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SF Year 1 > Lecture 8 > Flashcards

Lecture 8 Flashcards

1
Q

cWhat is the cytoskeleton?

A

A network of intracellular fibers that maintain the shape of a cell providing structural
strength, resistance to mechanical stress, and resilience to deformation. It also plays a role
in intracellular transport, and cell motility.

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2
Q

What three fibers are in the cytoskeleton

A
  • microfilaments
    -intermediate filaments
    -microtubules
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3
Q

What is the function of Microfilaments

A

Cell shape, motility, endo- and exocytosis,
secretion and vesicle transport

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4
Q

What are microfilaments composed of

A

G-actin
‣ Have binding site for ATP or ADP that
play a role in polymerization
‣ Highly conservative and ubiquitous
expression
-Polymerize with F actin

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5
Q

What are 4 special feature of microfilaments

A

✓ Very dynamic structures that can polymerize and
depolymerize rapidly within the cell
✓ Form a mesh below the plasma membrane.
✓ They link with proteins embedded in the membrane,
connecting with the ECM.
✓ The formation, growth, and dissolution of
microfilaments is strictly regulated by more than 100
proteins

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6
Q

______________-: affect normal actin polymerization/ depolymerization
results in changing the shape of any cells, inhibiting cell motility, and preventing the outgrowth of axons from ganglion

A

Fungal metabolites Cytochalasin
B and Phalloidin

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7
Q

What is the function of Intermediate filaments

A

Structural role, providing support to the nucleus
and the plasma membrane
✓ Form the most stable element of the cytoskeleton

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8
Q

What is the structure of an intermediate filament

A

strong, highly flexible fibers that provide mechanical support

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9
Q

______________: Cause: Rare, autosomal recessive mutation in the LMNA
gene, which results in the production of an abnormal lamin
A protein called progerin (a farnesylated form of prelamin
A, which is retained due to the mutation). Accumulation of
progerin destabilizes nuclei, altering their shape
predisposing patients to manifest signs of premature aging.
Clinical presentation: children are born looking normal and
begin to develop clinical signs of disease during year one.
Physical appearance and clinical findings change
dramatically each year they age. Life expectancy is 5-20
years. Children usually develop premature progressive
atherosclerosis and die of heart failure

A

Hutchinson Gilford disease

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10
Q

What is the treatment for hutchinson Gilford disease

A

oral farnesylation inhibitor that prevents the accumulation of progeria and protein like proteins resulting in restoration of nuclear morphology and extending patient lives

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11
Q

Intermediate filament disease can also result in ______________

A

skin diseases due to mutations in gene coding various keratins

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12
Q

_____________________
The defect in most common types of EBS
is in keratin 5 or 14, which makes up
intermediate filaments of the basal
keratinocytes leading to cytolysis of the
basal cells and blisters.

A

Epidermolysis Bullosa Simplex (EBS)

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13
Q

_______________________
Mutations in the keratin 1 and keratin 9
genes. Skin disorder characterized
clinically by diffuse, yellow thickening of
the skin of the palms and soles

A

Epidermolytic Palmoplantar
Keratoderma (EPPK)

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14
Q

What are the functions of microtubules

A

mitotic spindle formation and
function, intracellular movement of endocytic and exocytic vesicles

Structural components of cilia and flagella.

Maintain the structure of axons and dendrites as well as participate in the axoplasmic flow of material along neuronal
processes.

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15
Q

What are microtubules composed of

A

13 logitiudaly arranged protofilaments

Each protofilament is comprised of
globular α-tubulin and β-tubulin

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16
Q

_____________________
Mutations in genes affecting the synthesis of dynein, a cytosolic MAP that power ciliary and flagellar
movements.
Results in:
‣ male sterility due to immobile spermatozoa
‣ situs inversus (a mirror image of chest and abdominal organs compared to normal human anatomy) due to
lack of proper cell movement during embryogenesis
‣ chronic respiratory infections due to dysfunctional nasal cilia.

