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Flashcards in Basics Deck (98):
1

Kinesin

microtubule-associated motor protein that uses energy from ATP hydrolysis to perform anterograde transport of intracellular vesicles and organelles towards the rapidly-growing ends of microtubules (e.g. secretory vesicles in nerve terminals)

2

Blood-brain barrier

formed by tight junctions btwn nonfenestrated capillary endothelial cells

3

Tight junctions / zonulae occludentes

composed of transmembrane proteins (claudins, occludins) that associate w/actin filaments to form a belt-like seal around the apical intercellular space, permitting only transcellular movement

4

Desmosomes / maculae adherentes

spotlike junctions that anchor adjacent cells together via keratin intermediate filament interactions

5

Fenestrae

  • small pores w/i endothelial cells that allow free fluid exchange btwn intra- and extravascular space
  • found in capillaries perfusing:
    • intestine
    • renal tubules
    • endocrine glands

6

Gap junctions

  • composed of connexin proteins
  • create channels btwn cells to allow free passage of small ions (Ca2+) and molecules

7

Hemidesmosomes

Spotlike junctions that anchor the basal layer of epithelial cells to the basement membrane

8

Intermediate junctions / zonula adherens

  • located below tight junctions
  • form a belt-like anchor btwn adjacent cells in association w/actin microfilaments

9

Type I Collagen

Found in:

  • bone
  • tendons
  • ligaments
  • dermis
  • dentin
  • cornea
  • blood vessels
  • scar tissue

Affected in osteogenesis imperfecta

10

Type II Collagen

Found in:

  • cartilage
  • vitreous humor
  • nucleus pulposus

11

Type III Collagen

Found in:

  • skin
  • lungs
  • intestines
  • blood vessels
  • bone marrow
  • lymphatics
  • granulation tissue
  • keloids

Affected in Ehlers-Danlos Syndrome types 3 & 4

12

Type IV Collagen

Found in basement membranes

Affected in:

  • Alport Syndrome
  • Goodpasture Syndrome

13

Dynein

  • microtubule-associated motor protein that uses energy from ATP hydrolysis to perform retrograde transport of intracellular vesicles and organelles toward nucleus
  • also functions in ciliary and flagellar movement

14

Stratified squamous epithelium locations in respiratory tract

  • Oropharynx
  • Laryngopharynx
  • Anterior epiglottis
  • Upper 1/2 posterior epiglottis
  • True vocal cords

15

M-line

  • located in middle of sarcomere
  • Myosin filaments bound to structural proteins here

16

Z-line

  • 2 of these form boundary of 1 sarcomere
  • Actin filaments bound to structural proteins here

17

I-band

  • located around Z-line
  • region of sarcomere in which myosin does not overlap w/actin
  • decreases in size during mm contraction

18

H-band

  • located around M-line
  • decreases in size during mm contraction

19

A-band

  • extends over entire middle region of thick myosin filaments (larger than H-band)
  • does NOT change size during mm contraction

20

Type II Pneumocytes

cuboidal cells that cover ~5% of alveolar surface

  • regenerate alveolar lining ("stem cells")
  • produce surfactant

21

Type I Pneumocytes

  • flat cells that cover ~95% of alveolar surface
  • cannot regenerate on their own

22

Alveolar Macrophages

  • self-maintaining population
  • derived from fetal monocytes
  • clear inhaled particles from terminal respiratory units

23

Club / Clara Cells

  • nonciliated secretory cells
  • found in terminal portions of bronchioles
  • can act as regenerative source of ciliated cells in bronchioles

24

Osteocytes

  • long intracanicular processes extend thru ossified bone matrix
  • send signals to & exchange nutrients + waste w/other osteocytes w/i neighboring lamellae via gap junctions
  • maintain structure of mineralized matrix
  • control short-term release/deposition of Ca2+ (directly controlled by plasma Ca2+ concentration)
  • sense mechanical stresses and send signals to modulate activity of surface osteoblasts

