Edexcel A Level (IAL) Biology -8.12 Core Practical 18: Amylase in Germinating Cereal Grains- Study Notes- New Syllabus

CORE PRACTICAL 18

Investigating Amylase Production in Germinating Cereal Grains

🌱 Introduction

When cereal grains such as barley or wheat begin to germinate, they start producing amylase. This enzyme breaks stored starch into sugars that fuel the embryo’s early growth. This practical tracks how amylase activity changes over the first few days of germination.

🎯 Aim

To compare the amount of amylase produced at different stages of germination.

🧪 Key Idea

• Early germination: very little amylase.
• Later days: enzyme levels rise steadily.
• More amylase means faster starch breakdown → iodine colour disappears sooner.

⚙️Method

1. Soak cereal grains and allow them to germinate for several days (Day 0 to Day 3).
2. Each day, crush a sample of grains in water to extract their enzymes.
3. Mix the extract with starch solution.
4. At fixed intervals, remove small drops and add iodine.
5. Record how long it takes for the blue-black colour to fade.

Shorter decolourisation time = higher amylase activity.

📊 Variables

🔍 Expected Results

• Day 0: little or no starch breakdown.
• Day 1 to Day 3: iodine decolourises faster each day.

This happens because gibberellin from the embryo switches on genes in the aleurone layer. Amylase is made, which digests stored starch into sugars for the embryo.

⚠️ Common Mistakes

• Temperature not kept constant.
• Grains not crushed equally.
• Iodine volume not consistent.
• Delays between mixing the extract and testing with iodine.

Keep each step consistent to get reliable results.