Urinary System (Cambridge O Level Biology)

The kidneys excrete excess water in urine.

The main component of urine is water.

State two other substances that are excreted by healthy kidneys.

A scientist investigated the effect of drinking sugar solutions, of different concentrations, on the volume of urine produced.

• 1.5 dm³ of sugar solution A was consumed by a healthy adult.
• Urine was collected at thirty minute intervals for 150 minutes.
• The volume of urine produced every thirty minutes was added to the previous total volume.

• This procedure was repeated with sugar solutions B and C.

The results are shown in Fig. 1.

Fig. 1

Complete Table 1 using the information in Fig. 1.

Table 1

[3]

Suggest which of the three solutions, A, B or C, contained the most sugar.

Give a reason for your suggestion.

List two factors that will affect the volume and concentration of urine produced.

The body loses water in the urine.

State two other ways in which the body loses water.

The liver is an important organ in many processes.

The liver responds to changes in insulin concentration.

Insulin is a hormone.

[3]

The liver is also involved in the processing of amino acids.

[2]

The liver is also involved in the processing of toxins.

Lactic acid is an example of a toxin that is produced during vigorous exercise and processed in the liver.

Describe how lactic acid is processed.

[2]

Alcohol is another toxin that is processed in the liver.

The effect of alcohol consumption on the risk of dying from liver disease was investigated in men and women.

The results are shown in Fig. 1.

Fig. 1

Describe the results shown in Fig. 1.

Complete the sentences using words from the list.

You may use the words once, more than once or not at all.

Urea passes through the kidney and forms part of the urine.

Urine leaves the kidney in the ............................................. . This tube takes the urine to the .............................................. where the urine is stored until it leaves the body. It leaves the body through the ................................................... . 

The nephron consists of several different structures such as the Bowman's capsule and glomerulus.

Describe and explain how the structure of the glomerulus and Bowman's capsule help to remove urea from the bloodstream.

Table 1 shows the results of an investigation of the effects of a high protein diet on the synthesis of urea and the production of urine.

Table 1

Calculate the percentage increase in the mass of urea produced when switching from a normal diet to a high protein diet.

Show your working and give your answer to the nearest percent.

[2]

Explain why a high protein diet would result in a greater mass of urea being produced.

[3]

One of the symptoms of consuming too much protein for extended periods of time is dehydration.

Use the information in Table 1 to suggest an explanation for this.

The kidneys are responsible for osmoregulation, which involves maintaining the balance of water and mineral salts in the body.

Explain the importance of osmoregulation to cells.

Table 1 shows the concentration of different substances in blood plasma, filtrate entering the proximal convoluted tubule and urine.

Table 1

Explain the difference in concentration of protein in the blood plasma and filtrate.

Under normal circumstances there should be no glucose present in urine.

Explain the reason for this.

[2]

Suggest an explanation for the diagnosis that a doctor could make if glucose was present in the urine.

[2]

Fig. 1 shows one of the cells found in the proximal convoluted tubule of the nephron.

Fig. 1

Explain the presence of structure A in Fig. 1.

The concentration of substance X in different parts of the urinary system is shown in Table 1 at part (a).

Identify whether substance X can be considered a waste product or a useful substance to the body.

[1]

Use the information in Table 1 to explain your answer at part (i).

[2]

Suggest an explanation for the effect that this may have on the process of ultrafiltration.

Explain this symptom.

Patients suffering from kidney failure will have to undergo kidney dialysis on a regular basis while waiting for a kidney transplant.

During the process of dialysis, blood from the patient flows through a dialysis machine which contains a series of convoluted tubes. These tubes are made from a selectively permeable substance called a dialysis membrane.

The tubes are surrounded by a solution called dialysate, which ensures that the dialysis machine performs the same function as normal kidneys. Once the blood has flowed through the entire dialysis machine, it returns back to the body.

Fig. 1 shows the process of kidney dialysis.

Fig. 1

Describe and explain the possible composition of the dialysate.

In order for kidney dialysis to be effective, the dialysate must be constantly replaced with a fresh solution.

Suggest a reason for this.

Excess amino acids are broken down in liver cells to form molecules of urea.

Describe the pathway taken by a molecule of urea, from the liver of a mammal until it reaches the soil.