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Medfoundations I > Cell Bio > Flashcards

Cell Bio Flashcards

0
Q

NLS

A

Nuclear localization signal: short, basic amino acid sequence

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1
Q

Progeria

A

Mutation of Lamin A, characterized by rapid aging and cardiovascular disease; pts have shortered telomeres

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2
Q

Restrictive dermopathy

A

Laminopathy that prevents epithelium from growing; fetus “suffocates” in its own skin

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3
Q

Huntington’s disease

A

Neurodegenerative disease caused by improper localization of Huntingtin to the nucleus rather than the cytoplasm; caused by trinucleotide repeat expansion, acquires NLS

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4
Q

Factors affecting membrane fluidity:

  • Number of double bonds
  • Acyl chain length
  • Temperature
A

More cis double bonds: more fluid
More trans double bonds: no kinks, less fluid
Longer acyl chains: less fluid
Lower temp: less fluid

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5
Q

Phospholipid fusogenicity: HIV/Measles vs. Rabies/Influenza

A

HIV and measles enter the cell by fusing with plasma membrane, whereas rabies/influenza enter by receptor mediated endocytosis and fuse with endosome membrane

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6
Q

Lysosomal storage disorders - causes

A

Defective lysosomes cannot break down sphingolipids, which then accumulate and cause disease

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7
Q

Fabry’s & Gaucher’s

A

Lysosomal storage diseases, sphingolipids cannot be metabolized correctly

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8
Q

Tay-Sach’s

A

Lysosomal storage disease; sphingolipid metabolism defect

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9
Q

Nuclear membrane assembly/disassembly

A

Nuclear lamins normally unphosphorylated
Early in mitosis, kinases phosphorylate lamins, causes chromatin-nuclear membrane connection to break, beginning disassembly
Late in mitosis, phosphorylase returns lamin to unphos. state, allowing chromosome decondensation and membrane assembly

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9
Q

Lipid raft

A

Microdomain comprised of stiffer phospholipids, moving through membrane to bring lipids and proteins together
Critical for signal transduction, endocytosis, rapid re-organization of membrane for ECM modification and motility

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10
Q

Steps of glucose transport into blood through intestinal epithelial cell

A

Lumen: low glucose, low Na+ (due to Na+/K+ pump moving K+ in and Na+ out); glucose moves against its gradient and Na+ moves with its gradient
Cell has higher conc. of glucose than lumen and bloodstream
Blood side: glucose pumped out by permease (no ATP required)
Na+/K+ ATPase moves more Na+ out

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11
Q

Familial hypercholesterolemia vs. Tangier’s disease

A

FH: defect in LDL receptor, build up cholesterol in blood causing atherosclerosis; revealed mech. of cholesterol transport into cells
TD: defect in ABC ATPase that pumps cholesterol out of cells, leading to atherosclerosis; revealed mech of cholesterol transport out of cells

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12
Q

I-cell disease

A

Caused by defect in M6Pase or defective M6P receptor; leads to buildup of lysosomal substrates since lysosomes lack their enzymes

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13
Q

Microtubules: subunit, accessory proteins, hyperstable structures; motors, functions, drugs, significance

A

Made of tubulin. MAPs and tau proteins are accessory. Comprise cilia, flagella, centrioles. ATPases are dynein (retrograde) and kinesin (orthograde). Function for motility of cell, form mitotic spindle, and transport organelles/cargo. Affected by taxol, vinca alkaloids. Significant in Karageners syndrome, chemotherapy, dementias (tau-opathies)

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14
Q

Microfilaments: subunit, accessory proteins, hyperstable structures; motors, functions, drugs, significance

A

Subunit is actin, acessory proteins are numerous (importantly profilin). Structure: sarcomere, microvilli with myosin motors. Functions in phagocytosis, cytokinesis, cell motility, force generation, membrane stabilization. Important in hereditary spherocytosis, listeria, vaccinia

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15
Q

Intermediate filaments: subunit, accessory proteins, hyperstable structures; motors, functions, significance

A

Made of lamins, keratin, neurofilamin, vimentin, desmin, GFAP. No accessory proteins. Comprise desmosome and hemidesmosome. No motors. Functions in mechanical integrity (nucleus, cell-cell, cell-matrix). Significant in laminopathies, blistering diseases, cancer diagnosis

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16
Q

Vimentin

A

Intermediate filament present in most mesenchymal cells, incl. endothelial cells and fibroblasts

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17
Q

Desmin

A

Intermediate filament present in muscle cells

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18
Q

Glial fibrillary acidic protein (GFAP)

A

Intermediate filament present in glial cells (astrocytes)

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19
Q

Neurofilamin

A

Intermediate filament present in neurons

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20
Q

Keratin

A

Intermediate filament present in epithelial cells

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21
Q

Eicosanoids: classes and functions

A

Prostaglandins: PGE2 induces uterine contractions, vasodilation
Thromboxanes: TXA induces platelet aggregation, vasoconstriction
Leukotrienes: LTC4, LTD4, LTE4 induce vasodilation and bronchoconstriction in asthma; also play a role in anaphylaxis

