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40 Cards in this Set

  • Front
  • Back

What are enzymes classified as?


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

What is a major exception of enzymes being catalysts?

Ribozymes are RNA molecules that act as catalysts

What are the typical rate of enhancements of enzymes to a biochemical reaction?

10^8 to 10^12 are typical enzymes

T or F: Enzymes do not have an active site


What happens to enzymes at the active site?

Substrates bind to enzymes at the active site

What are serine proteases an exemplary class of?

Enzymes that have a common set of amino acids in their active site

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

What are enzymes usually named after?

The reaction that they catalyze

What does pyruvate decarboxylase do?

Removes a carboxylate group from the substrate pyruvate

What are ribozymes?

RNA molecules that act as catalysts

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

How can heat be added to a chemical reaction?

Adding energy in the form of heat

What determines the rate of a reaction?

The height of the activation energy barrier

What happens when the activation energy barrier is higher?

Less likely the reaction is to occur

What is the transition state?

The point of the highest energy of a reation

What is the symbol for activation energy?


What does the sign deltaG represent?

The spontaneity of a reaction, not how fast the reaction occurs

What does deltaG < 0 mean?

Spontaneous reaction

What does deltaG > 0 mean?

Non-spontaneous reaction

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

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

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

How do enzymes work?

By lowering the activation energy of a reaction

How do enzymes lower the activation energy?

By stabilizing and lowering the energy of the transition state

What cofactors do enzymes use to aid in catalysis?

Metal ions



Prosthetic groups

T or F: An enzyme can use acid catalysis, base catalysis, or both


What happens in acid-base catalysis?

Enzyme can manipulate the movement of protons that are donated or accepte

What is another named for a covalent catalysis?=

Nucleophilic catalysis

What happens in metal ion catalysis?

Mediate redox catalysis

What occurs in general acid catalysis?

H+ transfers from an acid to lower the free energy of the transition state

What occurs in general base catalysis?

H+ is abstracted by a base to lower the free energy of the transition state

T or F: All amino acids can play a role in acid-base catalysis

False, only som

What six amino acids can play a role in acid-base catalysis?

1. Asp

2. Glu

3. His

4. Lys

5. Cys

6. Tyr

What occurs in covalent catalysis?

Covalent E-S intermediate is formed

What do covalent catalysts do?

Accelerate reactions by forming a covalent bong between E and S

What three amino acids are in the activation sites of chymotrypsin?

1. His

2. Ser

3. Asp

What stabilizes the transition state?


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

What is induced fit?

When hexokinase binds to glucose (the substrate), a conformational change occurs in the enzyme to "fit" the substrate better