OCR GCSE Combined Science B (21st Century) Paper 5 June 2019 question paper

Cellular respiration takes place in living cells.

In which parts of a cell do the reactions of cellular respiration take place?

Tick (✓) two boxes.

Which processes need energy from cellular respiration?

Tick (✓) two boxes.

All living cells produce hydrogen peroxide (H₂O₂) as a waste product.

The cells in potatoes contain an enzyme called catalase. It breaks down H₂O₂ to water and oxygen, this is the equation for the reaction that takes place.

Mia investigates the effect of H₂O₂ concentration on the rate of this reaction.

She writes out her method.

1. Put a peeled potato in a liquidiser with some water to make potato extract.

2. Dip a paper disc in the potato extract. The potato extract is a source of catalase.

3. Drop the paper disc into a test tube containing H₂O₂ solution.

4. Wait until the disc has sunk to the bottom.

5. Time how long it takes for the disc to rise to the surface of the H₂O₂.

This is a diagram of her apparatus.

(c) Mia’s method lacks the detail needed for another scientist to reproduce her findings.

Suggest additional detail which would allow another student to follow the method exactly.

Bubbles form on the paper disc when it is in the H₂O₂ solution. This causes the disc to rise to the surface of the solution.

Mia thinks that if a disc rises more quickly, this means that the rate of reaction is faster.

Explain why she is correct.

The table shows Mia’s results.

Calculate the rate of reaction for 6.00% H₂O₂ solution.

Give your answer to 3 significant figures.

Rate =........ s^–1

Which conclusions are supported by the data in the table?

Tick (✓) two boxes.

Between 0.75% and 6.00% H₂O₂ the reaction rate increases by approximately 2.5 times.

Doubling the concentration of H₂O₂ halves the time taken for the disc to reach the surface.

Increasing the concentration of H₂O₂ decreases the rate of reaction.

Increasing the concentration of H₂O₂ increases the time taken for the disc to reach the surface.

The biggest difference in time taken for the paper disc to reach the surface is between 0.75 and 1.50% H₂O₂.

Describe what Mia could do to increase confidence in her data.

Herring are a type of fish. They live in the North Sea.

Fig. 2.1 shows the food web for a community living in the North Sea.

Fig. 2.1

Humans catch and eat herring.

Add humans to the food web in Fig. 2.1.

Explain why seals and killer whales are described as competitors.

What is the correct name for the process that produces food and biomass in food chains?

Diffusion Osmosis Photosynthesis Respiration Transpiration

What is the name of the biomass producer in the North Sea food web in Fig. 2.1 ?

Some students are studying the North Sea food web.

They discuss how fishing may affect the biodiversity of the North Sea.

Which student is correct?

Tick (✓) one box.

Explain your answer.

The bar chart in Fig. 2.2 shows how many herring were caught from the North Sea each year from 1960 to 2000.

In which year was the catch greatest and how big was it?

Year........

Catch........

By 1977 the herring population in the North Sea was so low that fishing for herring was banned.

Fishing restarted in 1984. A limit was put on the number of tonnes of herring that could be caught each year.

The limit was changed in 1996.

What evidence from the bar chart in Fig. 2.2 indicates that the limit was changed?

Calculate the rate of increase in the herring catch from 1984 to 1988.

Rate =........ million tonnes / year

Since 1998 North Sea herring fishing has been described as sustainable.

Explain what sustainable means in this context.

Influenza (flu) is a common human infection.

Infections are caused by pathogens. Pathogens can be spread in different ways.

Draw lines to connect each pathogen to how it is spread.

Coughing and sneezing can spread the virus that causes flu.

Look at the poster in Fig. 3.1.

Explain how following the advice in the poster (Fig. 3.1) could prevent the spread of flu.

In 2017 there was a flu epidemic in Australia. 170 000 people in Australia were infected. 72 of these people died. The population of Australia in 2017 was 25 000 000.

Calculate the probability of an individual person in Australia being infected in 2017.