A

Kartagener syndrome

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17
Q

_____________
‣Anti-cancer drugs: vinblastine and paclitaxel
‣Acute gouty arthritis: colchicine
‣Anti-fungal: griseofulvin

A

Pharmacological treatments that disrupt the microtubule
assembly or disassembly

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18
Q

The most abundant protein in
the human body
✓ Very long lived (10 years)
✓ Ubiquitously present in
different organs and systems

A

Collagen

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19
Q

What is the structure of collagen

A

fibrous protein compose of 3 alpha chains filing a triple strange rope like structure

The structure is stabilized by interchain H bonds

Different chains have different collagen fibers

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20
Q

What amino acids are prevalent in collagen

A

glycine and proline

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21
Q

______________________
Greatly decreased tensile strength of the
assembled collagen fibers due to lack of H-bond
formation
‣Easy bruising
‣Loose teeth and bleeding gums
‣Poor wound healing
‣Poor bone development

A

Vitamin C diffecieny Scurvey

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22
Q

______________ is a copper containing extracellular enzyme that oxidatively dominates some of the lysine and hydrolysine residues forming reactive aldehydes. They form covalent cross links in the mature collagen fibers

A

Lysyl oxidase

23
Q

_______________________:
Copper deficiency: mutations in the ATP7A gene (PM
Cu2+ transporter) leading to lack of Cu2+
‣ X-linked recessive (~30% of MNK are due to new
mutations and 70% are inherited)
‣ Symptoms: weak muscle tone (hypotonia), sagging
facial features, seizures, intellectual disability, and
developmental delay. The patients have brittle hair
(kinky hair disease)

A

Menkes Syndrome

24
Q

_________ copper overload

A

Wilson’s disease

25
Q

✓Defective collagens or the
processing enzymes:
‣ Classic form - collagen V
‣ Vascular form - collagen III
✓General features: hyperextensible skin,
hypermobile joints and abnormal tissue fragility
(easy bleeding/bruising)
✓May have blue sclerae
✓Most severe forms have potentially lethal
vascular problems due to defective collagen in
the arteries

A

Ehlers-Danlos Syndrome (EDS)

26
Q

✓“Brittle bone” disease
✓Over 80% due to autosomal dominant mutations in
genes for α1 or α2 chains in collagen I
✓Most common is replacement of Gly
✓Eight types (I-VIII):
‣ Type I (most common) - mild bone
fragility, hearing loss, and blue
sclerae
‣ Type II - the most severe form -
typically lethal in the perinatal
period
‣ Type III - severe - multiple
fractures at birth, short stature,
spinal curvature

A

Osteogenesis imperfecta

27
Q

_______________ is the most abundant protein in arteries

A

elastin

28
Q

________________ is an extensively interconnected rubbery network that can stretch and bend in any direction.

A

Elastin fiber

29
Q

_________________________ a family of large glycoproteins, fribilin 1 is a major one, provides a scaffold for elastin

A

Fribrillins

30
Q

_______________
autosomal dominant, mutation in fibrilan 1, arachondactyly, ectopia lensis upward, abnormally week arteries, patients dies midlife after a ruptured aorta

A

Marfan’s Syndrome

31
Q

______________
caused by chromosomal 7 deletion of 27 genes including elastin. Occurs due to random event during the formation of reproductive cells in % is inherited, developmental disorder, unique personality, distinctive facial features, cardiovascular problems

A

Williams Beuren Syndrome

32
Q

________________ the most abundant multi adhesive protein in connective tissue. Large protein, formed from two similar polypeptide chains linked by disulfide bonds

A

Fibronectin

33
Q

__________________ is a large cross shaped glycoprotein consisting of three polypeptides encoded by different genes

A

Laminin

34
Q

What are the functions of fibronectin

A

-Glues the cells to the fibrous meshwork of the extracellular matrix
-Embryogenesis necessary for proper movement of cells
-cancer role in metastasis

35
Q

What are the functions of laminin

A

-holds together the components of the basement membrane
-mediates interactions with the overlaying cells (adhesion)
-Helps trigger physiological responses, growth, movement

36
Q

______________:
- causes by the mutation in LAMA2 geneCause - mutations in LAMA2 gene (alpha-2 subunit found in skeletal muscle Laminin 2 and 4)
-Autosomal recessive
‣-Muscle weakness and atrophy, Appears in one of two ways: as a severe, early-onset type or a
milder, late-onset form

A

LAMA 2, muscular dystrophy

37
Q

___________ Large complexes of heteropolysacchrides chains associated with a small amount of protein
-95% carbohydrate
-5% protein

