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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
What type of hormone is ADH? What is its main function?
cyclic nonapeptide main regulator of body fluid osmolarity
26
What type of hormone is oxytocin? What is its major function in the body?
cyclic nonapeptide Stimulates lactation, uterine contraction during delivery
27
A deficiency in ADH causes what disease?
Diabetes insipidus
28
A dietary deficiency of iodine woudl result in excess secretion of what hormone?
Thyroid Stimulating Hormone
29
What are the iodinated dityrosine derivatives?
thyroxine and triiodothyronine
30
The thyroid hormones are released in response to what messenger? They stimulate what action?
Respond to TSH adn stimulate oxidations in many cells
31
How are the tyhroid hormones synthesized & excreted?
they are synthesized from tyrosyl residues in thyroglobulin thyroglobulin is exocytosed
32
How is iodine concentrated in the cells of the thyroid?
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
33
Iodide is transported to what location in the thyroid?
Iodide is trasnported to the follicle lumen
34
What enzyme oxidizes iodide to I+? Where is this enzyme located?
thyroperoxidase found only in thyroid tissue
35
What enzyme catalyzes the I+ tyrosine residues? This leads to what two products?
thyroperoxidase thyroglobulin containing monoiodotyrosyl (MIT) and diiodotyrosyl (DIT) residues
36
How are T3 and T4 produced & secreted into the circulation?
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
What is produced in higher quantity: T4 or T3? Which is more active?
More T4 is produced than T3 T3 is more active
38
How are thyroid hormones delivered to their target organs?
they are hydrophobic, so they requires carrier proteins Thyroxin binding globulin (**TBG**) and thyroxin bindig pre-albumin (**TBPA**) are the carrier proteins
39
Thyroid carrier proteins exhibit what type of binding? Why are they bound? Are they active while bound?
binding is not covalent binding increases the hormones half-life No, free hormones (T3 and T4) make up the active fraction
40
How is T4 converted to T3 at the target tissues?
targer tissues contain a deiodinaase
41
How is T4 inactivated?
T4 is converted to rT3 diodination, decarboxylation, deamination, glucuronidation
42
Where are T3 receptors located? What receptors are activators vs. silencers?
In the nucleus T3 receptors are members of steroid receptor super family _liganded receptors:_ activators _unliganded receptors:_ bind silencer elements
43
What is the synthesized precursor of PTH?
prepro-PTH
44
Stimulation of the PTH receptor results in activation of what enzyme?
adenylyl cyclase
45
How does PTH effect the body?
stimulates bone resorption - increasing serum [Ca2+] and depressing plasma Pi stimulates Pi secretion by the kidneys
46
Where is calcitonin produced?
parafollicular C cells of the thyroid
47
What is the biological effect of calcitonin?
lowers circulating Ca2+ and Pi levels increases Ca2+ excretion in the urine
48
How do parafollicular cells know when to release calcitonin?
C-cells in the gland have receptors that monitor calcium ions in the blood when calcium levels are high, they secrete calcitonin
49
What is the precursor to calcitonin?
preprocalcitonin
50
How is Vitamin D formed & transported?
formed when exposed to sufficient sunlight vitamin D-binding protein moves vitamin D from skin or intestine
51
What is the major form of vitamin D in the blood?
25(OH)-D3
52
What is the active form of vitamin D? Where is it actvated & what enzyme is responsible for its activation?
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
Parathyroid Horome is able to increase blood calcium concentration through what 3 methods? It participates in what type of feedback loop?
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
Where is ANP secreted from & in what circumstances does this happen?
secreted by **cardiac muscles** when sodium chloride intake is increased & when volume of extracellular fluid expands
55
What is the biological function of ANP?
natruiesis (excretion of sodium) diuresis (increase urine production) inhibition of aldosterone secretion
56
What type of cells secrete insulin? Where are they located?
beta-cells pancreas
57
What is the biological function of insulin?
increases glucose uptake & utilization increases lipogenesis stimulate formation of glycogen from glucose general anabolic effects
58
How is insulin transformed into its active form?
synthesized singel chain Preproinsulin processed into insulin by 2 proteolytic activities results in disulfide bonded dipeptide (A-chain & B-chain)
59
Insulin has what type of receptor? How does this receptor work?
