Exam 3

Question 1

Types of Keratin

Answer 1

Type I

acidic + negative charged

Type II

basic + positively charged

fibrous proteins = insoluble

Question 2

3 Alpha-keratin classification

Answer 2

Simple - embryonic and one-layered epithelia

Barrier - epidermis of the skin

Structural - hair and nails

Question 3

Strct of Keratin

Answer 3

right-handed alpha helix

entwined + linked

in a left-handed coiled-coil

2 alpha helix – two-chain coiled coils – protofilament – intermediate filament (32 alpha helix or 8 protofilaments)

Question 4

Arsenic Trap

Answer 4

Arsenic + heavy metals bind to thiol groups affecting crosslinking

disulfide bonds are reversible

Question 5

Strct of Collagen

Answer 5

3 left-handed alpha helix twist to form a

right-handed triple helix (3 coiled alpha helices)

short tight helix w/ only 3 AA per turn

(usually 4 AA per turn so tight turn present)

oppo of keratin

Question 6

What cells produce collagen?

What are its major AA components?

Answer 6

fibroblast, muscle cells, epithelia cells

33% glycine

21% proline + hydroxyproline

Question 7

Steps to Synthesis

Answer 7

in rER, preprocollagen is made

in lumen of ER + Golgi App, self-assembly of tropocollagen occurs, triple-helix formation

in ECM, cleavage of procollagen to collagen + self-assembly of collagen molecules into fibrils + fibers occurs

Question 8

Elastin

Answer 8

rubber-like properties allow for these tissues to return to a pre-stretched state

hydrophobic effect is the primary force that allows stretched elastin to reform

very stable (T_1/2=70 years)

insoluble + highly cross-linked

Question 9

Keratinopathies

epidermolysis bullosa simplex

Answer 9

mutation in KRT 5 + KRT14

severe blistering of the skin

due to severe tissue fragility

tissues is easily damaged by pressure + rubbing

Question 10

Collagenopathies

Osteogenesis Imperfecta

Answer 10

OI Type I

not enough collagen being produced

OI Type II

mutation causing sub for Gly Res = unstable collagen

THE PROBLEM

osteoclast outpace osteoblast = brittle fragile bones

Treat

bisphosphonates which inhibit osteoclast

Blue Sclera telltale sign

Question 11

Collagenopathy

Ehlers-Danlos

Answer 11

Single Gene Mutation

Defects in assembly or synthesis of Type V collagen

stretchable skin, hypermobile joints, short stature

Lethal Form

Type III Collagen Mutation

blood vessel aneurysms

Question 12

Scurvy

Answer 12

lack of Vit C

lack of hydroxylation of collagen Pro + Lys residues

bleeding gums, poor wound healing, fatigue

Question 13

Elastin

Answer 13

alternating hydrophobic + hydrophilic regions

hydrophobic effect

very very stable due to high crosslinking by lysyl oxidase

70 year half life

Question 14

alpha1 antitrypsin deficiency

Answer 14

alpha1 antitrypsin inhibits elastase

w/o alpha1 antitrypsin = active elastase

breakdown of elastic fibers in lungs = COPD

Question 15

I Cell Disease

Answer 15

defect in first step of mannose 6 P biosynthesis

inability to P mannose

leads to a lysosomal storage disorder

accumulation of glycoprotein + glycolipids

skeletal abnormailties

Question 16

Myasthenia Gravis

Answer 16

autoimmune disease

ionotropic NAChR are blocked by antibodies

Question 17

GLUT I Deficiency

Answer 17

important BBB

causes seizures + developmental delay

low CNS glucose w/o hypoglycemia

ketogenic diet

treat w/ triheptaonin (helps w/ FA metabolism)

Question 18

Cystic Fibrosis

Answer 18

defective chlorine transport

hyperviscous secretions

CFTR acts as a channel instead of a transporter

∆F508 mutation in Class II IV