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Biochem Exam 4 > Insulin & Glucagon > Flashcards

Insulin & Glucagon Flashcards

1
Q

When you think of insulin and glucagon what is important?

A

Substrate levels (very sensitive to what you are being exposed to, i.e. eating)

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2
Q

What hormones are mediated through neural signals instead of what you are eating?

A

Epinephrine and norepinephrine

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3
Q

What are the 4 major tissues for insulin/glucagon?

A

1) Liver (gluconeogenesis, FA synthesis, making of VLDLs, glycolysis)
2) Adipose
3) Muscle
4) Brain

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4
Q

What is the most important hormone coordinating use of fuels and where is it made?

A

Insulin; pancreas (beta cells of Islets of Langerhans)

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5
Q

What is the most powerful anabolic hormone?

A

Insulin

-Stimulates making of glycogen, TAGs and proteins

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6
Q

How many chains does insulin have? How are they linked?

A

2 chains; A chain and B chain attached by critical disulfide bond

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7
Q

What does the preproinsulin contain that proinsulin does not?

A

Signal sequence (guides the protein into the ER where it will be cut out)

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8
Q

Where does proinsulin go?

A

Golgi apparatus -> C-peptide will be cut -> final product (A + B) -> insulin ready to go just waiting for secretion

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9
Q

What increases secretion of insulin?

A

Glucose (#1 signal), AAs, and GI peptide hormones

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10
Q

What is the secretion of insulin by pancreatic beta cells closely coordinated with?

A

Glucagon by alpha cells

-Insulin goes up, glucagon goes down

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11
Q

How will a muscle cell know that you are releasing insulin from your pancreas?

A

Insulin surface receptor, i.e. receptor tyrosine kinase (RTK)

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12
Q

What happens once the insulin activates RTK?

A

Internal phosphorylation: tyrosine residues of beta subunit are auto-phosphorylated -> phosphorylates other proteins (insulin receptor substrate-IRS)

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13
Q

What does phosphorylated IRS promote in muscle and adipose cells?

A

Upregulation of GLUT-4 (glucose uptake)

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14
Q

What does phosphorylated IRS promote in liver and muscle cells?

A

Glycogen synthesis and protein synthesis

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15
Q

What does phosphorylated IRS promote in liver cells?

A

Fat synthesis

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16
Q

What does phosphorylated IRS downregulate in liver cells?

A

Gluconeogenesis and glycogenolysis

17
Q

What does phosphorylated IRS downregulate in adipose cells?

A

Lipolysis

-Inhibits HSL and activates lipoprotein lipase

18
Q

Where is active transport INSENSITIVE to insulin?

A

Epithelia of intestine
Renal tubules
Choroid plexus

19
Q

Where is facilitated diffusion INSENSITIVE to insulin?

A 
Erythrocytes
Leukocytes
Lens of eye
Cornea
Liver
Brain
20
Q

Where is facilitated transport SENSITIVE to insulin?

A

Skeletal/cardiac muscle

Adipose tissue

21
Q

What does insulin downregulate?

A

Glycogenolysis
Gluconeogenesis
Ketogenesis
Lipolysis

22
Q

What does glucagon/ephinephrine upregulate?

A

Glycogenolysis
Gluconeogenesis
Ketogenesis (FA oxidation)
Lipolysis

23
Q

What is glucagon known as?

A

Counterregulatory hormone (opposes insulin)

24
Q

What does glucagon do?

A

Maintain blood [glucose] by activation of hepatic glycogenolysis/gluconeogenesis

25
Q

What is glucagon secretion stimulated by?

A

Low blood glucose, some AAs and catecholamines

26
Q

What cells make and release glucagon?

A

Alpha cells in pancreas

27
Q

What does glucagon bind to?

A

Glucagon G protein-coupled receptor (heptahelical)

28
Q

What does glucagon activate?

A 
Adenylyl cyclase (2nd messenger) -> cAMP
-Glucagon is 1st messenger
29
Q

What does cAMP activate?

A

Protein kinase A -> catalytic subunits are activated -> phosphorylation cascade

30
Q

Where are glucagon receptors for glycogenolysis/gluconeogenesis/FA oxidation/ ketogenesis/uptake of AAs?

A

Liver cells (NOT MUSCLE!!!)

31
Q

What 2 things does glucagon downregulate in the liver?

A

Glycogenesis and FA synthesis

32
Q

When blood glucose gets below or equal to 40 mg/dl what happens?

A

Hypoglycemia

-Very bad -> CNS sx (confusion, aberrant behavior, coma)

Biochem Exam 4 (7 decks)

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