Liver and Deamination

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Aim of the Lesson:
To know the structure and function of
the liver
C grade – know the histology of the liver
(microscopic structures)
B grade – relate the microstructures of
the liver to their functions
A grade – describe the deamination of
amino acids and outline the formation of
urea in the urea cycle
Starter
Define Excretion.
Why is excretion an important
homeostatic function?
KEYWORDS:
Histology, deamination, hepatic, sinusoids, hepatocytes,
Kupffer cells, ammonia, ketoic acid, urea, ornithine cycle

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 PPQ: Describe the action of glucagon on liver cells in the
regulation of blood glucose concentration. [9]

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 PPQ: Describe the action of glucagon on liver cells in the
regulation of blood glucose concentration. [9]
1. glucagon binds to receptors in cell surface membrane (of liver cell)
2. receptor changes conformation
3. G-protein activated
4. adenylate cyclase activated
5. ATP converted to cyclic AMP
6. (cyclic AMP is) second messenger
7. (cyclic AMP) activates kinase protein
8. enzyme cascade: amplifies original signal of glucagon
9. ref. phosphorylase enzyme(s) / glycogen phosphorylase
10. glycogen broken to glucose
11. glucose, diffuses / passes out, of (liver) cell (into the blood)
12. through GLUT2 transporter proteins
13. AVP ; e.g. ref. to stimulating gluconeogenesis

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The liver is found in the upper right of the abdominal cavity,
just below the diaphragm. It is made of several lobes and
has four connections:
 bile duct
 hepatic artery
 hepatic portal vein
 hepatic vein
Liver

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Bile duct takes bile
from the liver to the gall
bladder (for storage) or
to the small intestine
where it neutralises
excess stomach acid
and emulsifies lipids.
Hepatic vein takes
blood back into the
general circulation. Its
composition is regulated
with excesses reduced
and shortages made up.
Hepatic artery brings
high pressure
oxygenated blood to the
liver. It is rich in O2 and
low in waste.
Hepatic portal vein
brings low pressure
blood from the intestine
to the liver. It is rich in
dissolved nutrients, low
O2 and high CO2.

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Histology of the liver
The liver is made up of 100 000 lobules (cylindrical structures)
 at their centre is a branch of the hepatic vein
 at the outside are branches of
 the hepatic artery
 hepatic portal vein
See notes

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https://www.youtube.com/watch?v=KtFJvlEDE2I

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Blood flows from the outer to the central vessel through
blood-filled channels or sinusoids lined with liver cells
called hepatocytes.
Hepatocytes:
 regulate the composition of the blood and remove
excess substances from the blood
 secrete materials into it which are in short supply or
have been made by the liver
Liver

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Sinusoids are in rows that radiate out from the centre and
hepatocytes are only ever one or two cells thick so the
diffusion path is short.
Bile canals are present with blind-ending channels which are
also lined by hepatocytes which secrete bile into the channel
that flows away from the centre of the lobule to a branch of
the bile duct at the periphery.
Sinusoids have large phagocytic Kupffer cells which capture
and engulf any bacteria that they encounter.
Liver

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Branch of hepatic
artery: brings high
pressure oxygenated
blood to the liver.
Branch of hepatic
portal vein: brings
blood rich in nutrients
to the liver from the
gut.
Kupffer cell or
macrophage: engulfs
bacteria and old or
damaged red blood cells.
Bile canal: a blind ending
canal into which bile is
secreted by the
hepatocytes.
Central vessel: takes
blood to the hepatic
vein to be returned to
the general circulation.
Sinusoid: a blood-
filled space lined with
hepatocytes.
Hepatocyte or liver
cell: controls composition
of blood, detoxifies and
produces bile.
Bile ductile: takes
bile to the gall bladder
for temporary storage.
Bile emulsifies fats.

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Feature Function
Hepatocyte
Sinusoid
Bile canal
Kupffer cells
Peripheral
vessels
 Complete the summary table about the liver
Liver

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Liver: injected section of lobules with central and peripheral vessels.
Peripheral vessels:
branches of hepatic
artery and hepatic portal
vein bring blood to the
lobule.
Central vessel: branch
of the hepatic vein
returns blood to the
general circulation.
Sinusoid lined with
hepatocytes: liver cells
remove excess
substances from the
blood and secrete
shortage substances into
the blood.

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Liver: detail of central vessel and hepatocytes.
Sinusoid lined with
hepatocytes: liver cells
remove excesses from and
secrete shortage substances
into the blood.
Central vessel: branch of
the hepatic vein which returns
blood to the general
circulation.
Macrophage or Kupffer
cell: engulfs pathogens and
removes damaged red cells
from the circulation. Produces
the bile pigment bilirubin.

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Liver
 Liver PPQ
1.
A – sinusoid ;
B – (branch of) bile duct ;
C – (branch of hepatic) portal vein / HPV ;
D – (branch of) hepatic artery ; [4]
2. bile pigments build up in blood ;
(pigments) do not enter gut / AW ;
AVP ; e.g. bile, canaliculi / duct, blocked / gall stones [2]

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Deamination and the Urea Cycle
• Excess amino acids cannot be stored in the body
• amino acids have about the same energy as
carbohydrates and so it would be extremely wasteful if
they were excreted
• instead, they are deaminated by the liver
• amino group is removed to produce ammonia
• leaves an organic acid (ketoic acid)
• respired or used to make carbohydrates and fats
• ammonia is very soluble and highly toxic
• converted to urea via the urea (ornithine) cycle
• energy-dependent reactions add it to CO2 to make
urea
 Refer to the notes :

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After deamination, the urea cycle forms the urea.
The urea cycle is an energy-consuming process that converts
toxic NH3 into urea. In the cycle, TWO molecules of NH3 are
added to CARBON DIOXIDE to produce urea.
Urea is still soluble, but is less toxic than ammonia.
It is secreted into the blood by the HEPATOCYTES (liver
cells) and transported to the KIDNEY for excretion.
 Draw a flow chart with the chemical equations to show
the stages of Deamination
Deamination and the Urea Cycle

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Deamination
⮚ Summarise the process of deamination in a flow chart
1. Excess amino acids are transported to the liver
2. The amino group is removed to produce ammonia
3. Ammonia is toxic and so is converted to urea
4. Urea is transported to the kidneys where it is excreted
⮚ Add the chemistry
⮚ How is ammonia
converted to urea?
NH2 + H → NH3
urea is made by adding CO2
Challenge: Water is also made when ammonia and CO2 are
combined. What is the balanced chemical equation for this?

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The urea cycle removes ammonia from the blood and makes
urea, which is eventually excreted as urine. This occurs in the
liver.
The Urea Cycle
Find out more about the urea cycle to answer the Doc questions

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Time to think