The Excretory System :
topic 13
Definition : Excretion is the removal of waste products of metabolism toxic ,
materials & substances in excess of requirements from the body.
The waste substances are removed from the
body by excretory organs
:
lungs liver ,
&
kidneys
Humans have I main
excretory products :
Carbon dioxide :
-
Made in
body tissues during respiration
Urea : Made in the liver from excess amino acids
-
Transported to lungs in the blood plasma
-
Carried to kidneys in the plasma where it is filtered
-
Diffuses out of blood into air
-
Leaves body dissolved in the form of urine
-
Must be removed as when it dissolves in water it forms an acidic solution
that lowers pH of cells , reducing activity of enzymes
·
Excretion is vital as toxic substances would build up
& reach a toxic level , destroying tissues.
·
Substances that a re excreted a re produced by body cells.
Substances that a re egested have been eaten & have passed through the
alimentary canal without
being digested & absorbed into the bloodstream
Assimilation : Food molecules that have been absorbed n ow become part of the cells or a re used
by the cells
-Liver : stores glucose by removing it from the blood &
storing it as
glycogen Shelps to regulate glucose
.
concentration in blood)
uses amino acids to make proteins ,
such as plasma proteins :
(fibrinogen : involved with blood clotting
.
breaks down excess amino acids
Converts fatty acids & glycero into fat ,
which is stored around the
body ,
e .
g under
.
skin)
produces cholesterol from fats
-Your body cannot store amino acids that it cannot use
,
so each molecule is broken down into two new molecules by the process of
deamination .
-
One molecule is converted to Carbohydrate or fat & used as a source of energy. The other molecule is ammonia (NHz) ,
which combines
with CO2 to form Urea.
The amino group
:
part of the amino acid molecule that contains
nitrogen
Bile : made in liver neutralises HCl that
,
comes from Stomach & emulsifies fats (breaks down large drops of fat into smaller ones)
topic 13
Definition : Excretion is the removal of waste products of metabolism toxic ,
materials & substances in excess of requirements from the body.
The waste substances are removed from the
body by excretory organs
:
lungs liver ,
&
kidneys
Humans have I main
excretory products :
Carbon dioxide :
-
Made in
body tissues during respiration
Urea : Made in the liver from excess amino acids
-
Transported to lungs in the blood plasma
-
Carried to kidneys in the plasma where it is filtered
-
Diffuses out of blood into air
-
Leaves body dissolved in the form of urine
-
Must be removed as when it dissolves in water it forms an acidic solution
that lowers pH of cells , reducing activity of enzymes
·
Excretion is vital as toxic substances would build up
& reach a toxic level , destroying tissues.
·
Substances that a re excreted a re produced by body cells.
Substances that a re egested have been eaten & have passed through the
alimentary canal without
being digested & absorbed into the bloodstream
Assimilation : Food molecules that have been absorbed n ow become part of the cells or a re used
by the cells
-Liver : stores glucose by removing it from the blood &
storing it as
glycogen Shelps to regulate glucose
.
concentration in blood)
uses amino acids to make proteins ,
such as plasma proteins :
(fibrinogen : involved with blood clotting
.
breaks down excess amino acids
Converts fatty acids & glycero into fat ,
which is stored around the
body ,
e .
g under
.
skin)
produces cholesterol from fats
-Your body cannot store amino acids that it cannot use
,
so each molecule is broken down into two new molecules by the process of
deamination .
-
One molecule is converted to Carbohydrate or fat & used as a source of energy. The other molecule is ammonia (NHz) ,
which combines
with CO2 to form Urea.
The amino group
:
part of the amino acid molecule that contains
nitrogen
Bile : made in liver neutralises HCl that
,
comes from Stomach & emulsifies fats (breaks down large drops of fat into smaller ones)
