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liver Flashcards

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1
Q

secretion definition
examples

A

release of substances from cells
e.g. beta cells secrete insulin
chromatin cells secrete adrenaline and noradrenaline

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2
Q

egestion definiton
example

A

removal of undigested food from the body
e.g. cellulose (fibre) not digested

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3
Q

excretion definition

A

removal of metabolic waste from the body

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4
Q

examples of 2 excreted substances

A

carbon dioxide
nitrogenous waste (urea)

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5
Q

how is CO2 formed
how and where is it excreted

A

aerobic respiration
excreted form gas exchange surfaces e.g. lungs (by diffusion then expired) or from surface of unicellular organisms

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6
Q

how is urea formed

A

deamination (amine group removed) and ornithine cycle converts excess amino acids into urea

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7
Q

how and where is urea excreted

A

kidneys remove it from the blood (ultrafiltration) then removed from body in urination
removed in sweat

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8
Q

why must CO2 be removed from body

A

excess CO2 is toxic
can cause respiratory acidosis

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9
Q

how is CO2 carried in blood

A

as H2CO3 ions
bound directly to haemoglobin

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10
Q

Effect of CO2 being carried in blood as H2CO3 ions

A

H+ is formed when H2CO3 dissociates into H+ and HCO3-
H+ binds to Hb (buffer) to form HHb (haemoglobin acid) which changes the shape of Hb so O2 unloading at low pO2 and high pCO2

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11
Q

how is CO2 carried in blood directly bound to Hb

A

forms carbaminohaemoglobin
(not competitively w O2)
at high pCO2 and low pO2, CO2 binding reduces Hb’s affinity for O2, aiding oxygen unloading

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12
Q

list functions of the liver

A

1.carbohydrate metabolism
2.target organ for insulin, glucagon and cortisol
3. target organ for adrenaline
4.enables interconversion of other substances with carbohydrate
5.urea formation
6.RBC synthesis (in foetus)
7.RBC destruction
8.bile, plasma protein and cholesterol synthesis
9.hormone breakdown
10. vitamin A,D B12, iron and glycogen storage
11. detoxification of alcohol/drugs

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13
Q

describe the role of the liver in carbohydrate metabolism

A

carbs carried as glucose in the blood (main respiratory substrate)
glucose not suitable for storage bc small and soluble
glucose converted to glycogen to be stored in LIVER and muscles

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14
Q

role of liver when blood sugar level is low

A

alpha cells in pancreas secrete glucagon into blood
glucagon= non-steroid hormone which binds to glycoprotein, g-protein coupled receptors on hepatocytes plasma membrane
activation of enzymes causes hydrolysis of glycogen to glucose (glycogenolysis)
also causes lipolysis (lipid hydrolysis)
gluconeogenesis forms new glucose
glucose passes into blood
BSL increases and glucagon no longer released (-ve feedback)
glucagon inhibits insulin

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15
Q

role of liver when blood sugar level too high

A

beta cells in pancreas secrete insulin into blood
insulin is a non-steroid hormone and globular protein which binds to tyrosine kinase receptors on plasma membrane of hepatocytes, causing glucose transporters to be inserted into membrane
hepatocytes take up glucose and respire it in glycolysis, convert it to glycogen (glycogenesis), or convert it to glycerol to produce fats (lipogenesis)
lowers BSL so no more insulin secreted (-ve feedback)
insulin inhibits glucagon

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16
Q

effect of adrenaline on liver cells

A

adrenaline released from adrenal medulla in times of stress
causes glycogenolysis to increase blood sugar level

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17
Q

what is the process by which new glucose is formed form non-carb sources

A

gluconeogenesis

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18
Q

when does gluconeogenesis take place

A

when supplies of glycogen are exhausted e.g. after fasting

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19
Q

describe gluconeogenesis using lactate/lactic acid

A

produced during anaerobic respiration
taken up by hepatocytes and converted to pyruvate then glucose

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20
Q

describe gluconeogenesis using lipids

A

glycerol from triglycerides can be broken down and converted into glucose

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21
Q

describe gluconeogenesis using amino acids

A

amino acids are deaminated
the nitrogen containing amine group is converted to ammonia and then urea which is excreted
the rest of the molecule is a keto acid and is converted to pyruvate then glucose

