AQA GCSE Combined Science: Trilogy · 4.2

Organisation

50 revision questions with answers for 4.2 Organisation in AQA GCSE Combined Science: Trilogy (spec 8464). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below. Not official AQA material.

All 50 questions and answers

Question 1 · Spec 4.2.1
Put these levels in order: organ, cell, organism, tissue, organ system.
Answer:
Cell → tissue → organ → organ system → organism.
Question 2 · Spec 4.2.1
How is a tissue different from an organ?
Answer:
A tissue is a group of cells with similar structure and function. An organ contains different tissues working together.
Question 3 · Spec 4.2.2.1
Why must large food molecules be digested?
Answer:
They must be broken into small soluble molecules that can be absorbed into the bloodstream.
Question 4 · Spec 4.2.2.1
What is an enzyme, and why is its action specific?
Answer:
An enzyme is a biological catalyst, usually a protein. Its active site's shape fits a particular substrate.
Question 5 · Spec 4.2.2.1
Why does excessive heat reduce enzyme activity?
Answer:
It changes the active site's shape: the enzyme is denatured and its substrate no longer fits.
Question 6 · Spec 4.2.2.1
How can pH affect an enzyme?
Answer:
Each enzyme has an optimum pH. Large pH changes alter the active site and may denature the enzyme.
Question 7 · Spec 4.2.2.1
Where is amylase produced, and what does it digest?
Answer:
The salivary glands, pancreas and small intestine produce amylase. It breaks starch into sugars.
Question 8 · Spec 4.2.2.1
Where are proteases produced, and what are their products?
Answer:
They are produced in the stomach, pancreas and small intestine. They digest proteins into amino acids.
Question 9 · Spec 4.2.2.1
Where are lipases produced, and what do they digest?
Answer:
The pancreas and small intestine produce lipases. They break lipids into glycerol and fatty acids.
Question 10 · Spec 4.2.2.1
Where is bile made and stored, and why is it alkaline?
Answer:
It is made in the liver and stored in the gall bladder. It neutralises stomach acid, providing suitable conditions for intestinal enzymes.
Question 11 · Spec 4.2.2.1
How does bile emulsification speed up fat digestion?
Answer:
It breaks fat into small droplets, increasing the surface area available for lipase action.
Question 12 · Spec 4.2.2.1 · Required practical
How do you test for reducing sugars with Benedict's solution?
Answer:
Add Benedict's solution and heat in a hot water bath. A positive result changes from blue towards green, yellow, orange or brick-red.
Question 13 · Spec 4.2.2.1 · Required practical
What are the tests for starch and protein?
Answer:
Iodine turns blue-black with starch. Biuret reagent turns lilac or purple with protein.
Question 14 · Spec 4.2.2.1 · Required practical
How can Sudan III be used to test for lipids?
Answer:
Add Sudan III solution and shake. A red-stained oil layer indicates lipids.
Question 15 · Spec 4.2.2.1 · Required practical
How do you investigate pH's effect on amylase?
Answer:
Mix amylase, starch and a pH buffer at a controlled temperature. Test samples with iodine every 30 seconds until starch is absent.
Question 16 · Spec 4.2.2.1 · Required practical
Why use a buffer and a water bath in the amylase investigation?
Answer:
The buffer controls pH; the water bath controls temperature, preventing temperature changes from confusing the effect of pH.
Question 17 · Spec 4.2.2.1 · Required practical
Starch disappears after 90 s. Calculate a comparative rate using 1/time.
Answer:
Rate = 1 / 90 = 0.011 s⁻¹, to two significant figures.
Question 18 · Spec 4.2.2.2
What is a double circulatory system?
Answer:
Blood passes through the heart twice per complete circuit: once for the lungs and once for the rest of the body.
Question 19 · Spec 4.2.2.2
Which ventricle pumps to the lungs, and which pumps to the body?
Answer:
The right ventricle pumps to the lungs; the left ventricle pumps around the body.
Question 20 · Spec 4.2.2.2
Why is the left ventricle's muscular wall thicker?
Answer:
It must generate greater pressure to pump blood around the whole body.
Question 21 · Spec 4.2.2.2
Name the vessels carrying blood into and out of the heart.
Answer:
Vena cava: body to heart; pulmonary artery: heart to lungs; pulmonary vein: lungs to heart; aorta: heart to body.
Question 22 · Spec 4.2.2.2
What do coronary arteries and heart valves do?
Answer:
Coronary arteries supply the heart muscle with oxygenated blood. Valves prevent backflow.
Question 23 · Spec 4.2.2.2
How are arteries adapted to their function?
Answer:
Thick muscular, elastic walls withstand and maintain high blood pressure as blood travels away from the heart.
Question 24 · Spec 4.2.2.2
How are veins adapted to return blood to the heart?
Answer:
They have a large lumen and valves that prevent backflow at low pressure.
Question 25 · Spec 4.2.2.2
Why are capillaries effective exchange vessels?
Answer:
Their walls are one cell thick, providing a short diffusion distance between blood and tissues.
Question 26 · Spec 4.2.2.2
What controls natural resting heart rate, and how can an irregular rhythm be corrected?
Answer:
A group of pacemaker cells in the right atrium controls it. An artificial pacemaker can supply electrical impulses.
Question 27 · Spec 4.2.2.2
Trace the path of inhaled air to the gas exchange surface.
Answer:
Air passes along the trachea and bronchi into the lungs, reaching the alveoli surrounded by capillaries.
Question 28 · Spec 4.2.2.3
What does blood plasma transport?
Answer:
Blood cells, carbon dioxide, urea, soluble products of digestion and hormones; it also distributes thermal energy.
Question 29 · Spec 4.2.2.3
How are red blood cells adapted to oxygen transport?
Answer:
They contain haemoglobin, have a biconcave shape for a large surface area and lack a nucleus, leaving more room for haemoglobin.
Question 30 · Spec 4.2.2.3
What are the functions of white blood cells and platelets?
Answer:
White blood cells defend against pathogens. Platelets help blood clot, limiting blood loss and pathogen entry.
Question 31 · Spec 4.2.2.4
How does coronary heart disease develop?
Answer:
Fatty material builds up in coronary arteries, narrowing them and reducing oxygen supply to heart muscle.
Question 32 · Spec 4.2.2.4
Compare stents and statins in treating coronary heart disease.
Answer:
Stents hold narrowed arteries open. Statins lower blood cholesterol, slowing fatty deposit formation; each has potential risks or side effects.
Question 33 · Spec 4.2.2.4
How can damaged heart valves or heart failure be treated?
Answer:
Valves may be replaced with biological or mechanical valves. Severe heart failure may require a donor heart; artificial hearts can provide temporary support.
Question 34 · Spec 4.2.2.5
What is health, and how do communicable and non-communicable diseases differ?
Answer:
Health is physical and mental well-being. Communicable diseases spread between organisms; non-communicable diseases do not.
Question 35 · Spec 4.2.2.5
Give an example of diseases interacting.
Answer:
Damage to the immune system increases susceptibility to infections; some viruses can also trigger cancers.
Question 36 · Spec 4.2.2.6
What is a risk factor, and why does correlation alone not prove causation?
Answer:
A risk factor is linked to an increased disease rate. Correlation may reflect other variables and does not establish a direct cause.
Question 37 · Spec 4.2.2.6
How do smoking and alcohol affect disease risk?
Answer:
Smoking increases lung disease, lung cancer and cardiovascular disease risk. Excess alcohol can damage the liver and brain.
Question 38 · Spec 4.2.2.6
Name lifestyle or environmental risks involving diet, pregnancy or radiation.
Answer:
Obesity raises Type 2 diabetes risk; smoking or alcohol can harm unborn babies; ionising radiation and ultraviolet exposure can increase cancer risk.
Question 39 · Spec 4.2.2.7
How do benign and malignant tumours differ?
Answer:
Benign tumours remain contained. Malignant tumours invade surrounding tissues and may spread via blood to form secondary tumours.
Question 40 · Spec 4.2.2.6
12 of 200 people in one group develop a disease. Calculate the percentage.
Answer:
12 / 200 × 100 = 6%. Compare equivalent groups and consider other risk factors before inferring a cause.
Question 41 · Spec 4.2.3.1
Name the main tissues in a leaf.
Answer:
Epidermal tissue, palisade mesophyll, spongy mesophyll, xylem, phloem and guard cells.
Question 42 · Spec 4.2.3.1
How are palisade and spongy mesophyll tissues adapted?
Answer:
Palisade cells contain many chloroplasts for photosynthesis. Spongy mesophyll has air spaces that allow gases to diffuse through the leaf.
Question 43 · Spec 4.2.3.2
How do root hair cells take up water and mineral ions?
Answer:
Water enters by osmosis; mineral ions can enter by active transport against a concentration gradient.
Question 44 · Spec 4.2.3.2
What does xylem transport, and how is it adapted?
Answer:
It carries water and mineral ions upwards. Hollow tubes form a continuous pathway; lignin strengthens their walls.
Question 45 · Spec 4.2.3.2
What is translocation, and which tissue carries it out?
Answer:
Translocation is the movement of dissolved sugars through phloem from leaves to other parts for use or storage.
Question 46 · Spec 4.2.3.2
What is transpiration?
Answer:
The loss of water vapour from leaves, mainly through stomata, following evaporation from leaf cells.
Question 47 · Spec 4.2.3.2
How do guard cells regulate water loss and gas exchange?
Answer:
They change the size of stomatal pores, controlling diffusion of gases and water vapour.
Question 48 · Spec 4.2.3.2
Why do light and high temperature usually increase transpiration?
Answer:
Light usually opens stomata. Higher temperature increases evaporation and diffusion of water vapour.
Question 49 · Spec 4.2.3.2
Why do wind and low humidity increase transpiration?
Answer:
They maintain a steep water-vapour concentration gradient between the leaf and surrounding air.
Question 50 · Spec 4.2.3.2
What does a potometer measure, and what is its main limitation?
Answer:
It measures water uptake as an estimate of transpiration. Some absorbed water is used by the plant rather than lost through leaves.

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