Download
slide1 n.
Skip this Video
Loading SlideShow in 5 Seconds..
Enzyme PowerPoint Presentation

Enzyme

423 Vues Download Presentation
Télécharger la présentation

Enzyme

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Enzyme

  2. What is an enzyme? • Enzyme actions • ‘Lock and key’ hypothesis • Effect of temperature on enzyme action • Effect of pH on enzyme action • Uses of enzymes in daily life

  3. What is an enzyme? • a catalyst: speeds up chemical reactions in the body • protein • no change after a reaction can be reused • a little amount is enough • specific • works within a narrow range of pH and temperature

  4. substrate Enzyme action: catabolic action enzyme-substrate complex products enzyme can be reused again

  5. Enzyme action: anabolic action substrates enzyme-substrate complex product enzyme can be reused again

  6. ‘Lock and key’ hypothesis • Explains the specificity of enzyme actions • Each key opens only one lock • Each enzyme acts on one or a few substrates that fits into its active site

  7. ‘Lock and key’ hypothesis lock is open lock = substrate lock and key = enzyme-substrate complex key =enzyme key has no change

  8. Effect of temperature on enzyme action • Works slowly at low temperature (inactive) • Does not work at high temperature (denatured) • Works best at a narrow range of temperature (optimum temperature)

  9. until it reaches a maximum (the optimum temperature). The optimum temperature is about 40 oC for most enzymes in human body. Effect of temperature on enzyme action Enzyme activity increases with a rise in temperature It then decreases with a further increase in temperature. Rate of enzyme action (arbitrary unit) Temperature (oC)

  10. Different enzymes have their own optimum pH. Effect of pH on enzyme action Enzyme activity increases with pH until a maximum (the optimum pH), then decreases as pH increases. Rate of enzyme action (arbitrary unit) pH

  11. Uses of enzymes in daily life • washing powder • cleaning solution of contact lens • meat tenderizers

  12. Summary Enzymes • are special proteins that speed up chemical reactions inside organisms (a biological catalyst) • take part in both catabolic and anabolic reactions • are specific • whose specificity explained by ‘lock and key’ hypothesis • whose activity changes with temperature and pH