3 marksFig. 1 shows the urinary system in humans.
Fig. 1
Identify structure A, B and D in Fig. 1.
2 marksGive the name of organ C and describe its function in the urinary system.
2 marksThe urinary system is responsible for the process of excretion.
Define the term excretion.
3 marksCarbon dioxide is one of the substances that is excreted by the body.
Explain the importance of excreting carbon dioxide.
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3 marksFig. 1 shows the structure of a nephron in the kidneys.
Fig. 1
Identify structure 1 in Fig. 1.
[1]
Describe the process taking place at structure 1.
[2]
2 marksThe fluid moving along structure 2 of the nephron in Fig. 1 is known as filtrate and it consists of various substances.
State two substances that will form part of the filtrate in Structure 2.
3 marks
Water is reabsorbed from the filtrate back into the blood at various points along the nephron, such as structure 3 in Fig. 1.
Identify structure 3 in Fig. 1.
[1]
Describe how the structure identified at part (i) allows water to be reabsorbed into the blood.
[2]
3 marksStructure 5 represents the collecting duct, which will adjust the amount of water reabsorbed into the blood depending on the needs of the body.
Complete the following sentences on reabsorption and excretion of water in the collecting duct.
On a hot, sunny day, the body will _________________ more water due to sweating. In order to conserve water, the collecting duct will reabsorb ____________________ water into the blood. This results in the excretion of _______________ urine that is more concentrated.
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1 markFig. 1 shows the general structure of an amino acid.
Fig. 1
During the process of deamination, the liver removes part of the amino acid.
Identify the part of the amino acid that is removed during deamination by circling it on Fig. 1.
[1]
3 marksOne of the products of deamination is urea.
Describe the fate of urea once it is produced by the liver.
2 marksUrea is a toxic substance that should not be allowed to accumulate in the body.
State two consequences of high urea levels in the body.
2 marksAmino acids are the building blocks of proteins.
Give two examples of proteins found in the body.
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4 marksThe 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.
5 marksTable 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
| diet | mass of urea produced / g | volume of urine produced / L |
| normal level of protein | 25.2 | 1.60 |
| high protein | 39.6 | 2.31 |
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]
2 marksOne 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.
3 marksThe 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.
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2 marksTable 1 shows the concentration of different substances in blood plasma, filtrate entering the proximal convoluted tubule and urine.
Table 1
| substance | concentration in blood plasma / g dm-3 | concentration in the filtrate / g dm-3 | concentration in the urine / g dm-3 |
| glucose | 1.0 | 1.0 | 0.0 |
| protein | 80.0 | 0.0 | 0.0 |
| urea | 0.4 | 0.4 | 0.4 |
| substance X | 7.5 | 7.5 | 2.1 |
Explain the difference in concentration of protein in the blood plasma and filtrate.
4 marksUnder 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]
2 marksFig. 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.
3 marksThe 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]
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3 marksSuggest an explanation for the effect that this may have on the process of ultrafiltration.
2 marksExplain this symptom.
3 marksPatients 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.
2 marksIn order for kidney dialysis to be effective, the dialysate must be constantly replaced with a fresh solution.
Suggest a reason for this.
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2 marksThe kidneys excrete excess water in urine.
The main component of urine is water.
State two other substances that are excreted by healthy kidneys.
5 marksA scientist investigated the effect of drinking sugar solutions, of different concentrations, on the volume of urine produced.
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
| description of measurement | volume / dm3 |
| total volume of urine produced 60 minutes after drinking solution C | |
| volume of urine produced between 30 minutes and 60 minutes after drinking solution B | |
| total volume of urine produced 150 minutes after drinking solution A |
[3]
Suggest which of the three solutions, A, B or C, contained the most sugar.
Give a reason for your suggestion.
2 marksList two factors that will affect the volume and concentration of urine produced.
2 marksThe body loses water in the urine.
State two other ways in which the body loses water.
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5 marksThe liver is an important organ in many processes.
The liver responds to changes in insulin concentration.
Insulin is a hormone.
[3]
3 marksThe liver is also involved in the processing of amino acids.
[2]
6 marksThe 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.
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2 marksExcretion 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
3 marksThe 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
| changing condition | volume of urine | concentration of urine |
| increase in water intake | ||
| increase in temperature | ||
| increase in exercise |
5 marksExcretion is a characteristic of living organisms.
Growth is another characteristic of living organisms.
Define the term growth.
[2]
State three characteristics of living organisms other than excretion and growth.
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3 marksComplete 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 ................................................... .
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