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22
Q

Hereditary spherocytosis

A

Mutation in protein involved with membrane-cytoskeleton interactions in erythrocytes – results in misshapen erythrocytes, which cannot squeeze through splenic capillaries –> hepatosplenomegaly

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23
Q

Diseases involving phagocytosis

A

Legionnaire’s, streptococcus, tuberculosis, leprosy, leishmaniasis, toxoplasmosis/coccidosis, listeriosis

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24
Q

Diseases of receptor-mediated endocytosis

A

Familial hypercholesterolemia, rabies, influenza

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25
Q

Diseases of ABC ATPase transporters

A

Cystic fibrosis, tumor drug resistance (MDR), Tangier disease

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26
Q

Destination of proteins translated on membrane-bound ribosomes

A

ER, plasma membrane, secretory vesicles, lysosomes, and Golgi apparatus

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27
Q

Destinations of proteins translated on free ribosomes

A

Peroxisomes, nucleus, mitochondria, cytoplasm

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28
Q

Nuclear localization signal

A

Peptide sequence that indicates a molecule should be transported into the nucleus, typically Lys-Lys-Arg-Pro-Arg. Mutations in this sequence result in localization in the cytoplasm

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29
Q

Diseases of defective peroxisomal targeting

A

Zellweger syndrome, neonatal adrenoleukodystrophy (NALD)

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32
Q

Key events in Golgi

A

Sorting - phosphorylation of oligosaccharides on lysosomal proteins
Trim sugars
Trim and add sugars
Add sugars
Process and sort, send to lysosome, plasma membrane, secretory vesicle

33
Q

Neoplasia

A

Irreversible proliferation of cells which continues even in the absence of an external stimulous

34
Q

Regeneration

A

One-for-one replacement of cells: new cells replace old, damaged cells in a precise way
i.e. renewal of damaged endothelial cells in blood vessels after angioplasty

35
Q

Hyperplasia

A

An increase in the number of cells in a tissue, where all cells are fully differentiated and functional

36
Q

Grave’s disease

A

Hyperplasia of thyroid cells leads to an increase in thyroid hormone and hyperthyroidism

37
Q

Restenosis

A

Hyperplasia of smooth muscle cells following vascular surgery, leading to re-blockage of the blood vessel

38
Q

Metaplasia

A

Pathologic, adaptive substitution of one cell type by another; commonly seen in the lung tissue of smokers and in sufferers of chronic inflammatory pelvic disease
In both cases, normal cells are replaced by tougher and more protective squamous epithelium

39
Q

Dysplasia

A

Changes in mitotic rate of cells, loss of positional control, and loss in uniformity of cell shape; often a precursor to cancer

40
Q

Pleiotropy

A

Where a change in a single gene causes multiple phenotypic effects

41
Q

Benign neoplasia

A

Proliferation of cells absent external factors where positional control is maintained
i.e. uterine fibroids - grow in place, don’t metastasize

42
Q

Malignant neoplasia

A

Loss of proliferation and position control - cancer

43
Q

Stages of the cell cycle

A 
G0 - quiescent state characterized by decreased protein synthesis, increased protein degradation, decreased RNA synthesis, decreased number of polyribosomes, and changes in cell morphology
G1 - cell prepares to replicate DNA
S - synthetic phase, DNA replicated
G2 - cell prepares to undergo mitosis
M - mitosis
44
Q

R point

A

Stage in the latter part of G1 where decision is made to either commit to mitosis; once decision is made, cell either completes division or undergoes apoptosis

45
Q

CDK

A

Cyclin-dependent kinase - regulate cell cycle/mitosis, regulate activation and inactivation of mitosis promoting factor (MPF); target specific substrates, i.e. Cyclin B/Cdk1 act on lamins & histones

46
Q

G1 phase cyclin/Cdk pair

A

Cyclin D & Cdk4 or Cdk6, upon sufficient accumulation, along with Cyclin E/Cdk 2, phosphorylate Rb protein to push cell into S phase

47
Q

G1/S phase cyclin/Cdk pair

A

Cyclin E & Cdk 2; along with Cyclin D/cdk4-6 phosphorylate Rb protein to push cell into S phase

48
Q

S phase cyclin/Cdk pair

A

Cyclin A & Cdk 2

49
Q

M phase cyclin/Cdk pair

A

Cyclin B & Cdk 1

50
Q

Rb protein

A

Retinoblastoma protein - exists in a hypophosphorylated state which suppresses cell growth; phosphorylation by Cyclins D & E inactivate Rb, releasing bound TF E2F, which initiates DNA transcription

51
Q

Features of necrosis

A
  • Triggered by sustained injury/insult, which causes cells to swell, organelle damage, and random chromatin degradation.
  • Cells lyse, causing inflammation
52
Q

