Exam questions · Biology
The Circulatory System
- 35 exam questions
- 91 marks
- 40 quick checks
The Heart and Double Circulation
Just this lesson-
1 State [1 mark]
Name the blood vessel that carries blood from the heart to the lungs.
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Model answer
The pulmonary artery.
Mark scheme
- Pulmonary artery — 1 mark
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2 Name [3 marks]
Figure 1 shows the human heart. Name the parts labelled A, B and C.
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Model answer
A is the right ventricle. B is the aorta. C is the vena cava.
Mark scheme
- A: right ventricle — 1 mark
- B: aorta — 1 mark
- C: vena cava — 1 mark
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3 Describe [2 marks]
Describe the function of the coronary arteries.
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Model answer
They supply the heart muscle with oxygenated blood. This gives the muscle the oxygen it needs for respiration to release energy for contraction.
Mark scheme
- Supply the heart (muscle) with blood — 1 mark
- Oxygen for respiration — 1 mark
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4 Explain [2 marks]
Explain why the wall of the left ventricle is thicker than the wall of the right ventricle.
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Model answer
The left ventricle pumps blood around the whole body, which is a long way, so it needs to generate a higher pressure. A thicker muscle wall contracts with more force.
Mark scheme
- Pumps blood to the whole body / further — 1 mark
- Thicker muscle gives a greater force / higher pressure — 1 mark
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5 Calculate [2 marks]
A student counts 18 pulses in 15 seconds. Calculate the heart rate in beats per minute.
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Model answer
There are four 15-second periods in a minute. 18 × 4 = 72 beats per minute.
Mark scheme
- Multiplies by 4 — 1 mark
- 72 beats per minute — 1 mark
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6 Explain [3 marks]
Explain why humans have a double circulatory system.
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Model answer
Blood loses pressure as it passes through the capillaries in the lungs. Returning it to the heart increases the pressure again before it is sent to the body. This means the blood reaches the body quickly, while the pressure in the lungs can stay low enough not to damage the thin alveoli.
Mark scheme
- Blood loses pressure in the lung capillaries — 1 mark
- The heart increases the pressure again — 1 mark
- Low pressure in the lungs protects them / higher pressure for the body — 1 mark
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7 Describe [4 marks]
Describe how the natural pacemaker and an artificial pacemaker control the heart rate.
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Model answer
The natural pacemaker is a group of cells in the right atrium. These cells send out electrical signals that make the heart muscle contract, which sets the natural resting heart rate. An artificial pacemaker is an electrical device. It sends regular electrical pulses to the heart to correct an irregular heartbeat.
Mark scheme
- Natural pacemaker in the right atrium — 1 mark
- Cells send electrical signals that make the heart contract — 1 mark
- Artificial pacemaker is an electrical device — 1 mark
- It corrects irregularities in the heart rate — 1 mark
Quick check
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1
Which chamber of the heart pumps blood to the body?
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D: Left ventricle
The left ventricle pumps oxygenated blood into the aorta, which carries it round the body.
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2
Which vessel brings oxygenated blood from the lungs to the heart?
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B: Pulmonary vein
The pulmonary vein carries oxygenated blood from the lungs to the left atrium.
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3
What do the coronary arteries supply?
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C: The heart muscle with blood
The coronary arteries run over the surface of the heart and bring oxygenated blood to the heart muscle.
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4
Why is the wall of the left ventricle thicker than that of the right?
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A: It pumps blood further
It has to pump blood to the whole body, so it needs to contract with more force.
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5
Where is the natural pacemaker of the heart?
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D: The right atrium
A group of cells in the right atrium sets the natural resting heart rate.
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6
A pulse is counted as 20 beats in 15 seconds. What is the heart rate?
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C: 80 beats per minute
20 × 4 = 80 beats per minute.
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7
Why do humans have a double circulatory system?
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B: To keep the pressure high round the body
The blood loses pressure in the lungs, so it returns to the heart to be pumped again to the body.
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8
What does an artificial pacemaker do?
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A: Corrects an irregular heart rate
It sends electrical pulses to correct an irregular heartbeat.
Blood Vessels
Just this lesson-
1 State [1 mark]
Name the type of blood vessel that carries blood away from the heart.
