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S3B2 Biochemistry > Hormones 2 & 3 > Flashcards

Hormones 2 & 3 Flashcards

1
Q

What is the master control center of the endocrine system?

What is its target organ?

A

hypothalamus

Target organ: Pituitary

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2
Q

Hypothalmic hormones stimulate what aspect of the pituitary?

A

anterior pituitary

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3
Q

How do hypothalmic hormones stimulat the release of pituitary horomnes?

A

stimulate exocytosis of pre-existing vesicles containing the various anterior pituitary hormones

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4
Q

What are the 7 hypothalamus hormones?

A
  1. Thyrotropin-Releasing hormone
  2. Prolactin-releasing hormone
  3. Prolactin release-inhibiting hormone
  4. Corticotropin-releasing hormone
  5. Gonadotropin-releasing horomone
  6. Growth hormone-releasing hormone
  7. Somatostatin
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5
Q

Thyrotropin-releasing horomone (TRH) has what effect on the pituitary?

A

Stimulates release of Thyroid Stimulating Horomone (TSH)

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6
Q

Prolactin-releasing factor (PRF) has what effect on the pituitary?

A

stimulates the release of prolactin (PRL)

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7
Q

Prolactin release-inhibiting horomone (PIH) has what effect on the pituitary?

A

Inhibits the release of prolactin (PRL)

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8
Q

Corticotropin-releasing horomone (CRH) has what effect on the pituitary?

A

Stimulates release of Adrenocorticotropic hormone (ACTH)

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9
Q

Gonadotropin-releasing horomone (GnRH) has what effect on the pituitary?

A

stimulates the release of Lutenizing hormone (LH) and Folicle-stimulating hormone (FSH)

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10
Q

Growth hormone-releasing horomone (GHRH) has what effect on the pituitary?

A

Stimulates the release of Growth Hormone (GH)

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11
Q

Somatostatin (SS) hormone has what effect on the pituitary?

A

Inhibits the release of Growh hormone (GH)

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12
Q

What are the characteristic features of the releasing horomones?

A
  • cyclic N-terminal
  • C-terminal is an amide instead of a free carboxylic acid group
  • generally stimulate Ca2+, IP3, PKC-linked pathway in anterior pituitary
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13
Q

What are the divisions of the pituitary?

A

anterior pituitary

posterior pituitary

incomplete intermediate lobe

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14
Q

What are the 6 hormones released by the anterior pituitary & what are their respective target organs?

A
  1. Thyroid Stimulating Hormone (TSH)
    • thyroid
  2. Prolactin (PRL)
    • mammary gland
  3. Adrenocorticotrophic Hormone (ACTH)
    • adrenal cortex
  4. Lutenizing Hormone (LH)
    • sex organs
  5. Folicule Stimulating Hormone (FSH)
    • sex organs
  6. Growth Hormone (GH)
    • bone, muscle, adipose tissue
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15
Q

What are the 2 protein hormones released by the anterior pituitary?

A

GH and Prolactin

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16
Q

GH has what type of receptor?

A

Single membrane pass receptor

Generates Jak/STAT cascade

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17
Q

What are the 3 glycoprotein hormones released by the pituitary?

Describe their subunit composition.

A

TSH, FSH, and LH

hetero dimer (alpha & beta subunits)

alpha subunits are all the same, but the beta is different & provides the biological activity

the beta subunit is NOT active without the alpha subunit

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18
Q

TSH, FSH, and LH utilize what type of receptor system?

A

Gs

adenylyl cyclase stimulated cAMP pathway

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19
Q

What is POMC & where is it expressed?

A

Pro-opiomelanocortin

285 aa precursor that can undergo differential processing to yield at least 8 peptides

expressed in both the anterior and intermediate lobes of the pituitary

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20
Q

What hormones are derived from POMC?

A
  • ACTH
    • ​main physiologically active product of CRH
  • MSH (melanocyte stimulating hormone)
    • stimulates melanin synthesis in the skin
  • Lipotropin
    • ​promotes release
  • Endorphins
    • ​decreases pain perception & euphoria
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21
Q

In what ways is POMC processed?

A

glycosylations

acetylations

extensive proteolytic cleavage @ basic protein sequences (tissue specific)

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22
Q

How are different products produced from POMC if they are all produced in the pituitary?

A

DIfferent cell types within the pituitary express different proteolytic activities which produce the different products

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23
Q

What horomones are produced in the hypothalamus & stored in the posterior pituitary?

They are associated wtih what carrier proteins?

A

Oxytocin & Vasopressin (ADH)

carrier proteins: neurophysins

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24
Q

How do oxytocin & vasopressin reach their target organs?

A

they are secreted directly into the systemic circulation

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25
Q

What type of hormone is ADH?

What is its main function?

A

cyclic nonapeptide

main regulator of body fluid osmolarity

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26
Q

What type of hormone is oxytocin?

What is its major function in the body?

A

cyclic nonapeptide

Stimulates lactation, uterine contraction during delivery

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27
Q

A deficiency in ADH causes what disease?

