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Lippincott Histo Exam 1

Terms in this set (79)

chaperone
FOUND IN THE NUCLEUS, CYTOPLASM, AND ER that assist other proteins in assuming their correct three-dimensional conformation
Hepatocytes from a liver biopsy are examined by electron microscopy. Identify the elongated organelles shown in the image.
ransmission electron micrograph reveals elongated, tubular mitochondria in the cytoplasm of hepatocytes.
A 23-year-old man presents with a 6-month history of yellow skin and sclerae. Physical examination shows mild jaundice and peritoneal ascites. The patient is subsequently diagnosed with α-1-antitrypsin deficiency. A liver biopsy stained with PAS reveals globular inclusions of misfolded α-1-antitrypsin (shown in the image). The abundance of these abnormal glycoproteins has apparently overwhelmed normal degra- dation pathways. Which of the following cellular processes describes the normal mechanism for specifically targeting and degrading misfolded proteins within cells?
(B) Activation of the ubiquitin-proteasome pathway
Abnormal or unwanted proteins are degraded within lysosomes or targeted for degradation by protea- somes. Proteasomes are protein complexes that bind and degrade proteins that have been "tagged" with ubiqui- tin, a 76-amino-acid protein.
A Prussian blue stain of a liver biopsy is shown in the image. This stain identifies which of the following elements?
Prussian blue is a common histochemical stain for iron.
A kidney biopsy from a 44-year-old man is examined by electron microscopy. The nucleus of an endothelial cell exhibits a peripheral ring of dark-stained chromatin (arrow, shown in the image). Which of the following best describes the functional significance of the dark-stained ring of marginal chromatin observed in this electron micrograph?
(D) Organization of inactive chromatin
- Heterochromatin
Chromatin is composed of DNA, RNA, and protein. In routine H&E slide preparations, nuclear chromatin binds hematoxylin and is said to be basophilic. Patterns of gene expression are regulated, in part, by global changes in chromatin packing. Inactive chromatin, heterochromatin, is highly condensed and deeply basophilic. Much of the heterochromatin in this endothelial cell is found along the periphery of the nucleus. This is referred to as marginal chromatin. By contrast, active chromatin, euchromatin, is dispersed within the nucleoplasm and lightly stained. Chromatin is supported and organized by structural pro- teins that provide points of attachment between chroma- tin and the inner nuclear membrane. None of the other cell processes describe the function of heterochromatin.
Which of the following proteins contributes to the struc- tural matrix that anchors chromatin to the nuclear mem- brane during interphase of the cell cycle?
(C) Lamin
A network of intermediate filament proteins is associated with the inner nuclear membrane. This nuclear (fibrous) lamina stabilizes the nuclear membrane, organizes chromatin, and regulates gene expression. It is composed largely of lamin A and lamin C proteins that form intermediate filaments. Lamin receptors bind these filamentous proteins to the nuclear membrane. During cell division, the nuclear lamina and nuclear membrane disintegrate to facilitate chromo- some segregation and separation. Lamin gene mutations are associated with a variety of diseases (laminopathies) including Hutchinson-Gilford progeria. Patients with 0002076914.INDD 14 3/21/2014 10:53:08 AM Cell Biology 15 progeria undergo accelerated aging. Perlecan (choice D) is a basement membrane protein. None of the other intermediate filament proteins (choices A, B, and E) anchors chromatin to the nuclear membrane.
An 85-year-old woman with Alzheimer disease dies in her sleep. At autopsy, hepatocytes are noted to con- tain golden cytoplasmic granules that do not stain with Prussian blue (shown in the image). This "wear- and-tear" pigment of aging (lipofuscin) accumu- lates primarily within which of the following cellular organelles?
C) Lysosomes
Lysosomes are acidic ves- icles that degrade proteins, lipids, and carbohydrates. They are filled with a variety of acid hydrolases that degrade macromolecules to their constituent parts (e.g., amino acids and simple sugars). In some situations, lyso- somes are unable to degrade cellular debris. Examples include (1) endogenous substrates that are not catabo- lized because a key enzyme is missing (lysosomal storage diseases), (2) insoluble endogenous pigments (lipofuscin and melanin), and (3) exogenous particulates (silica and carbon). Examination of this patient's liver at autopsy reveals insoluble "wear-and-tear" pigment of aging. These pigments are composed of cross-linked lipids and proteins (peroxidation products) that accumulate over time. Lipofuscin is stored within the lysosomes of long- lived cells in the brain, heart, and liver. None of the other organelles store lipofuscin.
