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METABOLISM

METABOLISM. Its regulation and the importance of maintaining a constant internal environment . What is Metabolism?. The total of ALL chemical reactions in a living organisms Reactions which: - BUILD UP large compounds from smaller molecules

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METABOLISM

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  1. METABOLISM Its regulation and the importance of maintaining a constant internal environment

  2. What is Metabolism? • The total of ALL chemical reactions in a living organisms • Reactions which: - BUILD UP large compounds from smaller molecules - BREAK DOWN large compounds into smaller molecules

  3. Building Up: Anabolic Reactions Glucose + Glucose + Glucose (lots & lots!) → Starch Plants make small monosaccharides GLUCOSE during photosynthesis then store it as the large polysaccharide STARCH

  4. Breaking Down: Catabolic Reactions Starch → Glucose + Glucose + Glucose Animals & plants breakdown large polysaccharides STARCH into the small monosaccharide GLUCOSE to use for ENERGY in CELLULAR RESPIRATION THINK: another large molecule BROKEN DOWN to smaller units ?

  5. Role of Enzymes • Enzymes are ESSENTIAL in REGULATING ALL these reactions. • They are called BIOLOGICAL CATALYSTS- without them reactions in living things would happen too slowly, and Energy would not be accessed • Enzymes control the RATE of chemical reactions that make up metabolism in living organisms. • THEY ARE NOT CONSUMED (used up) IN A REACTION THEY CATALYSE

  6. Chemical Composition of Enzymes LARGE PROTEIN MOLECULES (made of smaller subunits called…..) • Fold into SPECIFIC SHAPES according to the SEQUENCE of amino acids in them • FUNCTION of each enzyme is dependent on its shape • If shape of an enzyme changes its function is IMPAIRED

  7. Enzymes are Specific • An enzyme’s shape makes it specific to a given SUBSTRATE Substrate- the molecule/s being broken down or built up • Enzyme has an ACTIVE SITE which fits onto the substrate (change shape of active site= cannot fit onto substrate)

  8. Enzyme-Substrate Complex • http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_enzymes_work.html

  9. Enzymes reduce Activation Energy

  10. Induced Fit Model In this model the active site changes shape slightly then returns to its original shape

  11. Lock & Key Model In this model the active site DOES NOT change shape

  12. Sensitivity of Enzymes Enzymes are sensitive to changes in: • temperature: increases in temperature can DENATURE the enzyme and change the shape of the active site • pH: change in pH can have a similar effect on as temperature. In both situations the enzyme is unable to BIND to the substrate, hence its activity is INHIBITED

  13. Temperature There is an OPTIMUM TEMPERATURE at which the enzyme will work best

  14. pH There is an OPTIMUM TEMPERATURE at which the enzyme will work best

  15. Substrate Concentration

  16. Why is this all so important…..? • Biological reactions would not occur as quickly as needed without enzymes (they reduce energy needed for reactions to proceed • If temperature or pH of the internal environment of an organism changes, enzymes cannot do their job and so…..

  17. Therefore…. We need to keep our internal environment stable in terms of….. - AND -

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