Pearson Edexcel GCSE Combined Science · B8

Exchange and transport in animals

50 revision questions with answers for B8 Exchange and transport in animals in Pearson Edexcel GCSE Combined Science (spec 1SC0). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below.

All 50 questions and answers

Question 1 · Spec B8.1
Why must organisms exchange substances with their environment?
Answer:
They need reactants and nutrients and must remove waste products to keep cells functioning.
Question 2 · Spec B8.1
Why must oxygen and dissolved food reach body cells?
Answer:
They support respiration and provide material for growth and maintenance.
Question 3 · Spec B8.1
Why must carbon dioxide and urea be removed?
Answer:
They are waste products whose accumulation can disrupt normal cell function.
Question 4 · Spec B8.1
Why do cells need water and mineral ions?
Answer:
Water supports reactions and transport; mineral ions are required for normal cell processes.
Question 5 · Spec B8.2
Why can a single-celled organism rely mainly on diffusion?
Answer:
Its large surface area relative to volume and short diffusion distances allow sufficient exchange.
Question 6 · Spec B8.2
Why do large multicellular organisms need transport systems?
Answer:
They have smaller surface area:volume ratios and longer internal distances, making diffusion alone too slow.
Question 7 · Spec B8.2
Find surface area:volume ratio for a cube with 2 cm sides.
Answer:
Area = 24 cm²; volume = 8 cm³; ratio = 3:1.
Question 8 · Spec B8.2
How does surface area:volume ratio change as similarly shaped organisms grow?
Answer:
It decreases because volume increases faster than surface area.
Question 9 · Spec B8.3
How do many small alveoli improve gas exchange?
Answer:
They provide a large total surface area for diffusion.
Question 10 · Spec B8.3
Why are alveolar and capillary walls thin?
Answer:
They provide a short diffusion distance between air and blood.
Question 11 · Spec B8.3
How does blood flow help maintain gas-exchange gradients?
Answer:
It brings deoxygenated blood and carries oxygenated blood away, maintaining concentration differences.
Question 12 · Spec B8.3
Which direction do oxygen and carbon dioxide diffuse at alveoli?
Answer:
Oxygen enters blood; carbon dioxide moves from blood into alveolar air.
Question 13 · Spec B8.6
What does plasma transport?
Answer:
Blood cells, dissolved nutrients, hormones, urea and carbon dioxide, and it distributes thermal energy.
Question 14 · Spec B8.6
How do red blood cells carry oxygen?
Answer:
Haemoglobin binds oxygen, allowing it to be transported around the body.
Question 15 · Spec B8.6
How does a red blood cell's shape assist its function?
Answer:
Its biconcave shape gives a large surface area and short diffusion distance.
Question 16 · Spec B8.6
Why do mature human red blood cells lack a nucleus?
Answer:
This leaves more space for haemoglobin.
Question 17 · Spec B8.6
How do phagocytes defend against pathogens?
Answer:
They engulf and digest them.
Question 18 · Spec B8.6
How do lymphocytes defend against pathogens?
Answer:
They produce specific antibodies; some become memory cells for faster future responses.
Question 19 · Spec B8.6
What are platelets used for?
Answer:
Blood clotting, reducing blood loss and helping seal damaged vessels.
Question 20 · Spec B8.7
How are arteries adapted to high-pressure blood flow?
Answer:
They have thick muscular and elastic walls and relatively narrow lumens.
Question 21 · Spec B8.7
How are veins adapted to lower-pressure blood flow?
Answer:
They have large lumens and valves that prevent backflow.
Question 22 · Spec B8.7
Why are capillaries effective exchange vessels?
Answer:
Their narrow vessels and one-cell-thick walls provide close contact and short diffusion distances.
Question 23 · Spec B8.7
How do artery and vein directions differ?
Answer:
Arteries carry blood away from the heart; veins return it towards the heart.
Question 24 · Spec B8.8
What is a double circulatory system?
Answer:
Blood passes through the heart twice in one complete circuit: through lungs and through the body.
Question 25 · Spec B8.8