25

Parietal Cells

  • Oxyntic (pale pink), round, plate-like cells
  • Found predominantly in upper glandular layer of gastric mucosa
  • Secrete gastric acid (HCl) and intrinsic factor
  • Affected in chronic autoimmune gastritis

26

Chromaffin cells

  • derived from neural crest
  • located in adrenal medulla
  • modified postganglionic sympathetic neurons
  • receive sympathetic input (Ach) and secrete catecholamines

27

Heteroplasmy

inherited mixture of normal and damaged mtDNA

  • mitochondria randomly distributed btwn daughter cells during mitosis
  • responsible for clinical variability of mitochondiral diseases

28

Genetic Imprinting

selective inactivation of maternal or paternal alleles

29

Anticipation

  • increase in severity of genetic disorders in subsequent generations
  • seen in autosomal and XL trinucleotide repeats due to repeated amplification during gametogenesi

30

Variable Expressivity

differences in the severity of AD disorders

31

Ionizing radiation

  • DNA double-strand breaks
  • Free radical formation

32

Alkylating agents

DNA cross-linking

33

UV / non-ionizing radiation

Pyrimidine (thymine) dimers

34

Histone deacetylation

Decreased gene expression

  • acetylation weakens DNA-histone bond, making DNA more accessible for transcription

35

DNA methylation

  • At CpG Islands → inhibits gene transcription
  • During replication in prokaryotes → Template strand cytosine and adenine are methylated, which allows mismatch repair enzymes to distinguish between old and new strands

36

Homeobox genes

  • code for transcription factors that bind to regulatory regions on DNA to alter gene expression
  • critical for sequential development of organs and tissues along cranio-caudal axis during embryogenesis

37

Kozak consensus sequence

  • occurs on eukaryotic mRNA
  • helps initiate translation at methionine start codon (AUG)
  • (gcc)gccRccAUGG, where R = adenine or guanine
  • affected in beta-thalassemia mutations

38

Exons

protein-coding DNA regions

39

Introns

removed during intranuclear mRNA processing → not expressed in final mRNA sequence

40

Penetrance

proportion of ppl w/given genotype that express associated phenotype

41

Mosaicism

  • presence of 2+ cell lines, each with unique nuclear genome, in same person
  • can affect nearly all cells (if occurs early in developmet) or a limited # of somatic cells

 

42

Pleiotropy

occurrence of multiple, seemingly unrelated phenotypic manifestations, often in different organ systems, as a result of single genetic defect

43

Genetic linkage

tendency of alleles located near one another on the same chromosome to be inherited jointly

44

Locus heterogeneity

ability of one disease or trait to be caused by mutations in multiple different genes

45

Polyploidy

more than 2 complete sets of homologous chromosomes exist w/i organism or cell

46

Lyonization

  • Normal random deactivation of one X chromosome in females
  • Converts inactive X into condensed heterochromatin → Barr body
  • generally prevents XLR disorders from manifesting

47

Heterochromatin

  • Transcriptionally Inactive DNA
  • Condensed methylated DNA + deacetylated histones
  • ex: Barr body

48

Euchromatin

  • Active DNA w/high transcriptional activity
  • Loosely arranged → sterically accessible

49

Meiotic nondisjunction

  • Chromosome pairs fail to separate during meiosis I
  • Responsible for:
    • Turner Syndrome
    • Trisomy 13 / Patau
    • Trisomy 18 / Edwards
    • Trisomy 21 / Down

50

Robertsonian translocation

  • occurs btwn 2 acrocentric chromosomes
  • long arms fuse near centromeres, short arms are lost

51

Frameshift mutation

# of nucleotides not divisible by 3 is inserted into or removed from DNA sequence → different product

52

Uniparental disomy

individual inherits 2 copies of chromosome from 1 parent and no copies from other parent

