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Topics 3.6 & 7.6
Enzymes
| Question | Answer |
|---|---|
| Enzyme | A protein with a specific 3-D shape that catalyzes (speeds up) a reaction |
| Substrate | molecule with a unique 3-D shape that matches the active site of an enzyme. The substrate gets turned into a product via an enzyme. Also, called a reactant. |
| Reactant | another word for substrate |
| Active Site | Specific 3-D region of an enzyme that acts as the binding site for a substrate. The 3-D shape of the active site matches the 3-D shape of the substrate. |
| Metabolism | sum of all chemical reactions in living organisms (anabolic reactions + catabolic reactions = metabolism) |
| Anabolic Reactions | reactions that build up complex molecules, endergonic (takes in energy), biosynthetic (ex. photosynthesis) |
| Catabolic Reactions | reactions that break down complex molecules, exergonic (release energy), biodegrative (ex. cellular respiration) |
| Metabolic Pathways | All metabolic pathways are catalyzed by enzymes. They can be linear chains or cycles. |
| Induced Fit Model | An enzyme's active site changes shape to accept the substrate. Glove and hand analogy: when a hand enters a glove, both change shape together (hand= substrate and glove= active site of enzyme) |
| Enzyme-Substrate Specificity | Substrate fits into the active site of an enzyme because they have similar 3-D structures. They are specific to each other but not a rigid model! |
| Steps of Mechanism of Enzyme Action | substrate contacts the active site, the active site changes shape to accommodate the substrate, enzyme-substrate complex forms, activation energy is lowered and the substrate is converted into a product, the product is released from the active site |
| Equation of Mechanism of Enzyme Action | E + S <-> ES <-> E + P |
| Enzyme-Substrate Complex | formed when the substrate binds to the active site of the enzyme |
| Activation Energy | The minimum amount of energy needed to cause a reaction (the energy needs to convert a substrate into a product). |
| Catalyst | A molecule, such as an enzyme, that speeds up a chemical reaction (makes a reaction produce products faster) |
| Endergonic | Reaction that takes in energy (requires energy) |
| Exergonic | Reaction that releases energy |
| Competitive Inhibition | A substrate and competitive inhibitor molecule compete for the same active site because they both have similar 3D shapes. This slows down the rate of reaction because less product gets produced. It can be reversible by adding more substrate |
| Competitive Inhibitor | A molecule that competes with a substrate molecule for the active site of an enzyme. Both have a similar 3D shape. |
| Non-competitive Inhibition | a molecule, called an allosteric molecule, binds to an allosteric site on an enzyme. This causes a shape change in the active site so the substrate can no longer bind to it. When this occurs, the reaction slows down because less product is produced. |
| Allosteric Site | site on an enzyme that an allosteric molecule binds to (not the active site) for non-competitive inhibition |
| Allosteric inhibitor | molecule that binds to an allosteric site on an enzyme. When bound to this site, it causes a shape change in the active site of an enzyme. |
| End-product Inhibition | used to conserve energy and materials. In a chain of enzyme reactions an end-product is produced. When too much end-product is created, it binds to an allosteric site on the 1st enzyme in the chain which shuts down its production (negative feedback) |
| Effects of temperature on enzyme activity | As the temperature increases there are more collisions between substrates and enzymes which create more products. Increasing the temperature increases the reaction rate. If the temperature gets too hot, the enzyme will denature (unfold) and no longer work |
| Effects of pH on enzyme activity | acid pH (lots of H+ ions) and basic pH (lots of OH- ions) can interfere with the active sites preventing substrates from binding. Really high and really low pHs can denature the enzyme |
| Effects of substrate concentration on enzyme activity | the rate of reaction increases as substrate concentration increase. At a certain point it will remain at a constant rate because all the active sites of the enzymes are occupied |
| Denaturation | Unfolding of an enzyme or protein due to harsh conditions (low pH, high temp). The 3D shape breaks down because the bonds holding it together break apart |
| Lactase | An enzyme that breaks lactose into the sugars glucose and galactose. You can buy enzyme pills of lactase if you're lactose intolerant |
| How do enzymes speed up reactions? | They lower the activation energy so less energy is needed for a reaction to take place. Enzymes put strain on the bonds of the substrates so they need less energy to break and rearrange into products. |
| Chemical reaction | This is what an enzyme speeds up: Reactant (aka substrate) + enzyme <--> Product + enzyme |
| Negative Feedback | a mechanism used to control a change in physiology (homeostasis). This process shuts down the production of too much of something ("more gets you les"). Used in end product inhibition. |
Created by:
kelly.norris
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