Trace blood from the body to the lungs.
Answer:
Vena cava → right atrium → right ventricle → pulmonary artery → lungs.
Question 26 · Spec B8.8
Trace blood from lungs back to the body.
Answer:
Pulmonary veins → left atrium → left ventricle → aorta → body.
Question 27 · Spec B8.8
Why is the left ventricular wall thicker than the right?
Answer:
It must generate higher pressure to pump blood around the whole body.
Question 28 · Spec B8.8
Why are atrial walls thinner than ventricular walls?
Answer:
Atria push blood only into nearby ventricles rather than through the pulmonary or body circuits.
Question 29 · Spec B8.8
What do heart valves do?
Answer:
Prevent backflow, maintaining one-way blood movement.
Question 30 · Spec B8.8
What separates oxygenated and deoxygenated blood inside the heart?
Answer:
The septum separates the left and right sides.
Question 31 · Spec B8.8
Why does heart muscle need its own blood supply?
Answer:
Coronary arteries deliver oxygen and glucose for respiration and contraction.
Question 32 · Spec B8.9
What is cellular respiration?
Answer:
Energy-releasing chemical reactions that occur continuously in living cells.
Question 33 · Spec B8.9
Why is respiration described as exothermic?
Answer:
It transfers energy to the surroundings, while supplying energy for cell processes.
Question 34 · Spec B8.9
Name three uses of energy from respiration.
Answer:
Muscle contraction, active transport and synthesis of larger molecules.
Question 35 · Spec B8.10
State the aerobic respiration word equation.
Answer:
Glucose + oxygen → carbon dioxide + water.
Question 36 · Spec B8.10
How does anaerobic respiration differ in oxygen use and energy release?
Answer:
It does not require oxygen and transfers less energy per glucose molecule than aerobic respiration.
Question 37 · Spec B8.10
What is the product of anaerobic respiration in human muscles?
Answer:
Lactic acid.
Question 38 · Spec B8.10
What are the products of anaerobic respiration in yeast?
Answer:
Ethanol and carbon dioxide.
Question 39 · Spec B8.10
Why can yeast fermentation be useful commercially?
Answer:
Its ethanol is used in alcoholic drinks and carbon dioxide helps bread dough rise.
Question 40 · Spec B8.11 · Core practical
How can a respirometer measure respiration in germinating seeds?
Answer:
Measure oxygen uptake from movement of a liquid marker while carbon dioxide is absorbed by a separate chemical.
Question 41 · Spec B8.11 · Core practical
Why absorb carbon dioxide in a respirometer?
Answer:
It makes the gas-volume decrease reflect oxygen uptake rather than being offset by carbon dioxide release.
Question 42 · Spec B8.11 · Core practical
Why keep seeds away from the carbon dioxide absorbent?
Answer:
The chemical can damage living tissue; separate it using a suitable barrier.
Question 43 · Spec B8.11 · Core practical
Which variables should be controlled when comparing respiration rates?
Answer:
Organism mass and type, temperature, measurement duration and apparatus conditions.
Question 44 · Spec B8.11 · Core practical
How could temperature's effect on yeast respiration be investigated?
Answer:
Measure carbon dioxide production over equal times at different controlled temperatures, with equal yeast and glucose quantities.
Question 45 · Spec B8.11 · Core practical
A sample uses 3.0 cm³ oxygen in 6.0 min. Find rate.
Answer:
3.0 / 6.0 = 0.50 cm³/min.
Question 46 · Spec B8.12
What is stroke volume?
Answer:
The volume of blood pumped by one ventricle per heartbeat.
Question 47 · Spec B8.12
State the cardiac output equation.
Answer:
Cardiac output = stroke volume x heart rate.
Question 48 · Spec B8.12
A heart pumps 70 cm³ per beat at 80 beats/min. Find cardiac output.
Answer:
70 × 80 = 5,600 cm³/min = 5.6 dm³/min.
Question 49 · Spec B8.12
Cardiac output is 6,000 cm³/min at 75 beats/min. Find stroke volume.
Answer:
6,000 / 75 = 80 cm³ per beat.
Question 50 · Spec B8.12
Why does cardiac output usually increase during exercise?
Answer:
Heart rate and stroke volume rise, delivering more oxygen and glucose to working muscles.

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