A deck of flashcards for Undergraduate Study of Biology.
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| Catalyst | A substance/chemical agent that increases the rate of a chemical reaction without itself undergoing any permanent chemical change.
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| Enzyme | Biological molecules (proteins) that helps complex reactions. They are catalytic globular proteins. They catalyze metabolic reactions by lowering energy barriers (activation energy), without effecting the thermodynamics of the reaction.
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| Thermodynamics | A branch of science concerned with heat and temperature and their relation to energy and work.
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| Classification of enzymes | All enzymes are classified into 6 groups which indicates the type of chemical reaction catalyzed by the enzymes. Classes include hydrolase, isomerase, ligase or polymerase, lyase, oxidoreductase and transferase.
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| Hydrolase | A class of enzyme that catalyzes hydrolysis reactions (catabolic).
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| Isomerase | A class of enzyme that catalyzes rearrangement of atoms within a molecule (neither catabolic or anabolic).
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| Ligase or polymerase | A class of enzyme that catalyzes joining two or more chemicals together (anabolic).
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| Lyase | A class of enzyme that catalyzes splitting a chemical into smaller parts without using water (catabolic).
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| Oxidoreductase | A class of enzyme that catalyzes transfer of electrons or hydrogen atoms from one molecule to another.
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| Transferase | A class of enzyme that catalyzes movement of a functional group from one molecule to another (may be anabolic).
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| Active site | A region on an enzyme that binds to a protein or other substance during a reaction. Relative to the overall size of the enzyme molecule, it is a small region where the substrate binds (typically a pocket or a groove).
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| Enzyme substrate | A reactant that an enzyme acts on.
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| Enzyme-substrate complex | The intermediate formed when a substrate molecule interacts with the active site of an enzyme. Following the formation of an enzyme–substrate complex, the substrate molecule undergoes a chemical reaction and is converted into a new product.
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| What bonds are formed temporarily during enzyme-substrate complex? | Hydrogen bonds and ionic bonds.
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| Where do bonds form during enzyme-substrate complex? | Between the substrate molecule with the R groups of the amino acids of the active site and groups on the substrate molecules.
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| Activation energy (EA) (free energy of activation) | The minimum energy which must be available to a chemical system with potential reactants to result in a chemical reaction. It makes the reactants unstable, increases the speed of reactant molecules and creates more powerful collisions.
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| Gibb's free energy of activation | The difference between free energy of the products and the free energy of the reactants. ΔG = EA (products)– EA (reactants)
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| The transition state | The summit of enzyme reaction diagrams where the molecules are at an unstable point.
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| Proportionality of the reaction rate of enzyme | The reaction rate is proportional to the fraction of molecules that have a free energy ≥ ΔG.
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| Does enzyme affect the change in free energy (ΔG)? | No, they do not. They only quicken the reactions that would occur eventually.
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| What are the two hypotheses that explain the specificity of enzymes? | The specificity of binding depends on the arrangement of atoms in an active site. One hypothesis is Emil Fischer's lock and key hypothesis, while the other is Koshland induced fit hypothesis.
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| Emil Fischer's lock and key hypothesis | The active site has a distinct configuration which only allows a specific substrate to fit into it. The shape of the active site, and positions of different chemical groups only allow complementary structures to bind to the enzyme.
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| Problems with Emil Fischer's lock and key hypothesis | This model does not take into account the conformational flexibility of proteins.
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| In Emil Fischer's lock and key hypothesis, which is represents the key and which represents the lock? | The substrate acts as a key and the enzyme acts as the lock.
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| Koschland induced fit hypothesis | Suggests that the enzyme actually changes its form slightly to fit the shape of the substrate which is caused by binding of the substrate where as the substrate approaches, the enzyme makes small changes to its shape around the active site.
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| Enzyme kinetics | The study of the chemical reactions that are catalysed by enzymes. In enzyme kinetics, the reaction rate is measured and the effects of varying the conditions of the reaction are investigated.
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| What are the 2 events most frequently measured in enzyme kinetics? | The formation of products of the reactions and the disappearance of substrate.
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| Effect of temperature on enzymes | Each enzyme has an optimal temperature in which it can function. Increase in temperature increases the kinetic energy of molecules where collisions between substrates and active sites of enzymes are more rapid and frequent; the rate of reaction increase.
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| Would an increase in temperature always increase the rate of reaction? |
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