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Model answer
Artery.
Mark scheme
- Artery — 1 mark
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2 Name [3 marks]
Figure 1 shows three types of blood vessel. Name the parts labelled A, B and C.
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Model answer
A is the (muscular) wall of the artery. B is a valve. C is the wall of the capillary.
Mark scheme
- A: wall of the artery / muscle and elastic fibres — 1 mark
- B: valve — 1 mark
- C: wall of the capillary — 1 mark
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3 Explain [2 marks]
Explain why veins have valves.
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Model answer
The blood in veins is at low pressure, so it could flow backwards. The valves close to stop this happening, so the blood flows only towards the heart.
Mark scheme
- Blood at low pressure could flow backwards — 1 mark
- Valves prevent backflow — 1 mark
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4 Explain [3 marks]
Explain how the structure of an artery is related to its function.
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Model answer
An artery carries blood away from the heart at high pressure. Its wall is thick, with muscle and elastic fibres, so that it can withstand the pressure. The elastic fibres let the wall stretch and recoil as blood surges through.
Mark scheme
- Carries blood at high pressure — 1 mark
- Thick wall with muscle and elastic fibres — 1 mark
- Withstands the pressure / stretches and recoils — 1 mark
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5 Explain [3 marks]
Explain how a capillary is adapted for exchanging substances with the cells.
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Model answer
The wall of a capillary is only one cell thick, so the diffusion path is short. Capillaries form huge networks, which give a large surface area. The blood moves slowly through them, which gives time for substances to diffuse.
Mark scheme
- Wall one cell thick / short diffusion path — 1 mark
- Large surface area from many capillaries — 1 mark
- Slow flow gives time for diffusion — 1 mark
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6 Calculate [2 marks]
A volume of 450 cm³ of blood flows through a blood vessel in 90 seconds. Calculate the rate of blood flow in cm³ per second.
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Model answer
Rate = volume ÷ time = 450 ÷ 90 = 5 cm³ per second.
Mark scheme
- 450 ÷ 90 — 1 mark
- 5 cm³ per second — 1 mark
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7 Compare [4 marks]
Compare the structure of an artery with the structure of a vein.
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Model answer
The wall of an artery is thick, with muscle and elastic fibres, but the wall of a vein is thinner. An artery has a narrow lumen but a vein has a wider lumen. Veins have valves but arteries do not. Arteries carry blood at high pressure away from the heart, but veins carry blood at low pressure to the heart.
Mark scheme
- Artery wall thicker than vein wall — 1 mark
- Artery lumen narrower than vein lumen — 1 mark
- Veins have valves, arteries do not — 1 mark
- Artery high pressure away from the heart, vein low pressure towards it — 1 mark
Quick check
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1
Which blood vessel has valves?
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B: Vein
Veins have valves to stop the low-pressure blood flowing backwards.
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2
Why is the wall of a capillary only one cell thick?
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C: To give a short diffusion path
A thin wall gives a short diffusion path, so substances move across quickly.
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3
What do arteries carry?
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A: Blood away from the heart
Arteries carry blood away from the heart, and this blood is at high pressure.
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4
Which blood vessel carries deoxygenated blood away from the heart?
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D: Pulmonary artery
The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs.
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5
What gives artery walls the ability to stretch and recoil?
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B: Elastic fibres
Elastic fibres in the wall let it stretch with each surge of blood and then recoil.
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6
900 cm³ of blood flows through a vessel in 3 minutes. What is the rate of blood flow?
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C: 300 cm³ per minute
Rate = volume ÷ time = 900 ÷ 3 = 300 cm³ per minute.
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7
Why does blood flow slowly through capillaries?
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A: To give time for exchange
Slow flow gives more time for substances to diffuse between the blood and the cells.
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8
Which statement about veins is correct?
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D: They have a wide lumen and valves
Veins return blood to the heart at low pressure, so they have a wide lumen and valves.
The Lungs and Gas Exchange
Just this lesson-
1 Name [3 marks]
Figure 1 shows the lungs. Name the parts labelled A, B and C.
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Model answer
A is the trachea. B is a bronchus. C is the alveoli (air sacs).
