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A level Biology - Biological Molecules

This is a PowerPoint presentation for Topic 1 in the Edexcel Biology B A Level course that starts in 2015.

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A level Biology - Biological Molecules

  1. 1. A Level Biology MAKING SENSE OF Icons CC – The Pink Group Copyright©2017HenryExham Icons CC – The Pink Group Copyright©2017HenryExham
  2. 2. Copyright © 2015 Henry Exham • The basic unit of life is a cell. • To really understand how it works you need to know what it is made from. • In this topic you will learn about the most important molecules that are used to make cells and other important structures in biology. • This is the chemistry of life! 2 Biological Molecules Introduction
  3. 3. Biological Molecules MAKING SENSE OF 1.1 Carbohydrates 1.2 Lipids 1.3 Proteins 1.4 DNA and Protein Synthesis 1.5 Enzymes 1.6 Inorganic Ions 1.7 Water 3
  4. 4. Copyright © 2015 Henry Exham • Do you know the difference between monosaccharides, disaccharides and polysaccharides? • What is the structure of alpha and beta glucose? • What is the structure of ribose? • Can you explain how condensation reactions are used to form glycosidic bonds between sugar molecules, and hydrolysis reactions break these bonds? • Can you state the structures and bonding of the following molecules: sucrose, lactose, maltose, starch and glycogen. • How does the structure of glucose, starch, glycogen and cellulose relate to their function? 4 1.1 Carbohydrates Objective Questions
  5. 5. Copyright © 2015 Henry Exham • Cells use carbohydrates as a source of energy and a way of storing energy. • The source of energy is usually small simple sugars such as glucose. • Plants can store this in the form of starch, whilst animals store it as glycogen. • Carbohydrates are made of three elements: carbon, hydrogen and oxygen. • We can organise carbohydrates into different groups based on their size. 5 1.1 Carbohydrates Introduction
  6. 6. Copyright © 2015 Henry Exham Monosaccharides (one sugar) 6 1.1 Carbohydrates Mono, di and poly saccharides Disaccharides (two sugars) Polysaccharides (many sugars) Hexose Pentose Oligosaccharides (3-10 sugar units) Polysaccharides (more than 10)
  7. 7. Copyright © 2015 Henry Exham • Monosaccharides are simple sugars. • You should be familiar with the following examples: – Pentose Sugars (Ribose and Deoxyribose) these have 5 carbon atoms. – Hexose Sugars (Glucose, fructose and galactose) these have 6 carbon atoms. 7 1.1 Carbohydrates Monosaccharides You must be able to describe the structure of ribose and glucose in more detail.
  8. 8. Copyright © 2015 Henry Exham • This is the structure of the pentose sugar ribose 8 1.1 Carbohydrates Monosaccharides O CC C C OH OHOH H HH H CH2OH RIBOSE
  9. 9. Copyright © 2015 Henry Exham • Glucose actually exists in two forms (isomers) and you need to know both of them. 9 1.1 Carbohydrates Monosaccharides α-GLUCOSE β-GLUCOSE C C C O CC CH2OH OH H H H H H OH HO OH 1 23 4 5 6 C C C O CC CH2OH H H H H H OH OH HO OH 1 23 4 5 6 • The carbon atoms are numbered to help identify the molecule.
  10. 10. Copyright © 2015 Henry Exham • The difference is small, just the hydrogen and hydroxide swapped over on the 1st Carbon. • However this has a big impact when glucose forms polymers as we will see in the polysaccharides section. 10 1.1 Carbohydrates Monosaccharides α-GLUCOSE β-GLUCOSE 1 23 4 5 6 1 23 4 5 6 C C C O CC CH2OH H H H H H OH OH HO OH C C C O CC CH2OH OH H H H H H OH HO OH
  11. 11. Copyright © 2015 Henry Exham • Disaccharides are made up of two monosaccharides that have been joined together by a glycosidic bond. 11 1.1 Carbohydrates Disaccharides Disaccharide Monosaccharides Found in Maltose α-glucose + α-glucose Germinating seeds Sucrose α-glucose + fructose Sugar cane (table sugar) Lactose α-glucose + β galactose Milk
