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40 Cards in this Set
- Front
- Back
What are enzymes classified as? |
Catalysts |
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What is an enzyme? |
Usually a protein that acts as a catalyst to speed up the rate of a chemical reaction without being consumed itself |
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What is a major exception of enzymes being catalysts? |
Ribozymes are RNA molecules that act as catalysts |
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What are the typical rate of enhancements of enzymes to a biochemical reaction? |
10^8 to 10^12 are typical enzymes |
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T or F: Enzymes do not have an active site |
False |
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What happens to enzymes at the active site? |
Substrates bind to enzymes at the active site |
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What are serine proteases an exemplary class of? |
Enzymes that have a common set of amino acids in their active site |
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What are the characteristics of chymotrypsin? |
Hydrolyzed peptide bonds after Phe, Tyr, and Trp Hydrolyzes other amide or ester bonds after Phe, Tyr, or Trp |
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What are enzymes usually named after? |
The reaction that they catalyze |
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What does pyruvate decarboxylase do? |
Removes a carboxylate group from the substrate pyruvate |
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What are ribozymes? |
RNA molecules that act as catalysts |
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What are the three ways to increase the rate of a chemical reaction? |
1. Increasing the temperature 2. Increasing the concentration of the reacting substances 3. Adding a catalyst |
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How can heat be added to a chemical reaction? |
Adding energy in the form of heat |
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What determines the rate of a reaction? |
The height of the activation energy barrier |
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What happens when the activation energy barrier is higher? |
Less likely the reaction is to occur |
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What is the transition state? |
The point of the highest energy of a reation
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What is the symbol for activation energy? |
deltaG+ |
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What does the sign deltaG represent? |
The spontaneity of a reaction, not how fast the reaction occurs |
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What does deltaG < 0 mean? |
Spontaneous reaction |
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What does deltaG > 0 mean? |
Non-spontaneous reaction |
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Describe the free energy of a spontaneous reaction |
The reactants cause the free energy to increase, then the free energy drastically decreases into the products resulting in free energy being significantly lower |
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Why is the deltaG for a spontaneous reaction negative? |
When the free energy decreases, it lowers below the starting free energy, resulting in a negative deltaG |
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Describe the free energy of a non-spontaneous reaction |
As the reactants begin the reaction, the free energy increases then after peaking it slightly decreases into the products, but never going below the beginning free energy, resulting in a positive deltaG |
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How do enzymes work? |
By lowering the activation energy of a reaction |
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How do enzymes lower the activation energy? |
By stabilizing and lowering the energy of the transition state |
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What cofactors do enzymes use to aid in catalysis? |
Metal ions Coenzymes Cosubstrates Prosthetic groups |
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T or F: An enzyme can use acid catalysis, base catalysis, or both |
Tru |
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What happens in acid-base catalysis? |
Enzyme can manipulate the movement of protons that are donated or accepte |
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What is another named for a covalent catalysis?= |
Nucleophilic catalysis |
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What happens in metal ion catalysis? |
Mediate redox catalysis |
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What occurs in general acid catalysis? |
H+ transfers from an acid to lower the free energy of the transition state |
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What occurs in general base catalysis? |
H+ is abstracted by a base to lower the free energy of the transition state |
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T or F: All amino acids can play a role in acid-base catalysis |
False, only som |
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What six amino acids can play a role in acid-base catalysis? |
1. Asp 2. Glu 3. His 4. Lys 5. Cys 6. Tyr |
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What occurs in covalent catalysis? |
Covalent E-S intermediate is formed |
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What do covalent catalysts do? |
Accelerate reactions by forming a covalent bong between E and S |
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What three amino acids are in the activation sites of chymotrypsin? |
1. His 2. Ser 3. Asp |
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What stabilizes the transition state? |
Enzyme |
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What is the proximity and orientation effect? |
When enzymes bind substrates, the substrates are brought into proximity and in the correct orientation to make a chemical reaction favorable |
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What is induced fit? |
When hexokinase binds to glucose (the substrate), a conformational change occurs in the enzyme to "fit" the substrate better |