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Foundations 1 > Histo: Hormone structure, synthesis, storage, and secretion (lecture) > Flashcards

Histo: Hormone structure, synthesis, storage, and secretion (lecture) Flashcards

1
Q

What are the functions of the endocrine system?

A

To coordinate and integrate cellular activity within the whole body; maintain homeostasis (constant internal environment); regulate energy balance and fuel mobilization, utilization and storage

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2
Q

What are glands?

A

Discrete organ systems that produce a chemical messenger that exerts a biological effect

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3
Q

What are hormones?

A

Chemical messengers that exert biological effects on distant target cells

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4
Q

What are the different structural types of hormones?

A

Proteins and peptides ranging in size from small peptides to large glycoproteins; steroids; small amino acid derivatives (amines)

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5
Q

What are the different classes of hormone signaling?

A

Endocrine, exocrine, paracrine, and autocrine

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6
Q

What is endocrine signaling?

A

Product released into circulation (ductless); affects distant cells

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7
Q

What is exocrine signaling?

A

Product released into a duct for delivery to a surface (sweat/skin) or organ lumen (digestive enzymes/gut)

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8
Q

What is paracrine signaling?

A

Product released into interstitial space, affecting neighboring cells (localized)

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9
Q

What is autocrine signaling?

A

Produce released and affects releasing cell

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10
Q

What type of hormone is insulin?

A

Peptide, endocrine

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11
Q

Where is insulin produced?

A

Beta-cells of islets of Langerhans in pancreas; stored in storage granules

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12
Q

Where is insulin released to?

A

Circulation

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13
Q

What causes insulin to be released?

A

Elevated glucose levels in blood

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14
Q

What is the function of insulin?

A

Stimulate glucose uptake in target cells – fuel (glucose) utilization and energy homeostasis

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15
Q

The pancreas is located near the….

A

Duodenum (small intestine)

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16
Q

The exocrine tissue of the pancreas contains what kind of cells?

A

Acinar cells (appears darker in staining) - digestive enzymes

17
Q

The islets of Langerhans of the pancreas contain what kind of cells?

A

Alpha, Beta, Delta, PP (appears lighter in staining)

18
Q

What is the structure of insulin?

A

2 peptide chains (A has 21 a.a.s, B has 30 a.a.s) held together by disulfide bonds.

Monomer, dimer, or hexamer

19
Q

What are the steps in insulin synthesis?

A
  1. Transcription of gene into mRNA
  2. Initial translation of signal sequence on ribosome and binding to rough ER
  3. Synthesis of preproinsulin in lumen of ER
  4. Processing (folding, cleavage of signal sequence off, formation of disulfide bonds) to proinsulin in lumen of ER
  5. Processing (cleavage of C chain off) to mature insulin in the Golgi
  6. Package and storage in secretory vesicle/granule

Can take a few hours - days

20
Q

What is the structure of an insulin hexamer?

A

Quaternary; 2 central Zn2+ ions in center important for holding the structure together, coordinated by B10 histidine

21
Q

What is the importance of Zn in insulin hexamer structure?

A

Holds cell together for proper storage of insulin in secretory vesicles in the Beta cells

22
Q

What is the importance of the monomer form of insulin?

A

Insulin signaling and interacting with receptors

23
Q

What is the function of the hexamer form of insulin?

A

It is the fully mature storage form

24
Q

What are the steps of insulin secretion?

A
  1. Glucose uptake by Beta cell and conversion to G-6-P
  2. Glycolysis, Krebs cycle, electron transport, and ATP generation
  3. Elevated ATP - ATP inhibits K+ channels, K+ accumulates in cytoplasm
  4. Resulting in membrane depolarization (-70 mV to -50 mV)
  5. This opens voltage sensitive Ca2+ ion channels
  6. Resulting Ca2+ influx triggers exocytosis of insulin storage vesicles/granules
25
Q

(T/F) Cells work very hard to increase free Ca2+ in the cytoplasm.

A

False, they work hard to limit free Ca2+ in the cytoplasm.

26
Q

Why do cells want to limit free Ca2+ in the cytoplasm?

A

Ca2+ is used in many signaling events

27
Q

(T/F) Insulin secretion is a highly regulated pathway.

A

True

28
Q

What are the pools of secretory vesicles present in the cytoplasm of Beta cells? What do they result in?

A
  1. Pool that fuses rapidly to plasma membrane
  2. Pool that results in delayed fusion of secretory vesicles to the membrane

Result in biphasic release (2 phases: one sharp peak then a wider peak) of insulin in response to glucose.

29
Q

What is the structure of glucagon?

A

Peptide hormone (single polypeptide chain)

30
Q

Where is glucagon produced?

A

Alpha cells in islets of Langerhans

31
Q

When is glucagon released?

A

When blood glucose is low

32
Q

What is the function of glucagon?

A

To cause target cells to release storage form of glucose (glycogen) into blood.

Foundations 1 (11 decks)

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