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BIOC192 2024 > Lecture 31 - Coordinating Metabolism: Insulin and Glucose Transport > Flashcards

Lecture 31 - Coordinating Metabolism: Insulin and Glucose Transport Flashcards

1
Q

What is metabolic homeostasis

A

The body’s ability to maintain various metabolic processes to ensure molecules essential for life are kept at an optimal level

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2
Q

What is the preferred fuel type for the brain?

A

Glucose but can use ketone bodies as well

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3
Q

What is the preferred fuel type for resting skeletal muscle?

A

Fatty acids

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4
Q

What does resting skeletal muscle store?

A

Glycogen

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5
Q

What is the preferred fuel type for exercising skeletal muscle?

A

All; glucose, fatty acids, branch-chain amino acids

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6
Q

What fuels are exported from exercising skeletal muscle?

A

Lactate and alanine

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7
Q

What is the preferred fuel type for cardiac muscle?

A

Fatty acids

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8
Q

What is the preferred fuel type for the adipose tissue?

A

Fatty acids

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9
Q

What fuel is stored in adipose tissue?

A

Triacylglycerols

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10
Q

What fuel is exported from adipose tissue?

A

Fatty acids and glycerol

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11
Q

What is the preferred fuel type for the liver?

A

Amino acids, glucose and fatty acids

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12
Q

What fuel is stored in the liver?

A

Glycogen

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13
Q

What fuels are exported from the liver?

A

Triacylglycerols, glucose, ketone bodies

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14
Q

What is the prefered fuel for RBCs?

A

Glucose

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15
Q

What fuel is exported from RBCs?

A

Lactate

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16
Q

Why can the brain not use FAs?

A

They cannot cross the blood-brain barrier

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17
Q

What can the RBCs not use FAs?

A

They lack mitochondria

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18
Q

What is insulin?

A

A peptide hormone synthesised in the pancreas by the beta cells

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19
Q

When is insulin secreted?

A

In response to high glucose levels

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20
Q

What does insulin do?

A

Acts on the liver, muscle and adipose tissues to promote glucose transport and use

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21
Q

What happens to the body without insulin?

A

It starves

22
Q

What is type 1 diabetes?

A

An early onset form of diabetes, diagnosed by symptoms, blood glucose and glycated haemoglobin

23
Q

What are common symptoms of diabetes?

A

Glycosuria (glucose in urine) and the presence of ketones in the blood

24
Q

What causes type 1 diabetes?

A

An autoimmune condition leading to the loss of pancreatic beta cells and therefore no insulin secretion

25
Q

What is preproinsulin?

A

Initial form of insulin synthesised from transcription and translation - in the ER

26
Q

What does preproinsulin contain?

A

An A-chain, B-chain, C-peptide, and a signal sequence

27
Q

What is the signal sequence?

A

A chain that helps direct the protein into the ER but is removed by signal peptidase, leaving proinsulin

28
Q

What is proinsulin?

A

The A-chain, B-chain, and C-peptide of insulin. It moves to the Golgi and is packaged into secretory granules. Proprotein convertase enzymes in the granules cleave proinsulin to release active insulin (A-chain and B-chain) and C-peptide.

29
Q

What is the C-peptide?

A

A chain released during the cleavage of proinsulin along with insulin, has a longer half-life than insulin and can be used as a marker of insulin secretion

30
Q

What is the c-peptide important for?

A

Distinguishing between endogenous insulin and exogenous insulin

31
Q

How does glucose stimulate insulin secretion?

A

GLUT1 transports glucose into pancreatic beta cells, glucose is metabolised via glycolysis and the CAC to increase ATP levels. Increased ATP:ADP ratio inhibits ATP-gated K+ channels triggering membrane depolarisation and the opening of voltage-gated Ca2+ channels. The calcium influx induces exocytosis of insulin-containing secretory vesicles

32
Q

When are glucose levels the highest?

A

About an hour after eating

33
Q

When are insulin levels the highest?

A

About two hours after eating

34
Q

What is the incretin effect?

A

The phenomenon where oral glucose intake stimulates a greater insulin response compared to an equivalent amount of glucose administered intravenously

35
Q

Why does oral glucose stimulate insulin better?

A

Due to the action of gut-derived hormones; GLP-1

36
Q

Why does insulin have to be taken intravenously?

A

Gets broken down in GI tract

37
Q

What is GLP-1 in the L-cells of the intestine an example of?

A

A different way of processing the same protein (similar to insulin)

38
Q

What is GLP-1?

A

A peptide hormone synthesised in the intestine in response to nutrients

39
Q

What is GLP-1 made from?

A

Glucagon via convertase enzyme

40
Q

What does GLP-1 do?

A

Acts through its receptor to stimulate insulin secretion

41
Q

How is GLP-1 used to treat type 2 diabetes?

A

Agonists are developed

42
Q

How does GLP-1 promote weight loss?

A

Slows gastric emptying and reduces appetite

43
Q

What is GLUT4?

A

An insulin-regulated glucose transporter

44
Q

Where is GLUT4 found in muscle and adipose cells?

A

Intracellular storage vesicles

45
Q

What happen when insulin binds to its receptor?

A

A phosphorylation cascade is activated that regulates the trafficking of GLUT4 vesicles to the plasma membrane by regulating vesicle trafficking proteins

46
Q

What is GSV?

A

The GLUT4 storage vesicle

47
Q

What does AS160 do?

A

Regulates a GTPase protein Rab10 which is involved in the trafficking of vesicles

48
Q

What is IRS?

A

Insulin receptor substrate

49
Q

What is PIP2 and PIP3?

A

Membrane phospholipids

50
Q

What is the insulin receptor an example of?

A

A tyrosine kinase receptor

BIOC192 2024 (35 decks)

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