Diffusion

Figure 17 shows a beaker containing a potato cylinder in distilled water.

Explain why the mass of this potato cylinder will change when it is placed in distilled water.

A scientist investigated the rate of diffusion using three agar cubes of different sizes.

Each cube contained a pH indicator that changed from pink to colourless when placed in acid.

The cubes were placed in a beaker containing an acid.

Figure 18 shows some information about each cube.

Calculate the volume of cube C.

Explain the difference in the times taken for cubes A and B to become colourless.

* (c) Liquid agar was poured into a Petri dish and allowed to set.

A well was cut in the centre of the set agar.

Kiwi fruit juice was poured into the well.

Kiwi fruit juice contains an enzyme that causes set agar to break down into a liquid.

Figure 19 shows the results after 30 minutes.

Devise a plan to investigate the effect of different concentrations of kiwi fruit juice on the breakdown of set agar, using the equipment shown in Figure 19.

Your plan should include:

• measurements that need to be taken

• variables that need to be controlled.

Figure 3 shows a beaker containing a potato cylinder in distilled water.

Explain why the mass of this potato cylinder will change when it is placed in distilled water.

A scientist investigated the rate of diffusion using three agar cubes of different sizes.

Each cube contained a pH indicator that changed from pink to colourless when placed in acid.

The cubes were placed in a beaker containing an acid.

Figure 4 shows some information about each cube.

Calculate the volume of cube C.

Explain the difference in the times taken for cubes A and B to become colourless.

A teacher was demonstrating a process to students.

The teacher had a beaker of water and added five drops of food colouring to the beaker.

State the process being demonstrated.

A student asked if different food colourings spread evenly in the same amount of time.

Give two variables that would need to be controlled if the investigation was repeated with different food colourings.

The teacher repeated this process with water at different temperatures. Figure 11 shows the results of this experiment.

Draw a line graph to show the results in Figure 11.

Explain why the time taken decreased.

Figure 13 shows a root hair cell from a plant.

Name the part labelled X.

State one way that the structure of the root hair cell increases the volume of substances it absorbs.

Explain why root hair cells do not contain chloroplasts.

*(c) The arrows in Figure 15 show the direction of water movement through a tree.

Explain how water is moved from the soil, through the plant and into the air.

Alcohol is broken down by liver cells.

Which process moves alcohol from the blood into the liver cells?

If a person drinks too much alcohol, liver cells die and the person can develop cirrhosis of the liver.

The relative risk of developing cirrhosis of the liver is affected by two factors.

1. The volume of alcohol a person drinks in one week.

2. Whether the person drinks the alcohol on its own or with a meal.

Figure 7 shows how these two factors affect the relative risk of people developing cirrhosis of the liver.

Number of units of alcohol consumed per week

Figure 7

Person A drinks alcohol on its own.

Person B drinks alcohol with their meals.

Calculate the difference in risk for these two people when each one drinks 28 units of alcohol per week.

Using evidence from Figure 7, state two pieces of health advice for people about drinking alcohol.

Cystic fibrosis is a genetic condition that can also cause liver disease.

State where genes are found in cells.

Figure 8 shows the inheritance of cystic fibrosis in a family.

F represents the dominant allele that does not cause cystic fibrosis.

f represents the recessive allele that causes cystic fibrosis.

person C person D
person E (ff)

A scientist states that the genotype of person B is Ff.

Explain why the scientist is correct.

State the genotype of person C.

Figure 10 shows a single-celled pond organism (Amoeba proteus).

Which row of the table allows the net diffusion of oxygen into Amoeba proteus ?

Amoeba proteus uses oxygen for aerobic respiration.

Complete the equation for aerobic respiration.

glucose + oxygen _........ +_........ (+ energy is released)

Humans breathe faster when they exercise.

Which two changes allow the rate of respiration in the muscle to increase?

Figure 11 shows breathing data for a human at rest and when running at 5 metres per second on a running machine.

Calculate the mean volume of air breathed per minute when running at 5 metres per second.

