Homeostasis (Edexcel GCSE Biology)

Figure 1 shows a cross-section of human skin.

Figure 1

Describe the changes that occur when the brain detects a change in blood temperature

Higher Tier Only

Explain how vasoconstriction and vasodilation help to control body temperature

Describe how the pancreas responds to a rise in blood glucose concentration

Higher Tier Only

(i)An athlete takes part in a marathon race and only consumes water during the race.

State what would most likely happen to the athlete’s blood glucose concentration during the race.

(1)

(ii) Describe how the athlete's body would most likely responds to any changes in blood glucose concentration during the race.

(3)

Individuals with diabetes cannot control their blood glucose levels.

There are two types of diabetes: type 1 and type 2.

Explain the causes of type 1 and type 2 diabetes and how they can be controlled.  

Figure 1 shows the results of a blood glucose tolerance test for two people (A and B).

Figure 1

Explain which patient has diabetes.

Insulin is produced by an endocrine gland and is transported in the blood.

(i) Which row shows the endocrine gland and the target organs for insulin?

(1)

(ii) Which part of the blood transports insulin to its target organs?

(1)

Figure 1 shows the blood glucose and blood insulin concentration for a healthy person during one day.

Figure 1

The blood glucose concentration increases after a meal.

Explain why the blood glucose concentration then decreases.

State one cause of type 1 diabetes.

Explain how controlling the diet can be used to treat type 2 diabetes.

A scientist is planning to test a new treatment for type 2 diabetes.

She selects 300 volunteers who have type 2 diabetes.

State two other factors that the scientist should consider when selecting the 300 volunteers.

Figure 1 shows the urinary system of a human.

Figure 1

Name the structures labelled P and Q.

The kidney contains nephrons.

Figure 2 shows the concentration of glucose and protein found in the blood plasma and in the filtrate inside a nephron.

Figure 2

(i) Explain the difference in the concentration of protein in the blood plasma and in the filtrate in the nephron.

(2)

(ii) Explain how glucose moves from the blood plasma into the nephron.

(3)

Figure 3 shows a patient undergoing kidney dialysis.

Figure 3

Describe how dialysis removes unwanted substances from the blood.

Include examples of unwanted substances in your answer.

Blood is filtered in the kidney to remove unwanted substances.

Figure 1 shows part of a nephron.

Figure 1

Name the structures labelled P and Q.

Figure 2 shows information about some of the components in the blood and in the filtrate in this part of the nephron.

Figure 2

Higher Tier Only

(i) Calculate the difference in the number of red blood cells and the number of white blood cells in 1 cm³ blood.

Give your answer in standard form.

(2)

(ii) Explain why there are differences in the concentrations of some components in the blood and some components in this part of the nephron.

(2)

Higher Tier Only

State the name of the hormone that regulates the water content of the blood.

Iguanas are lizards.

Some species of iguana live on hot islands in the Pacific Ocean and use the environment to regulate their body temperature.

Figure 1 shows an iguana on a rock in the sunshine.

Cayambe, CC BY-SA 3.0 <https://creativecommons.org/licenses/by-sa/3.0>, via Wikimedia Commons

Figure 1

A marine biologist measured the oxygen consumption of an iguana at different temperatures.

Figure 2 shows the results.

Figure 2

(i) Describe how the body temperature of the iguana affects its oxygen consumption.

(1)

(ii) Explain why the body temperature of the iguana affects its oxygen consumption.

(3)

(iii) Iguanas do not have sweat glands.

When an iguana is too hot, it pants by opening its mouth to cool down.

Explain how this behaviour helps to cool the iguana down.

(2)

(i) Where in the human brain is the thermoregulatory centre?

(1)

High Tier Only

(ii) Explain the role of vasodilation in thermoregulation.

(4)

A student was investigating the effect of sweating.

The student set up two conical flasks each with a thermometer as shown in Figure 1.

Figure 1

Flask 1 was covered in wet tissue paper.

Flask 2 was covered with dry tissue paper.

Hot water was added to each of the flasks.

The temperature of the water in each flask was recorded every minute for 10 minutes.

State two variables that would need to be controlled in this investigation.

The results of this investigation are shown in Figure 2.

Figure 2

(i) Calculate the rate of temperature change in flask 1 from 1 to 8 minutes.

(2)

(ii) Compare the trends shown in the data for flask 1 and flask 2.

(2)

Explain how sweating helps to cool the body.

Which part of the brain controls internal body temperature?

Explain why it is important to control the internal temperature of the human body.

A person had symptoms including difficulty passing urine, aching in the lower abdomen, constant thirst and fainting.

A sample of their urine was tested.

The results are shown in Figure 1.

Figure 1

(i) A doctor analysed the results and asked the person to have further tests for type 2 diabetes.

Give a reason why the doctor came to this conclusion.

(1)

(ii) Explain why the doctor also concluded that the person had a kidney infection.

(2)

Describe how a student could test a sample of urine for the presence of protein.

Describe the route taken by urine from the kidney until it leaves the body.

Urine contains urea.

State how urea is formed in the human body.

A hospital patient was tested for diabetes.

A nurse recorded his mass and height.

Figure 1 shows these measurements.

Figure 1

Calculate the BMI of this patient using the information in Figure 1.

Blood samples were taken from this patient every four hours.

The glucose concentrations were recorded in Figure 2.

Figure 2

(i) Describe the trends shown in this data.

(3)

(ii) This patient was diagnosed as being type 2 diabetic.

Explain why the blood glucose concentration of this patient remained high from 4 hours to 8 hours.