Tyrosine Kinase receptor two tyrosines on each beta-chain within the tyrosine kinase domain are autophosphorylated
60
What type of cells secrete glucagon? Where are they located?
alpha-cells pancreas
61
What is the biological function of glucagon?
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
Is glucagon synthesized in its active form?
no, it is synthesized as a prepropeptide
63
Glucagon has what type of receptor? Describe the general action of this receptor.
**G-protein** coupled receptor cAMP as second messenger it activates PKA, which phosphorylates proteins
64
What is the biologic function of pancreatic polypeptide?
increases glycogenolysis regulatin of gastrointestinal activity
65
Pancreatic polypeptide is produced by what type of cells?
F-cells in the pancreas
66
What is the biological function of somatostatin?
inhibits glucagon & insulin secretion
67
What type of cells secrete somatostatin?
delta-cells
68
Norepanephrine is derived from what precursor? What is its general biological function? What are its receptors?
Tyrosine classic "fight-or-flight" response binds all catecholamine receptors except B2-adrenergic
69
Describe the regulatory process that happens in the body whne blood glucose is low.
* 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
Describe the regulatory process that happens in the body whne blood glucose is high.
* Insulin is secreted by the pancreas * promotes entry of glucose into cells * promotes glycogenesis & glycolysis * inhibits glycogenolysis & gluconeogenesis
71
Epinephrine is derived from what precursor? What is its general biologic function? It binds to what receptors?
tyrosine classic "fight-or-flight" binds to all classes of catecholamine receptor (alpha & beta)
72
What enzyme converts norepinephrine to epinephrine?
Phenylethanolamine-N-Methyltransferase (PNMT)
73
Where is PMNT found in the body? What substances stimulates it?
brain & adrenal medulla stimulated by glucocorticoids
74
a1 is coupled to what cellular receptor? What is the impact of this receptor?
Gg increased intracellular Ca2+ and smooth muscle contraction
75
a2 is coupled to what cellular receptor? What is the impact of this receptor?
Gi decrease in neurotransmitter release decrease levels of cAMP resulting in smooth muscle contraction
76
B receptors are coupled to what cellular receptor? What is the impact of this receptor?
Gs increases intracellular cAMP activity heart muscle contraction & smooth muscle relaxation glycogenolysis
77
What is the biological function of ghrelin?
appetite stimulation
78
What is the biological function of gastrin?
stimulates acid & pepsin secretion
79
What is the biological function of Glucagon-like peptide 1?
GLP-1 (2 forms) 1. potentiates glucose-dependent insulin secretion 2. inhibits glucagon secretion
80
What is the biological function of Secretin?
stimulates release of HCO3 and H2O
81
What is the biological function ofcholecystokinin?
CCK increases secretion of digestive enzymes from pancreas
82
What is the biological function of Vasoactive intestinal peptide?
VIP relaxes GI inhibits acid and pepsin secretion
83
What is the biological function of Pancreatic Polypeptide?
PP suppresses glucose-induced insulin secretion
84
What is the biological function of Neuropeptide Tyrosine?
NPY controls feeding behavior and energy homeostasis
85
What are the 8 horomones & peptides of the gut?
1. Ghrelin 2. Gastrin 3. Glucagon-like peptide 1 4. Secretin 5. Cholecystokinin 6. Vasoactive intestinal peptide 7. Pancreatic polypeptide 8. Neuropeptide tyrosine
86
What are the 3 hormones secreted from adipose tissue?
1. leptin 2. adiponectin 3. resistin
87
What is the biological function of leptin?
* regulates overall body weight by limiting food intake * increases energy expenditure
88
What is the biological function of adiponectin?
increases insulin sensitivity and fatty acid oxidation
89
What is the biological function of resistin?
induces insulin resistance

S3B2 Biochemistry (9 decks)

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