INQUIRY QUESTION: HOW DO CELLS COORDINATE ACTIVITIES WITHIN THEIR INTERNAL ENVIRONMENT AND THE EXTERNAL ENVIRONMENT? Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) Module 1.2. B)Enzymes Enzymes a n d Metabolism A simplified diagram mapping some of the metabolic reactions in the human body Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) Metabolism is the sum of all chemical reactions occurring within a living organism. The body needs to either build substances (synthesis) or break down larger substances (digestion). Synthesis Digestion + + Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) Sometimes digest larger substances to their smaller units in order to synthesise new required materials. These reactions are essential for life, however, on their own they are very slow. This initial energy is the activation energy. Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) Reactions require an initial amount of energy to get going, after which they will continue to react until the reaction is complete. Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) This c o n c ep t is explored further for those doing HSC Chemistry. The Biology course does not require you to know further than explored in this presentation. Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) These reactions need to b e catalysed. A catalyst is a substance that increases the rate of a reaction without being consumed by that reaction in the process. It lowers the activation energy a n d is free to catalyse the same reaction again. An Enzyme is a biological catalyst. Most metabolic reactions c a n a n d will only occur if there is an enzyme present to lower the activation energy. Enzyme Structure An analogy to this would b e a necklace m a d e of broken pieces of a magnet. Important: Know the difference between an amino acid, polypeptide a n d protein. Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) Enzymes are proteins. They are long chains of amino acids (polypeptide), which will naturally a n d spontaneously fold in on itself into a particular shape. Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) Enzymes (and indeed all proteins) have a very complex, irregular a nd specific structure. Each different structure also will catalyse a specific biological reaction. Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) Enzymes work by having an active site where the reactant(s), or substrate(s) will fit a n d react. This is the Enzyme-Substrate complex. Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) Substrates fit into an enzyme active site so specifically it is called the lock and key model. Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) The Lock a nd Key model works in conjunction with the induced fit model, whereby the enzyme will clamp down when the substrate enters the active site. Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) The main point here is that the shape of an enzyme is extremely important in its functionality of optimising the rates by decreasing the activation energies metabolic a n d other biological reactions. Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) Factors Affecting Enzyme Activity Outside of these ranges a n d they will begin to unravel a n d denature (process called denaturation). Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) Enzymes are sensitive to temperature a n d pH. They will work only within an optimal range of each. Temperature However, at a particular point (around 37 o C in humans) the enzymes will denature. There is an optimal point of temperature, a balance between substrate collisions a n d the enzyme maintaining its shape. Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) As temperature increases it increases the vibrations of particles, a n d hence increases the rate of collisions of the substrate into the active site of its enzyme. This in turn will increase the rate of reaction. Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) pH The other major factor that c a n denature an enzyme is pH. Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) Each enzyme is active within a (usually) narrow range along the pH scale. However, this c a n change depending on the part of the body in which the enzyme is required. Substrate Concentration As discussed earlier, enzymes are substrate-specific; a specific enzyme will only catalyse a specific reaction. However, unlike temperature a n d pH, an excess of substrate will not denature the enzyme, the reaction rate will simply plateau at the point of saturation. Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) The reaction rate in this case will also d e p e n d on the substrate concentration – there will b e an optimal concentration ratio. Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) Surface area to volume ratio of substances Watch the given video to understand this concept. https://www.youtube.com/watch?v=RY0aHmyo98E Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) Some toxic substances are poisonous because they inhibit the proper functioning of an enzyme. These are inhibitors. https://ib.bioninja.com.au/higherlevel/topic-8-metabolism-cell/unt itled-6/enzyme-inhibition.html Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) They c a n either link directly to the active site, blocking the substrate (competitive inhibitors) or attach elsewhere, altering the shape of the enzyme a n d the shape-specific active site (non-competitive inhibitors). Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) ►Watch: Enzymes https://www.youtube.com/watch?v=qgVFkRn8f10 Key Terms Metabolism ► Substrate ► Synthesis ► Enzyme-Substrate Complex ► Digestion ► Point of Saturation ► Activation Energy ► Homeostasis ► Catalyst ► Competitive Inhibitors ► Non-Competitive Inhibitors ► Enzyme ► Protein ► Amino Acid ► Polypeptide ► Active Site The End Biology 1.2 B) Enzymes (G. Guy - Fort Street High School) ►