaly
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ER - CORRECT ANSWERS ✔✔Continuous with nuclear envelope
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and SER/RER continuous
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,RER makes/modifies proteins for secetion, PM, Golgi, ER, and
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lysosome |\




SER for lipid/glycogen metabolism, detox (P450), and Ca stores
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RER protein synthesis - CORRECT ANSWERS ✔✔Signal peptide (N-
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terminus) on growing chain binds with SRP in cytosol, which
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binds to SRP receptor on ER membrane
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Ribosome-protein complex transferred to translocon, where N- |\ |\ |\ |\ |\ |\


terminus end moves through to lumen side as translation is still
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occurring on other side |\ |\ |\




Golgi - CORRECT ANSWERS ✔✔All RER-made proteins w/o ER
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retention signal move to cis-Golgi via transer vesicles
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Trans golgi is mature and sends vesicles to lysosome and PM
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Distrib glycoproteins such that intracellular organelles have
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oligosacc side chain facing inside and PM has facing outside`
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MTs - CORRECT ANSWERS ✔✔Made of 13 protofilaments, which
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are ab-tubulin linear polymers
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"-" end anchored to centrosomes
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Kinesins walk towards "+" end, and dyneins opposite
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Important for cilia, flagella, and mitotic spindle |\ |\ |\ |\ |\ |\




MFs - CORRECT ANSWERS ✔✔Made of F-actin in helical form
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Make up cortical actin network, which is anchored to PM by
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various proteins (dystrophin in mm, spectrin in RBC)
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Gives cell shape and connects it to the ECM and other cells
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, IFs - CORRECT ANSWERS ✔✔More permanent (no +/- ends) and
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ropelike structures |\ |\




Proteins involved are cell specific (desmin in mm, keratin in
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epithelial cells, lamins in nuclei) |\ |\ |\ |\




Nuclear envelope - CORRECT ANSWERS ✔✔2 membranes, each
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with a bilayer |\ |\ |\




Outer membrane has ribosomoes on outer side
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Nuclear lamina separates contents and inner membrane
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Nuclear pores where the inner and outer membranes fuse
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Nucleolus - CORRECT ANSWERS ✔✔Has granular part (outside-
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where rRNA made) and fibrillar part (core)
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Chromatin - CORRECT ANSWERS ✔✔DNA wrapped around histone
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octomere (2 x H2A, H2B, H3, H4)
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Scaffold proteins help condense chromatin
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Heterochromatin stains darker than euchromatin |\ |\ |\ |\




Cell cycle - CORRECT ANSWERS ✔✔M shortest and G1 most
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variable |\




Cyclin D-Cdk4 => move from G1 to S
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Cyclin A-Cdk1/2 => move from S to G2 and synthesize cyclin B
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Cyclin B-Cdk => move from G2 to M
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Rb inhib G1 => S (phosph by cyclin D to inactivate)
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