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Endocrine > Hormones & Receptors > Flashcards

Hormones & Receptors Flashcards

1
Q

Describe the structure of a G-protein coupled receptor

A
  • receptor
  • G-protein (with an α, β & γ subunit)
  • GDP molecule (that associates with the G-protein)
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2
Q

Explain the mechanisms of a G-protein coupled receptor

A
  • When the ligand binds, the receptor conformation changes
  • The GDP molecule is replaced by a GTP molecule
  • The GTP & alpha subunit dissociates from the receptor-protein complex
  • This causes a downstream effect (ion channel, enzymes etc)
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3
Q

What enzyme catalyses the hydrolysis of GTP to GDP + Pi

A

GTPase

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4
Q

Describe how a GPCR’s activity is terminated

A

GTPase hydrolyses GTP to GDP
GDP & a-subunit associate with the protein-receptor complex
The ligand dissociates

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5
Q

Give an example of a GPCR

A

Adrenoceptors

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6
Q

Describe the amplification of signalling that occurs after a single ligand binds to a single GPCR

A

The one α-subunit interacts with multiple secondary messengers

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7
Q

There are three type of G protein coupled receptors - q, s & i. Describe the intracellular signalling of GPCR q

A

Activation of phospholipase C (PLC) =>
PLC produces IP3 & DAG =>
IP3 activates the release of Ca from the ER to the cytosol &
DAG activates protein kinase C

(PLC, IP3, DAG, Ca, PKC)

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8
Q

There are three type of G protein coupled receptors - q, s & i. Describe the intracellular signalling of GPCR s

A

Activation of adenylyl cyclase (AC) =>
AC converts ATP to cAMP =>
cAMP activates protein kinase A

(AC, cAMP, PKA)

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9
Q

There are three type of G protein coupled receptors - q, s & i. Describe the intracellular signalling of GPCR i

A

Inhibits adenylyl cyclase
(I.e. negatively feedbacks GPCR s)

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10
Q

What is a kinase

A

A enzyme that transfers a phosphate group to a protein

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11
Q

One example of a kinase-linked receptor is receptor tyrosine kinase. Explain the mechanisms of this receptor

A

Ligand binds to 2 neighbouring receptor tyrosine kinases =>
The neighbouring receptors come together (dimerise) =>
The receptors phosphorylate each others tyrosine residues (transphosphorylation) =>
Signalling molecule activation & cellular response

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12
Q

Describe the structure of a receptor tyrosine kinase

A

Extracellular domain (where ligand binds)
Transmembrane domain (joins extra & intracellular domains)
Intracellular domain (contains tyrosine residues & kinases)

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13
Q

How many receptor tyrosine kinases does one ligand bind to

A

2! The receptors then dimerise & phosphorylate each other

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14
Q

Name two endocrine hormones that bind to kinase-linked receptors

A

Insulin
Growth hormone

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15
Q

What is autocrine regulation

A

Cell ‘self regulation’

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16
Q

What is paracrine regulation

A

Adjacent cell regulation

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17
Q

What is endocrine regulation

A

Chemicals (i.e. hormones) released from secretory cells are usually transported via the circulatory system to target cells

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18
Q

Name the three different types of hormones

A

Amine, peptide, steroid

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19
Q

Where are amine & peptide stored

A

Pre-synthesised & stored in vesicles

20
Q

How are amine & peptide hormones released from their vesicles

A

Released in response to stimuli by Ca+ dependant exocytosis.

21
Q

Amine vs peptide hormones

A

Peptides are usually pre-synthesised from longer precursors

22
Q

How are amine & peptide hormones transported in the blood and what effect does this have on their half life

A

They are hydrophilic - transported freely in plasma (& so shorter half life)

23
Q

Are steroid hormones pre-synthesised or are they synthesised & secreted upon demand

A

synthesised & secreted upon demand

24
Q

What stimulates the synthesis of steroids

A

Increased intracellular cholesterol uptake

25
Q

What molecule are steroid hormones derived from and what is the rate limiting step

A
  • Cholesterol → pregnenolone (rate limiting step)
  • Pregnenolone → specific steroid
26
Q

How are steroid hormones transported in the blood & what effect does this have on their half life

A

They are hydrophobic - transported bound to plasma proteins (& so longer half life)

27
Q

Summarise the half life of the three different hormone types

A
  • Amine T½ - seconds
  • Peptide T½ - minutes
  • Steroid & thyroid hormone T½ - hours to days
28
Q

What is the ratio between free ‘active’ and protein-bound hormones in the blood and what is the relevance of this

A

Free and protein-bound hormones are in equilibrium.
This helps maintain hormones levels

29
Q

What hormones bind to cortisol binding globulin

A

Cortisol & some aldosterone

30
Q

What hormones bind to thyroxine binding globulin

A

T4 & some T3

31
Q

What hormones bind to sex steroid binding globulin

A

Testosterone & oestradiol

32
Q

What hormones bind to albumin

A

Steroid hormones & thyroxine

33
Q

What hormones bind to transthyretin

A

Mainly thyroxine

34
Q

What two values control the plasma concentration of a hormone

A

Plasma concentration = Rate of secretion (most important!!) - rate of elimination

35
Q

What receptors do amine hormones bind to?

A

Hybrid nuclear receptors (thyroid)
GPCRs (adrenal medulla)

36
Q

Name 4 amine hormones

A

T3, T4 (thyroid),
noradrenaline, adrenaline (adrenaline medulla)

37
Q

What receptors do peptide hormones bind to?

A

GPCRs (all except insulin - kinase & GH - cytokine)

38
Q

Name 8 peptide hormones

A

Insulin, glucagon, somatostatin (pancreas),
Oxytocin, ADH (posterior pituitary),
GH (pituitary),
Calcitonin & PTH (thyroid/parathyroid)

39
Q

What receptors do steroid hormones bind to?

A

Type 1 & Type 2 nuclear receptors

40
Q

Name 7 steroid hormones

A

DHEA, aldosterone, cortisol (adrenal cortex)
Testosterone (testes & ovaries)
Oestradiol, progesterone (ovaries)
Oestrogen (mammary glands)

41
Q

What receptor allows the diffusion of glucose into pancreatic beta cells

A

GLUT 2

42
Q

Describe the steps that lead to insulin secretion

A
  • Increased blood glucose concentration
  • Increased glucose diffusion into B-cells by GLUT 2
  • Glucose phosphorylation & glycolysis
  • Increased ATP causes Katp channel closure
  • Membrane depolarisation, Ca+ influx, insulin secretion
43
Q

What is another name for a nuclear receptor

A

Ligand gated transcription factor
(hormone binding ‘actives’ the transcription factor)

44
Q

Describe the process involved in a steroid hormone regulating transcription & having its effects

A
  • Steroid hormone diffuses into cell & binds to its receptor
  • inhibitory HSP dissociates from the receptor
  • Receptor then moves to the nucleus
  • The receptor-steroid complex binds to HRE in DNA
  • Transcription rate & protein synthesis is altered
45
Q

Steroid binding to their receptor causes what protein to dissociate from the receptor

A

Inhibitory HSP (heat shock protein)

46
Q

Where does the receptor-steroid complex bind on DNA

A

Hormone response element (HRE)

Endocrine (22 decks)

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