Loading....
Coupon Accepted Successfully!

Biochemistry

Open Flashcards

Vitamins, Harmones and Hemoglobin

Question
58 out of 82
 

Which of the following statements correctly describes insulin?



A It is an anabolic signal to cells that glucose is scarce

B It is converted from proinsulin to insulin primarily following secretion from β cells

C It does not have a prohormone form

D Its action is antagonistic to that of glucagon

Ans. D Its action is antagonistic to that of glucagon

a. The action of insulin is antagonistic to that of glucagon, which is a catabolic hormone secreted by the α cells of the pancreas. The anabolic hormone called insulin is synthesized in the endo plasmic reticulum of pancreatic β cells as a nascent polypeptide chain called preproinsulin.

b. Immediately following synthesis, the amino terminal signal sequence of 16 residues is cleaved off to form proinsulin.

c. Proinsulin is composed of one continuous polypeptide that contains in sequence an A chain of 21 residues, a connecting peptide (C peptide) of about 30 residues, and a B chain of 30 residues.

d. The molecule is folded so that two disulfide bridges span the A and B chains. The proinsulin molecule is transported from the lumen of the endoplasmic reticulum to the Golgi apparatus, where it is packaged into storage granules.

e. In the Golgi apparatus and in the storage granules, proteolysis of the C peptide occurs. Exocytosis of the granules releases insulin as well as C peptides into the bloodstream.

Vitamins, Harmones and Hemoglobin Flashcard List

82 flashcards
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
12)
13)
14)
15)
16)
17)
18)
19)
20)
21)
22)
23)
24)
25)
26)
27)
28)
29)
30)
31)
32)
33)
34)
35)
36)
37)
38)
39)
40)
41)
42)
43)
44)
45)
46)
47)
48)
49)
50)
51)
52)
53)
54)
55)
56)
57)
58)
59)
60)
61)
62)
63)
64)
65)
66)
67)
68)
69)
70)
71)
72)
73)
74)
75)
76)
77)
78)
79)
80)
81)
82)