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Flashcards in Liver Biochemistry Deck (80):
1

What supplies most blood flow to liver?

portal vein

2

Bile canniculus

duct like structure that runs parallel to sinusoids

3

What are the 5 liver cell types

hepatocytes, endothelial cells, kupffer cells, hepatic stellate cells, pit cells

4

Kupffer cells

macrophages of liver

5

Hepatic stellate cells

specific to liver

6

Pit cells

NK cells that protect the liver against virus and tumor cells

7

Major function of the liver

central receiving, distribution, and recycling center

8

Major role of receiving, distribution and recycling center

monitoring, synthesizing, recycling, distributing, and modifying metabolites

9

How does liver convert harmful products

Converts into safe product and is excreted

10

2 vessels that provide blood to liver

portal vein and hepatic artery

11

Structure of liver cells

lack basement membrane, fenestrations in endothelial cells, low portal blood pressure

12

Functional reason for structure of liver

greater access and increased contact between liver and blood

13

What forms isopentenyl pyrophosphate?

3 acetyl CoAs

14

3 potential products from isopentenyl pyrophosphate

1. Steroids (cholesterol, bile, steroid hormones)
2. Lipid soluble vitamins (A, D, E, K)
3. Other (ubiquinone, heme tails)

15

Sources of acetyl CoA

oxidative decarboxylation, beta oxidation of fatty acids, breakdown of amino acids

16

What part of the cell is Acetyl CoA generated in

mitochondria

17

How does Acetyl CoA get into cytolasm

citrate shuttle

18

Example of some steroids derived from IPP

cholesterol, estradiol, cholic acid

19

Structure of cholesterol

allicyclic compound made of 4 fused rings

20

Cholesterol is the precursor of what active compounds

bile acids and salts, vitamin D, steroid hormones

21

What is the daily production of cholesterol

1g

22

T/F biosynthesis is proportional to dietary intake of cholesterol

F- biosynthesis is inversely proportional to dietary intake. The less you intake the more you make

23

What enzyme is used to make HMG CoA from acetoacetyl CoA?

HMG CoA synthase

24

What is the rate limiting enzyme in cholesterol synthesis

HMG CoA reductase

25

What are the rate limiting intermediates for cholesterol synthesis

HMG CoA to mevalonate

26

What does positive feedback for rate limiting step

insulin and thyroxine

27

What does negative feedback for rate limiting step

sterols and statins

28

Statins and ubiquinone formation?

Statins inhibit ubiquinone formation and will mess up TCA cycle and muscle formation so need to make sure patients are supplemented

29

Fate of cholesterol in all tissues

cholesterol incorporated into cellular membranes

30

Fate of cholesterol in liver

synthesize bile acids

31

Fate of cholesterol in adrenal glands, ovaries and testes

synthesize steroid hormones

32

Fate of cholesterol in skin

synthesize vitamin D

33

Main/Major fate of cholesterol

packaged into VLDL and released into circulation

34

Lipid rafts

microdomains enriched in cholesterol, sphingolipids, and gangliosides

35

What happens at lipids rafts

center for signal transduction processes and abnormal processing of proteins

36

Which way is the catalytic domain facing in choesterol

cytosol site where ubiquitination occurs

37

Which domain is facing the luminal side?

membrane domain

38

Direct inhibition of HMG CoA reductase

free fatty acids, bile acids, and oxysterols

39

T/F Statins are noncompetitive inhibitors of HMG CoA Reductase

F- statins are competitive inhibitors of HMG CoA Reductase

40

Where does the stain bind to compete for HMG CoA reductase

the active site, and statins have similar structures

41

Covalent modifications of HMG CoA Reductase

Active when dephosphorylated, inactive when phosphorylated

42

Low energy - high AMP levels on AMP

phosphorylates it through AMP activated kinase and inactivates it

43

Glucagon impact on HMGR

inhibits enzyme by preventing dephosphoylattion

44

Insulin impact on HMGR

activates HMGR phosphatase and promotes dephosphoylation

45

AMP kinase

puts phosphate on HMGR to inactivate it

46

HMGR phosphatase

takes phosphate off HMGR to activate it

47

Promoter for transcriptional Control of HMG

sterol regulatory element SRE

48

sterol regulatory element binding protein (SREBP)

sequence that binds trascription factors

49

What does SREBP interact with

SREBP cleave activating protein

50

What does SREBP-SCAP complex bind to?

INSIG

51

When does SREBP-SCAP complex bind to INSIG

in the presence of cholesterol

52

Is transcription slow or fast when cholesterol is present and binding to the SREBP-SCAP complex

slow

53

What promotes release of SREBP-SCAP complex from ER

low sterol

54

What binds to SRE to promote transcription of HMG CoA reductase

mature form of SREBP

55

What reduces translastion of HMG

vitamin E family (gamma-tocotrienol) and oxylanosterols

56

What happens to HMG when there is more cholesterol?

degrade HMG CoA reductase

57

Role of liver and cholesterol

cholesterol metabolism and homeostasis

58

Where does cholesterol biosynthesis occur?

liver

59

What does liver do to cholesterol

package it into VLDL, release it into blood, metabolize to LDL by peripherial tissues

60

How is dietary cholesterol delivered to the liver

chylomicron remnants

61

Inhibitors of HMG CoA Reductase

statins because they are competitive inhibitors
- citrus juices
- grapefruit juice

62

Function of cytochrome P450

convert linear isoprenoid squalene into cholesterol

63

What happens if you inhibit cytochrome P450

increase in statin levels leaving to toxic effects

64

Function of agents that induce cytochrome P450

decrease levels of statin in plasma

65

What is the precursor of bile acids and bile salts

hepatic cholesterol

66

Characteristics of strong detergents

amphipathic with polar and nonpolar regions

67

Where is bile made

hepatocytes

68

Where is bile stored and concentrated

gallbladder

69

What is bile made of

bile acids, cholesterol, phosphoipids, fatty acids, proteins, bile pigments, inorganic salts

70

Lipid emulsification

aids in lipid digestion, forming micelles to increase surface area of lipids

71

How is cholesterol is converted to bile salt

Cholesterol + Cytrochrome P450 --> 7a- hydroxycholesterol

72

2 fates of 7a-hydroxycholesterol

chenocholic acid and cholic acid

73

Difference between chenocholic acid and cholic acid

cholic acid the 2nd hydroxyl group is added at 12th position and bile acids can be conjugated

74

Taurocholic acid

taurine is added to replace CoA, lower pKa makes them efficient in surfactant ability

75

Glycocholic acid

glycine added to replace CoA

76

Difference between cholesterol and bile salt

to make a bile salt, remove H from carboxylic acid of cholesterol

77

Micelle

surrounded by bile salt and has hydrophobic and hydrophilic areas so we can digest certain things

78

Gallstones

bile supersaturated with cholesterol

79

Cholelithiasis

insufficient secretion of bile salts or phospholipds or excess cholesterol secretion

80

Chronic disturbance in bile salt metabolism

steatorrhea and deficiency in fat soluble vitamins