(3)

(iii) This patient did some exercise during these 24 hours.

Explain how the data in Figure 2 shows that this exercise occurred after 8 hours but before 12 hours.

(3)

Endocrine glands make hormones.

Which endocrine gland is situated in the head and is attached to the brain?

Diabetics cannot effectively control the concentration of glucose in their blood.

Person A has type 1 diabetes.

Person B has type 2 diabetes.

Draw one straight line from each person to the cause of their type of diabetes.

A scientist investigated how the waist to hip ratio affected the probability of developing type 2 diabetes.

The scientist chose 100 females in each of five waist to hip ratio groups and recorded if they developed type 2 diabetes.

Figure 1 shows the results.

Figure 1

(i) Describe the trend shown in Figure 1.

Use data from Figure 1 in your answer.

(2)

(ii) A female has a waist measurement of 78.3 cm and a hip measurement of 90.0 cm.

Calculate the waist to hip ratio for this female and use Figure 7 to estimate the probability that she will develop type 2 diabetes.

(2)

(i) The scientist also measured the BMI of the females.

BMI and waist to hip ratio are two factors that affect the probability of females developing type 2 diabetes.

State two other factors about the females in the study that would affect the probability of them developing type 2 diabetes.

(2)

(ii) State why an athlete may have a high BMI but still have a low probability of developing type 2 diabetes.

(1)

Figure 1 shows the human urinary system.

Figure 1

Urine is made by removing water, urea and salts from the blood.

Use the letter X to label where urine is made.

Which substance is converted to urea in the liver?

A patient cannot remove enough urea from the blood when making urine.

Figure 2 shows a dialysis machine attached to the arm of this patient.

Their blood is pumped out of their arm, passed through the dialysis machine, and then put back into the patient.

Figure 2

(i) Describe what happens to urea as the blood passes through the dialysis machine.

(2)

(ii) Two patients need to have dialysis treatment.

Patient A needs this treatment three times a week.

Patient B needs this treatment once a week.

Give one reason why patient B needs dialysis treatment less often than patient A.

(1)

Describe how to test for glucose in the dialysis fluid.

Urease is an enzyme that breaks down urea into smaller molecules.

Explain why urease will not break down starch into smaller molecules.

(i) The nephron is made up of a number of structures including the Bowman's capsule and glomerulus.

Describe these structures and explain how they help to remove urea from the bloodstream.

(3)

(ii) Explain how water is reabsorbed in the nephron.

(2)

(i) Urine contains the waste product urea.

State where urea is produced

(1)

(ii) Figure 1 shows the results of an investigation into the effect of a high protein diet on excretion in terms of synthesis of urea and production of urine.

Figure 1

Explain why an increase in dietary protein may result in an increase in synthesis of urea in the human body.

(3)

Osmoregulation is the balance of water and mineral salts in the body.

Explain why osmoregulation is important.

Higher Tier Only

ADH is a key hormone in the regulation of water content in the blood

Complete the following sentence about ADH.

ADH affects the collecting duct by __________ its permeability to water, __________ urine production

Higher Tier Only

Figure 1 shows the level of ADH in the blood of an amateur athlete measured over the period of one day. Their heart rate is shown in Figure 2.

Figure 1

Figure 2

Suggest what could account for the peaks in ADH levels from 03:00 to 08:00 hrs and around 18:00 hrs

Higher Tier Only

The kidney is responsible for maintaining the water balance of the body.

Describe how ADH affects urine production.

A small number of patients with diabetes are given a pancreas transplant.

Out of these patients, only about 15% suffer from type II diabetes.

Explain why pancreas transplants are not often used for the treatment of type II diabetes.

Glucose tolerance tests can be used to assess if a patient has diabetes. During the test, a patient (who has fasted for eight hours) drinks a sugary solution and the glucose concentration of the blood is measured at regular intervals.

Figure 1 shows the results of a blood glucose tolerance test for a patient with diabetes (patient A).

Figure 1

Patient B who does not suffer from diabetes, undertook the same glucose tolerance test. The glucose concentration in their blood prior to drinking the sugary solution was 5 mmol / L .

Draw a curve on the graph in Figure 1 to show the results you would predict for patient B.

In the glucose tolerance test, diabetes is diagnosed if the concentration of glucose in the blood is higher than 7 mmol / L from at least two different tests.

Explain why the results may sometimes be inaccurate. 

Higher Tier Only

Table 1 shows the composition of urine in a healthy individual.

Table 1

Explain what the missing values in Table 1 would most likely be.

Higher Tier Only

Following the consumption of drinks containing caffeine, urine production increases when compared to consuming the same volume of a non-caffeinated drink.

Suggest a biological mechanism for why this may happen.

Higher Tier Only

Explain how a dialysis machine filters blood.

Higher Tier Only

Explain why the majority of doctors consider kidney transplants to be a preferable solution compared to dialysis, for patients with kidney failure.

Higher Tier Only

Table 1 shows the number of single organ transplants that were performed in the UK in 2018.

Table 1

Suggest why kidney transplants were the most frequent organ transplant.

When cycling, a cyclist's body temperature increases.

Describe how body temperature is monitored by the brain.

The skin surface temperature and core body temperature of a cyclist were monitored before, during and after a race, as shown in Figure 1.

Figure 1

Core body temperature rises during exercise. When an individual stops exercising, their core body temperature starts to decrease.

How long did it take for the cyclist’s temperature to recover after the race?

Describe and explain the changes that occurred during the race to both the cyclist’s core body temperature and skin temperature.