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Chapter 4: 4.4 to 4.5


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chapter 4: 4.4 to 4.5

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Chapter 4: 4.4 to 4.5

  1. 1. CHEMICAL COMPOSITION OF THE CELL<br />4.4 LIPIDS<br />By: RumaizahMuhamad<br />
  2. 2. LIPIDS<br />Elements of lipids:<br />Carbon<br />Hydrogen<br />Oxygen<br />Some lipids contain:<br />Phosphorus<br />Nitrogen<br />Insoluble in water.<br />Soluble in:<br />Other lipids and <br />Organic solvents (eg; alcohol & ether)<br />
  3. 3. Types of Lipids<br />Fats<br />Oils<br />Waxes <br /><ul><li>found on cuticles of the epidermis of leaves, fruits and seeds of some plants
  4. 4. Waterproof: prevent entry and evaporation of water
  5. 5. Eg: sebum </li></ul>Phospholipids<br /><ul><li>Components of plasma membrane</li></ul>Steroids<br /><ul><li>Complex organic compounds
  6. 6. Including cholesterol and hormones
  7. 7. Eg: testosterone, estrogen and progesterone</li></ul>Triglycerides <br />
  8. 8. Fats & Oils<br />Fats & oils are triglycerides<br />* Each fatty acid consists of a long hydrocarbon chain with a different number of carbon atoms for different fatty acids.<br />
  9. 9. Fatty Acids<br />Saturated FATS<br />Fats containing saturated fatty acids  saturated fats<br />Unsaturated fats<br />Fats containing unsaturated fatty acids  unsaturated fats<br />
  10. 10. Fatty Acids<br />Saturated fats<br />Cannot form any chemical bond with other atoms.<br />All the bonds between the carbon atoms have maximum number of H atoms.<br />Eg: butter (solid at RT)<br />Unsaturated fats<br />Carbon atoms in hydrocarbon chain are not bonded to the maximum number of H atoms.<br />One double bond  monounsaturated fats<br />Two/ more double bond  polyunsaturated fats.<br />Eg: corn oil (liquid at RT)<br />
  11. 11. TEST YOURSELF<br />Tick (√) if the statement is true.<br />Lipids contain oxygen, hydrogen and carbon [ ]<br />Fats and oils are triglycerides [ ]<br />A triglyceride has one glycerol and three fatty acids [ ]<br />Saturated fats are liquid at room temperature [ ]<br />Unsaturated fats are essential to good nutrition[ ]<br />
  12. 12. 4.5 ENZYMES<br />Enzymes are biological catalyst that regulate almost all the cellular reactions.<br />It is needed in life processes to regulate biochemical processes in the cells  metabolism.<br />
  13. 13. Characteristics of Enzymes<br />Enzymes are proteins: synthesized by living organisms.<br />In enzymatic reactions:<br />Alter/ speed up the rates of chemical reactions but remain unchanged at the end of reactions.<br />
  14. 14. Cont.<br />Not destroyed by the reactions they catalyze.<br />Have specific sites called active sites to bind to specific substrates.<br />Highly specific  one enzyme can only catalyze one kind of substrate.<br /><ul><li>Eg: starch molecules can only fit to active sites of amylase, not sucrase.</li></ul>Only needed in small quantities.<br />Reversible: can catalyze reaction in either direction.<br />
  15. 15. Cont.<br />Activity of enzymes can be slowed down or completely stopped by inhibitors.<br />Eg: Lead, mercury<br />To function well, enzymes require helper molecules called cofactor.<br />Eg: <br />organic cofactor are derivatives of water-soluble vitamins such as Vit.B.<br />Inorganic cofactors: ferum and copper<br />
  16. 16. Naming of Enzymes<br />Named according to the name of the substrate it catalyses.<br />Adding suffix –aseat the end of the name of their substrate.<br />Eg: <br />Other enzymes were named before a systematic way of naming enzymes. Eg: pepsin, trypsin and rennin.<br />
  17. 17. The Sites of Enzyme Synthesis<br />Enzymes are proteins, therefore ribosomes are also the sites of enzyme synthesis.<br />Information for enzyme synthesis is carried by DNA.<br />Different sequences of bases in the DNA are coded to make different proteins.<br />During the process, messenger RNA is formed to translate the codes into a sequence of a.acids.<br />These a.a are bonded together to form specific enzymes according to DNA’s codes.<br />
  18. 18. Intracellular Enzymes<br />Intracellular enzymes: enzymes which are synthesized and retained in the cell for the use of the cell itself.<br />Found in cytoplasm, nucleus, mitochondria, chloroplast<br />Eg: oxidoreductase catalyses biological oxidation and reduction in mitochondria.<br />