Give your answer to one decimal place.

_........ dm³ per minute

Devise an investigation to compare the mean number of breaths per minute for men, with the mean number of breaths per minute for women, when running at 5 metres per second on a running machine.

Whilst running, the leg muscles of an athlete tightened up, causing cramp.

Name the product of anaerobic respiration that can cause cramp.

Figure 21 shows the human urinary system.

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 22 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.

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

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.

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.

Figure 7 shows the human urinary system.

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 8 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.

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

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.

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.

Figure 9 shows the structure and actual size of red blood cells (erythrocytes).

red blood cells side view of red blood cell (cut)

(Source: © N.Vinoth Narasingam/Shutterstock)

Figure 9

Calculate the image size of the top view of this red blood cell if this cell is

Give your answer in mm.

Explain how the shape of a red blood cell is related to its function.

State the role of haemoglobin inside the red blood cell.

Some blood transfusions contain red blood cells.

Red blood cells are stored in a solution containing 5.0% glucose and 0.9% salt.

Explain why red blood cells cannot be stored in pure water.

Figure 4 shows three cells.

What is structure X ?

The bacterial cell in Figure 4 has a flagellum.

State the function of a flagellum.

Give one other difference between the bacterial cell and the animal cell shown in Figure 4.

Substances move into and out of cells.

How does oxygen move into and out of cells?

A plant leaf cell is 0.04 mm long.

Calculate the length of the image after this cell has been magnified 500 times.

A student placed three different sized cubes of agar jelly into separate beakers containing the same concentration of hydrochloric acid.

The cubes contained a pink indicator.

This indicator becomes clear when in contact with an acid.

Figure 7 shows the results of the investigation after the cubes had been in the acid for 120 seconds.

The distance from the outside of cube B to the pink area was 3 mm.

Calculate the distance diffused by hydrochloric acid in one second.

The student wanted to confirm their results.

Give one improvement the student should make to this investigation to confirm their results.

Devise a method, using cubes of agar jelly, to investigate how temperature affects the rate of diffusion.

Some substances move into and out of cells by active transport.

Which is the correct description of the movement of a substance by active transport?

Some drugs used to treat cancer are taken into cells by active transport.

Figure 8 shows some causes of preventable cases of cancer in 2015.

What is the percentage of preventable cases of cancer that are caused by tobacco?

In 2015, data from Cancer Research UK suggested that 163 440 cases of cancer could have been prevented.

Calculate the number of preventable cases of cancer caused by alcohol.

Give your answer to the nearest whole number.

number of preventable cases of cancer caused by alcohol_........

A person with kidney disease may need kidney dialysis treatment.

Figure 15 shows an experiment to show how a dialysis membrane works.

Describe the method that would be used to find out what is present in the solution in the beaker, after one hour.

Explain how this experiment represents a simple model of kidney dialysis treatment.

*(b) The nephrons in the kidney remove unwanted substances from the blood.

Figure 16 shows the structure of a nephron.

Explain how substances are exchanged between the blood entering the nephron and the filtrate leaving the collecting duct.

Include reference to named structures of the nephron in your answer.

(a) Figure 10 shows alveoli from a lung.

Figure 10

Explain why these alveoli have the internal structure shown in Figure 10.

How does oxygen move across the alveolar membrane into the capillary?

Figure 11 shows the movement of molecules across a membrane.

at start
after 2 seconds
after 4 seconds

Figure 11

Describe how Figure 11 illustrates movement of molecules across a membrane.

*(c) Explain, using Fick’s law, the factors that affect the diffusion rate of molecules into and out of cells.

Figure 16 shows the urinary system of a human.

Name the structures labelled P and Q.

The kidney contains nephrons.

Figure 17 shows the concentration of glucose and protein found in the blood plasma and in the filtrate inside a nephron.

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

Explain how glucose moves from the blood plasma into the nephron.

*(c) Figure 18 shows a patient undergoing kidney dialysis.

Describe how dialysis removes unwanted substances from the blood.

Include examples of unwanted substances in your answer.