6- Control of Blood Ψ =)

Question 1

Alport syndrome (AS) is an inherited disorder that affects kidney glomeruli of both men and women. Affected individuals have proteinuria (high quantities of
protein in their urine).
Suggest how AS could cause proteinuria. (2)

Answer 1

• affects basement mem
• proteins ✔ pass into glomerular filtrate

basement mem = outer mem of glomerulus

Question 2

AS results from a sex-linked mutation.
In a male with AS, where would the sex-linked mutation be located? (1)
* The homologous section of a Y chromosome
* The homologous section of an X chromosome
* The non-homologous section of a Y chromosome
* The non-homologous section of an X chromosome

Answer 2

non-homologous section of X-chromosome

Question 3

Glucose and water are reabsorbed by the proximal convoluted tubule of a
nephron.
State the correct ways in which glucose and water are reabsorbed. (1)

Answer 3

• glucose- f. diffusion + a.t.
• H2O down Ψ gradient

Question 4

Describe and explain how three features of the cells in the proximal convoluted tubule allow the rapid reabsorption of glucose into the blood. (3)

Answer 4

1. microvilli- large s.a. for reabsorption
2. many channel proteins- f. diffusion
3. many mitochondria- ATP for a.t.
4. many carrier proteins- a.t./ co-transport
5. many ribosomes- produce carrier/ channel proteins

Question 5

Furosemide inhibits the absorption of sodium and chloride ions from the filtrate produced in the nephrons.
Explain how furosemide causes an increase in the volume of urine produced. (3)

Answer 5

• ↓ Ψ in filtrate
• ↓ H2O reabsorbed by osmosis from filtrate
• in collecting duct

Question 6

More than 99% of biological molecules are reabsorbed from the filtrate in the proximal convoluted tubule.
Despite this, the concentration of fluid in this tubule remains constant.
Explain why. (1)

Answer 6

H2O also reabsorbed

Question 7

When a person is dehydrated, the cell volume of an osmoreceptor decreases.
Explain why. (2)

Answer 7

• Ψ in blood ↓
• H2O moves out of osmoreceptors into blood by osmosis

Question 8

Creatinine is a breakdown product of creatine found in muscle tissues.
Apart from age and gender, give two factors that could affect the concentration of creatinine in the blood. (1)

Answer 8

1. exercise
2. muscle/ body mass
3. kidney disease
4. ethinicity

Question 8

Stimulation of osmoreceptors can lead to secretion of the hormone ADH.
Describe and explain how the secretion of ADH affects urine produced by the kidneys. (4)

Answer 8

• mem ↑ permeable to H2O
• ↑ H2O reabsorbed from distal convulted tubule + collecting duct
• ↓ vol
• ↑ concentrated