Mark scheme
- A: trachea — 1 mark
- B: bronchus — 1 mark
- C: alveoli — 1 mark
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2 State [2 marks]
Name the two gases exchanged in the alveoli and state the direction each one moves.
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Model answer
Oxygen moves from the alveoli into the blood. Carbon dioxide moves from the blood into the alveoli.
Mark scheme
- Oxygen from the alveoli into the blood — 1 mark
- Carbon dioxide from the blood into the alveoli — 1 mark
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3 Explain [2 marks]
Explain why the walls of the alveoli are only one cell thick.
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Model answer
A thin wall gives a short diffusion path. Oxygen and carbon dioxide can therefore diffuse across quickly.
Mark scheme
- Short diffusion path — 1 mark
- Faster diffusion of gases — 1 mark
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4 Explain [3 marks]
Explain why oxygen diffuses from the alveoli into the blood.
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Model answer
The concentration of oxygen is higher in the air in the alveoli than in the blood. Oxygen therefore diffuses down the concentration gradient. The gradient is kept steep by breathing and by the blood carrying oxygen away.
Mark scheme
- Higher concentration of oxygen in the alveoli — 1 mark
- Diffuses down the concentration gradient — 1 mark
- Gradient kept steep by ventilation / blood flow — 1 mark
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5 Calculate [2 marks]
A person takes 15 breaths per minute. Each breath takes in 400 cm³ of air. Calculate the volume of air breathed in per minute.
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Model answer
400 × 15 = 6000 cm³ per minute.
Mark scheme
- 400 × 15 — 1 mark
- 6000 cm³ per minute — 1 mark
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6 Explain [4 marks]
Explain how the lungs are adapted for gaseous exchange.
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Model answer
The lungs contain millions of alveoli, which give a very large surface area. The walls of the alveoli and capillaries are one cell thick, so the diffusion path is short. A rich supply of blood in the capillaries carries oxygen away and brings carbon dioxide, keeping the concentration gradient steep. Breathing ventilates the alveoli, which also keeps the gradient steep.
Mark scheme
- Millions of alveoli give a large surface area — 1 mark
- Walls one cell thick, short diffusion path — 1 mark
- Rich blood supply keeps the gradient steep — 1 mark
- Ventilation keeps the gradient steep — 1 mark
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7 Explain [3 marks]
A person has emphysema, a disease that destroys the walls of the alveoli. Explain why this person feels short of breath.
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Model answer
Destroying the walls reduces the surface area of the alveoli. Less oxygen can diffuse into the blood. The body cells therefore receive less oxygen for respiration, so the person feels short of breath.
Mark scheme
- Reduced surface area — 1 mark
- Less oxygen diffuses into the blood — 1 mark
- Less oxygen for respiration in cells — 1 mark
Quick check
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1
What are the tiny air sacs in the lungs called?
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C: Alveoli
Alveoli are the air sacs where gases are exchanged with the blood.
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2
Which gas diffuses from the blood into the alveoli?
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B: Carbon dioxide
Carbon dioxide is at a higher concentration in the blood arriving at the lungs, so it diffuses into the alveoli.
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3
What is the trachea?
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A: The windpipe
The trachea is the windpipe, which carries air from the mouth and nose to the bronchi.
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4
How many cells thick is the wall of an alveolus?
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D: One
The wall is one cell thick, which gives a short diffusion path.
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5
Which feature of the lungs keeps the concentration gradients steep by moving air?
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C: Ventilation
Ventilation, or breathing, moves fresh air in and stale air out.
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6
What surrounds each alveolus?
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B: A network of capillaries
A network of capillaries brings blood past the alveolus for gas exchange.
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7
A person breathes 20 times a minute and takes in 300 cm³ each time. What volume do they breathe in per minute?
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D: 6000 cm³
300 × 20 = 6000 cm³ per minute.
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8
Why do the lungs have millions of alveoli?
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A: To give a large surface area
Many alveoli give a very large surface area for gas exchange.
Blood
Just this lesson-
1 State [1 mark]
Name the part of the blood that carries oxygen.
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Model answer
Red blood cells (haemoglobin in the red blood cells).
