Term
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Definition
| biological catalysts that speed up metabolic reaction |
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Term
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Definition
| a chemical that speeds up the rate of reaction and remains unchanged and reusable at the end of the reaction |
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Term
| define metabolic reactions/metabolism |
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Definition
| the chemical reactions that take place inside living cells/organisms |
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Term
| what do enzymes catalyse? |
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Definition
| enzymes catalyse the conversion of substrate molecules to product molecules |
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Term
| define substrate molecules |
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Definition
| molecules that are altered by an enzyme-catalysed reaction |
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Term
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Definition
| molecules produced from substrate molecules by an enzyme-catalysed reaction |
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Term
| name 2 things enzymes affect |
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Definition
| 1. structure (e.g. production of collagen) 2. function (e.g.respiration) |
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Term
| what 2 levels do enzymes catalyse at? |
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Definition
| 1. cellular level (e.g. respiration) 2. organism level (e.g.digestion in animals) |
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Term
| name 4 differences between enzymes and chemical catalysts |
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Definition
| 1. E = requires low temp, normal pressure, neutral pH C = high temp, high pressure, high pH 2. E = able to work in conditions that sustain life C = not able to work in conditions that sustain life 3. E = more specific C = less specific 4. E = no unwanted products C = unwanted products |
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Term
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Definition
| indented area on the SA of an enzyme molecule, with a shape that is complementary to the shape of the substrate molecule |
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Term
| how many amino acids does the active site consist of? |
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Definition
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Term
| what is the tertiary structure of the active site complementary to? what does this mean? |
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Definition
| the complementary substrate molecule = enzymes are very specific |
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Term
| what 2 things can alter the active site? |
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Definition
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Term
| name 2 places enzymes work |
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Definition
| intracellular & extracellular |
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Term
| intracellularly, some enzyme-catalysed reactions are part of what? |
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Definition
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Term
| each metabolic pathway in a living cell is one of a series of what? |
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Definition
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Term
| each step in a metabolic pathway is catalysed by what? |
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Definition
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Term
| what 2 types of metabolic pathway are there? |
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Definition
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Term
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Definition
| where metabolites are broken down into smaller molecules |
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Term
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Definition
| where energy is used to synthesise larger molecules from smaller ones |
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Term
| name one example of an intracellular enzyme |
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Definition
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Term
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Definition
| in all living cells exposed to oxygen, specifically in peroxisomes (small vesicles) |
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Term
| what is the job of catalase? |
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Definition
| to prevent cell damage by oxygen |
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Term
| how does catalase prevent cell damage by oxygen? |
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Definition
| by breaking down hydrogen peroxide (atoxic by-product of metabolic reactions) to oxygen and water |
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Term
| what is the structure of catalase? |
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Definition
| 4 polypeptide chains and an iron haem group |
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Term
| what do white blood cells use catalase for? |
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Definition
| to kill invading microbes |
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Term
| catalase is the fastest acting enzyme. true or false? |
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Definition
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Term
| what is the optimum pH for human catalase? |
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Definition
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Term
| what is the optimum temp for human catalase? |
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Definition
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Term
| define extracellular enzymes |
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Definition
| enzymes that are secreted from the cell they were made in and act on the substrates extracellularly |
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Term
| name an example of an extracellular enzyme |
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Definition
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Term
| where is amylase produced? |
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Definition
| in the salivary glands & then secretes into saliva/mouth |
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Term
| what is the function of amylase? |
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Definition
| to catalyse the hydrolysis of starch into maltose |
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Term
| name another extracellular enzyme, besides amylase |
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Definition
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Term
| where is trypsin produced? |
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Definition
| pancreas = secreted into small intestine |
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Term
| what is the function of trypsin? |
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Definition
| it catalyses the hydrolysis of peptide bonds, specifically proteins into smaller peptides |
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Term
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Definition
| a substance that has to be present to ensure that an enzyme-catalysed reaction takes place at the appropriate rate |
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Term
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Definition
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Term
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Definition
| 1. prosthetic group 2. inorganic cofactors 3. organic cofactors |
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Term
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Definition
| a cofactor which is permanently bounds to an enzyme by covalent bonds |
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Term
| give an example of a prosthetic group |
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Definition
| zinc ion (Zn2+) for carbonic anhydrase |
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Term
| what is carbonic anhydrase? |
