Carbohydrates: Monosaccharides | A-level Biology | OCR, AQA, Edexcel

Carbohydrates: Monosaccharides in a Snap! Unlock the full A-level Biology course at http://bit.ly/2BwYEpV 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. Introduction to Carbohydrates
2. Monosaccharides
3. Glucose
4. Isomers of Glucose
5. Ribose

Introduction to Carbohydrates

Carbohydrates are organic molecules that have some important uses: Source and storage of energy, Structural function. Carbohydrates only contain carbon, hydrogen and oxygen. The general formula for a carbohydrate is:

Monosaccharides

The simplest carbohydrates are called monosaccharides - they are the monomer building blocks for more complex carbohydrates. Two monosaccharides join together to create a disaccharide. Many monosaccharides join together to create a polysaccharide - a carbohydrate polymer. Monosaccharides are soluble and sweet-tasting carbohydrates so are also known as sugars. Monosaccharides are single sugar monomers. They are the simplest carbohydrates. Monosaccharides all have the general formula: The molecular formula for each type of sugar can therefore be worked out by using the general formula. Two other commonly found hexose monosaccharides are fructose and galactose.

Glucose

Glucose is a hexose sugar with the molecular formula C6H12O6. Glucose is an important sugar for many reasons: It is the main source of energy in respiration, It is used as building blocks for larger carbohydrates. The properties of glucose make it well-adapted for its role: Small so easily transported in and out of cells through carrier proteins, Soluble so easily transported around an organism, Less reactive than other monosaccharides so breakdown must be catalysed and therefore controlled by enzymes.

Isomers of Glucose

Glucose has different structural forms, known as isomers. Isomers are molecules that have the same chemical formula but a different arrangement of atoms in space. Glucose has two isomers which are called α-glucose and β-glucose and they differ by the position of the hydroxyl (-OH) group. Different polysaccharides are formed depending on whether α-glucose or β-glucose is used as a building block.

Ribose

Another important sugar is ribose - it has five carbon atoms and so therefore it is a pentose sugar with a molecular formula C5H10O5. Ribose sugars are found in many important biological molecules such as ribonucleic acid (RNA), and ATP.

Summary

Carbohydrates are organic molecules composed of carbon, hydrogen and oxygen
Carbohydrates are made up from simple building blocks called monosaccharides
Two monosaccharides bonded together make a disaccharide and many monosaccharides bonded together make a polysaccharide
Glucose is a hexose sugar with two isomers: α-glucose and β-glucose
The structure of glucose makes it a good source of energy as it is easily transportable and not too reactive
Ribose is a pentose sugar which is found in RNA and ATP