The Internal Environment (Edexcel International A Level (IAL) Biology): Exam Questions

Homeostasis is the state maintained by living systems.

Feedback mechanisms are involved in maintaining homeostasis.

Describe the difference between a negative feedback mechanism and a positive feedback mechanism.

Which statement about the homeostasis of thermoregulation when the human body temperature is 37°C is correct?

The health of a kidney can be determined by measuring the glomerular filtration rate (GFR).

This method measures the rate at which a small molecule called creatinine is filtered from the blood.

(i) Explain how small molecules like creatinine are filtered from the blood in the glomerulus.

(3)

(ii) In 15 hours, a person excreted 1960 mg of creatinine in the urine.

Calculate the GFR for this person.

Give your answer to 3 significant figures.

(1)

Answer ..................................................

In type II diabetes, body cells take up less glucose in response to insulin.

Many people with type II diabetes are overweight or obese.

Some of these individuals have been given surgery to help weight loss.

A clinical trial investigated the effect of surgery on the uptake of glucose by body cells in the presence of insulin.

This trial used groups of people who were non‐diabetic, people in the early stage of diabetes (pre‐diabetic) and people who were type II diabetics.

(i) Comment on the results of this trial.

(3)

(ii) Calculate the difference that surgery makes to the mean uptake of glucose in the non‐diabetic group and the type II diabetic group.

(2)

Answer ....................................................

The kidney is involved in the process of homeostasis in a mammal.

Antidiuretic hormone (ADH) is required for homeostasis.

How many of these parts of the kidney respond to ADH?

• Bowman’s capsule

• collecting duct

• loop of Henle

• proximal tubule

The electron micrograph illustration shows a transverse section of part of a proximal tubule.

(i) Name the process by which the fluid moves from the plasma into the renal tubule (nephron).

(1)

(ii) Name the structures labelled S.

(1)

A student compared the left renal veins of two individuals.

(i) The diameter of the left renal vein of one individual was 4.71 mm.

Calculate the cross-sectional area of this vein.

(2)

(ii) The cross-sectional area of the left renal vein of the second individual was 0.194 cm².

Calculate the difference in the cross-sectional area in the left renal vein of these two individuals.

(1)

The table shows the concentration of glucose and urea in the blood plasma, glomerular filtrate and urine of an individual.

Explain the concentration of glucose and urea in the urine.

Use the information in the table to support your answer.

An individual produced 0.83 cm³ of urine each minute.

Calculate the volume of urine produced by this individual in 24 hours.

Assume the urine production is at a constant rate.

Give your answer in dm³, to two significant figures.

The kidneys perform important roles in filtering the blood and maintaining fluid levels in the body.

Each kidney contains up to a million functioning units called nephrons.

Each nephron consists of a filtering unit of tiny blood vessels called a glomerulus that is attached to a tubule.

The diagram shows part of a human kidney.

(i) Draw an arrow on the diagram to show the location of a single Bowman’s capsule (renal capsule).

(1)

(ii) Where in the kidney are most amino acids reabsorbed from the nephron?

(1)

(iii) Which row shows the correct pathway taken by a water molecule through the kidney nephron?

(1)

Explain how the loop of Henle acts as a countercurrent multiplier to produce concentrated urine.

Describe how ADH is involved in the control of the water potential of the blood.

Ecstasy (MDMA) is a recreational drug that can have serious toxic effects.

The effect of MDMA on ADH concentration in blood has been studied.

In one study, each person in a group of volunteers was given MDMA. The MDMA and ADH concentrations in the blood were measured.

The graph shows the results of this study.

(i)

Estimate how long it takes the MDMA concentration in the blood to become 0.0 μg dm⁻³.

(1)

(ii)

Calculate the rate of removal of ADH from the blood between 4 and 8 hours.

(2)

Taking MDMA causes a person to be very thirsty. This can lead to swelling of the brain, which can be fatal.

The table shows some laboratory results for one case in which a person suffered swelling of the brain.

Comment on the role of ADH in MDMA-induced brain swelling.

Use the information in the graph and table as well as your own knowledge to support your answer.

The diagram shows a nephron from a mammalian kidney.

Name the structures labelled A, B and C.

Describe how ultrafiltration produces filtrate in the nephron.

The sand cat (Felis margarita) is a small wild cat found in desert habitats. A study compared kidney function in the sand cat with the domestic cat (Felis catus).

The table shows the results of the study.

Calculate the ratio of urine concentration in the sand cat to the domestic cat.

Give your answer to two decimal places.

Using the data in the table and your own knowledge, explain how the sand cat's kidney adaptations enable it to survive in a desert environment.

Explain the effect of not drinking water for a prolonged period on urine production in sand cats.

Explain how the regulation of blood glucose concentration is an example of negative feedback.

Type 2 diabetes is a condition in which blood glucose regulation is impaired.

Scientists investigated gene expression in muscle cells from individuals without type 2 diabetes (the control group) and individuals with type 2 diabetes.

Table 1 shows the relative expression levels of four genes in the two groups of participants.

Calculate the percentage decrease in INSR expression between control individuals and diabetic individuals.

Give your answer to two decimal places.

Suggest which gene's expression change is most likely to be responsible for the reduced glucose uptake observed in the muscle cells of diabetic individuals.

Use information from the table to justify your answer.

Insulin is a peptide hormone.

Suggest how insulin could lead to changes in gene expression within muscle cells.