Fibrous Proteins Chapter 4 Flashcards
1
Q
page 43
Overview
- Collagen and elastin are examples of ?
- what is the general trait of collagen and elastin ?
- Fibrous structures exhibit what type of structure ?
A
- fibrous proteins of the extracellular matrix ECM
- serve structural functions in the body
- regular, secondary structures
2
Q
page 43
II. Collagen
- what is the most abundant protein in the human body ?
- how would you describe it’s structure ?
- what is the name of this structure ?
- how many helix are involved in forming this collagen ?
A
- Collagen (abundant)
- 3 polypeptide chains braided - rope like and rigid
- Alpha chains
- triple helix
3
Q
Collagen
- when collagen is dispersed as a gel; it supports ?
- Collagen can be formed in what forms ?
- collagen formed in tight parallel fibers support what ?
- Collagen that are “stacked” support what ?
- collagen in bone are arranged how ?
- when collagen in bone are arranged in angle; describe the support that it porvides ?
A
- vitrous humor of the eye
- gel, tight parralel fibers and in stacks
- tendons
- cornea of the eye; prevent light from scattering
- in an angle to each other
- it resist mechanical shear from any direction
4
Q
page 44.
TYPES of Collagen
- name all the types of “FIBRIL-FORMING collagen ?
- name the network forming collagen ?
- Name the two types of FIBRIL-ASSOCIATED collagen ?
A
- type I
- type II
- type III
- type IV
- type VIII
- type IX
- type XII
5
Q
page 45.
Structure
1. Amino Acid Sequence
- A.A. sequence : what amino acid is collagen rich of ?
- both of which are important in the formation of ?
- What type of AA dictates the helical confomation of the alpha chain (CANNOT be an ALPHA helix ! )
- What AA is the smallest & found in every THIRD position ?
- Residues part of the repeating sequence ?
A
- Glycine and Proline
- triple-stranded helix
- Proline
- Glycine
- Gly-X-Y ( X = proline and Y = Hydroxyproline
6
Q
Page 45.
Structure
2. Hydroxyproline and Hydroxylysine
- collagen contains “non-standard” A.A. which are ?
- what does the hydroxylation event refer to ?
- maximizes formation of interchain hydrogen bonds ?
A
- hydroxyproline and hydroxylysine (result from hydroxylation of proline and lysine)
- post transitional modification
- generation of hydroxyproline
7
Q
page 45
Structure
3. Glycosylation
- what group is glycosylated in this event ?
- what was attached to the polypeptide chain “before” triple helix formation
A
- the hydroxyl group of hydroxylysine residue of collagen is glycosylated.
- glucose and galactose
8
Q
page 45
C. Steps in Biosynthesis Colleagen
- polypeptide precursors are Formed where?
- Modified and then–are formed into how many helix ?
- The triple helix is Released into where ?
- what do mature ECM-collagen do ?
A
- polypeptide precursors are formed (synthesized) in FIBROBLASTS
- they are modified** – then **form the triple helix
- triple helix is relesead (secreted) into ECM
- mature ECM-collagen aggregate** and **cross-link to form collagen fibers
9
Q
Page 45
C. Biosyntheis
1. Pro -Alpha Chain formation
- one of the many proteins that function outside of the cell?
- precursors of alpha chains contain what ?
- what is the role of this N-terminal sequence ? give 3
A
- collagen
- special amino acid “sequence”** at their **N-terminal ends
- acts as a signal molecule
- (facilitate binding of ribosomes to the RER)
- directs passage of the precursor chain into the lumen of the RER
10
Q
steps of biosythesis of collagen proteins
A
- Pro- alpha chains formation – pre-pro Alpha chains
- hydroxylation
- Gycosylation
- Assembly and secretion
- extra cellular cleavage of procollagen molecules
11
Q
page 48.
Degradation
- collagen have half lives for as long as ?
- connective tissue remodel is constant in response to ?
- the breakdown of collagen is dependent on ?
- collagenases is big part of the family of ?
- Type I collagen’s cleavage specificity ?
- fragments are degraded by ?
A
- several years
- growth and injury of tissues
- proteolytic action of collagenases
- metalloproteinases
- makes three quarter and one quarter length fragments
- matrix proteienases
12
Q
page 48.
Collagenopathies
- Name three examples based from this text book ?
- Describe each disorder in general terms ?
A
- Scurvy
- Ehlers-Danlos syndrome
- Osteogenesis imperfecta
- deficient in vit C ( needed for hydroxylation) decreased collagen tensile strength
- Mutations to type V (severe mutations are in gene type III lethal vascular problems
- fragile bones( mutation in gene type I collagen) abnormal alpha chains prevent from folding into a triple helical-formation
13
Q
Elastin
- Define: Is elastin is soluble or insoluble ?
- elastin is made from a precursor called ?
- Where is tropoelastin secreted from ?
- Name examples of which tropoelastin interacts with
- mutations in fibrillin causes what type of syndrome ?
A
- insoluble protein polymer
- made from a “precursor” tropoelastin
- Tropoelastin: secreted from the cell
- Tropoelastin interacts with
- glycoprotein
- microfibrils (fibrillin)
- mutations in fibrillin ( causes Marfan Syndrome)
14
Q
Alpha 1 - Antitrypsin (AAT)
- where is AAT produced ?
- role of AAT (what does it inhibit) ?
- blood and other bodily fluids contain a protein called ?
- AAT inhibits a number of proteolytic enzymes like ?
- general inhibitor of what protein ?
- trypsin is converted into ___________ by the pancreas.
A
- produced primarily by the liver
- inhibits elastase-catalyzed degradation of elastin in the aveolar walls
- Alpha 1 Antitrypsin
- peptidases, protease and proteinase
- Trypsin
- Trypsinogen
15
Q
EDS (Ehlers- Danlos Syndrome)
A
Mutation in type V collagen
faulty collagen synthesis
hypermobile joints
joint dissociation
autosomal recessive or dominant
