AQA A level biology- Osmoregulation Complete
Questions And Answers
Where are osmoreceptors located?
Hypothalamus
When a person is dehydrated, the cell volume of an osmoreceptor decreases.
Explain why
1) Water potential of blood will decrease
2) Water moves from osmoreceptors into blood by osmosis
Describe and explain how the secretion of ADH affects urine produced by the
kidneys?
1) Permeability of (membrane/cells) to water is increased
2) More water absorbed (from/leaves) distal tubule/ collecting duct
3) Smaller volume of urine
4) Urine becomes more concentrated
Describe how urea is removed from the blood?
1) Hydrostatic pressure
2) Cause ultrafiltration at (bowman's capsule/glomeruli/renal capsule)
3) Through basement membrane
4) Enabled by small size urea molecule
Label a nephron
Explain how urea is concentrated in the filtrate?
1) Reabsorption of water by osmosis at the (proximal convoluted tubule/ descending
loop of henle)
2) Ions actively transported at the distal convoluted tubule/collecting duct (glucose
creates gradient)
What is urea?
Urea is a waste product of metabolism that is excreted by the kidneys in urine.
Describe how ultrafiltration produces glomerular filtrate?
1) Blood pressure/hydrostatic pressure
2) Small molecules (named example)
3) Pass through basement membrane (basement membrane acts as a filter)
, 4) Protein too large to go through (large molecule) so stays behind
5) Presence of pores in capillaries (podocytes=form a filtration barrier)
Explain how a lack of insulin affects reabsorption of glucose in the kidneys of
a person who does not secret insulin?
1) High concentration of glucose in blood
2) High concentration in tubule/in filtrate
3) Reabsorbed by (facilitated diffusion/active transport)
4) Requires proteins/carriers
5) These are working at maximum rate (are saturated)
6) Not all glucose is reabsorbed, some is lost in urine
Some desert mammals have long loops of henle and secrete large amounts of
ADH. Explain how these two features are adaptations to living in desert
conditions?
For general principle;
-More water from filtrate is reabsorbed by osmosis from the collecting duct due to
longer loop of henle.
For loop of henle;
-Sodium or chloride ions are absorbed from filtrate in ascending limb. Gradient
established in medulla (concentration of ions increases down medulla)
For ADH;
-Acts on (collecting duct/DCT/second CT) making cells more permeable, inserting
aquaporin's in plasma membranes
A diabetic and non-diabetic ate the same amount of glucose, one hour later the
glucose concentration in the blood of the diabetic was higher. Explain why?
In diabetic person;
-Lack of insulin (reduced sensitivity of cells to insulin)
-Reduced uptake of glucose by (cells/liver/muscles)
-Reduced conversion of glucose to glycogen (glycogenesis)
Why does the urine of a non-diabetic not contain glucose?
Questions And Answers
Where are osmoreceptors located?
Hypothalamus
When a person is dehydrated, the cell volume of an osmoreceptor decreases.
Explain why
1) Water potential of blood will decrease
2) Water moves from osmoreceptors into blood by osmosis
Describe and explain how the secretion of ADH affects urine produced by the
kidneys?
1) Permeability of (membrane/cells) to water is increased
2) More water absorbed (from/leaves) distal tubule/ collecting duct
3) Smaller volume of urine
4) Urine becomes more concentrated
Describe how urea is removed from the blood?
1) Hydrostatic pressure
2) Cause ultrafiltration at (bowman's capsule/glomeruli/renal capsule)
3) Through basement membrane
4) Enabled by small size urea molecule
Label a nephron
Explain how urea is concentrated in the filtrate?
1) Reabsorption of water by osmosis at the (proximal convoluted tubule/ descending
loop of henle)
2) Ions actively transported at the distal convoluted tubule/collecting duct (glucose
creates gradient)
What is urea?
Urea is a waste product of metabolism that is excreted by the kidneys in urine.
Describe how ultrafiltration produces glomerular filtrate?
1) Blood pressure/hydrostatic pressure
2) Small molecules (named example)
3) Pass through basement membrane (basement membrane acts as a filter)
, 4) Protein too large to go through (large molecule) so stays behind
5) Presence of pores in capillaries (podocytes=form a filtration barrier)
Explain how a lack of insulin affects reabsorption of glucose in the kidneys of
a person who does not secret insulin?
1) High concentration of glucose in blood
2) High concentration in tubule/in filtrate
3) Reabsorbed by (facilitated diffusion/active transport)
4) Requires proteins/carriers
5) These are working at maximum rate (are saturated)
6) Not all glucose is reabsorbed, some is lost in urine
Some desert mammals have long loops of henle and secrete large amounts of
ADH. Explain how these two features are adaptations to living in desert
conditions?
For general principle;
-More water from filtrate is reabsorbed by osmosis from the collecting duct due to
longer loop of henle.
For loop of henle;
-Sodium or chloride ions are absorbed from filtrate in ascending limb. Gradient
established in medulla (concentration of ions increases down medulla)
For ADH;
-Acts on (collecting duct/DCT/second CT) making cells more permeable, inserting
aquaporin's in plasma membranes
A diabetic and non-diabetic ate the same amount of glucose, one hour later the
glucose concentration in the blood of the diabetic was higher. Explain why?
In diabetic person;
-Lack of insulin (reduced sensitivity of cells to insulin)
-Reduced uptake of glucose by (cells/liver/muscles)
-Reduced conversion of glucose to glycogen (glycogenesis)
Why does the urine of a non-diabetic not contain glucose?
