HORMONES STRUCTURE AND GENERAL PROPERTIES

Question 1

What is Endocrinology?

Answer 1

Branch of medicine concerned with structure, function & disorders of endocrine glands.

Question 2

Why Communicate?

Answer 2

Endocrine functions are to :1)Maintain homeostasis (insulin & glucagon maintain blood glucose levels) 2) Regulate growth, development, differentiation & reproduction (menstrual cycle, pregnancy) 3) Respond to external stimuli (fight/flight response by stress hormones)

Question 3

How communicate?

Answer 3

Coordination of metabolism in mammals is achieved by neuroendocrine system. 1)Nervous system 2)Endocrine system

Question 4

Communication molecules:

Answer 4

1)Neurotransmitters 2)Hormones

Question 5

In the Nervous system

Answer 5

Electrical signals (nerve impulses) originate in
neuron & travel rapidly to where neurotransmitters are released. Chemical messenger (neurotransmitter) may travel only a micrometer, across synaptic cleft to next neuron.Target cell is close to site of release

Question 6

In Endocrine system

Answer 6

Hormones are secreted to blood stream & carried to target tissues that are away from the secreting cell.

Question 7

neurotransmitters & hormones interact with …

Answer 7

specific receptors on or in their target cells, triggering responses.

Question 8

What is a hormone?

Answer 8

Chemical messengers extremely potent & are produced in small amounts. Typical hormone has physiological effects at concentrations as low as 10^-10 M. As hormone concentration is low, a high- affinity interaction with receptor is necessary.

Question 9

Receptor:

Answer 9

cellular protein that binds hormone.
Binding of ligands to receptors:
➢is never covalent
➢always reversible
➢should be spesific & saturable

Question 10

Binding of hormone can be written as:

Answer 10

H + R ↔ HR. KD (Dissociation constant) = [H][R]/[HR].
KD :measure of affinity
KD : indicates concentration of hormone that causes 50% of receptors to be occupied

Question 11

Target Cell:

Answer 11

Any cell in which the hormone (ligand) binds to its receptor.

Question 12

Endocrine hormones are

Answer 12

released into the blood and carried to target cells throughout the body (e.g.insulin)

Question 13

Paracrine hormones are

Answer 13

released into the extracellular space and diffuse to neighboring target cells (e.g. eicosanoid hormones).

Question 14

Autocrine hormones are

Answer 14

released by and affect the same cell, binding to receptors on the cell surface (interleukin).

Question 15

Hormone Synthesis

Answer 15

Hormones are synthesized in endocrine glands designed for specific purpose.

Question 16

Endocrine gland

Answer 16

group of specialized cells that synthesize and secrete hormones.

Question 17

The endocrine gland may be

Answer 17

located in vicinity of target tissue/there may be a specific portal circulation between them.( e.g. Hypothalamic hormones are secreted into hypothalamo-hypophyseal portal veins & enter adenohypophysis (anterior pituitary).)

Question 18

Hormone classification

Answer 18

1. Mechanism of action
2. Chemical structure
3. Site of synthesis (endocrine organ) 4. Function
4. Mode of storage and secretion

Question 19

1. Mechanism of action

Answer 19

A.Group II hormones
B. Group I hormones

Question 20

A. General Mechanism of Action- Group II hormones

Answer 20

i. Peptide-protein and glycoprotein hormones
ii. Catecholamines iii. Eicosanoids
Water soluble, can’t diffuse across hydrophobic lipid cell membranes. cell surface receptors built into the plasma membrane

Question 21

i. Peptide-protein and glycoprotein hormones

Answer 21

40+ hormones. May have from 3-200+ aa residues. Synthesized as part of a larger molecule (preprohormone) on ribosomes that
contains a leader sequence (signal peptide) at its amino terminal end.

Question 22

i. Peptide-protein and glycoprotein hormones(part 2)

Answer 22

Signal peptide is removed in ER, resulting protein is prohormone. Prohormone undergoes posttranslational processing to produce mature hormone. Prohormones are packaged into secretory vesicles. Mature hormones are released by exocytosis

Question 23

i. Peptide-protein and glycoprotein hormones (part 3)

Answer 23

Hypothalamus hormones (CRF, TRF, GnRH, GHRH, Somatostatin). Pituitary hormones (ACTH,FSH,LH,TSH,GH, Oxytocin, Vasopressin). Calcitonin. Parathyroid hormon (PTH). Pancreas hormones (insulin, glucagon, somatostatin).

Question 24

i. Peptide-protein and glycoprotein hormones(part 4)

Answer 24

GIS hormones (Gastrin, Secretin, Cholecystokinin). In some cases, prohormone proteins yield 1 peptide hormone, but often several active hormones are produced from same prohormone.

Question 25

i. Peptide-protein and glycoprotein hormones(part 5)

Answer 25

POMC (Proopiomelanocortin) gene encodes a big polypeptide 258aa that’s progressively carved up into 9 biologically active peptides. Major Products of POMC Cleavage: 1)ACTH: Adrenocorticotropic
hormone 2)beta-LPH (beta-lipotropin) 3)gamma-MSH

Question 26

ii. Catecholamine Hormones

Answer 26

Hormones the brain, nerve tissues, & adrenal glands produce. These act as neurotransmitters & hormones vital to maintenance of homeostasis through the ANS.

Question 27

ii. Catecholamine Hormones (part 2)

Answer 27

Dopamine, norepinephrine (noradrenaline) , & epinephrine (adrenaline) are physiologically active molecules known as catecholamines. Body releases catecholamines in response to emotional/physical stress.

Question 28

ii. Catecholamine Hormones (part 3)

Answer 28

They’re responsible for body’s “fight/flight” response. They’re highly concentrated in secretory vesicles & released by exocytosis.