Excretion (OCR A Level Biology): Exam Questions

A student dissected a kidney. Fig. 1.1 shows one half of the dissected kidney.

Fig. 1.1

Draw a simple diagram of the kidney in Fig. 1.1 in the space below.

On your diagram, label the pelvis, medulla and cortex.

A photomicrograph of a stained section of kidney tissue is shown in Fig. 1.2.

Fig. 1.2

(i) State one function of the distal convoluted tubule.

 [1]

(ii) Describe the function of the structures labelled A in Fig. 1.2.

 [1]

(iii) Suggest which lumen, B or C, has the highest concentration of urea. Explain your answer.

 [1]

Water reabsorption in the kidney is controlled by the endocrine and nervous systems.

Aldosterone and ADH are hormones that act on the kidney.

Aldosterone causes sodium ions to be pumped from the collecting duct cells into tissue fluid.

Describe how the endocrine and nervous systems work together to increase water reabsorption from the collecting duct.

Diuretics are drugs that decrease the reabsorption of water into the blood from the kidney.

Diuretics can change the concentration of ions and other molecules in the blood.

Some diuretics are used to treat high blood pressure.

The table below lists three different diuretics, X, Y and Z, and some of their effects in the body.

(i) Suggest which of the diuretics, X, Y or Z, would be the most effective at reducing a person’s blood pressure. Explain your choice.

diuretic....................................................................... explanation...............................................................

[1]

(ii) Suggest which of the diuretics, X, Y or Z, would be the most appropriate for use by a person with type II diabetes. Explain your choice.

diuretic........................................................................... explanation..................................................................

[1]

Fig. 22.1 is a cross-section of part of the cortex of a mammalian kidney.

Image courtesy of Doc. RNDr. Josef Reischig, CSc. Licensed under CC BY-SA 3.0. Reused and distributed under conditions found at: https://creativecommons.org/licenses/by-sa/3.0

Fig 22.1

(i) Which letter identifies the region with the highest hydrostatic pressure?

[1]

(ii) Which two letters identify regions that do not contain plasma proteins?

[1]

Studies of the cell surface membranes of the distal convoluted tubule have provided the following evidence:

• Sodium-potassium pumps:

  • move potassium ions from the blood to the tubule fluid

  • move sodium ions from the tubule fluid to the blood

  • use ATP in these processes.

• Sodium-calcium co-transport proteins:

  • move calcium ions from the tubule fluid to the blood

  • move sodium ions into the tubule fluid

  • use the electrochemical gradient of sodium ions to drive this process.

(i) Using this information and your own knowledge, compare the processes occurring in the proximal and distal convoluted tubules.

[3]

(ii) Nephrogenic diabetes insipidus is a disease of the kidney that affects the regulation of water potential in the blood. One cause is lithium poisoning. Lithium ions enter the kidney tubules through sodium channels.

This prevents the cells of the collecting duct from responding to ADH in the blood.

State and explain one symptom you would expect to observe as a result of nephrogenic diabetes insipidus.

[2]

Fig. 22.2 shows a podocyte from the kidney. The many gaps between the microscopic processes form fenestrations in the Bowman’s capsule.

Fig. 22.2

(i) Explain why podocytes are usually unable to undergo mitosis.

[3]

(ii) Studies show that after damage by infection or injury, it is possible for nephron tissues to be regenerated. Adult stem cells are involved in this process.

What features of adult stem cells make them suitable for regeneration of tissues in the kidney?

[2]

The process of ultrafiltration in the kidney shares similarities with the formation of tissue fluid.

Describe the similarities and differences between ultrafiltration and the formation of tissue fluid.

A person’s glomerular filtration rate (GFR) provides an indication of the health of their kidneys. The GFR is a measure of the volume of blood that can be filtered by the kidneys every minute.

GFR can be estimated by monitoring the blood concentration of creatinine, which is a breakdown product of creatine phosphate in muscles.

(i) Suggest two characteristics of a patient that must be taken into account when using this GFR measurement to diagnose kidney damage.

Explain why each characteristic must be considered.

[4]

(ii) If kidney damage is suspected, the patient’s urine is likely to be tested for the protein albumin. 

Explain why the presence of albumin in the urine indicates kidney damage.

[1]

Cirrhosis of the liver can result from long-term liver damage. Alcohol or other toxins can cause this damage.

Scientists have suggested that cirrhosis can be detected by taking samples of body fluids and testing them for two different molecules: C-reactive protein and copeptin.

The liver produces these two molecules, and increased levels can indicate liver damage due to cirrhosis.

Different bodily fluids from a patient suspected of having cirrhosis were tested for C-reactive protein and copeptin.

Fig. 17.1 is a graph of the results.

Fig. 17.1

Different bodily fluids have different concentrations of the different molecules.

(i) Calculate the order of magnitude by which concentration of copeptin in the faeces is higher than the concentration of C-reactive protein in the saliva.

Show your working.

Answer = ................................ molecules cm^-3  [2]

(ii) Suggest why blood and faeces have the highest concentrations of C-reactive protein and copeptin.

[2]

Fig. 17.2 is an image of a Kupffer cell from the liver.

Fig. 17.2

(i) The diameter of the Kupffer cell in the image is 9.1 cm. Assuming it is spherical, calculate the actual volume of this cell. Note that a cm ruler has been added to Fig. 17.2.

Give your answer to four significant figures. Show your working.

[3]

(ii) Which type of microscope has been used to obtain this image? Explain your answer.

[2]

Fig. 17.1 is a diagram of the external view of a mammalian liver.

