Molecular Regulation of Insulin, Glucagon, and Developmental Processes

Fill-in-the-blank practice flashcards covering pancreatic islet hormone processing, glucose sensing, insulin/glucagon signaling pathways, and endocrine factors in fetal and developmental physiology.

In pancreatic islets, somatostatin is secreted by __________ cells and inhibits both insulin and glucagon secretion.

$$\delta\text{-cells}$$

Human preproinsulin contains a __________-amino-acid long signal peptide that guides the nascent protein into the endoplasmic reticulum.

$$24$$

The C-peptide is a __________-amino-acid chain that connects the insulin A and B chains in proinsulin.

$$31$$

C-peptide is cleaved out in the __________ and released into the bloodstream in equimolar amounts with insulin.

Golgi apparatus

C-peptide serves as a stable marker of beta-cell function because its blood half-life is __________ minutes, compared to 5–10 minutes for insulin.

$$30\text{--}35$$

Porcine (pig) insulin differs from human insulin by a single amino acid substitution at position __________ on the B-chain.

B30

Bovine (cow) insulin differs from human insulin by 3 amino acids located at positions A8, A10, and __________.

B30

In pancreatic beta cells, glucose phosphorylation is catalyzed by __________, which acts as the primary glucose sensor.

Glucokinase

When ATP levels rise in pancreatic beta cells, ATP-sensitive $K^+$ channels __________, leading to cell membrane depolarization.

close

Depolarization of the beta-cell membrane opens voltage-gated __________ channels, inducing exocytosis of insulin.

$$\text{Ca}^{2+}$$

In sympathetic regulation of insulin, activation of __________-adrenergic receptors decreases insulin secretion.

$$\alpha_2$$

The PI3K–Akt signaling pathway regulates GLUT4 translocation, lipogenesis, glycogen synthesis, and the inhibition of __________.

gluconeogenesis

The insulin-responsive glucose transporter found in heart, skeletal muscle, and adipose tissue is __________.

GLUT4

Cleavage of proglucagon by the enzyme __________ in pancreatic alpha cells produces mature glucagon.

PC2

In intestinal L-cells, proglucagon is cleaved by the enzyme __________ to yield GLP-1, GLP-2, and other peptides.

PC1/3

Hunger hormone ghrelin is secreted by specific enteroendocrine cells designated as __________ cells.

D/P1

Hypothalamic secretion of __________ stimulates growth hormone release from somatotropic cells, whereas somatostatin inhibits it.

GHRH

Thyroid hormone insufficiency during early human development can lead to severe neurodevelopmental deficits termed __________.

neurological cretinism

The placental hormone __________ maintains progesterone production from the corpus luteum during early pregnancy.

hCG (Human Chorionic Gonadotropin)

During labor, the placental hormone __________ acts to relax pelvic ligaments and soften the cervix.

Relaxin

In late gestation, fetal glucocorticoids promote lung maturation by stimulating type II pneumocytes to increase __________ production.

surfactant

Male sexual differentiation is initiated by the __________ gene on the Y chromosome, which activates downstream expression of SOX9.

SRY

Fetal testicular secretion of __________ promotes the regression of Müllerian ducts in male embryos.

AMH (Anti-Müllerian Hormone)

Conversion of testosterone to DHT for male external genital development is catalyzed by the enzyme __________.

$$5\alpha\text{-reductase}$$