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Key Words
EXCRETION: The removal of metabolic wastes from
the body
METABOLIC WASTE: Waste substances produced by
reactions inside cells
RESPIRATORY ACIDOSIS: Occurs when the blood pH
drops below 7.35. Breathing becomes difficult,
headaches, drowsiness and confusion develop.
DEAMINATION: Where the potentially toxic amino
group of proteins and amino acids is removed by the
liver, forming ammonia which is then converted to
urea in the ornithine cycle.…read more

Slide 2

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Where is it produced? In all living cells as a by-product of respiration In the liver, from breakdown of
essential amino acids (deamination)
Where is it excreted? The lungs. Carried in the blood first, then it In urine. Carried in the blood and
diffuses into the alveoli transported to the kidneys, then stored
in the bladder.
Why? Excess CO2 is toxic. More H+ ions are formed Proteins/amino acids can't be stored
which compete with the oxygen for the The toxic amino acid group is removed
haemoglobin, so less oxygen is transported by by deamination and converted to urea.
the blood The remaining part of the
Also forms carbaminohaemoglobin which has a protein/amino acid (keto acid) is
lower affinity for oxygen broken down to produce energy in
Causes respiratory acidosis by producing respiration.
carbonic acid (by dissolving in the blood plasma
and combining with water), the excess H+ ions
also make the blood more acidic.…read more

Slide 3

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The structure of the liver
· Liver cells need a very good blood supply, so the liver is
structured to give the cells lots of contact with the
· So the liver is divided into lobes, which are further
divided into lobules
· When the hepatic artery & portal vein enter the liver
they divide into smaller branches which run between
the lobules
· Where they enter the lobules, their blood becomes
mixed and enters a chamber called the sinusoid, which
is lined with hepatocytes…read more

Slide 4

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Slide 5

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The structure of the liver
· The hepatocytes lining the sinusoid are in close
contact with the blood, so molecules can be easily
exchanged between them
· Some hepatocytes produce bile which is secreted
into the bile canaliculus and flows into the bile
· Hepatocytes carry out a wide range of functions,
so have specialised organelles in their cytoplasm
· Kupffer cells are found in the sinusoid and break
down old red blood cells.…read more

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