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Gastrointestinal > liver physiology > Flashcards

liver physiology Flashcards

1
Q

how are vessels organised in the liver

A

in a hexagonal portal

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2
Q

functions of the liver

A

detoxification, energy storage, immune functions , synthesis of clotting

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3
Q

what are lipids

A

Esters of fatty acids and glycerol

Large and diverse naturally occurring organic compounds that are insoluble in water
Variety of structure and functions

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4
Q

how are lipids stored

A

adipocytes, hepatocytes,

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5
Q

lipid functions

A

energy reserve, hormone metabolism

Structural part of cell membrane

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6
Q

lipid transport?

A

Lipids are often transported as TGs or FAs bound to Albumin or within lipoproteins
TGs cannot diffuse through cell membrane
FA are released through lipases to facilitate transport into the cells
In the cell FA are re-esterified to TG

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7
Q

fatty acid uptake and regulation

A

Diffusion through the lipid bilayer of the cell membrane

Facilitated transport
Increases if increased substrate (↑supply) or increase in receptor molecules (↑ demand)

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8
Q

transporter systems of fatty acids

A

induction to increased expression may result in increased uptake of FA in the hepatocytes)
FAT - fatty acid translocase
FATP - FA transport polypeptide

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9
Q

what do lipoproteins consists of?

A

core of tg’s and cholestrol esters and a surface monolayer of phospholipids

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10
Q

where is iron absorbed and stored

A

duodenum made

Stored in liver

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11
Q

what transports iron around the body

A

transferrin

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12
Q

ferritin?

A

A blood protein that contains iron

Large spherical protein

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13
Q

where is ferritin found

A

Ferritin found in the cytoplasm of cells but can also be found in the serum.

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14
Q

xenobiotics

A

foreign substances with no nutritional value

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15
Q

how can xenobiotics damage cells

A

dna damage, react with o2 to make free radicals

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16
Q

function of phase1 biotransformation of xenophobes

A

to add or expose functional groups- OH, COOH, NH2 and SH to make the xenophobe more hydrophilic to be excreted from kidneys

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17
Q

where are cytochrome p450 found

A

present in smooth er

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18
Q

Function of cytochrome p450 in phase 1 reactions

A

Uses cytochrome p450 reductive to transfer electrons to nadph

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19
Q

outline phase 1 reactions

A

oxidation, hydrolysis and reduction
addition of an oh group to make it more polar
with cytochrome p450

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20
Q

POSITIVE NITROGEN BALANCE

A

). If the intake of nitrogen is greater than the excretion

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21
Q

NEGATIVE nitrogen BALANCE

A

, if excretion greater than intake

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22
Q

gain or lose proteins in positive N balance

A

gaining protein

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23
Q

gain or loose protein in negative N balance

A

lose

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24
Q

kwashiorkor

A

protein malutrition

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25
Q

amino acid absorption

A

The first stage is via a cell surface channel where it is co transported with a sodium ion. Then via the basal membrane is is actively transported into the portal veinous circulation by an ATP consuming process. From there it travels into the liver.

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26
Q

difference between essential and non essential amino acids

A

essential- amino acid that cant be synthesized by the body and must come from diet

non - essential- can be synthesised by the body

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27
Q

most important hepatic protiein

A

albumin

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28
Q

alpha ketoacid?

A

removal of amine group from amino acid left with carbon backbone

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29
Q

transamination

A

a chemical reaction that transfers an amino group to a ketoacid to form new amino acids
enzyme- aminotransferase

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30
Q

what happens to amino acids in the fasting state

A

stored in muscle as protein, broken down into monomer form of amino acid , to make atp
gluconeogenesis

31
Q

glucose alanine cycle

A

Excess alanine transferred to the liver and converted to pyruvate
Pyruvate can be used to produce glucose in gluconeogenesis
Glucose enters blood used by muscles
Glutamate to ammonium by oxidative deamination dissociates to ammonia , converted to urea

32
Q

why is albumin important

A

Binding and transport

  1. Maintenance of colloid oncotic
    pressure
  2. Free Radicals
  3. Anticoagulant effects
33
Q

What causes Albumin to decrease

A

Decreased synthesis

  1. Increased catabolism
  2. Increased loss
34
Q

Consequences of decreased Albumin

A

Decreased colloid oncotic pressure

  1. Decreased ligand binding
35
Q

Disease processes associated with

low Albumin

A 
Malnutrition
Liver disease
Renal disease
Burns / trauma
Sepsis
36
Q

why is bile important

A

Lipid digestion and absorption
Cholesterol homeostasis
Excretion of lipid soluble xenobiotics / drug metabolites / heavy metals

37
Q

What is bile?

A

digestive fluid produced by the liver and stored in the gall bladder

38
Q

what does bile formation depend on?

