AQA GCSE Combined Science: Trilogy Biology Paper 1 (Foundation), 2020: Question 6

Topics covered

• Digestive enzymes
• Small intestine and villi
• Microscopy
• Magnification calculations
• Diffusion and active transport
• Uses of glucose in the body

How marks are won

• Use exact biological key words
• Read multiple-choice options carefully
• In extended answers, link structure to function
• For calculations, show the rearranged equation and units

✅ Correct answer

amylase

💡 Key knowledge

Amylase is a carbohydrate-digesting enzyme. It breaks down starch into sugar molecules.

❌ Common errors

• Writing amylose — this is wrong.
• The mark scheme allows carbohydrase, but amylase is the clearest answer.

✅ Correct answer

small intestine

🧠 Exam technique

This is a recall question. If you see words like absorbed, think of villi in the small intestine.

❌ Common errors

• Large intestine absorbs mainly water, not most food molecules.
• Stomach is mainly for digestion, not most absorption.
• Liver does not absorb food from the gut in this context.

✅ Correct answers

• greater magnification
• higher resolving power

💡 Key knowledge

Electron microscopes let you see smaller sub-cellular structures and more detail inside cells because they have much better resolution.

🧠 Exam technique

If asked for an advantage, use a precise phrase like higher resolving power. That sounds stronger than a vague answer such as “better picture”.

✅ Correct answer

capillary

💡 Key knowledge

Capillaries are tiny blood vessels close to the surface of the villi. They carry absorbed glucose and other food molecules away.

❌ Common errors

• Artery and vein are too large here.
• In villi, the exchange surface is linked to capillaries.

📐 Calculations

1. Use the equation:
   magnification = image size ÷ real size
2. Substitute the values:
   20 = image length ÷ 0.8
3. Rearrange to find image length:
   image length = 20 × 0.8
4. Calculate:
   image length = 16 mm

✅ Final answer

16 mm

🧠 Exam technique

• Write the equation first to earn method marks.
• Keep the unit as mm because the real size is already in mm.
• Always check whether you need to multiply or divide.

❌ Common calculation traps

• Dividing by 20 instead of multiplying by 20.
• Forgetting the unit.
• Using the wrong equation order.

✅ Correct answer

diffusion

💡 Key knowledge

In Figure 7, there are more sugar molecules outside cell A than inside it, so sugar moves from high concentration to low concentration by diffusion.

🧠 Exam technique

When particles move down a concentration gradient, the answer is usually diffusion.

✅ Correct answer

active transport

💡 Key knowledge

Cell B already has many sugar molecules inside, so moving more sugar in goes against the concentration gradient. This needs active transport.

❌ Common errors

• Writing diffusion when movement is against the gradient.
• Forgetting that active transport requires energy.

✅ Correct answers

• respiration
• to form glycogen
• to make amino acids / proteins
• to make lipid / fat

❌ Common errors

The mark scheme says do not accept answers like “to make energy” or “to use energy”. Better wording is for respiration or as an energy source.

🧠 Exam technique

In biology, avoid saying the body “makes energy”. Say the sugar is used in respiration to transfer energy.

✅ What a strong answer includes

• many microvilli
• large surface area
• wall is one cell thick / thin
• short diffusion pathway
• capillaries close to the surface
• good blood supply
• blood carries absorbed sugar away
• this maintains a concentration gradient
• many mitochondria
• respiration transfers energy for active transport

💡 Key knowledge

To get full marks, you must not just list features. You must link each feature to how it helps absorption.

Level 2 (3–4 marks): relevant points are given in detail and logically linked.
Level 1 (1–2 marks): simple points are stated but links are unclear.

✅ Model 4-mark answer

Villi have many microvilli, which gives a large surface area for absorption of sugar molecules. The wall of the villus is thin / one cell thick, so there is a short diffusion distance. The villi have a good blood supply with capillaries close to the surface, which carries sugar away and maintains a concentration gradient. The cells also have many mitochondria to release energy in respiration for active transport of sugar.

❌ Common errors

• Listing features only, with no explanation.
• Saying “large villi” instead of large surface area.
• Forgetting to mention blood flow or mitochondria.
• Not linking mitochondria to energy for active transport.

Key answers to remember

• 06.1 amylase
• 06.2 small intestine
• 06.3 greater magnification / higher resolving power
• 06.4 capillary
• 06.5 16 mm
• 06.6 diffusion
• 06.7 active transport
• 06.8 respiration

Final exam advice

• Use exact terms from biology.
• In calculations, always show working.
• In 4-mark explanations, link every adaptation to its function.
• Be careful with concentration gradient questions: down = diffusion, against = active transport.