Features of apoptosis

A
  • Triggered by specific signals that activate apoptotic genes, which causes cell shrinkage while maintaining organelle morphology.
  • Chromatin condenses and is systematically degraded, and the nucleus is broken up.
  • Cell membrane blebs, and eventually phagocytosed; no inflammation
    DNA gel shows ladders rather than smear of DNA, indicating systematic degradation
53
Q

Polycystic kidney disease

A
  • Disorder that results in uncontrolled apoptosis of kidney cells
  • Tissue develops cysts that interfere with normal function
54
Q

Phases of apoptosis

A

1) Induction - intrinsic (Bcl mediated) & extrinsic (Fas/TNF mediated) pathways
2) Modulation
3) Execution

55
Q

1) Physiologic activators of apoptosis
2) Damage-related activators
3) Therapy-associated activators

A

1) TNF-alpha, FasL, GF withdrawal, glucocorticoids
2) Viral infection, heat shock, toxins, tumor suppressors, free radicals
3) UV/gamma irradiation, chemotherapy

56
Q

Features of extrinsic apoptosis

A
  • Receptor-mediated, Fas/TNF-alpha
  • FasL binds to Fas, activates executioner caspases:
    • break down cytoskeletal proteins
    • activate endonucleases
57
Q

Features of intrinsic apoptosis

A
  • Caused by injury, mediated by Bcl proteins
  • Bad phosphorylated, binds to Bcl-Xs at outer mitochondrial membrane
  • Bax/BAK oligomerize and cause mitochondrial outer membrane permeabilization
  • Cytochrome c released, binds to Apaf-1, which cleaves inactive zymogen to form caspase 9, which activates other caspases
58
Q

Immunologic privilege

A

Conferred by extrinsic apoptosis: immune privileged express FasL, bind Fas on T cells and cause them to apoptose

59
Q

Hashimoto disease

A

Apoptosis of thyrocytes caused by autoimmune targeting by T lymphocytes

60
Q

Polydactyly/syndactyly

A

Extra/fused fingers, caused by abnormal apoptosis between digits during fetal development

61
Q

Caspases

A

Cytosolic aspartate-specific cysteine proteases
Activated by cleavage of zymogens, regulated by Bcl-2 family proteins
Involved in apoptotic cascade

62
Q

Bcl-2 family proteins

A

Pro- or anti-apoptotic proteins found on mitochondrial membrane
Ratio of pro-apoptotic vs anti-apoptotic Bcl members determins life and death of cells

63
Q

Inducers of apoptosis: physiologic, damage, therapy, proteins

A

Physiologic activators: i.e. TNF-alpha, FasL; glucocorticoids
Damage related activation: viral infection, heat shock, free radicals
Therapy: UV/gamma radiation, chemo
p53: triggers DNA degradation and apoptosis

64
Q

IAPs in stroke: clinical significance

A

Inhibitors of apoptosis can protect stroke victims from excessive loss of neurons

65
Q

Scurvy

A

Vitamin C deficiency that results in faulty cross-linking of collagen fibrils
Leads to spots on skin, spongy gums, bleeding from mucous membranes

66
Q

Ehler-Danlos syndrome

A

Connective tissue disorder caused by defect in collagen synthesis and assembly

67
Q

Osteogenesis imperfecta

A

Genetic disorder caused by mutation in type I collagen, results in multiple fractures and brittle bones

68
Q

Menke’s disease

A

X-linked recessive disease, causes deficiency in copper utilization resulting in faulty collagen cross-linking

69
Q

Alport syndrome

A

Genetic disorder in which collagen IV is absent or non-functional
2nd most common inherited cause of kidney failure

70
Q

Goodpasture syndrome

A

Autoimmune disease in which antibodies against collagen IV destroy basement membrane

71
Q

Proteoglycans

A
  • Comprised of hyaluronan (long repeating sugars), have protein cores attached to them surrounded by sugars
  • Regulate hydration state of tissues & cartilage
  • Resistance to impact in cartilage
  • Reservoir for GFs and cytokines
72
Q

Chondrodysplasia

A

Disorder in which chondrocytes do not mature and differentiate, causing malformed cartilage

73
Q

Matricellular proteins

A

Fibronectin - cellular “glue” - binds cells and ECM, made by mesenchymal cells
Laminins - made by epithelial cells, bind ECM, anchored in cell and attached to actin fibers
CCN family of proteins

74
Q

CCN proteins

A

CCN1 & CCN2: placentation, angiogenesis, fibrosis
CCN3: tumor formation & metastasis
CCN5: inhibit smooth muscle cells

75
Q

Integrins

A

Mediate cell-cell and cell-ECM interactions

Literally thousands of combinations of alpha and beta chain subunits

76
Q

Cadherins

A

Adhere cells, important part of desmosomes

77
Q

Pemphigus

A

Autoimmune disease where antibodies destroy (hemi)desmosomes

78
Q

Elastin

A

Major structural protein, present in laminae of large arterial walls and provide structural strength and flexibility

79
Q

Marfan’s Syndrome

A

Individuals posses a defect in fibrillin that cross-links elastin in artery wall, resulting in aorta aneurysm

Medfoundations I (3 decks)

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