Excretion in Humans (Cambridge (CIE) IGCSE 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

(i)

Complete Table 1 using the information in Fig. 1.

Table 1

[3]

(ii)

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

Give a reason for your suggestion.

[2]

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.

(i)

Define the term hormone.

[3]

(ii)

Describe how the liver responds to an increase in insulin concentration.

[2]

Extended Only

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

(i)

Describe how excess amino acids are broken down.

[2]

(ii)

State the name of the process that assembles amino acids to form proteins.

[1]

Extended Only

The liver is also involved in the processing of toxins.

(i)

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]

(ii)

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.

Excretion is the removal of toxic substances or substances in excess, from the body. 

Excess water is excreted from the lungs and the kidneys.

State the name of one other substance that is excreted from

• The lungs

  • The kidneys. 

The volume and concentration of urine varies with changing conditions.

Table 1 shows three changing conditions.

Write increase or decrease in each of the boxes in Table 1 to show how each change affects the volume and the concentration of urine.

Table 1

Excretion is a characteristic of living organisms.

Growth is another characteristic of living organisms.

(i)

Define the term growth.

[2]

(ii)

State three characteristics of living organisms other than excretion and growth.

[3]

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 ................................................... . 

Extended only

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.

Extended only

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

(i)

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]

(ii)

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

[3]

Extended only

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.

Extended only

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.

Extended only

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.

Extended only

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

(i)

Explain the reason for this.

[2]

(ii)

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

[2]

Extended only

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.

Extended only

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

(i)

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

[1]

(ii)

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

[2]

Extended only

Glomerulonephritis is a set of kidney diseases that affect the glomeruli in the kidneys. One of the effects of glomerulonephritis is a thickening of the capillary walls of the glomerulus due to the presence of extra endothelial cells.

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

Extended only

If left untreated, glomerulonephritis may lead to kidney failure. One of the symptoms of kidney failure is swelling of the legs, ankles and feet.

Explain this symptom.

Extended only

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.

Extended only

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

Suggest a reason for this.