1.3 Carbohydrates: Polysaccharides | AQA A Level Biology Topic 1 (3.1.2)

Polysaccharides | AQA A-level Biology In this lesson, we explore the three polysaccharides you need to know for AQA A-level Biology: starch, glycogen and cellulose. You'll learn how the small structural difference between alpha and beta glucose leads to completely different polymer structures — and how those structures determine their functions. In this video, we cover: The difference between alpha and beta glucose How condensation reactions form glycosidic bonds The structure and function of starch The differences between amylose and amylopectin The structure and function of glycogen Why glycogen is more highly branched than starch The structure of cellulose How hydrogen bonds form between cellulose chains How microfibrils give cellulose its strength and rigidity Why cellulose is important in plant cell walls The key A-level Biology principle that structure determines function This video is part of my AQA A-level Biology series. If you're following the series in order, the previous lessons cover polymers, monosaccharides and disaccharides. The next lesson will cover lipids. If you have any questions, leave them in the comments and I'll answer them as quickly as I can. Chapters: 00:00 Introduction to polysaccharides 00:20 Introduction 01:20 Alpha and beta glucose 03:38 The compact structure of starch 04:22 The branched structure of glycogen 05:05 Starch vs glycogen 05:56 The structure of cellulose 09:09 Summary: starch, glycogen and cellulose 10:34 Key takeaway: structure determines function Image credits: glucose - By Oliva93 - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index...