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Biochemistry

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Amino Acids, Proteins and Porphyrins

Question
81 out of 107
 

Triple helix is found in



A Cystine
B Collagen

C Pectin
D DNA

Ans. B collagen

1. Extra cellular matrix contains 3-major class of Biomolecules

a. Structural proteins — collagen and Elastin

b. Specialized proteins: - Fibrillin, fibronectin and Laminin

c. Proteoglycans

2. Collagen:

a. Most abundant protein in animal word, constitutes about 25% of the protein in mammals

b. About 19 distinct types of collagen, are identified in human tissue.

c. All collagen types have a Triple helical structure.

d. A striking characteristic of collagen is the occurrence of glycine residues on every third position ie.

(gly-x-y-gly-x-y….. ) n. About 100 of x-position are proline and about 100 of Y-position are

Hydroxyproline.

e. Post translational Hydroxylation of prolineHydroxyproline by Prolyl Hydroxylase, whose co-

factors are vit. C and α-Ketoglutarate which are also cofactors for lysyl hydroxylase (converts lysine hydroxylysine).

3. Glycosylation of Hydroxylysinethrough an 0-Glucosidic linkage, unique to collagen.

f. 6. Collagens are further stabilized by the formation of covalent cross-links mediated by Lysyl oxidase

(a copper dependent enzyme)

g. 7. Abnormities of collagen synthesis eg.

A. Osteogenesisimperfectaabnormalities in gene coding for pro-collagen α-1 (i.e. Type I- collagen)

B. Ehlers’ Danlos-syndrome (EDS) -

Type IV EDS: - Most serious vascular type - due to abnormalities in type III collagen. (Autosomal dominant)

Type VI EDS: - Due to deficiency of Lysyl Hydroxylase.

Type VII, C; EDS Deficiency of pro-collagen-N-Proteinase.

C. Menkes’s disease: - Abnormal copper transport due to mutation in ATP7A gene C/B

kinky hair, Growth retardation.

D. Alport’s syndrome: - Due to mutation in genes encoding Type IV collagen.

E. EpidermolysisBullosa: - Due to mutation in COL7A1 affecting the structure of type VII collagen

Epidermolysisbullosa simplex - Due to mutation in Keratin 5

DNA is Double helix structure.

Amino Acids, Proteins and Porphyrins Flashcard List

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