The diagram in Fig. 3.2 shows a flu virus.

The virus is made from four different proteins.

The virus is approximately 0.1 m in diameter.

Which device must scientists have used to look at the virus so that they could draw such a detailed diagram?

Tick (✓) one box.

Infants under the age of 6 months are too young to be vaccinated against flu.

Doctors recommend that older children and adults are vaccinated. Explain how this helps protect infants from flu.

* Read the article about flu viruses and vaccination.

Flu virus proteins change rapidly due to a high mutation rate.

Each year doctors develop a vaccine for the flu virus they expect to be the most common that year.

It takes several months to make a flu vaccine.

In most years a vaccinated person is 40 to 60% less likely to develop flu.

Use the information in the article to explain:

• how vaccination and the immune system protect against flu

• why the vaccine is never 100% effective.

Flu can increase the risk of other diseases such as pneumonia.

Pneumonia is a disease of the lungs, caused by an infection.

Suggest why having flu increases the risk of catching pneumonia.

An adult man has a lung volume of 5 litres and a lung surface area of 70 m². (ii)

Write down the simplest surface area to volume ratio for this man’s lungs.

Pneumonia causes fluid to collect in the alveoli of the lungs.

The diagram in Fig. 3.3 shows this happening in one alveolus.

Suggest how the fluid collecting in the alveoli will affect gas exchange and explain why the symptoms of pneumonia, include feeling tired and weak.

Huntington’s disease is caused by a faulty allele of a single gene.

Write down the expected percentage of Huntington’s disease phenotypes.

Huntington’s disease is caused by the production of a damaged protein.

Proteins are polymers.

Which molecules are joined together to make a protein?

Tick (✓) one box.

DNA is also a polymer.

Describe the structure of DNA.

Explain how changes to the DNA polymer can cause changes to the protein polymer.

The structure of red blood cells is adapted to carry oxygen.

Changes to the red blood cells in people with SCD mean they carry less oxygen. Explain why.

What must be added to cells so that the nuclei can be seen using a light microscope?

Only red blood cells can contain the protein haemoglobin.

Explain why other specialised cells cannot produce haemoglobin.

A team of scientists claimed to have cured SCD in a man in 2017.

They added an extra gene to some of his stem cells. These stem cells specialise to become red blood cells.

All the blood tests they performed showed that the man had been cured of SCD.

They published their results in a scientific journal so that other scientists could read about the cure.

Evaluate the scientists’ claim to have cured SCD.

The scientists used adult stem cells from the man for the procedure.

Why does the use of adult stem cells cause fewer ethical issues than the use of embryonic stem cells?

The diagrams show two stages of the heartbeat. The shading shows which chambers and arteries contain blood at the end of each stage. The arrows show the direction in which the blood moved.

Put ticks (✓) in the boxes that correctly describe each stage.

A scientist investigated how maggots respond to light.

She set up a card circle with a light source on one side. Four areas were marked on the card circle. Maggots were placed on the centre of the circle as shown in Fig. 6.1.

The light was switched on and the maggots moved on the card circle. The number of maggots in the positive, negative and neutral areas was recorded after three minutes.

The experiment was repeated using four different light intensities.

The scientist put her results in a table.

Use the data in the table to suggest the lowest light intensity that can be detected by the maggots.

Explain your answer.

Light intensity........ arbitrary units

Suggest how the scientist could develop the investigation to find out whether maggots can detect different colours of light.

Maggots can respond to stimuli such as light because they have a nervous system. Neurons in the nervous system connect to each other at synapses.

Fig. 6.2 shows a synapse.

Use Fig. 6.2 to explain the role of transmitter substances in transmitting impulses between neurons.

Explain why active transport can take place in phloem but not in xylem.

Companion cells contain soluble proteins.

Explain why these proteins cannot diffuse across the cell membrane into the phloem.

Fig. 7.2 shows a cross section through a leaf, as seen with a light microscope.

Describe how you could make a temporary slide of a cross section through a leaf.