Fibrous Proteins and Proteoglycans 🧬

Question 1

Hydroxyproline in Collagen

Answer 1

Hydroxyproline residues are needed for collagen stability and require vitamin C for their formation. A deficiency in vitamin C can lead to scurvy.

Question 2

Collagen Synthesis

Answer 2

Collagen is synthesized as soluble procollagen before release into the extracellular matrix.

Question 3

Aortic Dissections

Answer 3

Rupture of aortic dissections leads to a high number of deaths. Main characteristics include unusual tall stature, long limbs, arachnodactyly, scoliosis, and increased joint flexibility.

Question 4

Proteoglycans

Answer 4

Proteoglycans fill the extracellular space and attract water. They are involved in many functions, like shock absorbing in joints and they also facilitate cell migration and wound healing.

Question 5

Osteogenesis Imperfecta (OI)

Answer 5

Brittle bone disease caused by mutations in COL1A1 or COL1A2 genes, affecting collagen Type I and resulting in bone fragility.

Question 6

Marfan Syndrome

Answer 6

Hereditary defect in the FBN1 gene encoding fibrillin-1, resulting in abnormalities in elastic fibers and affecting the skeleton, cardiovascular system, and eyes.

Question 7

Cross-linking

Answer 7

Cross-linking in elastin is initiated by lysyl oxidase, leading to the formation of allysine residues such as desmosine and isodesmosine, unique to elastin.

Question 8

Collagen Structure

Answer 8

Collagen is a triple-helix of three a-chains which are about 1,000 amino acids long. It can be covalently cross-linked and provides mechanical strength in tendons and bones.

Question 9

Lysyl Oxidase

Answer 9

Lysyl oxidase is involved in covalent cross-linking between tropocollagen molecules, contributing to collagen stability. It requires copper for its role, and copper deficiency can have negative effects.

Question 9

Glycine in Collagen

Answer 9

Glycine, with the smallest side chain, is found in each third position of collagen, contributing to its distinctive amino acid composition.

Question 10

Procollagen

Answer 10

Formed in fibroblasts, osteoblasts, or chondroblasts with propeptides.

Question 11

Biosynthesis of Collagen Type I

Answer 11

Involves expression of COL1A1 and COL1A2 genes, pro-a1 and pro-a2 chains linked by chaperones, and hydroxylation of proline and lysine residues.

Question 12

Lysyl Oxidase

Answer 12

Enzyme that oxidatively deaminates lysine or hydroxylysine residues in collagen, forming allysine or hydroxyallysine residues.

Question 13

Menkes Disease

Answer 13

An X-linked disease caused by defective copper absorption and impaired lysyl oxidase activity, leading to symptoms like kinky hair, skin hypopigmentation, and osteoporosis.

Question 14

O-glycosylation

Answer 14

Process of linking activated sugars directly to proteins step by step. The first sugar is linked in the endoplasmic reticulum (ER) and additional sugars are added in the Golgi membrane.

Question 15

Collagenopathies

Answer 15

Group of connective tissue disorders caused by collagen gene mutations affecting collagen Type V or collagen Type III, leading to various symptoms.

Question 16

N-glycosylation

Answer 16

Formation of a mannose-rich oligosaccharide bound to dolichol pyrophosphate then linked to the nitrogen of an asparagine side chain in one step. Modifications occur in the ER and Golgi.

Question 17

Ehlers-Danlos Syndromes

Answer 17

Disorder involving abnormal collagen Type III or V due to gene mutations or deficient enzymes. Vascular form leads to fragility of skin and vessels, while the classic form causes joint hypermobility and skin hyperextensibility.

Question 18

mRNA

Answer 18

mRNA is a molecule that carries genetic information from DNA to the ribosome for protein synthesis.

Question 19

Tropoelastin

Answer 19

Tropoelastin is a soluble linear polypeptide secreted by elastogenic cells into the extracellular matrix (ECM), consisting of about 700 amino acids.

Question 20

Fibrillin-1

Answer 20

Fibrillin-1 is a large glycoprotein that forms the microfibrillar scaffold in elastic fibers, providing biomechanical support and interacting with integrins and growth factor signaling.

Question 21

Marfan Syndrome

Answer 21

Genetic disorder affecting elastic fibers due to mutation in the fibrillin-1 gene. Characteristics include tall stature, long limbs, arachnodactyly, lens dislocation, aortic root dilation, and abnormal rib cage.