Test 162  (Biochemistry )

1. With regard to collagen molecule:

a. it is formed from trimers

b. it is formed from polypeptides containing a chains

c. glycine accounts for one-third of amino acids found
    within collagens

d. it contains less hydroxyproline than elastin

e. ascorbate is essential for hydroxylation of proline 
 

Answera.T   b.T   c.T   d.F   e.T
Elastin contains little or no hydroxyproline.
 
 

2. Type I collagen:

a. contains two a1 chains and one a2 chain

b. is the most common collagen

c. is the main type of collagen found in basement 
    membrane

d. is found in skin and bone

e. is found in cornea 
 

Answera.T   b.T  c.F  d.T  e.T
The alpha chains determine the types of collagen. 
Type 4 is the main type of collagen found within the basement membrane.
.
 
 

3. Elastin:

a. is synthesized only by the liver

b. contains cross-linking polypeptides involving lysine

c. is the most common connective tissue in lungs

d. is digested by a1-antitrypsin

e. can be stretched to several times its length and can 
    still return to its original shape.
 

Answer
a.F   b.T  c.T   d.F  e.T
Elastin is synthesized by liver and macrophages and other body tissues. Alpha1-antitrypsin prevents elastase from digesting the elastin.
 

4. Vitamin B₁₂:

a. is fat-soluble

b. requires a glycoprotein from absorption

c. contains a haeme ring

d. is required for the conversion of homocysteine to 
    methionine

e. is need for myelination of nerve fibres

Answer
a.F   b.T  c.F  d.T  e.T
Vitamine B12 is water soluble.
Intrinsic factor is a glycoprotein. Corre ring rather than haeme ring is found in vitamin B12. 
 
 

5. In mucopolysaccharidoses:

a. the production of proteoglycan is increased

b. proteoglycan degradation is reduced

c. the lysosomal enzyme is defective

d. the urine excretes excess oligosaccharides

e. the body has an increased accumulation of 
    glycoaminoglycans
 

Answer
a.F   b.T  c.T d.T  e.T
The synthesis of proteoglycan but the degradation is defective due to defective lysosomal enzyme.
.

 

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