A

proteoglycans

38
Q

_______________ protein with a variable but typically small amount of carbohydrate

A

glycoproteins

39
Q

__________________ a gel like matrix forming the basis of the body’s ground substance, flexible support for extra cellular matrix, sieve influencing the movement of materials through the ecm, contribute to the viscous lubricating properties

A

Proteoglycans

40
Q

What are 3 proteoglycan structures

A

-proeoglycan monomers
-hyleronic acid
-link protein

41
Q

___________________
Large complexes of negatively charged heteropolysaccharide chains
‣ Unbranched
‣ Repeating disaccharide units [acidic sugar-amino sugar]n
‣ amino sugar:
* Is acetylated (eliminates its (+) charge)
* Can be sulfated(enhancing the (-) charge)

A

Glycosaminoglycans GAGS

42
Q

How are gylcosoaminoglycans divided

A

-monomeric composition
-type of glycosidic linkage
-degree and location of sulfate units

43
Q

__________________ most abundant GAG in the body, found in cartilage and tendons, ligaments, and aorta, form proteoglycan aggregates through non covalent association hold fibers in a tight, strong network

A

Chondrian 4 and 6 sulfates

44
Q

_______________ most heterogenous GAG because they contain additional monosaccharides such as L glucose, N acetylneuraminic acid and mannose. Found in cornea and loose connective tissue

A

Keratan sulfates

45
Q

________________________ different from other GAG not sulfated, not covalently attached to protein, and not limited to animal tissue but also found in bacteria, serves to lubricate and absorb shock. Found in synovial joints, nitrous humor of the eye, umbilical cord,

A

Hyaluronic acid

46
Q

______________ disaccharide unit. Found in the skin and blood vessels, heart valves

A

Dermatin Sulfate

47
Q

_____________dissachride unit, alpha linkage joins the sugars, unlike other GAG that are extracellular, this is intracellular component of mast cells that line arteries, especially in liver, lungs and skin serves as an anticoagulant

A

Heparin

48
Q

What are the steps of synthesis of GAG’s

A
  1. core protein
  2. Carbohydrate chains
  3. Sulfanation
49
Q

How are GAG’s degraded

A

endocytosis (internalization)
lysosomes (specific acid hydrolase)

50
Q

_____________
defect in the sulfation of the growing glycosaminoglycan chains
Genetics:
‣ Autosomal recessive disorders
Characteristics:
‣ affect the proper development and
maintenance of the skeletal system
‣ Result in a normal-sized
trunk and abnormally shortened limbs
and extremities
‣ Over 100 specific skeletal dysplasias
affecting different proteins

A

Chondrodysplasias
*defect in GAG synthesis

51
Q

_________________________- deficiency of any one of the lysosomal hydrolases
involved in the degradation of heparan sulfate and/or dermatan sulfate
Genetics:
‣ Autosomal recessive (1:25,000 births)
‣ Exception - Hunter syndrome (X-linked)

Diagnosis:
‣ Identification of non-reducing end of the oligosaccharide
‣ Enzyme activity assay for specific lysosomal hydrolases

Symptoms:
‣ Progressive disorders - apparently normal at birth, gradually deteriorate, severe
cases may result in childhood mortality
‣ GAGs accumulate in the lysosomes of various tissues and results in
oligosaccharides in the urine
‣ Skeletal and extracellular matrix deformities, and mental retardation

A

Mucopolysaccharidoses

*defect of degradation

52
Q

____________
-iduronate sulfatase deficiency
-X linked deficiency
-wide range of severity; corneal clouding but mild to severe physical deformity and developmental disability
-enzyme replacement therapy available
-degradation and derma tan sulfate and heparin sulfate affected

A

Hunter syndrome

*Characterized by a rash

53
Q

______________________
-Alpa idurondiase deficiency, most severe form of MPS I, corneal clouding, developmental disability, awarding, coarse fascial features, upper airway obstruction, hearing loss,
- degradation of derma tan sulfate and heparin sulfate affected

A

Hurler Syndrom

54
Q

___________ four enzymatic difficentcies on the heparin sulfate causing severe nervous system disorder and developmental disabilities

A

Sanfilippo syndrome

SF Year 1 (20 decks)

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