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Definition
| an enzyme founds in red blood cells |
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Term
| what is the function of carbonic anhydrase? |
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Definition
| to catalyse the interconversion of CO2 to H2O to carbonic acid = allows CO2 to be carried in blood from tissues to lungs |
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Term
| define an inorganic cofactor |
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Definition
| an ion cofactor which is no permanently bound to enzymes and is not changed or used up in a reaction |
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Term
| what are the 2 jobs of inorganic cofactors? |
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Definition
| 1. they help enzyme and substrate bind together to form an enzyme-substrate complex 2. change the charge distribution on the SA of the substrate/active site, making it easier to form bonds in the enzyme-substrate complex |
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Term
| name an example of an inorganic cofactor |
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Definition
| chloride ions (Cl-) for amylase |
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Term
| what is the job of amylase? |
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Definition
| to digest starch to maltose |
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Term
| define an organic cofactor |
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Definition
| a small organic non-protein molecule that binds temporarily to the active site at the same time that the substrate binds. they are chemically changed in the reaction and have to be recycled to original state, often by other enzymes |
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Term
| what are organic cofactors also known as? |
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Definition
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Term
| name an example of an organic cofactor/co-enzyme |
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Definition
| vitamins -they are a source of co-enzyme |
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Term
| what is the job of vitamins? |
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Definition
| to act as carriers, moving chemical groups between different enzymes |
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Term
| explain the lock and key model |
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Definition
| 1. substrates & molecules have KE 2. successful collisions form an enzyme-substrate complex if the active site and substrate are complementary = temporary hydrogen bonds form between enzyme and substrate 3. enzyme-product complex 4. product leaves active site 5. enzyme is now free for new substrates |
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Term
| what is the induced - fit model? |
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Definition
| a model which shows that when an enzyme enters the active site, the active site changes shape slightly (moulds around substrate) |
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Term
| explain the induced-fit model |
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Definition
| 1. active site is complementary to substrate 2. on binding, the R groups of the amino acid give a more precise conformation that exactly fits the substrate 3. forms an enzyme-substrate complex 4. hydrogen, ionic bonds, london forces & hydrophobic/philic reactions bind the substrate to the active site |
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Term
|
Definition
| a substance that has to be present to ensure that an enzyme-catalysed reaction takes place at the appropriate rate |
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Term
|
Definition
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Term
|
Definition
| 1. prosthetic group 2. inorganic cofactors 3. organic cofactors |
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Term
|
Definition
| a cofactor which is permanently bounds to an enzyme by covalent bonds |
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Term
| give an example of a prosthetic group |
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Definition
| zinc ion (Zn2+) for carbonic anhydrase |
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Term
| what is carbonic anhydrase? |
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Definition
| an enzyme founds in red blood cells |
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Term
| what is the function of carbonic anhydrase? |
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Definition
| to catalyse the interconversion of CO2 to H2O to carbonic acid = allows CO2 to be carries in blood from tissues to lungs |
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Term
| what do enzymes do to the activation energy of a reaction? |
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Definition
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Term
| why can't the temperature in living cells be raised too much? |
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Definition
| lipids would melt & proteins would denature |
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Term
| what happens if a substance is heated? |
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Definition
| the heat energy causes molecules to move faster = increases rate of collision & force with which they collide |
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Term
| explain what happens when a mixture containing enzyme and substrate is heated? |
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Definition
| 1. heat is added to enzyme & substrate solution 2. both molecules gain KE 3. = move faster 4. = increases rate of successful collisions 4. = increases rate of formation of ES complexes 5. = increases rate of formation of EP complexes |
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Term
| enzyme's have an optimum temperature. what is the optimum temperature? |
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Definition
| the temperature at which the rate of reaction is at its highest |
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Term
| give an example of a bacteria that has enzymes which function well in the cold |
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Definition
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Term
| give an example of a bacteria that has enzymes which function well in the heat |
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Definition
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Term
| as well as making molecules move faster, what else does increasing temperature do to molecules? |
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Definition
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Term
| explain what vibration does to molecules/enzymes |
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Definition
| 1. breaks some weak bonds (e.g. ionic & hydrogen) which hold the tertiary structure of enzyme's active site together 2. active site begins to change 3. substrate fits in less well 4. rate of reaction begins to decrease 5. even more heat irreversibly changes the active site completely 6. = no longer complementary 7. = denatured |
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Term
| draw a graph showing the effect of temperature on rate of reaction |
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Definition
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Term
| does vibration change the primary structure of an enzyme? |
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Definition
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Term
| what is the equation for rate of reaction? |
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Definition
| 1/time to reach end point |
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Term
| what is the unit for rate of reaction? |
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Definition
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Term
| what is the temperature coefficient, and its equation? |
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Definition
| Q (little 10) = rate of reaction (T + 10) degrees Celsius / rate of reaction T degrees Celsius |
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Term
| what, approximately, is Q(little 10) in a test? what does this mean? |
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Definition
| 2 - for every 10 degrees Celsius the rise in temp, the rate of reaction is doubled |