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22
Q

what triggers gluconeogenesis

A

cortisol

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23
Q

why can the body not store excess amino acids

A

the amine groups are potentially toxic

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24
Q

why would it be wasteful to excrete excess amino acids

A

they contain almost as much energy as carbohydrates

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25
what happens to excess amino acids
transported in the blood plasma to the liver some of them are converted to other amino acids (TRANSAMINATION) the rest are deaminated
26
why is transamination useful
the diet cannot provide all the amino acids needed
27
what is deamination
the removal of the amine group (NH2)
28
deamination reaction
amino acid + Oxygen -> keto acids + ammonia
29
in what cycle is urea formed
ornithine cycle
30
what happens to the ammonia formed in deamination why
converted to urea (less soluble and less toxic than ammonia so needs less water for removal)
31
what animal excretes ammonia
fish
32
what does ornithine act as
a carrier molecule on which urea is assembled
33
ornithine recycling?
ornithine is reformed at the end of the cycle and can be reused in the next cycle
34
what is used to form urea in the ornithine cycle
ornithine CO2 ammonia
35
what binds to ornithine in ornithine cycle
CO2
36
role of liver synthesising RBC
in foetus bone marrow not fully developed so RBC made in liver from mitosis of stem cells, which then differentiate (lose mitochondria, nucleus etc)
37
role of liver in destruction of RBC
RBC destruction involves white blood cells nd hepatocytes haemoglobin broken down: Globin broken down into amino acids Haem groups converted into bilirubin (used to make bile or is an excretory waste product)
38
role of liver in bile synthesis
bile is made from the breakdown for haemoglobin stored in gall bladder bile emulsifies fats to increase SA for lipase enzymes neutralises stomach acid so optimum pH for digestive enzymes
39
examples of plasma proteins synthesised in liver
e.g. fibrinogen converted to fibrin in blood clotting albumin causes oncotic pressure of the blood and transports steroid hormones e.g. oestrogen, cortisol
40
roles of cholesterol
major components of cell membranes (regulates and maintains fluidity of phospholipid bilayer) used to make steroid hormones used to make vitamin D transported as a lipoprotein
41
role of liver in breakdown of hormones
liver breaks down fat soluble substances into water soluble substances that can be excreted in the urine e.g. steroid hormones (testosterone etc)
42
what is vitamin B12 needed for
manufacturing coenzymes (cofactors) like NAD and FAD Haemoglobin synthesis
43
how does the liver render dangerous substances/molecules as less toxic
oxidation reduction methylation combination with other molecules (kidneys eliminate breakdown products)
44
how does the liver break down hydrogen peroxide
uses catalase enzyme 2H2O2 -> 2H2O + O2
45
examples of drugs the liver breaks down
antibiotics paracetamol cocaine
46
steps of ethanol metabolism in liver
1: ethanol to ethanal uses ethanol dehydrogenase enzyme NAD converted to reduced NAD 2: ethanal to ethanoate uses ethanal dehydrogenase enzyme NAD converted to reduced NAD 3: ethanoate to acetyl coA (oxidation so lots of NAD in)
47
ethanol properties
C2H5OH small lipid-soluble toxic an damages cells oxidation of ethanol releases 30kJ/g of energy broken down into harmless products
48
use of acetyl-coA produced in ethanol metabolism
to Krebs cycle to be used to make energy as ATP used for fatty acids synthesis (this pathway favoured if lots of NADH)
49
effects of alcohol consumption
reduced NAD accumulates therefore reactions oxidised by NAD are less likely to occur therefore fatty acids accumulate bc not oxidised therefore fats deposited in the liver -> fatty liver -> cirrhosis
50
describe how exchange pathways function to maintain relatively constant concentrations of biochemicals in the liver cell
blood acts as transport fluid and has a high HP tissue fluid created as fluid leaves capillaries, and bathes liver cells blood transports glucose/a.a's/glycerol/FAs from gut to liver cell by FD/AT blood transports O2 from alveoli to liver cells for aerobic respiration CO2 released by liver cell into blood by diffusion CO2 transported as HCO3- or carbaminohaemoglobin CO2 excreted by alveoli liver cell deaminates excess amino acids & passes ammonia to ornithine cycle urea diffuses into blood liver releases glucose due to action of glucagon/glycogenolysis liver makes steroid hormones & releases into blood by endocytosis
51
where is the liver located
below the diaphragm overlaps the stomach towards the RHS of the body
52
liver weight
1.5kg
53
how much of body mass does liver make up
3-5%
54
where does bile leave the liver
via the hepatic duct to the gall bladder
55
describe blood flow into the liver
hepatic artery carries oxygen blood from aorta to liver hepatic portal vein carries deoxy blood from small intestine to liver (rich in nutrients)
56
describe blood flow out of the liver
hepatic vein carries deoxy blood containing amino acids, glucose, plasma proteins, lipids, cholesterol, CO2, urea to the vena cava to the heart
57
how many lobules does the liver contain
up to 100,000
58
lobule diameter
look like hexagons 1mm in diameter each
59
what are individual liver cells called
hepatocytes
60
what are lobules made up of
hepatocytes
61
what are hepatocytes arrange in to make up lobules
cords
62
where do lobules radiate from and to
from centre towards periphery
63
thickness of lobules
2 cells thick in close contact w blood
64
what runs alongside each lobule (at the corners)
interlobular blood vessels (between the lobules)
65
what are interlobular blood vessels branches of
the hepatic artery and hepatic portal vein
66
what's at the centre of each lobule
branch of the hepatic vein (interlobular vessel)
67
what connects the interlobular and intralobular vessels
sinusoids
68
what are sinusoids lined by
endothelial cells
69
what are the pores in endothelial cells of sinusoids called
fenestrations
70
do sinusoids endothelial cells have a basement membrane
no
71
why do sinusoids endothelial cells not have a basement membrane
allows hepatocytes to get easy access to nutrients
72
where are kupffer cells
along the walls of the sinusoids
73
what are kupffer cells
large macrophages which remove bacteria destroy old RBCs and WBCs (produces bilirubin to form bile)
74
where do hepatocytes shed bile
into bile canaliculi
75
what do bile canaliculi connect up with
a bile ductile these eventually reach the main bile duct (hepatic duct)
76
what do hepatocytes contain
prominent nuclei Golgi aparatus many mitochondria glycogen granules fat droplets lysosomes peroxisomes rough and smooth ER
77
can hepatocytes replicate
yes
78
past what point can the liver not regenerate
if 65% of liver lost it can regenerate past this it cannot
79

biology (27 decks)

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