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Biochemistry > Biochemistry of the liver > Flashcards

Biochemistry of the liver Flashcards

1
Q

What are the functions of the liver?

A

Bile production
Elimination of unwanted molecules
Secretion of plasma proteins
Storage of important molecules

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2
Q

Which molecules, of endogenous origin, are excreted in the bile?

A

Steroid hormones

Bilirubin

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3
Q

Which molecules, of exogenous origin, are excreted in the bile?

A

Lipid soluble substances ingested as drugs

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4
Q

What happens to drugs that are metabolised in the liver?

A

Made more polar to make excretion easier

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5
Q

What is the function of cytochrome P-450 enzymes?

A

They catalyse the phase 1 reaction of metabolism in the liver - changing an unwanted molecule to a derivative e.g. by oxidation or hydroxylation

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6
Q

What is phase 2 of liver metabolism?

A

Conjugation of new OH group on derivative

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7
Q

Give an example of a drug which can cause hepatotoxicity through production of a toxic metabolite.

A

Paracetamol

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8
Q

In paracetamol overdose, what pathway is overwhelmed and what does this result in?

A

Conjugation pathway is overwhelmed, so toxic metabolite builds up in liver causing hepatocellular damage

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9
Q

What causes prehepatic jaundice?

A

Excess production of bilirubin due to haemolysis

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10
Q

What might cause posthepatic jauncide?

A

Bile duct obstruction e.g. gallstone

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11
Q

Why might you get pale stools and dark urine in post hepatic jaundice?

A

Pale stools due to reduction of faecal bile pigment

Dark urine due to excretion of water soluble bilirubin conjugates

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12
Q

What causes intrahepatic jaundice?

A

Generalised hepatocyte dysfunction

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13
Q

What is the treatment for intrahepatic jaundice in neonates?

A

Phototherapy with blue-white light

Isomerises bilirubin to more soluble form which can be excreted in bile

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14
Q

After a meal, which pathway is excess glucose diverted towards?

A

Pentose phosphate pathway to make NADPH for biosynthetic processes

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15
Q

Where are amino acids for gluconeogenesis taken from in the postabsorptive state?

A

Muscle protein is degraded to provide amino acids

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16
Q

Where does glycerol used in gluconeogenesis come from?

A

Glucagon stimulates lipolysis by hormone-sensitive lipase

17
Q

What happens to the fatty acids after lipolysis in the postabsorptive state?

A

Fatty acids metabolised, ketone body formation increases

18
Q

What are ketone bodies used for?

A

Used as a source of energy by heart and skeletal muscle

19
Q

What is the main energy substrate in the starving state?

A

Fatty acids

20
Q

What can the brain adapt to use as fuel instead of glucose in the starving state?

A

Ketone bodies

21
Q

What are the functions of plasma proteins?

A

Maintenance of oncotic or colloid osmotic pressure
Transport of hydrophobic substances e.g. sterioid hormones, free fatty acids, bilirubin and cholesterol
pH buffering
Enzymatic e.g. blood clotting

22
Q

What are the functions of alpha globulins?

A

Transport lipoproteins, lipids, hormones and bilirubin

e.g. ceruloplasmin or retinol binding protein

23
Q

What are two examples of beta globulins and what do they do?

A

Transferrin - transports Fe3+ and is an indicator of iron deficiency
Fibrinogen - inactive form of fibrin, causes clotting of blood when activated

24
Q

What is the most abundant plasma protein?

A

Albumin

25
Q

What is albumin?

A

A small, negatively charged, water-soluble plasma protein

It is the main determinant of plasma oncotic pressure

26
Q

What are some of albumin’s transport functions?

A

Albumin has multiple binding sites for hydrophobic molecules
Transports important endogenous lipophilic substances:
Bilirubin
Thyroid hormones
Drugs e.g. aspirin

27
Q

How is iron transported in the blood?

A

Transported as ferric ion Fe3+ bound to transferrin

28
Q

How is copper transported in the blood?

A

Transported bound to ceruloplasmin

29
Q

Why is copper-bound ceruloplasmin essential?

A

Regulations of redox reactions

Transport and use of iron

30
Q

What is a deficiency of copper called?

A

Wilson’s disease

31
Q

What does the core of lipoproteins consist of?

A

Hydrophobic lipids i.e. cholesterol esters and trigylcerides

32
Q

What does the shell of lipoproteins consist of?

A

Polar lipids i.e. phospholipids

Apoproteins

33
Q

Which lipoproteins are dietary fats transported in?

A

Chylomicrons

34
Q

Which lipoproteins are synthesised fats transported in?

A

VLDL

35
Q

What is the function of HDL?

A

Removes excess cholesterol from cells - cholesterol is esterified with fatty acids and transported back to the liver where it is excreted as bile salts via the biliary system or faeces

36
Q

Which vitamins does the liver store?

A

Vitamin A
Vitamin D
Vitamin B12
(Iron)

37
Q

What is the function of cholesterol in cells?

A

Essential component of the membranes - increases rigidity

38
Q

What is HMG-CoA reductase?

A

Involved in cholesterol synthesis - catalyses the irreversible formation of mevalonic acid

39
Q

What is the function of vitamin D?

A

Regulation of calcium and phosphorus metabolism

Biochemistry (9 decks)

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