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Term
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Definition
| whether a substance is acidic (0-6), alkaline (8-14), neutral (7) |
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Term
| what do acids such as hydrochloric acid and sulphuric acid dissociate into? |
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Definition
| protons and a negatively charged ion |
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Term
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Definition
| something than resists changes in pH |
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Term
| what are buffers used in, and to do what? |
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Definition
| used in experiments to maintain the desired pH |
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Term
| explain how pH affects bonds within molecules |
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Definition
| 1. small changes in pH either side of the optimum pH slow the rate of reaction, because the active site shape is disrupted 2. if the optimum pH is restored, the H bonds can re-form = restores active site shape 3. at extremes of pH, the enzyme's active site may be denatured |
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Term
| explain the effect of acids on enzymes |
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Definition
| 1. hydrogen ions are attracted to the negative parts of the molecule 2. excess hydrogen ions interfere with ionic and hydrogen bonds of the tertiary structure of the enzyme 3. the hydrogen ions almost 'replace' the hydrogen bonds that existed in the tertiary structure due the their attraction to the negative charge 4. changes shape of active site |
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Term
| explain the effect of alkalis on enzymes |
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Definition
| 1. hydroxide ions are attracted to the positive parts of the molecule 2. excess hydroxide ions interfere with hydrogen bonds and ionic bonds of the tertiary structure of the enzyme 3. the hydroxide almost 'replaces' the hydrogen bonds that existed in the tertiary structure due to their attraction to the positive charges 4. changes the shape of the enzyme |
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Term
| draw a graph for the effect of pH on enzymes |
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Definition
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Term
| do all enzymes have the same optimum pH? |
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Definition
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Term
| what is the optimum pH of amylase? |
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Definition
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Term
| what is the optimum pH of pepsin? |
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Definition
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Term
| what is the optimum pH of trypsin? |
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Definition
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Term
| what is the effect of increasing the number of substrate molecules? |
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Definition
| the substrate concentration increases |
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Term
| increasing the substrate concentration increases the rate of reaction. explain why? |
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Definition
| more enzyme-substrate complexes can form = more product formed. substrate complex is the limiting factor |
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Term
| what happens when the substrate concentration reaches its maximum? |
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Definition
| all the enzyme's active sites become occupied, so even if more substrates are added there will be no enzymes for them to 'enter'. active site concentration is now the limiting factor |
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Term
| draw a graph for substrate concentration agains rate of reaction |
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Definition
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Term
| what does the availability of enzymes in cells depend on? |
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Definition
| the rate of synthesis of the enzymes and the rate of degradation |
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Term
| what is enzyme degradation? |
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Definition
| where abnormally shaped enzymes are eliminated |
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Term
| what is the benefit of enzyme degradation? |
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Definition
| it regulates metabolism by removing superfluous enzymes |
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Term
| what happens when enzyme concentration increases? |
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Definition
| more active sites are available = more successful collisions = more ES complexes formed = greater rate of reaction. enzyme concentration is the limiting factor |
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Term
| what happens the substrate concentration is fixed/limited but the enzyme concentration continues to increase? |
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Definition
| there will be no further increase in rate of reaction because active sites of extra enzymes will not be occupied. substrate concentration becomes the limiting factor |
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Term
| what does the availability of enzymes in cells depend on? |
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Definition
| the rate of synthesis of the enzymes and the rate of degradation |
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Term
| what is enzyme degradation? |
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Definition
| where abnormally shaped enzymes are eliminated |
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Term
| what is the benefit of enzyme degradation? |
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Definition
| it regulates metabolism by removing superfluous enzymes |
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Term
| what happens when enzyme concentration increases? |
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Definition
| more active sites are available = more successful collisions = more ES complexes formed = greater rate of reaction. enzyme concentration is the limiting factor |
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Term
| what happens the substrate concentration is fixed/limited but the enzyme concentration continues to increase? |
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Definition
| there will be no further increase in rate of reaction because active sites of extra enzymes will not be occupied. substrate concentration becomes the limiting factor |
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Term
| draw a graph for enzyme concentration against rate of reaction |
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Definition
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Term
| why is the initial rate of reaction always the fastest? |
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Definition
| because there is greater chance of the substrates and enzymes colliding |
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Term
| why does the rate of reaction slow as time proceeds? |
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Definition
| because the rate of successful collisions decreases because some of the substrates/enzymes may collide with product molecules |
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Term
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Definition
| a substance that reduces or stops a reaction of an enzyme |
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Term
| define a competitive inhibitor |
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Definition
| inhibition of an enzyme, where the inhibitor molecule has a shape to that of the substrate molecule & competes with the substrate for the enzyme's active site and prevents the formation of ES complexes |
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Term
| what happens when a competitive inhibitor blocks the enzyme's active site? |
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Definition
| it blocks it = prevents substrate binding with active site |
