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FTM Exam 1 > Lecture 27 > Flashcards

Lecture 27 Flashcards

1
Q

Soft tissue

A

Closely packed cells with little ECM between

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2
Q

Connective tissue

A

Less cells more ECM

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3
Q

Components of ECM

A

Proteinaceous fibres embedded in a gel-like ground substance

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4
Q

Mechanical properties of ECM depend on

A

Amount of proteinaceous fibers

Type of proteinaceous fibers

Orientation of these fibers

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5
Q

ECM undergoes constant remodeling by

A

MMP = matrix metalloproteinases

Need zinc and include collagenases

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6
Q

Dysregulation of MMP

A

Spread of cancer cells

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7
Q

Types of fibrous proteins

A

Collagen
Elastin
Keratin
Tropomyosin

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8
Q

Characteristics of fibrous proteins

A

Low H2O solubility
Large amounts of repetitive secondary structures
Long cylindrical shape
Structural and strength

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9
Q

Collagens

A

Superfamily of proteins
Insuluble
In all tissue and organs but vary amount, more in cartilage, cornea, skin
Major ECM protein

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10
Q

Structure of collagen

A

Triple-helix structure

3 long individual alpha-chains > 600-3000 aa

25 different alpha-chains: same length but vary in primary sequence, encoded by diff genes
Homometric or heterometric

Diff mechanical properties

Center of alpha chains: repetitive aaa sequence rich in proline and lysine, glycine repeats each 3 aa

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11
Q

Hydroxylated proline and lysine by

A

Prolyl hydroxylase co factor with ascorbate, happen post-tl before triple helix formation

Add OH to form more H bonds, increase stability

Lysine: glycosylation by galactose or glucose

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12
Q

Collagen biosynthesis

A

Pre pro-alpha-chain with ER signal sequence > into ER, remove signal seq > hydroxylate proline and lysine > add sugar to selected hydroxylysine, pro-alpha chain
> 3 pro-alpha-chains form intra- & interchain disulfide bonds, with non-helical c/N terminal extensions = propeptides, pro-collage
> vesicles containing pro-collage bud off from ER > fuse with Golgi > secretory vesicles > release to ECM
>remove propeptides by C/N-pro-collagen peptidase > tropocollagen

Fragile & soluble to stable and insoluble, persistant

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13
Q

Fibillogenesis

A

Collagen molecules align in a staggered fashion overlapping its neighbors > cross linking due to lysyl oxidase > fibrills

Lysine by lysyl oxidase > allysine > aldehyde gp of allysine spontaneously nucleophilic addition with amino gp of lysine, form covalent bond, increase stability and insolubility

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14
Q

Lysyl oxidase dependent on

A

Cu2+

Copper chelating drug: penicillin
Inhibit this enzyme, reduce cross-linking: occipital horn syndrome and Menkes disease

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15
Q

Hole region

A

40 nm gap between adjacent collagen molecules in a row along the fibril axis

Sugar attached to 5’-hydroxylsyl residue in the hole region may be involved in the organization of fibril assembly

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16
Q

collagen involved in

A

Bone formation, site of bone mineralization

Collagen in teeth and bone is impregnated with calcium phosphate

17
Q

Causes for Collagen disorder = collagenopathy

A

Genetic defects in collagen genes

Genetic defects in genes encoding enzymes involved in collagen biosynthesis

Dietary deficiency of vitamin C, required for enzyme

Deficiency in copper

18
Q

Scurvy

A

Vitamin C deficiency

Inhibit hydroxylation of lysine and proline
Reduced interchain H bond, unstable collagen, unwound at low T

Subcutaneous extravasation of blood due to capillary fragility

Children: bone disease, hemorrhages, healing defects

Adults: hemorrhages, healing defects

Causes: malnutrition, chronic alcoholics, unsupplmented formula milk

19
Q

Ehlers-Danlos syndrome = EDS

A

Inherited disorder

Defects in processing enzymes

Affects connective tissues: skin, joint, blood vessel

6 forms of syndrome

Flexible joints
Stretchy or fragile skin

20
Q

Classical EDS

A

Type I and II
Mutations in the genes COL5A1 and COL5A2 encoding type V collage

Characterized by:
Fragile hypertensible skin
Joint hypermobility
Delayed wound healing
Hypotonia with delayed motor development

Mutated chains not secreted > degraded or accumulate > vascular problems

21
Q

Osteogenesis imperfecta

A

Brittle bone disease, bone easily bend and fracture

8 forms, type I to VIII

COL1A1 and COL1A2 mutations

22
Q

OI Type 1 = OI tarda

A

Often misdiagnosed as child abuse

Mutations in COL1A1 gene

Quantitative alterations: less synthesis of type 1 collagen, alpha1 and alpha2 chains

Characteristics:
Bone fractures
Blue or grey tint to the sclera
Hearing loss in adulthood
Retarded wound healing
Rotation/twisting of the spine
23
Q

OI Type II = congenita

A

Mutation in either COL1A1 or COL1A 2, most severe form

Point mutation and exon rearrangements in region coding for triple helical

Gly replaced by aa with bulky side chains

Prevent triple helix formation

Affected infants die in utero or shortly after birth from pulmonary hypoplasia

Deletion mutation of 84aa from alpha1 Col1A1 gene > shortened chains, prevent triple helix > all alpha chains degraded > lower levels of typr I collagen, lethal

24
Q

2 structural elements for elastin fibers

A

Central core of elastin

Surrounding network of fibrillin microfibrils sheath

25
Q

Elastin produced by

A

Fibroblasts and smooth muscle cells

26
Q

Elastin structure

A

Single polypeptide 750 aa, long, fibrous, water-insoluble

Enriched in nonpolar aa: gly, ala, val

Proline and lysine, not glycosylatednor hydroxylated

Strech and flexibility: lungs, skin, uterus, bv
Dominant ECM in arteries

27
Q

Production of elatin

A

Precursor named tropoelastin, secreted into ECM

Lysyl oxidase converts lys to allysine

Desmosine crosslinks: aldol condensation btwn 3 allysine and 1 lysine, yellow hue

Rubbery network

28
Q

Microfibril sheath

A

Embed elastin

Composed of fibrillin, glycoprotein, scaffold

2 isoforms, fibrillin-1 and -2 encoded by FBN-1 and FBN-2

29
Q

Marfan’s Syndrome

A

Defects in fibrillin 1 gene
AD
Results in:
Changes in mechanical properties of ECM
Loss of control of the bioavailability of many substances : TGF-beta
Excessive TGF-beta signaling > long bones, regulate connective tissue growth and architecture

30
Q

Symptoms of Marfan’s Syndrome

A

Skeletal abnormalities: overgrowth of longbones, scoliosis

Ocular changes: bilateral subluxation or dislocation

Cardiovascular lesions: mitral valve prolapse, dilation of ascending aorta

Aortic hemorrhage

FTM Exam 1 (23 decks)

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