Mark scheme
- Red blood cells — 1 mark
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2 Name [3 marks]
Figure 1 shows some of the components of blood. Name the parts labelled A, B and C.
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Model answer
A is a red blood cell. B is a white blood cell. C is a platelet.
Mark scheme
- A: red blood cell — 1 mark
- B: white blood cell — 1 mark
- C: platelet — 1 mark
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3 State [2 marks]
Name two substances carried in the plasma, and state where each one is carried to.
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Model answer
Carbon dioxide is carried to the lungs. Urea is carried to the kidneys. Accept glucose carried to the body cells, or hormones carried to their target organs.
Mark scheme
- A named substance — 1 mark
- Its correct destination — 1 mark
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4 Explain [3 marks]
Explain how a red blood cell is adapted to carry oxygen.
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Model answer
It contains haemoglobin, which joins with oxygen. It has no nucleus, so there is more room for haemoglobin. Its biconcave shape gives a large surface area for oxygen to diffuse in and out.
Mark scheme
- Contains haemoglobin — 1 mark
- No nucleus so more room for haemoglobin — 1 mark
- Biconcave shape gives a large surface area — 1 mark
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5 Describe [2 marks]
Describe the function of platelets.
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Model answer
Platelets help the blood to clot at a wound. The clot forms a scab that stops the bleeding and prevents microorganisms entering.
Mark scheme
- Help the blood to clot — 1 mark
- Stops blood loss / stops pathogens getting in — 1 mark
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6 Describe [3 marks]
A photograph of blood shows many small round cells, a few much larger cells with a dark purple centre, and some tiny fragments. Describe how you can identify each of these using what you know about blood cells.
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Model answer
The many small round cells with no nucleus are red blood cells. The few larger cells with a dark stained nucleus are white blood cells. The tiny fragments with no nucleus are platelets.
Mark scheme
- Small round cells with no nucleus are red blood cells — 1 mark
- Larger cells with a nucleus are white blood cells — 1 mark
- Tiny fragments are platelets — 1 mark
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7 Evaluate [4 marks]
Blood transfusions use blood products from donors. Evaluate the risks and benefits of using blood products.
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Model answer
A transfusion can save the life of a person who has lost a lot of blood or who has a blood disorder. However, there are risks. The donor blood could be infected with a pathogen, although screening reduces this risk. If the blood group is not matched, the patient can have a serious reaction. Some patients may have an allergic reaction. On balance the benefits usually outweigh the risks because blood is screened and matched.
Mark scheme
- Benefit: saves life / replaces lost blood — 1 mark
- Risk: infection from donor blood — 1 mark
- Risk: mismatched blood group / allergic reaction — 1 mark
- A conclusion weighing risks and benefits — 1 mark
Quick check
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1
Which part of the blood carries oxygen?
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B: Red blood cells
Red blood cells contain haemoglobin, which joins with oxygen.
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2
Which part of the blood helps it to clot?
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D: Platelets
Platelets are cell fragments that help blood clot at a wound.
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3
Which blood cell has a nucleus?
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C: White blood cell
White blood cells have a nucleus. Red blood cells and platelets do not.
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4
What is carried in the plasma from the liver to the kidneys?
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A: Urea
Urea is made in the liver and carried in the plasma to the kidneys.
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5
Why do red blood cells have no nucleus?
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B: To make more room for haemoglobin
It leaves more room for haemoglobin, so the cell can carry more oxygen.
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6
What is the red pigment in red blood cells?
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C: Haemoglobin
Haemoglobin joins with oxygen in the lungs and releases it in the tissues.
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7
What do phagocytes do?
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D: Engulf pathogens
Phagocytes are white blood cells that engulf and digest pathogens.
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8
Which component of blood is a fragment of a cell?
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A: Platelets
Platelets are small fragments of cells with no nucleus.
Coronary Heart Disease and Its Treatment
Just this lesson-
1 State [1 mark]
State what is meant by coronary heart disease.
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Model answer
Fatty deposits build up in the coronary arteries and narrow them, reducing the blood flow to the heart muscle.
