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HUNT241 > BIOC Lecture 2: Insulin > Flashcards

BIOC Lecture 2: Insulin Flashcards

1
Q

What is the key metabolic pathways active in the goldfish when it is producing ethanol?

A

Glycolysis

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2
Q

What is the difference between humans and goldfish’s metabolic rate?

A

Goldfish have a very reduced metabolic rate, therefore function less efficiently

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3
Q

Without oxygen, what do goldfish convert lactate to?

A

Ethanol

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4
Q

What is insulin synthesised as?

A

A pre-pro-peptide

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5
Q

What is a pre-sequence?

A

A signal that helps tell the cell where this protein is going to go in the cell

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6
Q

What is the specific pre-sequence for insulin synthesis?

A

Responsible for export from the cytosol of the cell into secretory granules

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7
Q

What is pro-sequence?

A

segment of a protein that assists in folding, stabilization, regulation of activity, ensuring the protein is only active under appropriate conditions and at the correct location

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8
Q

What is the pro-sequence of insulin important for?

A

For proper folding of insulin and is then removed

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9
Q

Mature insulin has how many chains of amino acids?

A

2 chains of AA’s - with cleavages

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10
Q

Insulin will only function when?

A

the 2 components are properly folded and connected

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11
Q

What type of bonds does insulin have?

A

disulfide bonds (C-C) as well as secondary and tertiary structure interactions

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12
Q

Where are alpha and beta cells made?

A

Pancreas

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13
Q

What do beta cells cause the release of?

A

Insulin

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14
Q

What does insulin lead to?

A

Decrease in blood sugar

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15
Q

What do alpha cells cause the release of?

A

Glucagon

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16
Q

What does glucagon lead to?

A

Increased blood sugar

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17
Q

What does insulin typically form?

A

Hexamers with Zn in beta cells

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18
Q

What does insulin form in the blood?

A

Monomers

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19
Q

What does circulating insulin interact with?

A

Receptors on some tissues (fat, muscle, liver etc)

20
Q

What is an insulin receptor synthesised as?

A

One protein - cleaved for full function

21
Q

What gives rise to different receptor isoforms?

A

Splicing variants during mRNA

22
Q

Where are insulin receptors found?

A

As a dimer on the surface of various cell types

23
Q

What is a dimer?

A

when two similar molecules or proteins link up together

24
Q

What three domains play a specific role in the insulin receptors function?

A

Extracellular, transmembrane, cytosolic

25
Q

What happens when no ligand is present?

A

The receptor is inactive

26
Q

What does binding of ligand do to receptors?

A

Causes structural changes and activates receptor (tyrosine kinase domain)

27
Q

What happens in a normal person when blood glucose levels rise?

A
  • Insulin is released by beta cells
  • Receptor stimulated, GLUT4 receptors move to cell surface
  • Glucose uptake
28
Q

What is happening in the body of people with Type 1 diabetes?

A

No functional insulin: autoimmune disease or variant insulin

29
Q

What is happening in the body of people with Type 2 diabetes?

A

Reduced receptor sensitivity: obesity (common) or rare genetic receptor variants

30
Q

What are beta cells sensitive to?

A

Insulin sensitive

31
Q

What does the uptake of glucose stimulate?

A

Oxidative metabolism and production of ATP

32
Q

What does increased metabolic activity stimulate?

A

The conversion of proinsulin and the release of insulin

33
Q

What do storage granules fuse with?

A

With membrane and are released into the bloodstream

34
Q

How many glucose transporters are know in humans?

A

As many as 20

35
Q

How many main transporters are there?

A

4

36
Q

What are the 4 main glucose transporters?

A

GLUT 1, 2, 3, 4

37
Q

What is the function of GLUT 1?

A

Bidirectional and found in foetal tissues. In adults, found in erythrocytes and in low levels in most cells where it allows basal uptake of glucose for respiration

38
Q

Where is GLUT 2 found?

A

In kidney, liver, pancreatic B cells, basolateral membrane of small intestine

39
Q

What is the function of GLUT 2?

A

Largely responsible for the insulin-independent uptake of glucose, and for release of glucose during periods of gluconeogenesis.

40
Q

What is the function of GLUT 3?

A

Glucose uptake in neurones and also in the placenta

41
Q

What is the function of GLUT 4?

A

Insulin-dependent glucose uptake

42
Q

Where is GLUT 4 found?

A

In striated muscle and adipose tissue

43
Q

Where does GLUT 4 transition between?

A

Vesicles within the cell and plasma membrane

44
Q

What are the processes of GLUT4 activation?

A

Endo- and exocystosis

45
Q

What does insulin favour?

A

GLUT4 location in plasma membrane

HUNT241 (22 decks)

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