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EXCRETION (The Need for Excretion (chemical reactions in living cells…
EXCRETION
The Need for Excretion
chemical reactions
in living cells produce
waste
products
to keep an organism
alive
where
complex
substances
break down
into
simpler
ones called
catabolic
reactions (
catabolism
)
glucose
is
oxidised/broken down
into
carbon dioxide
and
water
by releasing the energy during
cellular respiration.
proteins
and
amino acids
are
deaminated
in the liver to form urea
where
simple
substances are
built up
to form
complex
substances called
anabolic
reactions (
anabolism
)
the
formation
of
new proteins
from amino acids
the
conversion
of glucose into
glycogen
in the liver and muscles
the process of
photosynthesis
in green plants
the
sum
of all the chemical reactions in the body of an organism is called
metabolism
(
metabolic
reaction)
produces
waste
products
may be
harmful/toxic
if they
accumulate
in the body
must be removed by
excretion
what is
excretion
?
where
metabolic waste products
and
toxic
substances are
removed
from the body of an organism
metabolic waste products
and
toxic substances
are known as
excretory products
most
unicellular
organism e.g:
amoeba
are able to
excrete
their waste products by
diffusing into the surroundings
larger
organisms e.g: animals with
impermeable
skin, need
special excretory organs
Excretion in Humans