Regulation of water content
Multiple-choice questions (p. 24)
Short questions (p. 25)
Urea is a nitrogenous compound produced from deamination of excess amino acids in liver.
Urine is a liquid containing water, salts, urea and other unwanted substances. It is produced after ultrafiltration and reabsorption in the kidney.
Plasma is the liquid portion of blood. It contains water and substances including glucose, amino acids, salts, urea and plasma proteins.
1m Glomerular filtrate is the fluid that is filtered out of the glomerulus into the Bowman’s capsule. Its composition is similar to plasma, except there are no plasma proteins.
Excretion is the process of removal of metabolic waste from the body.
1m Osmoregulation is the regulation of water content in relation to the amount of salts in the body.
It is to maintain the diffusion gradient between the blood and the dialysis fluid.
It is to prevent infection / contamination of the blood / the body system.
Structured questions (p. 25)
HKCEE Human Biology 2005 I Q4a
HKCEE Biology 2006 I Q9a
(a) (i) 6566.7%
The urea content in urine is much higher because a large amount of water is
reabsorbed/the amount of water reabsorbed along the kidney tubule is relatively
much greater than that of urea
The water content of glomerular filtrate is greater than that of the plasma
because protein is too large to pass the wall of the glomerulus and
that of the Bowman’s capsule
The proportion of water in the glomerular filtrate thus increase
The person cannot produce sufficient insulin
to stimulate liver cells to convert glucose into glycogen
The level of glucose in the blood may become so high/exceed the threshold value
that glucose cannot be completely reabsorbed in the kidney
Thus it appears in the urine
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