A-level Biology OCR [New Spec] - Carbohydrates: Disaccharides | A-level Biology | OCR, AQA, Edexcel

Carbohydrates: Disaccharides in a Snap! Unlock the full A-level Biology course at http://bit.ly/2tjNVLa created by Adam Tildesley, Biology expert at SnapRevise and graduate of Cambridge University. SnapRevise is the UK’s leading A-level and GCSE revision & exam preparation resource offering comprehensive video courses created by A* Oxbridge tutors. Our courses are designed around the OCR, AQA, SNAB, Edexcel B, WJEC, CIE and IAL exam boards, concisely covering all the important concepts required by each specification. In addition to all the content videos, our courses include hundreds of exam question videos, where we show you how to tackle questions and walk you through step by step how to score full marks. Sign up today and together, let’s make A-level Biology a walk in the park! The key points covered in this video include: 1. Disaccharides 2. Forming Glycosidic Bonds 3. Hydrolysis of Glycosidic Bonds Disaccharides Disaccharides are formed by joining two monosaccharides together in a condensation reaction. Like monosaccharides, disaccharides are sweet-tasting and soluble carbohydrates - they are sugars. Disaccharides are sugars that are composed of two monosaccharides joined together in a condensation reaction. Different combinations of monosaccharides determine which disaccharide is formed: α-glucose and α-glucose combine to form maltose, Maltose is found in germinating seeds as more complex carbohydrates are broken down for energy, α-glucose and fructose combine to form sucrose, Sucrose is transported in the phloem to provide sugars to other parts of the plant. α-glucose and galactose combine to form lactose. Lactose is found in mammalian milk to provide energy for infant mammals. Forming Glycosidic Bonds Two monosaccharides are joined together through a condensation reaction to form a disaccharide. A condensation reaction forms water as one oxygen and two hydrogen atoms are removed from the monosaccharides. This bonds the monosaccharides together, forming a disaccharide. This bond is known as a glycosidic bond. A glycosidic bond is a covalent bond formed between two monosaccharides by a condensation reaction. Glycosidic bonds are named depending on which carbon atoms they are formed between. In maltose, the bond is formed between carbon 1 and carbon 4 so it is called a 1,4 glycosidic bond. Hydrolysis of Glycosidic Bonds Disaccharides are broken down through a hydrolysis reaction to form two monosaccharides. A hydrolysis reaction requires water as one oxygen and two hydrogen atoms are added to the disaccharide. This breaks the glycosidic bond and forms two monosaccharides. Condensation and hydrolysis reactions in carbohydrates can be summed up as follows: Summary Disaccharides are sugars that are composed of two monosaccharides joined together Maltose, sucrose and lactose are three examples of disaccharides Disaccharides are formed by condensation reactions between two monosaccharides, forming water and a glycosidic bond Disaccharides are broken down by hydrolysis reactions into two monosaccharides, requiring water and breaking the glycosidic bond