53

Stop codons

  • UAG
  • UAA
  • UGA

54

Western Blot

used to detect polypeptide in mixed sample

  • potential targets separated by gel electrophoresis
  • separated proteins transferred to nitrocellulose membrane and probed w/1° Ab specific for target
  • membrane then washed and treated w/2° marked Ab that binds to 1° Ab and can be detected

55

ELISA

used to detect polypeptide

  • pt serum tested directly
  • probed w/1° Ab specific for target
  • then treated w/2° marked Ab that binds to 1° Ab and can be detected

56

Northern Blot

Analyzes mRNA

  • Sample separated by gel electrophoresis
  • Bands transferred to membrane & hybridized w/probe containing nucleotide sequence complementary to mRNA of interest

57

Southern Blot

Analyzes DNA

  • DNA fragmented using restriction endonucleases
  • Fragmented DNA separated by gel electrophoresis
  • Transferred to membrane and hybridized using radiolabeled DNA probe containing complementary sequence
  • Can detect restriction site mutations

58

Microarray

  • Similar to Northern and Southern blotting, but involves hybridization w/large # of probes at once
  • Genomic DNA or cDNA being analyzed is labeled w/fluorescent tag and placed on gene chip containing complementary sequences for a large # of genes
  • Degree of fluorescence corresponds to mRNA expressed

59

Southwestern Blot

Analyzes DNA-binding proteins

  • Uses principles of Southern and Western Blots
  • DNABPs recognized by ability to bind specific oligonucleotide probes

60

Neurophysins

  • carrier proteins for oxytocin and vasopressin / ADH → shuttle toward nerve terminals in posterior pituitary
  • produced in neuronal cell bodies of hypothalamic nuclei

61

Oxytocin Production Site

Hypothalamic paraventricular nucleus

62

Vasopressin / ADH production site

Hypothalamic supraoptic nuclei

63

GLUT-4

  • Glucose transmembrane carrier protein → facilitated diffusion
  • Insulin-sensitive
  • Glucose uptake into skeletal mm, adipocytes

64

GLUT-2

  • Glucose transmembrane carrier protein → facilitated diffusion
  • Modulates pancreatic beta-cells (insulin release)
  • Facilitates glucose export from liver, small intestine, kidneys

65

5a-reductase

Testosterone → DHT

66

Aromatase

Androgen → Estrogen

67

Thyroid Peroxidase

  • Iodide oxidation to iodine (I- → I2)
  • Iodine organification w/thyroglobulin (I2 + TG → MIT, DIT)
  • Iodotyrosine coupling (MIT + DIT → T3; DIT + DIT → T4)

68

AP generation & propagation

  1. Excitatory stimulus
  2. Ligand-gated Na+ channels open → depol
  3. AP propagates, reaches axon terminal
  4. Voltage-gated Ca2+ channels open
  5. Fusion & release of NT vesicles into synaptic cleft

69

Golgi Tendon Organ

  • Sensory receptors located at jct of mm & tendon
  • Innervated by group Ib sensory axons
  • Connected in series w/extrafusal skeletal mm fibers
  • Respond to tension/stretch (inhibit contraction)
    • GTO signals inhibitory interneurons in spinal cord
    • Alpha motor neurons send negative feedback to mm

70

A-delta fibers

  • Thin, myelinated nerve fibers
  • Free endings detect temp & nociceptive stimuli
  • Assoc w/sharp pain
  • Make up afferent portion of reflex arc that mediates withdrawal from noxious stimuli

71

Intrafusal Muscle Fibers

  • aka Muscle Spindles
  • Connected in parallel w/extrafusal mm fibers
  • Innervated by group Ia and II sensory axons
  • Sensitive to changes in mm length
  • Mediate myotatic stretch reflex (deep tendon reflexes)
    • monosynaptic reflex activation of alpha motor neuron
    • causes contraction to resist stretch

