Transcript Enzymes
Enzymes Enzymes a Fun Introduction http://www.youtube.com/watch?v=XTUm-75-PL4&safe=active Enzymes: what they are http://www.youtube.com/watch?v=hoBhOdQV7vw&safe=active Enzyme Function http://www.youtube.com/watch?v=E_r3omrnxw&feature=rellist&playnext=1&list=PLC7ZMTERKSOJO 48-GKSQYXM6Z0YH-ZBLG&safe=active Enzymes and Chemical Reactions – To function properly, cells must carry out thousands of chemical reactions – All chemical reactions require energy Activation Energy: the initial push of energy to get a chemical reaction started – Enzymes lower the activation energy needed to begin a reaction Enzymes • Large complex protein molecules • Organic Catalysts: speed up the rate of chemical reaction in living things – Rate of Reaction: how quickly product is produced over time • Enzymes are not chemically changed by a reaction, so they can be reused over and over by the cell. • You only need a small amount of enzyme to catalyze thousands of reactions each second. • Enzymes often work with co-enzymes (non-proteins like vitamins). Making Enzymes: – Protein molecules synthesized at ribosomes – Most used within cells – Some passed out of cell (secreted) to catalyze reactions outside cell • Ex: Digestive Enzymes Enzymes are Specific: – Can only work with one specific substrate – Specificity is due to shape – If shape is altered for some reason, enzyme will not function properly Active Site: location on enzyme where substrate binds and reacts Lock and Key Model Enzyme binds with a specific substrate at active site. (like key in lock) – Enzyme substrate complex forms – Reaction takes place – Substrate gets altered. – Products get released – Enzyme can go on to react with more substrate. Induced Fit Model: (flexible enzyme) – Substrate and enzyme may not fit exactly. – When substrate joins, the enzyme changes shape slightly making the fit more exact. (flexible lock) Note: – Certain metabolic genetic disorders involve a single amino acid in an enzyme being changed. – The enzyme shape is altered and it cannot function properly • Ex: – Sickle Cell Anemia Names of Enzymes: – Start with beginning of substrates name – End in “-ase” – Ex: • Protease – enzyme reacts with proteins • Lipase – enzyme reacts with lipids • Sucrase – enzyme reacts with sucrose (disaccharide) Factors Influencing Enzyme Action – Temperature – pH levels – Concentration of Available Substrate Changing Temperature • For most enzymes in humans, the optimum temp. to function properly is about 98.6°F (37°C) – If too cold – reaction slow – As it heats up - reaction speeds up – If too high - reaction stops, enzyme denatures • Denaturation – At temp. above or below the optimum, the enzyme starts to lose its shape and stops functioning. – Active site no longer fits substrate Enzyme has Denatured Biologist Pick Up Line Different organisms have different optimum temp. for enzyme activity Changing pH Levels • Each enzyme has an optimum pH at which it functions best. Ex: Digestive Enzymes Pepsin: works in stomach (acidic pH) Trypsin: works in small intestine (slightly basic pH) Salivary Amalase: works in mouth (neutral pH) What is the optimum pH for each of these enzymes to function? Changing Concentration of Substrate • As concentration of available substrate increases, more is available to react with enzyme so rate of reaction increases. • Eventually rate of reaction will level off as available enzymes are all being used. (point of enzyme saturation)