Topic Two (1.2): Carbohydrates

Introduction

Another chemistry-heavy topic, here you will learn about the structure of sugars and how they can polymerise to form larger storage molecules such as starch and glycogen. It’s quite common to get a diagram of a sugar molecule you might not have seen before in the exam, and for the question to ask you to draw a disaccharide made of two of these molecules. The key thing here is to look at where there are two OH groups next to each other. You may have to turn one molecule upside down, or make a Z shaped bond to align them, because you can’t simply rotate the different groups around that corner carbon molecule!

Reading

Edexcel AS/A Level Biology Student Book 1 pages 8 to 13, pages 22 to 24

Edexcel International AS/A Level Biology Lab Book pages 6 to 9

Read and Make Notes

Read pages 8 to 13, making appropriate notes and completing the ‘in-text’ questions.

 Consolidate

Now consolidate your understanding by working through these additional resources:

EXPLORE – Carbohydrate Topic (Khan Academy) Links to an external site.

REVIEW – Carbohydrates (PowerPoint) Download REVIEW – Carbohydrates (PowerPoint)

REVIEW – Glycosidic Bonds Poster Download REVIEW – Glycosidic Bonds Poster

READ – Carbohydrates Factsheet Download READ – Carbohydrates Factsheet

REVIEW – Carbohydrates Poster Download REVIEW – Carbohydrates Poster

WATCH – Carbohydrate Condensation Reactions (Nutrition) Links to an external site.

 Practical Knowledge

• Read pages 6 to 9 in the Lab Book and fill in the Dilutions Planning boxes on pages 6 and 8.

WATCH – Benedict’s Test (YouTube) Links to an external site.

WATCH – Iodine Test (YouTube) Links to an external site.

OBSERVE – Core Practical 1 Results Download OBSERVE – Core Practical 1 Results

• Fill in the Results boxes on pages 7 and 8 based on the pictures in the Core Practical 1 results.
• Complete the Analyses on pages 7 and 9 and answer the questions on page 9. Check your answers in the back of the book and using the model answers on Canvas.

OBSERVE – Practical 1 Model Answers Download OBSERVE – Practical 1 Model Answers

 Tasks

Complete the following:

• Complete questions 3 and 4 on page 24.
• Do the Extension on pages 22 to 23.

Top Tips

Make sure that you understand the following key points:

• How sugar molecules combine in a condensation reaction – don’t forget the water molecule that’s released!
• Be able to connect the structure of amylose and amylopectin to their different properties and functions.
• Remember that glycogen is made in the liver of animals, starch is ONLY made in plants.
• Know what monomers make up sucrose, lactose and maltose.

Key Terms

Check that you know all of the terms in the Subject Vocabulary boxes on pages 10 and 13 and add any you don’t know to your glossary.