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FA - Biochemistry > Biochem - Cellular (Collagen synthesis, structure, & conditions) > Flashcards

Biochem - Cellular (Collagen synthesis, structure, & conditions) Flashcards

Pg. 79-81 in First Aid 2014 Sections include: -Collagen -Collagen synthesis and structure -Osteogenesis imperfecta -Ehlers-Danlos syndrome -Menkes disease -Elastin

1
Q

What is the most abundant protein in the human body?

A

Collagen

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2
Q

Briefly describe the modification of collagen.

A

Extensively modified by posttranslational modification

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3
Q

What is the function of collagen?

A

Organizes and strengthens extracellular matrix

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4
Q

What are the types of collagen? Where is each mainly found?

A

(1) Type I - Bone, Skin, Tendon (2) Type II - Cartilage (including hyaline) (3) Type III - Reticulin (4) Type IV - Basement membrane; Think: “Be (So Totally) Cool, Read Books”

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5
Q

What is the most common type of collagen? What percentage of collagen is this type?

A

Type I - Most common (90%)

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6
Q

Where/In what context(s) is Type I collagen found (give 7)?

A

Bone (made by osteoblasts), Skin, Tendon, dentin, fascia, cornea, late wound repair; Think: “type I: bONE”

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7
Q

In what condition is production of type I collagen decreased?

A

Decreased production in osteogenesis imperfecta type I

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8
Q

Where is Type II collagen found (give 3)?

A

Cartilage (including hyaline), vitreous body, nucleus pulposus; Think: “type II: carTWOlage”

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9
Q

Where is Type III collagen found (give major category & 5 examples)?

A

Reticulin - skin, blood vessels, uterus, fetal tissue, granulation tissue

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10
Q

In what condition is Type III collagen deficient?

A

Type III: deficient in the uncommon, VASCULAR type of Ehlers-Danlos syndrome (Think: “ThreE D”)

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11
Q

Where is Type IV collagen found (give 3)?

A

Basement membrane, basal lamina, lens; Think: “type IV: under the FLOOR (basement membrane)

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12
Q

In what condition is Type IV collagen defective?

A

Defective in Alport syndrome

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13
Q

In what condition is Type IV collagen targeted by autoantibodies?

A

Targeted by autoantibodies in Goodpasture syndrome

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14
Q

Where does collagen synthesis occur? What is the mechanism and amino acids involved?

A

Synthesis (RER); Translation of collagen alpha chains (preprocollagen) - usually Gly-X-Y (X and Y are proline or lysine).

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15
Q

What amino acid content best reflects collagen synthesis, and why?

A

Glycine content best reflects collagen synthesis (collagen is 1/3 glycine)

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16
Q

Where does collagen hydroxylation occur? What occurs during this?

A

Hydroxylation (RER); Hydroxylation of specific proline and lysine residues (requires vitamin C; deficiency –> scurvy)

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17
Q

What is required for hydroxylation of collagen? What condition results from deficiency of this?

A

Hydroxylation of specific proline and lysine residues (requires vitamin C; deficiency –> scurvy)

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18
Q

Where does glycosylation of collagen occur? What occurs during this?

A

Glycosylation (RER); Glycosylation of pro-alpha-chain hydroxylysine residues and formation of procollagen via hydrogen and disulfide bonds (triple helix of 3 collagen alpha chains)

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19
Q

What condition results from problems forming triple helix of collagen?

A

Problems forming triple helix –> osteogenesis imperfecta

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20
Q

What occurs during exocytosis of collagen?

A

Exocytosis of procollagen into extracellular space

21
Q

What are 4 steps of collagen synthesis/modification that occur inside fibroblasts?

A

(1) Synthesis (RER) (2) Hydroxylation (RER) (3) Glycosylation (RER) (4) Exocytosis

22
Q

What occurs during proteolytic processing of collagen?

A

Cleavage of disulfide-rich terminal regions of procollagen, transforming it into insoluble tropocollagen.

23
Q

What occurs during cross-linking of collagen?

A

Reinforcement of many staggered tropocollagen molecules by covalent lysine-hydroxylysine cross-linkage (by Cu2+-containing lysyl oxidase) to make collagen fibrils

24
Q

What condition results from problems with cross-linking of collagen?

