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Carbohydrates

Carbohydrates. 1. Identify monosaccharides , disaccharides and polysaccharides ( eg starch) and relate structure to their roles in providing and storing energy 2. Describe how monosaccharides form disaccharides and then polysaccharides. STARTER. What is a carbohydrate?

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Carbohydrates

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  1. Carbohydrates 1. Identify monosaccharides, disaccharides and polysaccharides (eg starch) and relate structure to their roles in providing and storing energy 2. Describe how monosaccharides form disaccharides and then polysaccharides

  2. STARTER • What is a carbohydrate? • Can you give some examples of carbohydrates?

  3. What are carbohydrates? • Group of substances that are important in many biological processes • Provide energy and are used to built body structures • Contain carbon, hydrogen and oxygen Eg glucose C6H12O6 Sugars Starch Glycogen Cellulose

  4. SUGARS Are either monosaccharides (single sugar units), Disaccharides (two combined sugar units), And Polysaccharides (long chains of sugar units) Monosaccharides Can be joined by condensation reactions to form Disaccharides Polysaccharides.

  5. C C O C C C C Monosacharides • (CH2O)n – any number • If n=3, triose (glyceraldehyde) • If n=5, pentose (fructose, ribose) • If n=6, hexose (glucose, galactose) • Monosaccharides are used for • Energy • Building blocks

  6. Turn to your info sheet • Make a copy of glucose from fig 3. It is worth learning this structure as you might be asked to identify it. • You will only be asked to draw the simplified structure, make a copy of this from the info sheet. • Look at the diagram of fructose. Use the diagrams to write down the chemical formula of each molecule, what do you notice?

  7. Testing for monosaccharides • All monosaccharides and some disaccharides are reducing sugars – this means that the can donate electrons to other chemicals (benedicts reagent) • Benedicts Reagent is an alkaline solution of copper sulphate. When heated with a reducing sugar it forms an insoluble red precipitate of copper oxide

  8. Disaccharides • Formed from two monosaccharides • Joined by a glycosidic bond • A condensation reaction: • glucose + glucose  maltose • glucose + galactose  lactose • glucose + fructose  sucrose

  9. Reactions • Condensation reactions allow monosaccharides to make polysaccharides • Hydrolysis reactions allow polysaccharides to break apart

  10. C C C C O O C C C C C C C C Condensation reaction OH OH

  11. C C C C O O C C C C C C C C Condensation reaction OH OH

  12. C C C C O O C C C C C C C C Condensation reaction O H2O

  13. C C C O O C C C C C C C C C Condensation reaction 1 4 O A disaccharide 1,4 glycosidic bond

  14. Testing for non-reducing sugars • Some disaccharides are non-reducing sugars, in order to detect these we need to first break them down into their monosaccharide components. • We do this using Hydrochloric Acid. • We can then test using Benedicts Reagent.

  15. Polysaccharides • Polymers formed from many monosaccharides (linked by glycosidic bonds) • Three important examples: • Starch (amylose and amylopectin) • Glycogen

  16. Amylose -glucose 1,4 glycosidic bonds Spiral structure Amylopectin -glucose 1,4 and some 1,6 glycosidic bonds Branched structure Starch Insoluble store of glucose in plantsformed from two glucose polymers:

  17. Glycogen • Insoluble compact store of glucose in animals

  18. Cellulose • Main structural sugar in plants • Structural component of plant cell walls • Very strong • Also permeable to numerous substances • About 33% of plant matter • Most common organic compound on Earth

  19. O O O O O O O O O O O O O -O- -O- -O- -O- -O- -O- -O- -O- -O- -O- -O- -O- Forms chains which run parallel with hydrogen bonds between the chains to form microfibrils Microfibrils are strong Being fibrous, cellulose is structurally important in plant cell walls

  20. Insoluble store of glucose in plants formed from two glucose polymers amylose and amylopectin single sugar units A bond, formed by a condensation reaction that joins two monosaccharides Important biological molecules that contain carbon, hydrogen and oxygen allow monosaccharides to make polysaccharides by removing a water molecule allow polysaccharides to make monosaccharides by adding a water molecule A molecule made of two sugar units joined by a glycosidic bond A compound with the same chemical formula but a different chemical structure.

  21. A polymer of glucose molecules which has a branched structure. A polymer made up of lots of sugar units, joined together by glycosidic bonds A polymer of glucose which is unbranched and forms a spiral structure The carbohydrate energy store found in animals

  22. Which sugar molecule am I? a) A single sugar, the main substrate of respiration b) A disaccharide formed from glucose and glucose. c) A polysaccharide found in starch and formed from branched chains of glucose molecules (1,4 and 1,6 bonds) d) The energy storage molecule in animals e) A polysaccharide formed from alpha glucose chains in tight spirals.

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