Mark scheme
- Fatty deposits narrow the coronary arteries — 1 mark
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2 Name [3 marks]
Figure 1 shows a healthy coronary artery and an artery affected by coronary heart disease. Name the parts labelled A, B and C.
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Model answer
A is the artery wall. B is the fatty deposit. C is the (narrowed) lumen.
Mark scheme
- A: wall of the artery — 1 mark
- B: fatty deposit — 1 mark
- C: lumen — 1 mark
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3 Explain [3 marks]
Explain how coronary heart disease can lead to a heart attack.
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Model answer
Fatty deposits narrow the coronary arteries. Less blood flows through them, so the heart muscle receives too little oxygen. The muscle cannot respire enough to release the energy it needs, so it cannot contract and the person has a heart attack.
Mark scheme
- Narrowed coronary arteries — 1 mark
- Less oxygen reaches the heart muscle — 1 mark
- Not enough energy released by respiration for contraction — 1 mark
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4 Describe [2 marks]
Describe how a stent treats coronary heart disease.
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Model answer
A stent is a mesh tube put inside the narrowed artery. It holds the artery open so that blood can flow freely again.
Mark scheme
- A tube/mesh placed in the artery — 1 mark
- Keeps it open so blood flows — 1 mark
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5 Explain [2 marks]
Explain how statins reduce the risk of coronary heart disease.
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Model answer
Statins lower the level of cholesterol in the blood. This slows down the rate at which fatty material is deposited in the arteries.
Mark scheme
- Lower blood cholesterol — 1 mark
- Slows the build-up of fatty deposits — 1 mark
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6 Give [2 marks]
Give one advantage and one disadvantage of using a mechanical heart valve rather than a biological valve.
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Model answer
Advantage: it lasts a long time. Disadvantage: the patient needs to take drugs for life to stop the blood from clotting.
Mark scheme
- An advantage, such as lasts longer — 1 mark
- A disadvantage, such as lifelong drugs — 1 mark
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7 Evaluate [6 marks]
A patient with heart failure could have a heart transplant or be fitted with an artificial heart. Evaluate these two treatments.
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Model answer
A heart transplant gives the patient a natural, working heart, which can allow a long and active life. However, there are not enough donors, so patients may wait a long time. The patient must take drugs for life to stop the body rejecting the heart, and these make infection more likely. An artificial heart is available straight away, so it can keep a patient alive while they wait for a donor, or give their own heart time to rest and recover. However, it is a mechanical device, so there is a risk of infection, blood clots or the device failing, and it is usually only used as a short-term measure. A transplant is the better long-term treatment, but an artificial heart is useful in the short term.
Mark scheme
- Transplant: a natural working heart — 1 mark
- Transplant: shortage of donors / rejection drugs — 1 mark
- Artificial heart: available immediately — 1 mark
- Artificial heart: keeps patient alive or lets the heart rest — 1 mark
- Artificial heart: risks such as infection, clots or device failure — 1 mark
- A conclusion that weighs the two — 1 mark
Quick check
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1
What builds up inside the coronary arteries in coronary heart disease?
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C: Fatty material
Layers of fatty material build up in the arteries and narrow them.
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2
What does a stent do?
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A: Holds an artery open
A stent is a mesh tube that holds a narrowed artery open.
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3
What do statins do?
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B: Lower blood cholesterol
Statins lower blood cholesterol, which slows the build-up of fatty deposits.
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4
What is the main disadvantage of a mechanical heart valve?
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D: The patient needs drugs for life to prevent clotting
Mechanical valves make blood clots more likely, so the patient needs blood-thinning drugs for life.
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5
Why are patients given drugs after a heart transplant?
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C: To stop the body rejecting the new heart
The drugs stop the immune system rejecting the donor heart.
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6
When might an artificial heart be used?
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A: To keep a patient alive while waiting for a transplant
An artificial heart can keep a patient alive while they wait for a donor heart, or let their heart rest.
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7
Why is coronary heart disease called a non-communicable disease?
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B: It cannot be passed from person to person
It is not caused by a pathogen, so it cannot be passed from person to person.
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8
Why does a narrowed coronary artery cause chest pain?
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D: The heart muscle does not get enough oxygen
Less blood flows to the heart muscle, so it lacks oxygen for respiration.