  12. 12. Copyright © 2015 Henry Exham • A condensation reaction occurs in order to form a glycosidic bond between two monosaccharides. • For example here are two α-glucose molecules. 12 1.1 Carbohydrates Disaccharides O HH OH HO 1 23 4 5 6 O HH OH HO 1 23 4 5 6 • In a condensation reaction water is removed to form the bond. • In this case this would form a 1,4-glycosidic bond because it is between carbon 1 on one molecule and 4 on the other. O HH HO 1 23 4 5 6 O HH OH O 1 23 4 5 6
  13. 13. Copyright © 2015 Henry Exham • You can do the opposite reaction to split disaccharides into monosaccharides. • This is called a hydrolysis reaction and water is put in. 13 1.1 Carbohydrates Disaccharides O HH HO 1 23 4 5 6 O HH OH O 1 23 4 5 6 O HH O HH O 1 23 4 5 6 O HH OH HO 1 23 4 5 6 HydrolysisCondensationH2O H2O
  14. 14. Copyright © 2015 Henry Exham • If you continue joining together monosaccharides with glycosidic bonds you can make very long chains of sugars. • Thee are called polysaccharides. 14 1.1 Carbohydrates Polysaccharides • They are perfect for storing sugar in a cell because: – They are insoluble so do not affect water potential in the cell. – They are compact and take up little space.
  15. 15. Copyright © 2015 Henry Exham 15 1.1 Carbohydrates Polysaccharides
  16. 16. Copyright © 2015 Henry Exham STARCH • Starch is the energy store used by plants. • When the plant makes glucose in photosynthesis it stores it as starch because starch is insoluble and compact. • Starch is made up of two compounds. – Amylose – Amylopectin 16 1.1 Carbohydrates Polysaccharides
  17. 17. Copyright © 2015 Henry Exham STARCH-Amylose 17 1.1 Carbohydrates Polysaccharides AMYLOSE Made of between 200-5000 α- glucose molecules all joined by 1,4-glycosidic bonds. This causes the molecules to coil up into a spiral.
  18. 18. Copyright © 2015 Henry Exham STARCH-Amylopectin 18 1.1 Carbohydrates Polysaccharides AMYLOPECTIN Branched polymer of α-glucose made up from a combination of 1,4-glycosidic bonds and 1,6-glycosidic bonds. This branching changes the properties of the molecule. The side chains can be easily broken off when energy is required.
  19. 19. Copyright © 2015 Henry Exham GLYCOGEN 19 1.1 Carbohydrates Polysaccharides GLYCOGEN This is the energy store for animals and fungi. Made of many α-glucose molecules and a combination of 1,4-glycosidic bonds and 1,6-glycosidic bonds. Basically the same as amylopectin but with even more branching!
  20. 20. Copyright © 2015 Henry Exham CELLULOSE • You have probably come across cellulose before when learning about plant cells. • It is a very strong substance used for making cell walls. • In order to achieve this is has a very specific structure. 20 1.1 Carbohydrates Polysaccharides
  21. 21. Copyright © 2015 Henry Exham CELLULOSE • Made of β-glucose molecules joined by 1,4-glycosidic bonds. • Alternate molecules are inverted so the bonding can take place. • Because of the glycosidic bonds pointing up and then down it makes a straight chain rather than a coil like in amylose. 21 1.1 Carbohydrates Polysaccharides
  22. 22. Copyright © 2015 Henry Exham CELLULOSE • But also because of this the strands can form cross- links with other strands. 22 1.1 Carbohydrates Polysaccharides =Hydrogen bonds • These cross links are made from hydrogen bonds and they give cellulose its great strength.
  23. 23. Copyright © 2015 Henry Exham 23 End of sample Download To download the whole presentation visit
  24. 24. This PowerPoint is protected under copyright. It is designed for educational use. Either personal study or to be presented to a class. It may be edited or duplicated for these purposes only. It must not be shared or distributed online in any format. Some images used are under a separate creative commons license, these are clearly marked. Copyright © 2015 Henry Exham Brought to you by TERMS AND CONDITIONS