Osmoregulation

Table 1 shows four statements and the names of four parts of a nephron.

Protein is not normally present in the urine of a person.

Explain why.

Glomerular sclerosis (GS) is a type of kidney damage that can cause protein to be present in the urine.

High-protein diets are linked to GS in adults.

Scientists investigated the development of GS in underweight, 5-day-old rats.

They fed:

• 14 rats a high-protein milk diet

• 14 rats a normal-protein milk diet.

From day 21, they fed both groups of rats the same diet of solid food. At 160 days old, they examined nephrons in the rats’ kidneys for GS.

They identified the number of nephrons with GS for each group of rats.

Rats fed a high-protein diet had a larger number of nephrons with GS than rats fed a normal-protein diet. The scientists performed a statistical test on these data and they calculated P < 0.01

A journalist reported on this investigation and stated ‘feeding high-protein milk to underweight human babies could cause kidney damage in adults’.

Use all of the information provided to evaluate this statement.

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

Antidiuretic hormone (ADH) binds to V receptors found in cell-surface membranes in two parts of a nephron.

Name the two parts of a nephron where V receptors are found.

V receptors only bind with ADH.

Suggest and explain why.

A decrease in blood pressure stimulates the release of ADH.

Give the location of the receptors that detect a decrease in blood pressure and explain how the release of ADH will affect blood pressure.

Name the part of the body which releases antidiuretic hormone (ADH) into the blood.

Alcohol decreases the release of ADH into the blood.

Suggest two signs or symptoms which may result from a decrease in ADH.

Describe the effect of ADH on the collecting ducts in kidneys.

Neonatal diabetes is a disease that affects newly born children. The disease is caused by a change in the amino acid sequence of insulin.

This change prevents insulin binding to its receptor. Explain why this change prevents insulin binding to its receptor.

Phosphoinositide 3-kinase (PI3K) is an enzyme in several metabolic processes.

Figure 5 shows the role of PI3K in the control of blood glucose concentration.

A decrease in the activity of PI3K can cause type II diabetes.

Use Figure 5 to explain why.

Using your knowledge of the kidney, explain why glucose is found in the urine of a person with untreated diabetes.

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.

AS results from a sex-linked mutation.

In a male with AS, where would the sex-linked mutation be located?

Tick () one box.

Scientists investigated the use of transplanted stem cells to treat AS in mice.

The scientists set up four experimental groups.

Group A – 40 wild type* mice Group B – 40 AS mice Group C – 40 AS mice that received stem cells from AS mice Group D – 40 AS mice that received stem cells from wild type mice

*Wild type mice are mice not affected by AS.

After 20 weeks, the scientists measured the quantity of protein in the urine using a scale from 0 (lowest quantity) to +++++ (highest quantity).

The results the scientists obtained are shown in Table 2.

Using all the information, evaluate the use of stem cells to treat AS in humans.

Answer space for this question continues on the next page

The scientists carried out further work to investigate how the transplanted stem cells developed after transplantation.

• The scientists transplanted stem cells from wild type male mice into AS female mice.

• After 20 weeks, they found that the quantity of protein in the urine of these female mice had significantly decreased.

• They examined cells from glomeruli in the female mice. Some of these cells contained a Y chromosome.

Suggest how the transplanted stem cells reduce proteinuria.

Describe how ultrafiltration occurs in a glomerulus.

Glucose and water are reabsorbed by the proximal convoluted tubule of a nephron.

Put a tick () in the box next to the correct ways in which glucose and water are reabsorbed.

The equation shows the relationship between urine concentration in arbitrary units () and mean length of the loop of Henle in mm ().

Calculate the mean length of the loop of Henle in an organism that produces urine with a concentration of 16.56 arbitrary units.

Scientists investigated the relationship between the thickness of the kidney medulla of different species of mammals and the concentration of their urine.

Figure 1 shows their results.

Explain the pattern shown by the results in Figure 1.

Furosemide and CVT are drugs used to remove excess fluid from the body. Scientists investigated the effect of these drugs on the volume of urine produced by human volunteers. The scientists used the following method.

• They divided volunteers into three groups, A, B and C at random.

• They gave all the volunteers the same food for 3 days.

• After 3 days, they gave the volunteers in group A a tablet containing furosemide, the volunteers in group B a tablet containing CVT and the volunteers in group C a placebo (a tablet that did not contain either drug).

• They then found the mean volume of urine produced by each group in the 4 hours after taking the tablets.

Some of the results the scientists obtained are shown in Table 1. A value of 2 standard deviations from the mean includes over 95% of the data.

All the volunteers were given the same food for 3 days.

Suggest and explain one reason why they were given the same food.

Using Table 1, what can you conclude about the effectiveness of furosemide and CVT in the removal of excess fluid from the body?

Furosemide is sometimes used to treat high blood pressure.

Suggest how furosemide would cause a decrease in blood pressure.

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.

The scientists also measured the mean rate of flow of blood plasma into the kidneys.

The results the scientists obtained are shown in Table 2.

The mean rate of flow of blood plasma is 60% of the mean rate of blood flow into the kidneys.

How much greater is the flow of blood into the kidneys with furosemide than with group C (placebo) over the 4 hours of the investigation? Give your answer in cm³.