72

Pacinian Corpuscles

  • Rapidly-adapting mechanoreceptors
  • Subcutaneous tissue of skin, mesentaery, peritoneum, joint capsules
  • Mediate touch, proprioception, vibratory sensation
  • Innervated by myelinated A-beta fibers

73

Ruffini's End Organs

  • Slowly-adapting mechanoreceptors
  • Skin, subcutaneous tissue, joint capsule
  • Mediates touch, proprioception, vibratory sensation
  • Innervated by myelinated A-beta fibers

74

Osteoblasts

  • Synthesize bone matrix
  • Release alkaline phosphatase

75

Osteoclasts

  • Absorb bone
  • Release:
    • Urinary deoxypyridinoline (collagen breakdown; most reliable)
    • Urinary hydroxyproline (collagen breakdown)
    • Tartrate-resistant acid phosphatase

76

Mu receptors

  • G protein-linked receptors
  • Increased K+ efflux → hyperpolarization of postsynaptic neurons
  • Other possible 2nd messenger pathways:
    • Inhibition of adenylyl cyclase
    • Inhibition of Ca2+ conductance
    • Inhibition of transmitter release

77

Length Constant

  • aka Space Constant
  • Measure of how far along an axon an impulse can propagate
  • Decreased w/demyelination (impaired stimulus transmission)

78

Threshold

  • Memb potential value required to initiate AP
  • Determined by intrinsic properties of voltage-gated Na+ channels

79

Summation

  • Additive effects of multiple postsynaptic potentials on target neuron memb potential
  • Can occur in dendrites, cell body, axon hillock (NOT axon)

80

Temporal Summation

additive effects of sequential impulses from same neuron over time

81

Spatial Summation

additive effects of simultaneous impulses from several different neurons

82

Time Constant

  • Represents time it takes for change in memb potential to achieve 63% of new value
  • Lower = quicker change, increased axonal conduction speed
  • Increased w/demyelinization (slowed)

83

Hepcidin

  • Acute-phase reactant made by liver
  • Central regulator of iron homeostasis
    • High iron / inflamm conditions → increased synth
    • Hypoxia / increased erythropoeisis → decreased synth
  • Binds ferroportin → ferroportin internalized & degraded → decreased intestinal iron absorption + inhibited macrophage iron release

84

DMT-1

Transporter that facilitates iron absorption from proximal small intestine

85

Chromatin

  • Condensed form of DNA that allows fit into nucleus
  • Negatively charged DNA loops twice around positively charged histone octamer to form nucleosome “beads on a string.”

86

Histones

  • Rich in lysine and arginine
  • Positively-charged
  • DNA wraps around to form chromatin
  • H1 binds to nucleosome and to “linker DNA,” thereby stabilizing the chromatin fiber.

87

DNA synthesis occurs during this phase of replication

S phase

88

Histone synthesis occurs during this phase of replication

S Phase

89

Nucleosomes

  • "Beads on a string"
  • DNA wound around histone

90

Chromatin Structure

A image thumb
91

Histone Acetylation

Relaxes DNA coiling, allowing for transcription

92

Histone methylation

  • Usually reversibly represses DNA transcription
  • can activate it in some cases depending on location.

93

NucleoSide

base + (deoxy)ribose

94

NucleoTide

  • base + (deoxy)ribose + phosphaTe
  • linked by 3′-5′ phosphodiester bond

95

Purines

  • Adenosine, Guanine (PURe As Gold)
  • 2 rings

A image thumb
96

Pyrimidines

  • Cytosine, Thymine
    • Cytosine deamination → Uracil
  • 1 ring

A image thumb
97

Strength of bonds btwn DNA bases

  • G-C bond (3 H bonds) stronger than A-T (2 H bonds)
  • Increased G-C content → increased DNA melting temp

98

3 Amino acids necessary for purine synthesis

  1. Glycine
  2. Aspartate
  3. Glutamine