Most Common GCSE Biology Questions

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As students prepare for their GCSE Biology exams, certain questions frequently arise, reflecting key areas of the syllabus. These questions not only test foundational biological concepts but also encourage deeper understanding and application of knowledge. This article outlines some of the most common GCSE Biology questions, providing insights and explanations to aid in your revision.

Question: Bile is produced in the liver and is released into the small intestine. Bile helps the digestion of lipid in the milk. Describe how.

Answer: Bile emulsifies fats in the milk, increasing the surface area for lipase to act upon, thus aiding in lipid digestion.

Explanation: Bile contains salts that break down large fat globules into much smaller droplets in a process known as emulsification. This dramatically increases the surface area available for the enzyme lipase to work on, enabling it to more efficiently break down lipids into fatty acids and glycerol. This process is essential for the effective digestion and absorption of fats.

Question: Give two factors that affect the concentration of cholesterol in the blood.

Answer: Diet and genetics significantly influence blood cholesterol levels.

Explanation: Dietary intake of saturated and trans fats can raise blood cholesterol levels, while foods rich in unsaturated fats may lower it. Additionally, genetics play a pivotal role; some individuals have inherited conditions that increase cholesterol production in the liver, elevating blood cholesterol levels irrespective of dietary habits.

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Question: Many people suffer from stomach ulcers caused by a species of bacteria called Helicobacter pylori. The stomach is lined with a protective lining of mucus. Helicobacter pylori are acid-tolerant bacteria which can damage this mucus lining. Suggest how an infection with Helicobacter pylori might result in a stomach ulcer developing.

Answer: Helicobacter pylori can lead to stomach ulcers by damaging the protective mucus lining, exposing the stomach lining to acidic gastric juices.

Explanation: Helicobacter pylori’s acid tolerance allows it to thrive in the stomach’s acidic environment, where it damages the protective mucus layer. This damage exposes the stomach’s epithelial lining to harsh gastric acids, leading to inflammation, irritation, and eventually, ulcer formation. The bacteria may also stimulate an immune response, causing further harm to the stomach lining.

Question: Name the three parts of the human digestive system that produce amylase.

Answer: The salivary glands, pancreas, and small intestine produce amylase.

Explanation: Amylase is an enzyme crucial for starch digestion. The salivary glands secrete salivary amylase, beginning starch breakdown in the mouth. The pancreas releases pancreatic amylase into the small intestine to continue starch digestion. Lastly, the small intestine itself produces amylase, ensuring the complete breakdown of starch into simpler sugars.

Question: Explain how amylase breaks down starch. Answer in terms of the ‘lock and key theory’.

Answer: Amylase breaks down starch into maltose by fitting into starch molecules like a key fits into a lock, catalyzing the breakdown process.

Explanation: The “lock and key” theory posits that enzymes have specific active sites shaped perfectly for their substrate molecules. For amylase, this means its active site matches the shape of starch molecules. When starch binds to this site, amylase catalyzes its breakdown into maltose. This specificity ensures efficient and correct enzymatic reactions, crucial for digestion.

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Question: What is the role of the guard cells in plant leaves?

Answer: Guard cells regulate gas exchange and water loss by controlling the opening and closing of stomata.

Explanation: Guard cells are specialized cells flanking each stoma on a leaf’s surface. They swell to open the stoma, allowing gas exchange necessary for photosynthesis (CO2 in, O2 out) and transpiration (water vapor out). Conversely, they shrink to close the stoma, reducing water loss in dry conditions. This regulation is crucial for maintaining plant water balance and ensuring efficient photosynthesis.

Question: How does vaccination provide immunity against specific diseases?

Answer: Vaccinations stimulate the immune system to produce antibodies against a disease without causing the disease itself.

Explanation: A vaccine introduces a harmless component of a pathogen (like killed or weakened microbes or their toxins) into the body. This triggers the immune system to respond as if it were a real infection, producing specific antibodies to combat the pathogen. This “memory” enables the immune system to quickly recognize and fight off the pathogen if exposed to it in the future, providing immunity.

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