Endocrine System Biochemistry 1

Question 1

Which endocrine gland has one of the highest concentrations of vitamin C in the body?

Answer 1

Adrenal gland. Both the adrenal medulla and cortex rely highly on ascorbic acid as a cofactor for steroidogenesis and catecholamine synthesis.

Question 2

What kind of hormones act on plasma membrane receptors coupled with regulatory molecules like G proteins?

Answer 2

Water-soluble hormones (ex: amino-acid based hormones, except the thyroid hormone)

Question 3

What mineral is needed as a cofactor for G-protein cell signaling?

Answer 3

Magnesium is required for the stimulation of adenylyl cyclase and locks the G protein’s alpha subunit in a conformation where it can dissociate from the beta-gamma dimer.

Question 4

When is a G-protein active?

Answer 4

If GTP is bound to it then it is active, but it is inactive when GDP is bound to it

Question 5

What kind of hormones act on intracellular receptors?

Answer 5

Lipid-soluble hormones (ex. steroid hormones)

Question 6

True or false: insulin and glucagon are synthesized by their parent endocrine cells as prohormones.

Answer 6

True. Prohormones are inactive precursors of hormones. This is beneficial so that there can be ample supply nearby when they are needed and thus can be activated.

Question 7

What element does insulin bind to in its hexamer form for storage?

Answer 7

Zinc

Question 8

What type of signal transduction pathway does insulin work through to increase the uptake of glucose?

Answer 8

Tyrosine Kinase. This eventually affects GLUT4 translocation and thus increase glucose uptake.

Question 9

What are some examples of second messengers?

Answer 9

DAG and IP3. Second messengers are intracellular molecules that (when exposed to first messengers) signal various physiological changes.

Question 10

What cofactor is used in conversion of norepinephrine to epinephrine?

Answer 10

S-Adenosyl methionine (SAM) This conversion is catalyzed by norepinephrine N-methyl transferase.

Question 11

Which hormone has the greatest control over free fatty acid release from adipose tissue?

Answer 11

Catecholamines. They bind to beta-adrenergic receptors and activate G protein activity.

Question 12

Which other hormones activate lipolysis in adipose tissue?

Answer 12

Glucagon, adrenocorticotropic hormone, alpha-melanocyte-stimulating hormone, and thyroid-stimulating hormone. Lipolysis is the process where lipids are broken down (by hydrolysis) to release fatty acids.

Question 13

What hormones are needed to stimulate conversion of cholesterol to pregnenolone in endocrine organs?

Answer 13

Adrenocorticotropin hormone in the adrenals and luteinizing hormone in the ovaries and testes

Question 14

The process by which androgens are transformed into estrogens is called what?

Answer 14

Aromatization, because the reactions are catalyzed by the aromatase enzyme.

Question 15

What steroid hormones can peripheral or nonendocrine tissue create?

Answer 15

Adipose tissue can, using aromatase enzymes, convert androstenedione to estrone

The skin can convert testosterone into dihydrotestosterone (dht)

Question 16

Which hormones secreted by the anterior pituitary are protein-based?

Answer 16

Growth hormone, thyroid-stimulating hormone, adrenocorticotropin hormone, follicle stimulating hormone, luteinizing hormone, and prolactin releasing hormone. Hormones can be derived from amino acids, proteins, cholesterol, or vitamins.

Question 17

What stimulates IGFS?

Answer 17

Growth Hormone. IGFS are insulin-like growth factors.

Question 18

What effect does IGFS have in the body?

Answer 18

Stimulates amino acid uptake and movement from the blood to cells

Stimulates cell growth and proliferation

Stimulates uptake of sulfur into cartilage matrix

Increases skeletal growth

Question 19

What is the precursor to dopamine, norepinephrine, and epinephrine?

Answer 19

Phenylalanine (which converts to tyrosine).

Question 20

What cofactor is used in the decarboxylase step of DOPA –> Dopamine?

Answer 20

Vitamin B1 and B6

Question 21

What common beverage inhibits ADH release?

Answer 21

Alcohol, thus it results in copious urine output. Inhibiting ADH induces more loss of water by urination.

Question 22

Which amino acid is a building block for thyroid hormone and dopamine?

Answer 22

Tyrosine. Tyrosine turns into L-DOPA which turns into dopamine. Tyrosine also eventually can become thyroid hormones once acted upon by thyroid peroxidase (TPO).

Question 23

What are the necessary cofactors for conversion of T4 to T3?

Answer 23

Copper, iron, selenium, and zinc. 5’-deiodinase is especially dependent on selenium.