Excretion P.24-25
What are the main Excretory products in the body?
Excretory organ Molecules and ions exrceted
The lungs CO2
The liver Amino acids, nitrogen containing part of
molecule.
The skin Salts. Urea, water, uric acid and ammonia
The kidney The urea is removed from blood to form part of
urine
Why is excretion important?
Carbon Dioxide excretion:
Hydrogen ions and Hydrogen carbonate ions are released when carbonic acid dissociates in the RBC
and the plasma.
What are the consequences of this?
CO2 produced in every living cell because of respiration and is passed to bloodstream
where transported mostly as HCO3- to lungs where CO2 diffuses into alveoli to be
excreted as we breathe out
HCO3- forms H+ ions which combine haemoglobin and actively compete with O2 for
space reducing oxygen transport. CO2+ Haemoglobin = carbaminohaemoglobin
which has a lower affinity for O2 than normal haemoglobin
Excess CO2 dissolves in blood plasma and H2) to form H2CO3 which dissociates to
release H+ ions which lower pH. Breathing rate increases to help remove excess CO2.
If blood pH drops below 7.35 symptoms.
Nitrogenous compounds – the body cannot store excess amino acids so they are deaminated and
converted into UREA in the Liver (see later)
1
, 2
What are the main Excretory products in the body?
Excretory organ Molecules and ions exrceted
The lungs CO2
The liver Amino acids, nitrogen containing part of
molecule.
The skin Salts. Urea, water, uric acid and ammonia
The kidney The urea is removed from blood to form part of
urine
Why is excretion important?
Carbon Dioxide excretion:
Hydrogen ions and Hydrogen carbonate ions are released when carbonic acid dissociates in the RBC
and the plasma.
What are the consequences of this?
CO2 produced in every living cell because of respiration and is passed to bloodstream
where transported mostly as HCO3- to lungs where CO2 diffuses into alveoli to be
excreted as we breathe out
HCO3- forms H+ ions which combine haemoglobin and actively compete with O2 for
space reducing oxygen transport. CO2+ Haemoglobin = carbaminohaemoglobin
which has a lower affinity for O2 than normal haemoglobin
Excess CO2 dissolves in blood plasma and H2) to form H2CO3 which dissociates to
release H+ ions which lower pH. Breathing rate increases to help remove excess CO2.
If blood pH drops below 7.35 symptoms.
Nitrogenous compounds – the body cannot store excess amino acids so they are deaminated and
converted into UREA in the Liver (see later)
1
, 2