A 55-year-old woman learns that she has high levels of serum cholesterol (greater than 280 mg/dL; nor- mal less than 200 mg/dL) and is at increased risk for development of ischemic heart disease. The patient asks you to explain the normal pathway for serum cho- lesterol uptake and clearance. You explain to her that low-density lipoprotein (LDL) receptors present in her liver bind LDL cholesterol and internalize it by forming coated vesicles (endosomes). Which of the following structural proteins mediates LDL receptor internaliza- tion by organizing small buds of plasma membrane into endosomes?
(B) Clathrin
The LDL receptor is a trans- membrane glycoprotein that regulates plasma cho- lesterol by mediating endocytosis and recycling of apolipoprotein (apo) E. Lacking LDL receptor function, high levels of LDL circulate, are taken up by tissue mac- rophages, and accumulate to form arterial plaques (ath- eromas). Receptor-mediated endocytosis is a mechanism for uptake of specific ligands and receptors that is regu- lated by clathrin. Clathrin stabilizes small invaginations of the plasma membrane, forming coated vesicles (endo- somes). Coated vesicles are transported to lysosomes, where ligands and receptors are separated, and receptors are recycled to the plasma membrane. None of the other proteins regulates receptor-mediated endocytosis.
A 23-year-old woman complains of recurrent bone pain and increasing abdominal girth. Physical examination reveals enlargement of the patient's liver and spleen (hepatosplenomegaly). A spleen biopsy reveals large macrophages, with a fibrillar appearance reminiscent of "wrinkled tissue paper" (shown in the image). The patient is subsequently diagnosed with Gaucher disease. She carries mutations in the genes for glucocerebrosi- dase. Without this hydrolytic enzyme, glucocerebro- side accumulates within which of the following cellular organelles?
(C) Lysosomes
Gaucher disease is charac- terized by the accumulation of glucosylceramide in the lysosomes of macrophages. The underlying abnormality in Gaucher disease is a deficiency in glucocerebrosidase— a lysosomal acid hydrolase. The hallmark of this disor- der is the presence of lipid-laden macrophages (Gaucher cells) in the spleen, liver sinusoids, lymph nodes, lungs, and bone marrow. Gaucher cells are derived from resi- dent macrophages in the respective organs (e.g., Kupffer cells in the liver and alveolar macrophages in the lung). None of the other organelles stores glucosylceramide in patients with Gaucher disease.
Epithelial cells line the gastrointestinal tract, respiratory tree, cardiovascular system, and genitourinary system and cover the skin. Which of the following cellular prop- erties best distinguishes lining/coating epithelial cells from other cells/tissues in the body?
(A) Apical and basal membrane domains
Lining/coating epithelial cells exhibit polarity. They have distinct apical and basal membrane domains; they feature close apposition of lateral mem- brane borders; and they synthesize a basal lamina that provides attachment and structural support
Adipocytes, nerves, and muscle cells secrete a pericellular matrix that is referred to as
lamina externa
Your instructor reminds you that epithelial cells have membrane channels that permit ions and small signal- ing molecules to pass between adjacent cells. Which of the following proteins forms these intercellular (gap) junctions?
(B) Connexins
A portion of the upper esophagus, collected at autopsy, is fixed with formalin, embedded in paraffin, sectioned at 6 μm, stained with H&E, and examined by light microscopy (shown in the image). Identify the type of epithelium
(B) Nonkeratinized stratified squamous
This section of the esophagus reveals a stratified epithe- lium composed of multiple cell layers. Basal stem cells (arrowheads, shown in the image) undergo sequential changes in cell size, shape, nuclear morphology, and gene expression as they are pushed up toward the sur- face. The upper layer of this stratified epithelium is com- posed of squamous cells. This tissue is referred to as a nonkeratinized stratified squamous epithelium, because it lacks an external coating of insoluble keratin protein. Evidence of nuclear pyknosis (chromatin condensation) in the superficial region of this epithelium indicates that the keratinocytes are undergoing cellular senescence. None of the other types of epithelium describes histo- logic features of the esophageal mucosa.
You are investigating the role of cell adhesion mol- ecules in embryonic development. Sections of a gas- trula-stage mouse embryo are stained with periodic acid-Schiff reagent and counterstained with methylene blue. Which of the following families of proteins forms anchoring junctions between adjacent epithelial cells in the neural ectoderm of this embryo (arrow, shown in the image)?
(A) Cadherins

epithelial tis- sue is characterized by the presence of anchoring junc- tions that bind cells together and organize cytoskeletal proteins. Anchoring junctions include (1) zonula adhe- rens junctions (cadherins linked to actin microfila- ments) and (2) macula adherens junctions (cadherins linked to intermediate filaments). Cadherins are a fam- ily of calcium-dependent proteins that mediate cell adhesion, cell migration, and transmembrane signal- ing. Cadherins mediate epithelial cell-cell adhesion by forming "zipper-like" molecular interactions at the cell surface.
Cloudins and occludins FORM
TIGHT JUNCTIONS ZONULA OCCLUADENS
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