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Term
| what does the amount of competitive inhibition depend on? |
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Definition
| the relative concentration of substrate and inhibitor molecules |
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Term
| more competitive inhibitor = |
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Definition
| greater rate of collision with active site = greater effect of inhibition |
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Term
| how can the amount of competitive inhibition be reduced? |
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Definition
| increase substrate concentration |
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Term
| what do competitive inhibitors compete with substrates to form? |
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Definition
| enzyme-inhibitor complexes |
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Term
| is the competitive inhibitor changed by the enzyme? |
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Definition
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|
Term
| is most enzyme inhibition by competitive inhibitors reversible? |
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Definition
|
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Term
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Definition
| when a competitive inhibitor binds irreversibly to the enzyme's active site |
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Term
| draw a competitive inhibition graph |
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Definition
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Term
| define non-competitive inhibition |
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Definition
| inhibition of an enzyme where the competitor molecule attaches to a part of the enzyme which is not the active site. this changes the shape of the active site, which prevents ES complexes forming, as the enzyme's active site is no longer complementary in shape to the substrate molecule |
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Term
| what is the name of the site where non-competitive inhibitors attach to on an enzyme? |
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Definition
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Term
| explain how non-competitive inhibitors work |
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Definition
| 1. they attach to allosteric site 2. disrupts tertiary structure and therefore shape 3. makes active site no longer complementary to substrate molecule 4. no ES complexes can be formed |
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Term
| does increasing substrate concentration limit the amount of non-competitive inhibition? |
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Definition
|
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Term
|
Definition
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Term
| do all non-competitive inhibitors bind reversibly to the allosteric site? |
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Definition
| no, some bind irreversibly |
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Term
| what is end-product inhibition? |
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Definition
| after the catalysed reaction has been completed, the product molecules may stay bound to the enzyme = the enzyme cannot form more product than the cell needs. it is NEGATIVE FEEDBACK |
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Term
| what do metabolic processes e.g. respiration, rely on? |
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Definition
| a series of enzyme-catalysed reactions |
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Term
| in a metabolic sequence, the product of one enzyme becomes... |
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Definition
| ...the substrate of another enzyme |
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Term
| what is the benefit of a metabolic sequence? |
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Definition
| it increases the efficiency of metabolic reactions without having to increase the substrate concentration & it reduces diffusion time |
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Term
| name 2 metabolic poisons that act as enzyme inhibitors |
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Definition
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Term
| what does cyanide inhibit? |
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Definition
| aerobic respiration & catalase |
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Term
| explain how cyanide acts as an inhibitor |
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Definition
| 1. KCN is hydrolysed to form hydrogen cyanide when ingested 2. hydrogen cyanide = very poisonous gas 3. hydrogen cyanide dissociates into H+ ions and CN- ions 4. CN- ions bind to enzymes found in mitochondria = inhibits final stage of aerobic respiration |
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Term
| what enzyme does snake venom inhibit? |
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Definition
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Term
| what is the job of acetylcholinesterase? |
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Definition
| it is necessary at neuromuscular synapses to break down acetlycholine (a neurotransmitter) |
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Term
| what happens if acetylcholinesterase is inhibited by snake venom? |
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Definition
| the acetlycholine stays in the synapse = muscles stay contraced = paralysis |
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Term
| name 5 medicinal drugs that act by enzyme inhibition |
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Definition
| 1. aspirin 2. ATPase inhibitors 3. ACE inhibitors 4. protease inhibitors 5. nucleoside reverse transcriptase inhibitors |
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Term
| what is the job of aspirin? |
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Definition
| to prevent the production of prostaglandins, which are cell signalling molecules that make nerve cells mores sensitive to pain when tissues are damaged |
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Term
| what does aspirin reduce the risk of? |
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Definition
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|
Term
| what is the job of ATPase inhibitors? |
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Definition
| to treat heart failure and atrial arrhythmia |
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Term
| how do ATPase inhibitors work? |
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Definition
| they inhibit the sodium potassium pump in the cell membranes of heart-muscle cells. allows more Ca2+ ions to enter = strengthens heart muscle |
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Term
| what do ACE inhibitors inhibit? |
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Definition
| the angiotension converting enzyme which increases blood pressure |
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Term
| name 2 advantages of taking ACE inhibitors |
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Definition
| 1. lowers blood pressure in patients with hypertension 2. minimises risk of second heart attack in people with myocardial infarction |
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Term
| what is the job of protease inhibitors? |
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Definition
| to treat some viral infections |
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Term
| how do protease inhibitors work? |
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Definition
| they prevent the replication of the virus particles within the host cell by inhibiting protease enzymes, often competitively |
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Term
| what are nucleoside reverse transcriptase inhibitors used to treat? |
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Definition
|
|
Term
| what enzymes do nucleoside reverse transcriptase inhibitors inhibit? using what? |
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Definition
| enzyme involved in making DNA, using the viral RNA as a template |
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Term
|
Definition
| a toxin which is ingested |
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