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32 Cards in this Set
- Front
- Back
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How do cells perform energy transformations?
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Chemical reactions
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What do chemical reactions involve?
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Breaking of bonds in reactants and forming of bonds in products
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What must the cell overcome in order for the any reaction to take place?
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Activation (free) energy barrier
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What would happen without this activation (free) energy barrier?
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There would be spontaneous and uncontrolled reactions.
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How must the reactants overcome this barrier?
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They must absorb energy...known as Activation Energy (Ea)
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How and when is the energy supplied?
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It is supplied by ATP during phosphorylation
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What happens to the reactions as a result of absorption of energy?
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Reactants become unstable; are in the activated state (transition state)
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What happens when reactants are in the transition state?
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They can react with one another
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If ^G is negative
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Reaction is exergonic, Gi is greater than Gf.
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What is used to reduce activation energy (Ea)?
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Enzyme
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What is an enzyme
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A catalytic protein that increases the velocity (rate) of a reaction without itself being changed in the process.
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Specificity
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A function of an enzyme's unique 3-D globular shape, which is determined by the tertiary conformation of this protein molecule.
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Substrate
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Type of molecule on which a given enzyme acts
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Active Site
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Location on which Enzyme Interacts with its substrate
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What happens while the enzyme is bound?
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The enzyme is catalyzing the reaction.
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What happens when there is a reaction of an enzyme specific for 2 different substrates?
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Each substrate binds to an active site, and 2 different products are yielded and released.
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Lowering Ea 1-Stress
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The enzyme stresses the bound substrate molecule by bending the bonds that need to be broken, so less Ea is required
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Lowering Ea 2- Orient
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Orients 2 different substrate molecules optimally for the reaction to occur
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Lowering Ea 3-Provides
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Provides the microenvironment with optimal conditions for the reaction
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How does temperature affect the activity of an enzyme and the catalyzed reaction?
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Each enzyme has an optimal temperature for catalyzing a specific reaction. An increase in temperature causes molecules to collied with the active site more quickly, speeding up the rate of the reactioin. It causes denaturation
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Denaturation
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Loss of natural molecular configuration, with accompanying loss of catalytic capacity.
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How does pH affect the activity of an enzyme and the catalyzed reaction?
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There is an optimal value for pH and if the pH deviates too much from this, then denaturation occurs.
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How do cofactors affect the activity of an enzyme and the catalyzed reaction?
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They assist the enzyme. They may bind permanently with the enzyme, or reversibly along with the substrate molecule at the active site of the enzyme molecule. May be organic or inorganic.
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How does substrate concentration affect the activity of an enzyme and the catalyzed reaction?
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At very low substrate concentration, increases in the velocity of the reaction are linearly proportional to increases in substrate concentration. At very high [S], increases in [S] have minimal effects on the reaction velocity (rate)
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Vmax
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Maximum velocity at saturating [S]. At this value of [S], every enzyme molecule is almost continuously occupied in the process of catalysis
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Km
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Michaelis constant. At this value, v=1/2vmax.
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What do we know about the inflection point of the plot?
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It is the value of [S] at which we note that increases in [S] begin to have diminished the impact on velocity (v)
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What can we do, knowing the km value of a reaction?
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We can extimate how "good" and enzyme is, in the sense that the lower the Km value, the lower the [S] range in which the enzyme is effective
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What affect to inhibiotrs and effectors have on the activity of an enzyme and the catalyzed reaction?
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They affect the activity (capacity) of the enzyme molecule.
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Irreversible inhibitor
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binds covalently to the enzyme molecule, causing an irrevocable loss of catalytic activity. They are usually toxic to cells.
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What are found in irreversible inhibitors
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Heavy metal ions. The lethality of both pesticides and nerve gases is a function of their irreversible inhibitions of respective enzymes. Penicillion irreversibly inhibits an enzyme essential to cell wall formation in certain species of bacteria.
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Reversible Inhibitors
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Form easily dissociable bonds with enzyme milecules. The two most common forms are competitive and noncompetitive
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