BIOMOLECULES OF LIFE (Carbohydrates)

1 EJC H2 Biology T1W7 Carbohydrates and Lipids Biomolecules of Life (Part 1) 1. Overview of Topic Compounds that contain carbon atoms are said to be organic and the branch of chemistry that specializes in the study of carbon compounds is called organic chemistry. Most organic compounds also contain hydrogen atoms and also elements oxygen, nitrogen, sulphur and phosphorus. The Biomolecules of Life topic in Core Idea 1 explores how carbon atoms, by bonding with four other atoms, form a diverse range of organic mole cules which forms the ba sic constituents of cells. Two major types of organic compounds will be cover ed in this topic: carbohydrates and lipids. Proteins and enzymes will be covered later. Nucleic acids will be covered in the Core Idea 2: Genetics and Inheritance. These four major classes of biomolecules function as molecular building blocks for macromolecules to be assembled. Macromolecules are often called polymers because each polymer molecule is a long molecule consisting of many similar or identical building blocks linked by covalent bonds. Each repeating unit of a smaller molecule is called a monomer. 2. Learning Outcomes a. Describe the structure and properties of the following monomers: i. α-glucose and β-glucose (in carbohydrates) ii. glycerol and fatty acids (in lipids) iii. amino acids (in proteins) (knowledge of chemical formulae of specific R - groups of different amino acids is not required). b. Describe the formation and breakage of the following bonds: i. glycosidic bond ii. ester bond iii. peptide bond c. Describe the structures and properties of the following biomolecules and explain how these are related to their roles in living organisms: i. starch (including amylose and amylopectin) ii. cellulose iii. glycogen iv. triglyceride v. phospholipid d. Explain primary structure, secondar y structure, tertiary structure and quaternary structure of proteins, and describe the types of bonds that hold the molecule in shape (hydrogen, ionic, and disulfide bonds, and hydrophobic interactions). e. Explain the effects of temperature and pH on protein structure. f. Describe the molecular structure of the following proteins and explain how the structure of each protein relates to the function it plays: i. haemoglobin (transport) ii. collagen (structural)

2 EJC H2 Biology T1W7 Carbohydrates and Lipids iii. G-protein linked receptor (signalling) (knowledge of details of the number of amino acids and types of secondary structures present is not required.) The highlighted Learning Outcomes will be covered in Biomolecules of Life (Part 2) where proteins and enzymes will be presented together in the next serie s of lectures. 3. References Alberts, B., Johnson, A., Lewis, J., Morgan, D., Raff, M., Roberts, K. and Walter, P. (2014) Molecular Biology of the Cell (Fifth Edition) (Garland Science) ISBN 0815344643 Jones, M. and Jones, G. (2004) Advanced Biology. Chapte r 1: The Molecules of Life. Cambridge University Press. Koolman, J. and Roehm, K. (2005) Color Atlas of Biochemistry (Second Edition) (Thieme Publishing Group) ISBN13 9783131003720 Raven, P. H., Johnson, G. B., Mason, K. A., Losos, J. and Singer S. (2013) Biology (Tenth Edition) (McGraw-Hill) ISBN 007338307 Reece, J. B., Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V. and Jackson, R. B. (2011) Campbell Biology (Ninth Edition) (Pearson Higher Education) ISBN 0321739752 Contents 1. Overview of Topic ................................ ................................ ................................ . 1 2. Learning Outcomes ................................ ................................ ............................... 1 3. References ................................ ................................ ................................ ............ 2 4. Carbohydrates ................................ ................................ ................................ ...... 3 Properties of Monosaccharides ................................ ................................ ................. 4 Structure of Monosaccharides ................................ ................................ .................. 4 - and -glucose ................................ ................................ ................................ ........... 5 Disaccharides ................................ ................................ ................................ ............ 6 Polysaccharides ................................ ................................ ................................ ........ 7 Starch ................................ ................................ ................................ ................... 7 Glycogen ................................ ................................ ................................ ............... 9 Cellulose ................................ ................................ ................................ ............... 9 5. Lipids ................................ ................................ ................................ .................. 13 Properties of Lipids ................................ ................................ ................................ . 13 Structure of Lipids ................................ ................................ ................................ .. 13

3 EJC H2 Biology T1W7 Carbohydrates and Lipids Triglycerides ................................ ................................ ................................ ........ 14 Phospholipids................................ ................................ ................................ ...... 15 Glycolipids ................................ ................................ ................................ .......... 16 Sterols and steroids ................................ ................................ ............................. 16 Functions of Lipids in Biological Systems ................................ ................................ . 17 4. Carbohydrates Carbohydrates are organic compounds consisting of the elements carbon, hydrogen and oxygen, with atoms in the ratio of C:H:O = 1:2:1. Its general formula is (CH 2O) n. They can be classified in different ways . Classification Complexity Simple carbohydrates : Monosaccharides containing one monomer Disaccharides containing two monomers Complex carbohydrates: Oligosaccharides containing 3-10 monomers Polysaccharides containing >100 monomers Number of C atoms Triose (3-carbon sugars) Tetrose (4-carbon sugars) Pentose (5-carbon sugars) Hexose (6-carbon sugars) Heptoses (7-carbon sugars) Reducing properties Reducing sugars Non-reducing sugars Position of Carbonyl (C=O) group Aldose (Sugars having an aldehyde group) Ketose (Sugars having a ketone group) Important Monosaccharides in the H2 Biology Syllabus Number of C atoms General Name Chemical Formula Name Significance 3 Triose sugar C3H6O3 Glyceraldehyde Intermediate compound in respiration & photosynthesis 5 Pentose sugar C5H10O5 Ribose Component of RNA and ATP Deoxyribose Component of DNA 6 Hexose sugar C6H12O6 Glucose Main source of energy for cellular respiration Fructose An energy source. Component of sucrose. Galactose Component of lactose. Found in dairy products.

4 EJC H2 Biology T1W7 Carbohydrates and Lipids Properties of Monosaccharides Physical properties:  Monosaccharides are sweet and have crystalline structures  Readily soluble due to presence of numerous –OH groups (polar) that can form hydrogen bonds with water  Pentoses and hexoses can exist as rings which are more stable as building blocks for dissacharides and polysaccharides. Chemical Properties:  Monosaccharides are reducing sugars. They contain a carbonyl group (C = O) (aldehyde or ketone group) that donates electrons to Cu 2+ to Cu + in the Benedict’s