Cellular Structures Flashcards
7 cards from real Histology Certification practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Cellular Structures flashcards as text
In polarized epithelial cells, which protein complex restricts lateral diffusion of membrane proteins between the apical and basolateral domains?
Answer: Tight junctions (zonula occludens)
Tight junctions create a paracellular seal and form a 'fence' that limits the lateral diffusion of membrane lipids and proteins between apical and basolateral domains.
Autophagosomes, which sequester cytoplasmic cargo for lysosomal degradation, are characterized by having:
Answer: A double membrane derived in part from the ER and other sources
Autophagosomes are double-membrane vesicles whose phagophore (isolation membrane) is contributed by the ER, mitochondria, and Golgi, enclosing cytoplasmic material for delivery to lysosomes.
The acrosome of spermatozoa is a specialized secretory vesicle derived from the:
Answer: Golgi apparatus
The acrosome develops from proacrosomal granules produced by the Golgi apparatus during spermiogenesis and contains hydrolytic enzymes needed for zona pellucida penetration.
Which cytoskeletal protein forms the contractile ring during cytokinesis and is also the primary component of the thin filaments in muscle sarcomeres?
Answer: Actin
Actin polymerizes into the contractile ring at the cleavage furrow during cytokinesis and forms the thin filaments of sarcomeres in muscle cells.
Euchromatin appears pale in H&E-stained nuclei because it is:
Answer: Loosely packed and transcriptionally active, with less DNA per unit volume
Euchromatin is decondensed, gene-rich, and transcriptionally active, resulting in less DNA per unit area and therefore less hematoxylin staining compared to heterochromatin.
The 'unit membrane' concept proposed by Robertson describes the plasma membrane as a:
Answer: Trilaminar structure (two electron-dense lines flanking an electron-lucent zone) universal to all biological membranes
Robertson's unit membrane model described the trilaminar appearance seen in TEM (two dark lines ~2.5 nm thick flanking a light zone ~3.5 nm) as a universal feature of all cellular membranes.
Which finding in a histological preparation would indicate that a cell is undergoing necrosis rather than apoptosis?
Answer: Cell swelling, membrane rupture, and surrounding inflammatory infiltrate
Necrosis involves cellular swelling, loss of plasma membrane integrity, release of cytoplasmic contents, and a secondary inflammatory response, distinguishing it from the orderly, non-inflammatory process of apoptosis.