  19. 19. Extracellular enzymes<br />Extracellular enzymes: enzymes which are synthesized in the cell but secreted from the cell to work externally.<br />Eg: digestive enzymes  produced by the pancreas but are transported to the duodenum (the site for enzyme action).<br />Production of extracellular enzymes.<br /> Refer to topic 2.3, appreciating the uniqueness of the cell.<br />
  20. 20. TEST YOURSELF!<br />List down 5 characteristics of enzyme operations.<br />____________________________________<br />____________________________________<br />____________________________________<br />____________________________________<br />____________________________________<br />Define:<br />Intracellular enzymes<br />Extracellular enzymes<br />
  21. 21. Mechanism of Enzyme Action<br />Polypeptide chains of enzyme folded into a three-dimensional shape includes a ‘pocket’ called ACTIVE SITE.<br />Active site  complements its substrate (substrate must fit enzyme precisely).<br />The mechanism of enzyme action can be explained by the ‘lock and key’ theory.<br />
  22. 22. Lock <br />Key<br />The ‘lock and key’ hypothesis of enzyme action<br />
  23. 23. Factors Affecting Enzyme Activity<br />Temperature<br />pH<br />Substrate concentration<br />Enzyme concentration<br />
  24. 24. Effects of TEMPERATURE<br />Low temperature (T): enzyme-catalyzed reaction takes place slowly.<br />Increase temperature: Reaction between substrate and enzyme accelerated.<br />For every 10⁰C rise in T, rate of reaction is doubled.<br />Optimum T: temperature at which enzyme catalyses a reaction at the maximum rate.<br />Human : 37⁰C<br />Plants : 25⁰C<br />Beyond optimum T : enzymes lose their activities and denatured.<br />
  25. 25.
  26. 26. Beyond optimum T<br />No longer increase rate of reaction.<br />The bonds that hold enzyme molecules together begin to break at high T.<br />Thus, destroying active site.<br />Denaturation is irreversible.<br />
  27. 27. TEST YOURSELF!<br />Question 1 – 6. Tick (√) if the statement is true.<br />All enzymes are proteins [ ]<br />Most intracellular enzymes work best in neutral conditions. [ ]<br />Extracellular enzymes work inside the cell [ ]<br />The reaction of enzymes takes at the active site in the enzyme molecule. [ ]<br />The rate of enzyme reaction depends on the temperature and light intensity. [ ]<br />Enzymes are destroyed by heat because enzymes, being proteins, are denatured at high temperature. [ ]<br />The way a substrate’s molecule fits into an enzyme’s _________ is explained by the lock and key hypothesis. The enzyme is the ____________ and the substrate is the _____________.<br />The enzyme activity is influenced by __________, ____________, ______________ concentration and enzyme concentration.<br />
  28. 28. Effects pH on enzymes<br />Sensitive to the changes of pH.<br />Optimum pH : pH at which the rate of reaction is at the maximum/ fastest.<br />Eg: <br />Pepsin  function in acidic condition (pH2) in stomach<br />Trypsin  function in alkaline condition (pH8.5) in duodenum.<br />
  29. 29. A change in pH:<br />Alter the charges on active sites and substrate surface<br />Reduce ability of both molecules to bind with each other.<br />Effects of pH on enzymes : reversible.<br />When pH in environment reverts to optimum level, the ionic charges on active sites are restored.<br />Thus, the enzymes resume their normal function.<br />
  30. 30.
  31. 31. Effects of substrate concentration<br />Increase [substrate] : <br />More substrate available to bind to the active site.<br />Increase collisions between substrate and enzyme molecules.<br />More products will be produced.<br />
  32. 32. Rate of reaction : directly proportional to [substrate] until reach a maximum rate.<br />
  33. 33. Effects of enzyme concentration<br />When [enzyme] increase: <br />more enzymes available.<br />more active sites for catalytic reaction.<br />Rate of reaction: <br />increase if only there is abundant supply of substrate and other factors (pH, T, pressure and constant).<br />Proportional to [enzyme]<br />
  34. 34.
  35. 35. The Use of enzymes<br />Enzyme technology: the use of enzymes in industrial processes.<br />By using your textbook and reference book, please find the examples of enzymes used in industries. <br />
  36. 36. The importance of Chemical Composition in Cells<br />