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S3B2 Biochemistry > Hormones 1 > Flashcards

Hormones 1 Flashcards

1
Q

What are the 3 communication systems in the human body & what chemical messengers do each of them use?

A
  • Nervous system: neurotransmitters
  • Endocrine system: hormones
  • Immune system: cytokines
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2
Q

What are the 8 glands that make up the endocrine system?

A
  1. Hypothalamus
  2. Pituitary gland
  3. Thyroid gland
  4. Parathyroid gland
  5. Adrenal glands
  6. Pancreas
  7. Pineal gland
  8. Reproductive glands
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3
Q

What are the 2 ways to classify hormones?

A

Chemical structure & abilty to dissolve in water

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4
Q

Describe the difference between endocrine, paracrine & autocrine.

A
  • Endocrine: Hormones are substances that are synthesized in one organ & transported by the circulatory system to act on another tissue
  • Paracrine: Hormones that act on adjacent cells
  • Autocrine: Hormones that act on the cells where they are produced
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5
Q

How do hormones cause specific responses in specific tissues if they are part of the systemic circulation?

A

They stimulate a specific response through the receptors present on specific organs

organs, tissues, or cells lacking the specific receptor do not respond to its stimulating effects

Some horomes have several targers & some only have one

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6
Q

What is the name of a chemical that binds with a high degree of specificity to a receptor?

A

ligand

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7
Q

What are the types of horomones receptors & what are their binding sites?

A
  • Plasma membrane receptors or intracellular receptors
  • Generally proteins
    • Binding site specific for chemical messenger
    • Bindign site involved in transmitting the message
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8
Q

What is it called when the message from a receptor is converted to an intracellular response?

A

Signal transduction

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9
Q

Describe the intracellular cascade that results from the binding of insulin.

A
  • Insulin binds to the receptor –> autophosphorylation of the receptor on specific Y residues
  • This catalyzes the phosphorylation (on Y residues) of Insulin Receptor Substrates (IRS 1-4)
  • This results in a stimulation of a nuber of different kinases that effectively perform the functions of the cell
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10
Q

Describe the Jak/STAT kinase cascade

A
  • hormone binding induces dimerization of the receptor
    • associated proteins (Jak) are phosphorylated & activated
  • Active Jak phosphorylates the intracellular domains (Y residues) of the receptor
  • STAT & other cytosolic proteins bind to the phosphorylated receptor and are phosphorylated by Jak
  • STAT-P dimerize & enter the nucleus
    • activate transcription by binding to response elements
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11
Q

How can Jak activate proteins other than the STAT pathway?

A

proteins can bind to the receptor through SH2 domain to be phosphorylated & activated by Jak

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12
Q

What does STAT stand for?

A

Signal Transducers and Activators of Transcription

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13
Q

Describe the cascde produced by G-protein-coupled receptors.

A
  • GDP is bound to alpha subunit of G-protein
  • hormone binding displaces GDP for GTP
  • The G-protein dissociates from the receptor & the alpha-GTP dissociates from the beta & gamma subunits
  • the alpha-subunit of GTP auto-hydrolyzes to GDP
  • The alpha, beta & gamma subunits reassemble with the receptor
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14
Q

What is the effect of binding Gs?

A

adenylyl cyclase is stimulated

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15
Q

What is the effect of binding Gi?

A

adenylyl cyclase is inhibited

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16
Q

What is the effect of binding Gq?

A

phospholipase C stimulated

17
Q

Describe how cAMP acts as a second messenger for G-protein-coupled receptors.

A
  • Adenylyl cyclase converts ATP to cAMP
  • cAMP stimulates PKA by binding to regulatory subunits & releasing active catalytic subunits
  • catalytic subunits PKA phosphorylate proteins
  • this signal is attenuated by cAMP phosphodiesterase
18
Q

What are the two forms of guanylyl cyclase?

A

membrane bound and soluable

19
Q

How does cGMP act as a secondary messenger?

A
  • cGMP stimulates protein kinase G (PKG)
  • PKG phosphorylates a number of smooth muscle proteins
  • leads to relaxation of smooth muscle & vasodilation
20
Q

What molecule stimulates the soluble form of guanylyl cyclase?

A

NO

21
Q

What molecule stimulates the membrane bound guanylyl cyclase?

A

Atrial natriuetic factor (ANF)

22
Q

Describe the second messenger system stimulated by Gq receptor.

A
  • hormone binds receptor, activating Gq protein
  • alpha-GTP subunit stimulates membrane bound phospholipase C
  • Phospholipase C cleaves phosphotidylinositol 4,5-biphosphate (PIP2) into diacylglycerol (DAG) and inositol 1,4,5-triphosphate (IP3)
  • IP3 interacts with receptor in ER, causing release of Ca2+, DAG or both
23
Q

What are the two types of intracellular receptors?

A

cytosolic receptors & nuclear receptors

24
Q

Describe the response of cytosolic receptors & provide an example of a hormone that uses this type of system.

A

Sex steroids

  • Steroid hormones diffuse into the cell
  • They bind to specific receptor & displace heat shock protein (HSP) attached to an allosteric site
  • Hormone receptor complex enters the nucleus & binds to the specific DNA region, hormone responsive element (HRE)
  • Starts transcription and translation
25
Q

Describe the response of nuclear receptors & provide an example of a hormone that uses this type of system.

A

Thyroid hormone, retinoids & vitamin-D

  • hormones diffuse through the cell membrane & into the nucleus and bind to a specific receptor
  • Hormone-receptor complex binds to a specific region of DNA called HRE
  • Transcription & translation start
26
Q

What is the Endocrine Axis?

A

Hypothalamus

Pituitary

Other Target Endocrine Glands

27
Q

What is the feedback regulation invovled with the Endrocrine Axis?

A

Feed-back regulation by the Thyroid hormone at the Pituitary and Hypothalamic level

(Negative feed-back mechanism)

28
Q

What type of hormones have receptors located on the cell membrane?

A

amino acid derivitives

peptide

protein

29
Q

What tyep of hormones have receptors inside the cell?

A

Steroid

S3B2 Biochemistry (9 decks)

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