Excretion & the liver

Which statements about excretion and homeostasis are true, and which are false?

Tick (✓) one box in each row.

Fig. 19.1 is a drawing of a longitudinal section of a kidney.

Fig. 19.1

Identify the parts of the kidney labelled T, U and V.

Fig. 19.2 is a photomicrograph of a cross-section of part of the kidney.

Fig. 19.2

Using the letter T, U or V from Fig. 19.1, identify the part of the kidney that was used to make the cross-section in Fig. 19.2.

Give a reason for your identification.

Letter representing part of the kidney........

Fig. 19.3 is a diagram of a single nephron.

Fig. 19.3

Complete the table using the most appropriate letter or letters, W to Z, to show which part(s) of the nephron correspond to each of the statements.

Each letter may be used once, more than once or not at all.

Fig. 19.3 shows an increasing solute concentration.

Outline the processes in the loop of Henle that cause the solute concentration to increase.

An adult was advised to change their diet to reduce their body mass before undergoing surgery.

Over a period of several weeks their body mass reduced by 1 kg.

Suggest what happened to the 1 kg of body mass.

Which of the options is not a function of the liver?

A production of urea in the ornithine cycle

B removal of amino groups from amino acids

C storage of excess amino acids as protein

D storage of glucose as glycogen

The figure shows the results of three pregnancy tests using test strips with mobile and fixed (immobilised) monoclonal antibodies that bind to human chorionic gonadotrophin (hCG).

The mobile monoclonal antibodies are labelled with coloured beads.

The Results line and the Control line contain the fixed monoclonal antibodies.

Each strip is dipped in a sample of urine up to the stop line. They are then laid flat for 10 minutes and read.

Stop line Stop line

Which of the statements about these pregnancy tests is true?

A In Strip 1 hCG has bound to mobile antibodies that have been captured by fixed antibodies on the Control line. The pregnancy test is positive.

B In Strip 2 hCG has bound to the mobile antibodies and these have been captured by fixed antibodies on the Results line. The pregnancy test is positive.

C In Strip 3 hCG has bound to the mobile antibodies and these have been captured by fixed antibodies on the Results line. The pregnancy test is negative.

D In Strip 3 hCG has bound to the mobile antibodies and these have been captured by fixed antibodies on the Results line. The pregnancy test is positive.

The liver is an organ with a wide variety of functions.

Fig. 18.1, in the insert, shows a light micrograph of a section of normal human liver.

Identify the structures labelled N and O in Fig. 18.1.

The walls of the structure labelled M in Fig. 18.1 are lined with cells.

Suggest and explain how these cells are adapted to carry out their function.

Liver is a rich source of the enzyme catalase.

The table below describes examples of three terms from the list below.

coenzyme competitive inhibition enzyme-product complex

induced-fit lock and key non-competitive inhibition

prosthetic group secondary structure tertiary structure

Complete the table by choosing a term from the list that matches each example.

Fig. 18.2 shows the effect of concentration of hydrogen peroxide on the rate of reaction of catalase.

Cyanide ions inhibit catalase, even at high concentrations of hydrogen peroxide.

Sketch a line on Fig. 18.2 to show the effect of repeating the experiment in the presence of cyanide ions.

[Answer on Fig. 18.2]

The oxygen dissociation curves for adult haemoglobin and fetal haemoglobin are shown in Fig. 6.1.

Outline why it is important that fetal haemoglobin has a higher oxygen affinity than adult haemoglobin.

Myoglobin is a protein found in muscles. Oxygen binds to myoglobin.

A student described the oxygen dissociation curve for myoglobin as follows:

• When oxygen first becomes available, myoglobin saturation increases at a constant rate of 8% per mmHg of oxygen.

• When there is a slightly higher partial pressure of oxygen, the rate of oxygen binding slows gradually until the myoglobin is 100% saturated.

• The partial pressure at which myoglobin reaches 100% saturation is the partial pressure at which adult haemoglobin is 80% saturated.

Sketch an oxygen dissociation curve for myoglobin on Fig. 6.1 based on the description provided above.

........ Answer on Fig. 6.1........

Haemocyanin is an oxygen‑binding pigment that is found in many invertebrate animals, including lobsters.

Fig. 6.2 shows the oxygen dissociation curves for haemoglobin and haemocyanin.

What can you conclude about the habitat of a lobster?

When old red blood cells are broken down, each haem group is converted to a molecule called bilirubin. Bilirubin passes through the digestive system. Bilirubin gives faeces their characteristic colour.

Explain why bilirubin production and processing is an example of excretion.

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.

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.

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.