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LC Gastroenterology Week 6 > Biochemical aspects of liver metabolism > Flashcards

Biochemical aspects of liver metabolism Flashcards

1
Q

What is the livers principle roles?

A 
Final destination of absorbed products from the liver 
Bile production 
Elimination of unwanted molecules 
Secretion of plasma proteins 
Storage of important molecules 
Regulation of metabolism
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2
Q

Describe the plasma proteins?

A

Albumin
Alpha globulins
Beta globulins
Gamma globulins (immunoglobulins)

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3
Q

What allows separation of proteins by size - plasma proteins?

A

Electrophoresis

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4
Q

What are the main functions of plasma proteins?

A 
Maintenance of oncotic or colloid osmotic pressure 
Transport of hydrophobic substances 
pH buffering 
Enzymatic 
Immunity
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5
Q

What is the function of alpha goblin?

A

Transports lipids, bilirubin, lipoproteins and some dietary metals

Retinol binding protein - transports Vitamin A

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6
Q

What is the function of beta globulins?

A

Transferrin - transports Fe3+, indicator of iron deficiency

Fibrinogen - inactive form of fibrin, clotting of the blood

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7
Q

What does transferrin do?

A

Transports Fe3+ - indicator of iron deficiency

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8
Q

What does fibrinogen do?

A

Inactive form of fibrin

Clotting of the blood

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9
Q

Describe albumin?

A

Most abundant plasma protein - main determinant of plasma oncotic pressure

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10
Q

What stimulates the production of albumin?

A

Insulin stimulates the production of albumin

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11
Q

What causes a decrease of albumin levels?

A

Starvation/low protein diet

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12
Q

What does albumin transport?

A

Endogenous lipophilic substances
Fatty acids
Bilirubin
Thyroid hormones

Exogenous
Drugs like aspirin

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13
Q

What is bilirubin the breakdown product of?

A

Breakdown product of haem

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14
Q

What is iron transported as?

A

Ferric iron Fe3+

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15
Q

What is Ferric iron Fe3+ bound to when being transported?

A

Transferrin

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16
Q

Where is iron stored?

A

In cells bound to ferritin

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17
Q

What is copper bound to when transported in the blood?

A

Ceruoplasmin

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18
Q

What is copper essential for?

A

The regulation of redox reactions, transport and use of iron

19
Q

What is a deficiency of copper called?

A

Wilsons disease

neurological symptoms and liver pathology due to copper accumulation in tissues…. [Cu2+] is not bound by ceruloplasmin and so is improperly metabolised and excreted

20
Q

What are steroid hormones derived from?

A

Cholesterol

21
Q

What is thyroxine transported in the blood?

A

Bound to thyroid-binding globulin

22
Q

What is cortisol transported in the blood?

A

Bound to cortisol-binding globulin

23
Q

Describe lipoproteins?

A

Core of hydrophobic lipids
Surround by a shell (phospholipid, and apoproteins)
Free cholesterol dispersed throughout

Fat transport between organs and tissue

24
Q

What is the function of HDL?

A

Reverse cholesterol transport

25
Q

What is the function of LDL?

A

Cholesterol transport to peripheral tissues

26
Q

Describe reverse cholesterol transport by HDL?

A

It removes excess cholesterol from cells

27
Q

What is the liver the only organ capable of metabolising and excreting?

A

Cholesterol

28
Q

When cholesterol is esterifed with fatty acids and transported back to the liver what does the liver do?

A

It excretes it as bile salts via the biliary system or faeces

29
Q

What does the liver store?

A

Vitamins A, D and B12

Iron

30
Q

Where does the iron stored in the liver come from?

A

The breakdown of haemoglobin, soared associated with ferritin

31
Q

What is cholesterol as essential component of?

A

Mammalian cell membranes - increases the rigidity

32
Q

What is cholesterol the precursor for?

A

Three important classes of biologically active compounds

  • bile acids
  • steroid hormones
  • Vit D
33
Q

Where is cholesterol stored?

A

It can be incorporated into lipoproteins and thus solubilised (located in the core of the molecule)
IT can be stored in lipid droplets

Majority of it is esterified to a wide range of long chain fatty acids

30% is circulating in free form

34
Q

Where is cholesterol synthesised?

A

In virtually all cells

Mainly in the liver

35
Q

What does synthesis of 1mol of cholesterol require?

A

Source of C atoms - 18mol of acetly-CoA

Source of reducing power - 16 mol of NADPH

Significant amounts of energy - 36mol of ATP

36
Q

What does HMG-CoA reductase do?

A

Catalyses the irreversible formation of mevalonic acid

It is a rate limiting enzyme

37
Q

What is HMG-CoA reductase a target for?

A

Cholesterol lowering drugs - statins

38
Q

What is cholesterol synthesis controlled by?

A

Hormones

HMG-CoA reductase

39
Q

Describe steroid hormones as a product of cholesterol?

A

Three groups
Corticosteroids (adrenal cortex)
Androgens (testis)
Estrogens (ovary)

40
Q

What is the main metabolic product of cholesterol?

A

Bile salts

41
Q

Where are bile salts synthesises and secreted by?

A

The liver

42
Q

What do bile salts act as?

A

Dtgergents for emulsifying ingested lipids

43
Q

What are bile salts recycled by?

A

The enterohepatic circulation

LC Gastroenterology Week 6 (8 decks)

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