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  • Glucose and fructose occur in fruits, e.g. grapes. Sucrose is the familiar table sugar and comes from sugar beet or sugar cane. Maltose is produced by germinating barley and is the sugar used in brewing beer. Note that the names of most sugars end in ‘-ose’.
  • Glucose and fructose have the same formula but differ in the way the hydrogen and oxygen atoms are distributed. Maltose and sucrose, with the same formulae, differ in a similar way. Starch is represented by a single long chain of up to 1000 glucose units but, in fact, the main component of starch is a branched chain
  • Most proteins are very large molecules, made up of hundreds of amino acids. Enzymes are proteins which carry out specific reactions in cells. They are more fully explained in slides 10-28
  • A protein which loses its shape is said to be denatured . This change cannot be reversed. Egg white is a protein (albumen). When it is heated it is denatured and changes from a clear, runny liquid to a white solid. This cannot be reversed. If an enzyme is denatured it can no longer carry out its normal function.
  • The fatty acids in a lipid may be all the same. In olive oil, for example, the fatty acid is oleic acid. Alternatively they may be different as shown in the slide.
  • In photosynthesis (see ‘How Plants Get Their Food’ ) water reacts with carbon dioxide to form glucose. 6CO 2 + 6H 2 O = C 6 H 12 O 6 + 6O 2

Transcript

  • 1. The Chemicals of Living Cells
  • 2. 2 The chemicals of lifeAll living organisms are made up of chemical substancesReactions between these substances keep the cytoplasm(and the organism) alive. They are living processes. The chemical substances described in the next series of slides are carbohydrates, proteins and lipids.
  • 3. 3 CarbohydratesCarbohydrates contain the elements carbon, hydrogenand oxygenFamiliar carbohydrates are sugar and starchGlucose, fructose, maltose and sucrose are sugars Glucose and fructose have the same formula, C6H12O6 Sucrose and maltose have the same formula, C12H22O11 Carbohydrates provide the main source of energy for respiration in living organisms
  • 4. 4 Glucose C H 6 12 O6 C HO C HO C H C O C C HO C H C C H C OH 5 of the carbon atoms may be arranged in a ring H C OH C H2OHA glucose molecule as a This molecule is often representedstraight chain simply as a hexagon
  • 5. Classification of sugars• MONOSACCHARIDES: with a single carbon ring. - glucose and fructose• DISACCHARIDES: 2 carbon rings. - maltose (glucose – glucose) - sucrose ( glucose – fructose)• POLYSACCHARIDES: - Glycogen (animal cells) - Starch ( plant cells) - Cellulose ( cell wall of plant cells)
  • 6. 5 Other carbohydrates2 molecules of glucose can sucrose is formed whenjoin together to form a a molecule of glucose andmolecule of maltose a molecule of fructose combine Starch and cellulose are formed from hundreds of glucose molecules joined maltose to form a long chain part of a starch molecule
  • 7. 6ProteinsProteins are made up of carbon, hydrogen and oxygenmolecules but with the addition of nitrogen-Carbohydrates are made up of glucose units.-Proteins are made up of units called amino acids-There are about 20 different amino acids. Examples areglycine (Gly), alanine (Ala), valine (Val) and cysteine (Cyst) -Proteins make up the structure of cells; cytoplasm, nucleus cell membranes and enzymes, haemoglobin, antibodies, hormones, fibrin.
  • 8. Protein structure and shape 7 The way the amino acids join up, gives a protein molecule a particular shape, which is different for every protein Ser-Cyst-Val-Gly-Ser-Cyst Ala Val Val-Cyst-Ser-Ala-Ser-Cyst-Gly Val- Cyst-Ala-Ala-Ser-Gly This is a small, imaginary protein molecule showing how it acquires a shape High temperatures or certain chemicals can cause the protein molecule to lose its shape and its properties.
  • 9. Lipids 8Lipids are fats and oilsThey are made up from glycerol and fatty acidsExamples of fatty acids are stearic acid, oleic acid andpalmitic acid H2 C O stearic acid H C O oleic acid A simple lipid H2 C O palmitic acid glycerol fatty acids
  • 10. FOOD TESTS• Scientists often need to know wether or not a particular type of molecule is present in a solution.• For e.g, a doctor might try to detect glucose in a urine sample (if it is present suggests the patient has diabetes)• Simple chemical tests can be carried out on biological solutions.
  • 11. Test for lipids: The emulsion test• Ethanol is added to the unknown solution, and the mixture is gently shaken.• The mixture is poured into a test tube containing an equal volume of water.• If a lipid is present, a milky- white emulsion is formed.
  • 12. A milky emulsion shows that a lipid is present
  • 13. 9Salts and waterIn addition to proteins, carbohydrates and lipids, cytoplasmcontains salts and waterWater makes up the bulk of cytoplasmAll the chemical reactions in cytoplasm take place insolution, i.e. in waterWater itself takes part in many of these chemical reactionsSalts of sodium, potassium and calcium and many othersplay an important part in these reactions
  • 14. 29 Question 1The correct formula for glucose is(a) C12H22O11(b) C5H10O5(c) C4H8O4(d) C6H12O6
  • 15. 30 Question 2Which is the most accurate description of a carbohydrate?A carbohydrate contains(a) carbon and oxygen(b) carbon, oxygen and nitrogen(c) carbon, hydrogen and oxygen(d) carbon and hydrogen
  • 16. 31 Question 3When two molecules of glucose combine, they form(a) maltose(b) sucrose(c) fructose(d) ribose
  • 17. 32 Question 4Which is the most accurate description of a proteinProteins contain(a) carbon, hydrogen and oxygen(b) carbon, hydrogen, oxygen and nitrogen(c) carbon, hydrogen and nitrogen(d) carbon, nitrogen and oxygen
  • 18. 33 Question 5Which statements are correct?Proteins are present in(a) cell membranes(b) cell walls(c) cytoplasm(d) nucleus
  • 19. 34 Question 6High temperatures damage proteins by(a) decomposing them(b) changing their chemical composition(c) changing their shape(d) making them soluble
  • 20. 35 Question 7A protein is made up of a series of (a) glucose units (b) fatty acids (c) amino acids (d) carbohydrates
  • 21. 36 Question 8Lipids are made up of(a) glycerol and amino acids(b) glycerol and fatty acids(c) protein and fatty acids(d) starch and fatty acids