Fig. 17.1

Identify, with reasons, each of the blood vessels labelled A – C in Fig. 17.1.

A .........................................

B .........................................

C .........................................

One of the main functions of the liver cells is the formation of urea by the ornithine cycle, an outline of which is shown in Fig. 17.2.

Fig. 17.2

(i) Step 1 of the cycle takes place in the organelle represented by D.

Identify organelle D.

[1]

(ii) During the cycle ornithine moves into organelle D and citrulline moves out of the organelle.

Suggest the method by which these molecules move into and out of the organelle during the cycle. Give reasons for your choice.

[2]

(iii) How has the ammonia that is used in step 1 been formed?

[1]

(iv) Identify the compound labelled X in Fig. 17.2.

[1]

The image below shows a light micrograph of a section of human liver tissue.

(i) Identify the structure labeled M in the image.

[1]

(ii) The measured length of structure M is 0.4 cm.

Calculate the actual length of structure M in µm, giving the answer to three significant figures.

[3]

(iii) Suggest and explain one way in which the cells lining structure M are adapted to carry out their function.

[2]

The structure labelled N in the image from part (a) can become blocked by a blood clot or tumour, a condition called Budd-Chiari syndrome.

(i) Explain why symptoms that may arise in a patient with a blockage in structure N include abdominal swelling and pain.

[3]

(ii) The spleen is an organ that is responsible for filtering pathogens and old or damaged red blood cells from the blood. It is linked to the liver via the portal vein system as shown in the diagram below:

Suggest and explain the impact that Budd-Chiari syndrome may have on the spleen.

[2]

One of the main functions of the mammalian liver is the formation of urea via the ornithine cycle.

An outline of the ornithine cycle is shown below.

(i) The stage of the ornithine cycle that occurs in the mitochondria is referred to as a rate-limiting step.

Explain what this means.

[2]

(ii) Adenosine monophosphate (AMP) is a nucleotide consisting of a phosphate group, a ribose sugar and one adenine base.

Describe the two reactions that would take place at stage 2 on the diagram to produce AMP from ATP.

[2]

If there is a problem with the ornithine cycle, the level of ammonia in the blood will rise, causing hyperammonemia.

(i) Treatment for hyperammonemia includes removing protein from the diet.

Suggest why this is an appropriate treatment for hyperammonemia.

[3]

(ii) Hepatic ischaemia is damage to the liver caused by an inadequate oxygen supply. It may occur as a result of low blood pressure.

Suggest why low blood pressure may also lead to hyperammonemia.

[2]

Keto acid is another product formed during the deamination of an amino acid. Keto acid may enter the Krebs cycle to be respired or converted into glucose.

(i) Suggest other biological molecules that keto acid may be converted into for storage.

[2]

(ii) Keto acid enters the Krebs cycle as acetyl coenzyme A.

Describe the stage of respiration that also produces acetyl coenzyme A to be used in the Krebs cycle.

[3]

The table below shows the concentration of some components of blood, glomerular filtrate and urine.

(i) Calculate the percentage increase in the concentration of urea in the urine compared to the blood and glomerular filtrate.

[2]

(ii) Explain the high levels of urea and inorganic ions in urine compared to blood and glomerular filtrate.

[2]

An individual's kidney function can be assessed by measuring their Glomerular Filtration Rate (GFR).

(i) GFR is estimated based on the concentration of creatinine in the blood plasma. Creatinine is produced naturally by the body and is filtered from the blood by the kidneys. Use this information to suggest two properties of creatinine.

[2]

(ii) An individual’s estimated GFR (eGFR) can be calculated using the following formula:

                                 eGFR = GFR x               . 

A man has a GFR of 67 cm³min^-1 and a body surface area of 2.03 m².

Calculate the eGFR for this man, giving the answer to three significant figures

[2]

(iii) An eGFR of below 60 indicates some reduction in kidney function.

Determine what the result from part (ii) indicates about the man’s kidney function.

[2]

Kidney failure can be treated with haemodialysis.

Explain why it is important to maintain a counter-current flow of blood and dialysate throughout the dialysis process.

The image below shows a cross section of the cortex of a mammalian kidney.

(i) Name two molecules that would be found in region D.

[2]

(ii) Identify the region that has the highest hydrostatic pressure and explain why.

[3]

Gestational diabetes insipidus is a rare complication of pregnancy caused by excessive vasopressinase activity.

Vasopressinase is an enzyme produced by the kidney which destroys the mother’s ADH (also called vasopressin).

Suggest and explain a symptom that a mother may have as a result of gestational diabetes insipidus.

A synthetic hormone similar to vasopressin, called desmopressin can be used to treat gestational diabetes insipidus.

Suggest how desmopressin can be used to treat this disease.

Urine can be used for a variety of medical diagnoses.

(i) Increased levels of protein in the urine can be an indicator of high blood pressure.

Suggest why.

[2]

(ii) Suggest what white blood cells in urine may indicate.

[2]

Urine can also be tested for the use of anabolic steroids in sport.

The graph below shows tests carried out by the International Olympic Committee (IOC) on athletes between 1986 and 1994.

• The bars represent the number of urine samples tested.

• The line shows the percentage of samples testing positive for elevated levels of the steroid testosterone.

(i) Calculate the change in the number of samples testing positive for elevated levels of testosterone between 1986 and 1993.

[3]

(ii) Anabolic steroids are sometimes used by athletes to rapidly build muscle mass.

Explain how anabolic steroids increase muscle mass.

[2]

 Use data from the graph above to evaluate the following statement:

“Steroid abuse in sport has decreased since 1988”.