A

Problems with cross-linking –> Ehlers-Danlos

25
Q

What are 2 steps of collagen synthesis/modification that occur outside fibroblasts?

A

(1) Proteolytic processing (2) Cross-linking

26
Q

What is osteogensis imperfecta? What is another name for it? What causes it?

A

Genetic bone disorder (brittle bone disease) caused by a variety of gene defects

27
Q

What is the most common form of osteogenesis imperfecta? What is the phenotypic defect in this case?

A

Most common form is autosomal dominant with decreased production of otherwise normal type I collagen

28
Q

What are 4 manifestations of osteogenesis imperfecta?

A

OI manifestations can include: (1) Multiple fractures with minimal trauma; may occur during birth process (2) Blue sclerae due to translucency of the connective tissue over the choroidal veins (3) Hearing loss (abnormal ossicles) (4) Dental imperfections due to lack of dentin

29
Q

With what may osteogenesis imperfecta be confused?

A

May be confused with child abuse

30
Q

What skeletal findings may be seen in the x-ray of a child with osteogenesis imperfecta?

A

Severe skeletal deformity and limb shortening due to multiple fractures in a child

31
Q

What is Ehlers-Danlos syndrome? How does it present (3 symptoms)?

A

Faulty collagen synthesis causing hyperextensible skin, tendency to bleed (easy bruising), and hypermobile joints.

32
Q

How many types of Ehlers-Danlos syndrome exist? How do they vary? What are the options for inheritance?

A

6 + types. Inheritance and severity vary. Can be autosomal dominant or recessive.

33
Q

What are 3 conditions/outcomes with which Ehlers-Danlos syndrome can be associated?

A

May be associated with joint dislocation, berry and aortic aneurysms, organ rupture.

34
Q

What is the most common type of Ehlers-Danlos syndrome? What defines it?

A

Hypermobility type (joint instability): most common type

35
Q

What 2 symptoms are associated with classical type of Ehlers-Danlos syndrome? What causes it?

A

Classical type (joint and skin symptoms): caused by a mutation in type V collagen

36
Q

What 2 symptoms are associated with vascular type of Ehlers-Danlos syndrome? What causes it?

A

Vascular type (vascular and organ rupture): deficient type III collagen

37
Q

What is Menkes disease, and what causes it?

A

Connective tissue disease caused by impaired copper absorption and transport

38
Q

Menkes disease leads to decreased activity of what, and why?

A

Leads to decreased activity of lysyl oxidase (copper is a necessary cofactor)

39
Q

What are 3 symptoms associated with Menkes disease?

A

Results in brittle, “kinky” hair, growth retardation and hypotonia

40
Q

What is elastin? What are 6 locations in which it is found?

A

Stretchy protein within skin, lungs, large arteries, elastic ligaments, vocal cords, ligamenta flava (connect vertebrae –> relaxed and stretched conformations)

41
Q

What is the function ligamentum flava?

A

ligamenta flava (connect vertebrae –> relaxed and stretched conformations)

42
Q

In what 2 amino acids are elastin rich, and in what form are they?

A

Rich in proline and glycine, nonhydroxylated forms

43
Q

What forms scaffolding for tropoelastin?

A

Tropoelastin with fibrillin scaffolding

44
Q

What takes place to give elastin its elastic properties, and where does it occur?

A

Cross-linking takes place extracellularly and gives elastin its elastic properties

45
Q

What breaks down elastin? What normally inhibits this enzyme?

A

Broken down by elastase, which is normally inhibited by alpha1-antitrypsin

46
Q

What causes Marfan syndrome?

A

Marfan syndrome - caused by a defect in fibrillin, a glycoprotein that forms a sheath around elastin

47
Q

What deficiency causes Emphysema, and what results from this deficiency?

A

Emphysema - can be caused by alpha1-antitrypsin deficiency, resulting in excess elastase activity

48
Q

What causes wrinkles of aging?

A

Wrinkles of aging are due to decreased collagen and elastin production

FA - Biochemistry (31 decks)

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