UNIT 12: EXCRETION
Excretion: the removal from organisms of the waste products of metabolism, toxics
materials, substances in excess of requirements
Excretory Produced in Excreted through
products
Carbon dioxide All cells during respiration Lungs
Excess water Food and drinks Kidneys and skin
and salts
Urea, ammonia Break down of excess amino acids by Kidneys
the liver
Deamination: the removal of the nitrogen-containing part
of amino acids to form urea
Functions of the liver
Converts excess amino acids into urea and
carbohydrates in a process called deamination
Converts glucose into glycogen
Assimilation of amino acids by converting them to
proteins, including plasma proteins (fibrinogen)
Break down old red blood
cells, storing the iron and excreting the remains of the
haemoglobin as bile pigments
Ureter: a tube that leads from a kidney to the bladder
Bladder: has stretchy walls to store urine
Nephron (kidney tubules)
Blood is filtered when it passes through the kidney.
Useful substances are reabsorbed and the final liquid is
urine
The amount of concentration of urine is affected by
water intake, temperature and exercise
o The volume is increased, concentration is decreases
when: drink a lot of water, low surrounding
temperature, not exercising
Filtration: Glomerulus
Small molecules dissolved in blood are squeezed out of
the blood into the renal capsule
The blood vessel bringing blood to the glomerulus is
quite wide but the one taking blood away is quite narrow
-> blood in the glomerulus cannot get away easily
High pressure builds up, squeezing the blood in the
glomerulus against the capillary walls
Excretion: the removal from organisms of the waste products of metabolism, toxics
materials, substances in excess of requirements
Excretory Produced in Excreted through
products
Carbon dioxide All cells during respiration Lungs
Excess water Food and drinks Kidneys and skin
and salts
Urea, ammonia Break down of excess amino acids by Kidneys
the liver
Deamination: the removal of the nitrogen-containing part
of amino acids to form urea
Functions of the liver
Converts excess amino acids into urea and
carbohydrates in a process called deamination
Converts glucose into glycogen
Assimilation of amino acids by converting them to
proteins, including plasma proteins (fibrinogen)
Break down old red blood
cells, storing the iron and excreting the remains of the
haemoglobin as bile pigments
Ureter: a tube that leads from a kidney to the bladder
Bladder: has stretchy walls to store urine
Nephron (kidney tubules)
Blood is filtered when it passes through the kidney.
Useful substances are reabsorbed and the final liquid is
urine
The amount of concentration of urine is affected by
water intake, temperature and exercise
o The volume is increased, concentration is decreases
when: drink a lot of water, low surrounding
temperature, not exercising
Filtration: Glomerulus
Small molecules dissolved in blood are squeezed out of
the blood into the renal capsule
The blood vessel bringing blood to the glomerulus is
quite wide but the one taking blood away is quite narrow
-> blood in the glomerulus cannot get away easily
High pressure builds up, squeezing the blood in the
glomerulus against the capillary walls