A

Diabetes insipidus

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28
Q

A dietary deficiency of iodine woudl result in excess secretion of what hormone?

A

Thyroid Stimulating Hormone

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29
Q

What are the iodinated dityrosine derivatives?

A

thyroxine and triiodothyronine

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30
Q

The thyroid hormones are released in response to what messenger?

They stimulate what action?

A

Respond to TSH adn stimulate oxidations in many cells

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31
Q

How are the tyhroid hormones synthesized & excreted?

A

they are synthesized from tyrosyl residues in thyroglobulin

thyroglobulin is exocytosed

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32
Q

How is iodine concentrated in the cells of the thyroid?

A

Na+/K+-ATPase-driven pump pumps Na+ outside of the cell

When Na+ reenters the cell, it brings iodide with it via the sodium iodide symporter (NIS)

So, as Na+ continually gets pumped out, iodide gets concentrated in the thyroid cells

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33
Q

Iodide is transported to what location in the thyroid?

A

Iodide is trasnported to the follicle lumen

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34
Q

What enzyme oxidizes iodide to I+?

Where is this enzyme located?

A

thyroperoxidase

found only in thyroid tissue

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35
Q

What enzyme catalyzes the I+ tyrosine residues?

This leads to what two products?

A

thyroperoxidase

thyroglobulin containing monoiodotyrosyl (MIT) and diiodotyrosyl (DIT) residues

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36
Q

How are T3 and T4 produced & secreted into the circulation?

A

MIT and DIT residues are combined on thyroglobulin

this mature thyroglobulin is taken into vesicles by thyrocytes where it fuses with lysosomes

the lysosomal proteases degrade the thyroglobulin, releasing amino acids & T3 and T4

T3 and T4 are then secreted into the circulation

37
Q

What is produced in higher quantity: T4 or T3?

Which is more active?

A

More T4 is produced than T3

T3 is more active

38
Q

How are thyroid hormones delivered to their target organs?

A

they are hydrophobic, so they requires carrier proteins

Thyroxin binding globulin (TBG) and thyroxin bindig pre-albumin (TBPA) are the carrier proteins

39
Q

Thyroid carrier proteins exhibit what type of binding?

Why are they bound?

Are they active while bound?

A

binding is not covalent

binding increases the hormones half-life

No, free hormones (T3 and T4) make up the active fraction

40
Q

How is T4 converted to T3 at the target tissues?

A

targer tissues contain a deiodinaase

41
Q

How is T4 inactivated?

A

T4 is converted to rT3

diodination, decarboxylation, deamination, glucuronidation

42
Q

Where are T3 receptors located?

What receptors are activators vs. silencers?

A

In the nucleus

T3 receptors are members of steroid receptor super family

liganded receptors: activators

unliganded receptors: bind silencer elements

43
Q

What is the synthesized precursor of PTH?

A

prepro-PTH

44
Q

Stimulation of the PTH receptor results in activation of what enzyme?

A

adenylyl cyclase

45
Q

How does PTH effect the body?

A

stimulates bone resorption - increasing serum [Ca2+] and depressing plasma Pi

stimulates Pi secretion by the kidneys

46
Q

Where is calcitonin produced?

A

parafollicular C cells of the thyroid

47
Q

What is the biological effect of calcitonin?

A

lowers circulating Ca2+ and Pi levels

increases Ca2+ excretion in the urine

48
Q

How do parafollicular cells know when to release calcitonin?

A

C-cells in the gland have receptors that monitor calcium ions in the blood

when calcium levels are high, they secrete calcitonin

49
Q

What is the precursor to calcitonin?

A

preprocalcitonin

50
Q

How is Vitamin D formed & transported?

A

formed when exposed to sufficient sunlight

vitamin D-binding protein moves vitamin D from skin or intestine

51
Q

What is the major form of vitamin D in the blood?

A

25(OH)-D3

52
Q

What is the active form of vitamin D?

Where is it actvated & what enzyme is responsible for its activation?

A

25(OH)-D3 is converted to 1,25(OH)2-D3 in the renal tubule by 1 alpha-hydroxylase

active form also called cholecalciferoal or calcitriol

53
Q

Parathyroid Horome is able to increase blood calcium concentration through what 3 methods?

It participates in what type of feedback loop?

A
  1. Osteoclastic activity
    • releasing calcium
  2. Reabsorption of calcium by kidney tubules
  3. Along with vitamin D3, absorption of calcium from the intestine

Negative feedback - once calcium level is increased, PTH’s secretion is inhibited by the parathyroid gland

54
Q

Where is ANP secreted from & in what circumstances does this happen?

A

secreted by cardiac muscles when sodium chloride intake is increased & when volume of extracellular fluid expands

55
Q

What is the biological function of ANP?

A

natruiesis (excretion of sodium)

diuresis (increase urine production)

inhibition of aldosterone secretion

56
Q

What type of cells secrete insulin?

Where are they located?

A

beta-cells

pancreas

57
Q

What is the biological function of insulin?