A

Formation depends on the hepatic SYNTHESIS and cannalicular SECRETION of bile acids (=major organic anion in bile)

39
Q

breakdown product of red blood cells

A

bilirubin

40
Q

where are bile acids synthesised ?

A

Synthesised from cholesterol in hepatocytes of the acini

41
Q

what does amphipathic mean

A

hydrophillic and hydrophobic parts

42
Q

Fat soluble vitamins

A

A d e k

43
Q

Function of copper and storage

A

Helps to form rbc

Transported in plasma bound to ceruloplasmin

44
Q

Three types of plasma protein

A

Albumin

Fibrinogen and globulin

45
Q

Most common plasma protein and function

A

Albumin
Maintains oncotic pressure
Binds and transports large hydrophobic molecules

46
Q

Which clotting factors does the liver produce

A

All but 8

47
Q

Where is iron stored

A

In the liver as ferritin in kuppfer cells

48
Q

What are microsomes

A

Fragments with endoplasmic reticulum and ribosomes

49
Q

Define lipophilic

A

Able to pass through plasma membranes

50
Q

Phase 2 reaction outline

A

Adding a glucaronic acid group
Increase hydrophilicity
Done by glucuronosyltransferase

51
Q

What reactions are non microsomal enzymes involved in

A

All conjugation reactions except glucoronidation

52
Q

What is the role of fad

A

Accept electrons from nadph

53
Q

Function of complement proteins

A

Aid in immune response

54
Q

Role of urea cycle

A

Series of enzymatic reactions

Convert ammonia into urea

55
Q

Where does urea cycle happen

A

Mitochondria of hepatocytes

56
Q

How does ammonia get into liver mitochondria

A

Glutamine synthesise
Adds ammonia to the amino acid glutamate forming glutamine
Once in the liver glutamine hydrolyses the products back into their original form

57
Q

Urea cycle steps

A

Ammonium and co2 combine to make carbomoyl phosphate
This allows ornithine to be converted to citruiline
citruiline to arginine
Arginine is cleaved by arginase into urea and ornithine and the cycle repeats

58
Q

In what three forms is energy stored in the body

A

Triglycerides 78%
Protein 21%
Carbohydrate 1%

59
Q

Where is most body fat stored

A

Adipocytes

60
Q

Three types of lipoprotein and where they’re formed and function

A

Hdl liver good cholesterol , removes excess via excretion in bile
LDL plasma delivers cholesterol to cells
Vldl synthesised in hepatocytes triglyceride delivery from liver to adipocytes

61
Q

Function of lipoprotein

A

Transport cholesterol through the blood

62
Q

Function of lipoprotein lipase

A

Hydrolyses triglycerides into 2 fatty acids and one monoglyceride molecule

63
Q

Function of hepatic lipase

A 
Found in liver and adrenal cells 
Converts IDL ( intermediate density lipoprotein ) into LDL thereby packaging it with more triglycerides to be released into the body .
64
Q

describe the steps in beta oxidation of fatty acids

A
  • CoA binds to the end of a fatty acid chain: fatty acyl CoA.
  • ATP -> AMP + 2Pi.
  • Fatty acyl CoA is a substrate for beta-oxidation.
  • Acetyl CoA is split off from FA and 2H+ are transferred to coenzymes.
  • H+ enter OP and another CoA attaches to repeat the cycl
65
Q

Difference between white and brown fats

A

White few mitochondria , little endoplasmic reticulum , stores energy
Brown fat lots of mitochondria , expending energy and heat production

66
Q

Constituents of bile

A 
Bile salts 
Lecithin 
Hco3- 
Cholesterol 
Bile pigments
67
Q

How is bile secreted

A

Secreted under the action of cholecystokinin
CCK released in response to increased fatty acid conc in duodenum
Gall bladder contracts
Bile released into duodenum via sphincter of oddi

68
Q

Where are bile salts reabsorbed and how

A

In the terminal ileum via portal vein 95%

69
Q

What is bilirubin

A

Pigment that gives bile it’s yellow colour

By products of haem metabolism

70
Q

Bilirubin metabolism

A

Hb-> haem and glob in with macrophage
Haem —> biliverdin with haem oxidase
Biliverdin to bilirubin via biliverdin reductase
Unconjugated bilirubin transported to the liver via albumin carrier
Glucoronic acid conjugates it via glucoronyl transferase
Released in bile via duodenum

71
Q

What is enterohepatic circulation

A

Movement of bile acid molecules from the liver to the small intestine and back to the liver

72
Q

How is urobilinigen made

A

Intestinal bacteria in the terminal ileum reduce the cb into urobilinigen

73
Q

Three types of jaundice

A

Pre hepatic
Hepatic
Post hepatic

Gastrointestinal (8 decks)

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