AQA GCSE Biology 4.2.2 Animal Tissues, Organs and Organ Systems Exam Questions

About AQA GCSE Biology 4.2.2 Animal Tissues, Organs and Organ Systems

This is one of the largest sections of AQA GCSE Biology and is examined on Paper 1. It covers the human digestive system and enzymes, the heart, blood vessels and blood, and the causes and treatments of coronary heart disease. It also introduces health and non-communicable disease, the effect of lifestyle factors, and benign and malignant tumours. Two required practicals sit here: food tests and the effect of pH on amylase. Examiners frequently set enzyme graphs and rate calculations, heart structure diagrams, evaluation of treatments for heart disease, and data on lifestyle and disease.

What you need to know

• Digestive system and enzymes Enzymes are biological catalysts with an active site that fits a specific substrate (lock and key model). Carbohydrases such as amylase break starch into sugars, proteases break proteins into amino acids, and lipases break lipids into fatty acids and glycerol. High temperatures and extremes of pH denature enzymes by changing the shape of the active site.
• Bile Bile is made in the liver and stored in the gall bladder. It is alkaline, neutralising hydrochloric acid from the stomach, and it emulsifies fat into small droplets, increasing the surface area for lipase.
• Required practicals: food tests and amylase Benedict's test (blue to brick red on heating) for reducing sugars, iodine (orange to blue-black) for starch, biuret (blue to purple) for protein, and ethanol (white emulsion) or Sudan III for lipids. For amylase, time how long it takes starch to disappear at different pH values, testing with iodine; rate = 1000 / time.
• Heart and blood vessels The heart pumps blood around a double circulatory system. The right ventricle pumps to the lungs, the left ventricle to the body. The natural pacemaker in the right atrium controls resting heart rate. Arteries have thick muscular, elastic walls; veins have valves; capillaries are one cell thick for exchange.
• Blood Blood is a tissue of plasma, red blood cells (haemoglobin, no nucleus, biconcave), white blood cells and platelets (clotting). You should recognise these from photographs and diagrams.
• Coronary heart disease Fatty material builds up in coronary arteries, reducing blood flow to heart muscle. Treatments include stents, statins (reduce blood cholesterol), replacement of faulty valves with biological or mechanical valves, and heart transplants or artificial hearts. Evaluate the advantages and disadvantages of each.
• Health, lifestyle and cancer Health is a state of physical and mental wellbeing. Risk factors include diet, smoking, exercise, alcohol and carcinogens. Benign tumours stay in one place in a membrane; malignant tumours invade tissues and spread in the blood to form secondary tumours.

Common mistakes in 4.2.2 Animal Tissues, Organs and Organ Systems

• Saying enzymes are killed at high temperature. Enzymes are not alive; they are denatured because the active site changes shape.
• Saying bile is an enzyme or that it digests fat. Bile emulsifies fat and neutralises acid; lipase digests the fat.
• Mixing up the sides of the heart. The right side receives deoxygenated blood from the body and pumps it to the lungs; diagrams show the right side on the left of the page.
• Saying arteries carry oxygenated blood and veins deoxygenated blood. Arteries carry blood away from the heart and veins towards it; the pulmonary artery carries deoxygenated blood.
• Saying statins unblock arteries. Statins reduce blood cholesterol, slowing the build-up of fatty material.

Try three 4.2.2 Animal Tissues, Organs and Organ Systems exam-style questions