Clinical cases and Situational tasks

44. A 22-year-old soldier collapses from dehydration during maneuvers in the desert and is sent to a military hospital. Prior to enlisting, a physician observed a high level of glucose in his urine during an examination. At first, he was not allowed to enlist because he was suspected of being a diabetic. Further tests, however, determined that his insulin level was normal. A glucose tolerance test exhibited a normal pattern. Laboratory tests following his dehydration episode repeat the previous findings, but further testing of the urine reveals that only D-glucose is elevated. Other sugars were not elevated. Deficiency in which transporter caused the dehydration of this patient’s?

Answer: The patient has normal levels of blood insulin and exhibits a normal glucose tolerance test. This indicates that glucose absorption from the intestine is normal as is clearance of glucose from the blood. The presence of glucose in the urine is most likely a kidney problem. Because the defect seems to involve only D-glucose and no other sugar, this points to a transporter with high specificity. The kidney has the GLUT 2, SGLT1, and SGLT2 transporters. GLUT 2 and SGLT1 are present in other tissues, and a defect in these would be expected to result in more serious sequelae. SGLT2 is a sodiumdependent glucose transporter specific to the kidney that has a high specificity for glucose. The glucose is present in the urine because of a failure to reabsorb it as a consequence of a defect in SGLT2. This leads to a loss of water also, because it is reabsorbed with glucose.

Section XVII Biochemical constituents of connective tissue

1. What biochemical process is not typical for connective tissue of elderly persons?

A. Reduction of collagen

B. Reduction of water

C. Increasing of collagen

D. Reduction of glycosaminoglycans

E. Reduction of hyaluronic acid

2. What amino acids are rare in elastin - a protein component of elastin fibers?

A. Nonpolar

B. Polar

D. Acidic

E. Basic

3. Name hormones that inhibit synthesis of proteoglycans and collagen in connective tissue:

A. Glucocorticoids

B. Somatomedins

C. Somototropin

D. Insulin

E. Androgens

4. Increased content of oxyproline in blood and urine with lesions of joints and bones is observed due to increased catabolism of:

A. Collagen.

B. Hyaluronic acid.

C. Glycosaminoglycans.

D. Proteoglycans.

E. Elastin.

5. What amino acids, which comprise the structure of collagen, are genetically encoded?

A. Hydroxyproline, hydroxylisine

B. Serine, glycine

C. Alanine, valine

D. Glutamic acid, glutamine

E. Phenylalanine, tryptophan

6. Influence of hypovitaminosis C on the structure of collagen fibers caused by decreased activity of enzymes:

A. Lysyl hydroxylase, proline hydroxylase

B. Lysyl oxidase, lysyl hydroxylase

C. Glycosil transferase

D. Procollagen peptidase

E. Collagenase.

7. Hydroxyproline is an important amino acid within the collagen biosynthesis. Indicate vitamin which is participated in the formation of this amino acid by hydroxylation of proline?

A. C

B. D

C. B₁

D. B₂

E. B₆

8. Defection of the structure of collagen fibers occurs during deficiency of vitamin C due to the fact that this vitamin is a cofactor of:

A. Lysine hydroxylase, proline hydroxylase

B. Lysine hydroxylase and collagenase

C. Glycosil transferase

D. Procollagen peptidase

E. Collagenase

9. Indicate the most common amino acid residues in collagen.

A. Oxyproline, oxylysine, glycine, proline

B. Tryptophan, cysteine, glycine, methionine

C. Lysine, arginine, cysteine, tryptophan

D. Tryptophan, oxylysine, cysteine, valine

E. Asparagine, glutamine, lysine

10. Gram-positive bacteria produce a protective capsule of hyaluronic acid, which increases their pathogenicity. What enzyme can "destroy" the protective capsule?

A. Hyaluronidase

B. Carboxypeptidase

S. Aminopeptidase

D. Alpha glycosidase

E. Collagenase

11. What class of glycosaminoglycans, due to the large number of carboxyl groups, binds large amounts of water and supports tissue turgor?

A. Hyaluronic acid.

B. Dermatan sulfate.

C. Keratan sulfate.

D. Heparin.

E. Chondroitin sulphate

12. Insolubility of collagen connective tissue and its metabolic resistance to various agents is caused by amino acid composition and special structure of the protein. Indicate amino acids that quantitatively dominate in the structure of collagen?

A. Glycine, proline, alanine

B. Methionine, serine, threonine.

C. Phenylalanine, tyrosine, tryptophan.

D. Cysteine, threonine, glutamine.

E. Arginine, histidin, phenylalanine.

13. Protein procollagen is synthesized by fibroblasts of connective tissue. Thereafter glycosylation occurs. What carbohydrates bind to procollagen?

A. Galactose, glucose

B. Fructose, mannose

C. Ribose, deoxyribose

D. Arabinose, sucrose

E. Ribulose, xylulose

14. Collagen and elastin are fibrillar elements of connective tissue. Specify the amino acid, which is a component only of the collagen and its determination is used to diagnose several disorders of connective tissue:

A. Hydroxyproline

B. Proline

C. Glycine

D. Lysine

E. Hydroxylysine

15. After wound healing a scar was formed. What is the main component of this type of connective tissue?

A. Collagen

B. Elastin

C. Hyaluronic acid

D. Chondroitin sulfate

E. Keratan sulfate

16. What factors trigger the biosynthesis of glycosaminoglycans?

A. Vitamin A, manganese ions

V. Vitamin D, iron ions

S. Vitamin D, calcium ions

D. Vitamin C and copper ions

E. Vitamin E, zinc ions