A

increases glucose uptake & utilization

increases lipogenesis

stimulate formation of glycogen from glucose

general anabolic effects

58
Q

How is insulin transformed into its active form?

A

synthesized singel chain Preproinsulin

processed into insulin by 2 proteolytic activities

results in disulfide bonded dipeptide (A-chain & B-chain)

59
Q

Insulin has what type of receptor?

How does this receptor work?

A

Tyrosine Kinase receptor

two tyrosines on each beta-chain within the tyrosine kinase domain are autophosphorylated

60
Q

What type of cells secrete glucagon?

Where are they located?

A

alpha-cells

pancreas

61
Q

What is the biological function of glucagon?

A

increases lipid mobilization and glycogenolysis in order to increase blood glucose levels

  • stimulate cells to break down glycogen into glucose
  • stimulate cells to convert noncarbohydrates into glucose
62
Q

Is glucagon synthesized in its active form?

A

no, it is synthesized as a prepropeptide

63
Q

Glucagon has what type of receptor?

Describe the general action of this receptor.

A

G-protein coupled receptor

cAMP as second messenger

it activates PKA, which phosphorylates proteins

64
Q

What is the biologic function of pancreatic polypeptide?

A

increases glycogenolysis

regulatin of gastrointestinal activity

65
Q

Pancreatic polypeptide is produced by what type of cells?

A

F-cells in the pancreas

66
Q

What is the biological function of somatostatin?

A

inhibits glucagon & insulin secretion

67
Q

What type of cells secrete somatostatin?

A

delta-cells

68
Q

Norepanephrine is derived from what precursor?

What is its general biological function?

What are its receptors?

A

Tyrosine

classic “fight-or-flight” response

binds all catecholamine receptors except B2-adrenergic

69
Q

Describe the regulatory process that happens in the body whne blood glucose is low.

A
  • glucagon is secrete by the pancreas
    • increases glycogenolysis in the liver
    • stimulates gluconeogenesis in the liver
  • glycogenolysis releases glucose from the liver
    • increases blood glucose level
70
Q

Describe the regulatory process that happens in the body whne blood glucose is high.

A
  • Insulin is secreted by the pancreas
    • promotes entry of glucose into cells
    • promotes glycogenesis & glycolysis
    • inhibits glycogenolysis & gluconeogenesis
71
Q

Epinephrine is derived from what precursor?

What is its general biologic function?

It binds to what receptors?

A

tyrosine

classic “fight-or-flight”

binds to all classes of catecholamine receptor (alpha & beta)

72
Q

What enzyme converts norepinephrine to epinephrine?

A

Phenylethanolamine-N-Methyltransferase (PNMT)

73
Q

Where is PMNT found in the body?

What substances stimulates it?

A

brain & adrenal medulla

stimulated by glucocorticoids

74
Q

a1 is coupled to what cellular receptor?

What is the impact of this receptor?

A

Gg

increased intracellular Ca2+ and smooth muscle contraction

75
Q

a2 is coupled to what cellular receptor?

What is the impact of this receptor?

A

Gi

decrease in neurotransmitter release

decrease levels of cAMP resulting in smooth muscle contraction

76
Q

B receptors are coupled to what cellular receptor?

What is the impact of this receptor?

A

Gs

increases intracellular cAMP activity

heart muscle contraction & smooth muscle relaxation

glycogenolysis

77
Q

What is the biological function of ghrelin?

A

appetite stimulation

78
Q

What is the biological function of gastrin?

A

stimulates acid & pepsin secretion

79
Q

What is the biological function of Glucagon-like peptide 1?

A

GLP-1 (2 forms)

  1. potentiates glucose-dependent insulin secretion
  2. inhibits glucagon secretion
80
Q

What is the biological function of Secretin?

A

stimulates release of HCO3 and H2O

81
Q

What is the biological function ofcholecystokinin?

A

CCK

increases secretion of digestive enzymes from pancreas

82
Q

What is the biological function of Vasoactive intestinal peptide?

A

VIP

relaxes GI

inhibits acid and pepsin secretion

83
Q

What is the biological function of Pancreatic Polypeptide?

A

PP

suppresses glucose-induced insulin secretion

84
Q

What is the biological function of Neuropeptide Tyrosine?

A

NPY

controls feeding behavior and energy homeostasis

85
Q

What are the 8 horomones & peptides of the gut?

A
  1. Ghrelin
  2. Gastrin
  3. Glucagon-like peptide 1
  4. Secretin
  5. Cholecystokinin
  6. Vasoactive intestinal peptide
  7. Pancreatic polypeptide
  8. Neuropeptide tyrosine
86
Q

What are the 3 hormones secreted from adipose tissue?

A
  1. leptin
  2. adiponectin
  3. resistin
87
Q

What is the biological function of leptin?

A
  • regulates overall body weight by limiting food intake
  • increases energy expenditure
88
Q

What is the biological function of adiponectin?

A

increases insulin sensitivity and fatty acid oxidation

89
Q

What is the biological function of resistin?

A

induces insulin resistance

S3B2 Biochemistry (9 decks)

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