Chapter 6 - How Enzymes Work

Front 1

What are enzymes classified as?

Back 1

Catalysts

Front 2

What is an enzyme?

Back 2

Usually a protein that acts as a catalyst to speed up the rate of a chemical reaction without being consumed itself

Front 3

What is a major exception of enzymes being catalysts?

Back 3

Ribozymes are RNA molecules that act as catalysts

Front 4

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

Back 4

10^8 to 10^12 are typical enzymes

Front 5

T or F: Enzymes do not have an active site

Back 5

False

Front 6

What happens to enzymes at the active site?

Back 6

Substrates bind to enzymes at the active site

Front 7

What are serine proteases an exemplary class of?

Back 7

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

Front 8

What are the characteristics of chymotrypsin?

Back 8

Hydrolyzed peptide bonds after Phe, Tyr, and Trp

Hydrolyzes other amide or ester bonds after Phe, Tyr, or Trp

Front 9

What are enzymes usually named after?

Back 9

The reaction that they catalyze

Front 10

What does pyruvate decarboxylase do?

Back 10

Removes a carboxylate group from the substrate pyruvate

Front 11

What are ribozymes?

Back 11

RNA molecules that act as catalysts

Front 12

What are the three ways to increase the rate of a chemical reaction?

Back 12

1. Increasing the temperature

2. Increasing the concentration of the reacting substances

3. Adding a catalyst

Front 13

How can heat be added to a chemical reaction?

Back 13

Adding energy in the form of heat

Front 14

What determines the rate of a reaction?

Back 14

The height of the activation energy barrier

Front 15

What happens when the activation energy barrier is higher?

Back 15

Less likely the reaction is to occur

Front 16

What is the transition state?

Back 16

The point of the highest energy of a reation

Front 17

What is the symbol for activation energy?

Back 17

deltaG+

Front 18

What does the sign deltaG represent?

Back 18

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

Front 19

What does deltaG < 0 mean?

Back 19

Spontaneous reaction

Front 20

What does deltaG > 0 mean?

Back 20

Non-spontaneous reaction

Front 21

Describe the free energy of a spontaneous reaction

Back 21

The reactants cause the free energy to increase, then the free energy drastically decreases into the products resulting in free energy being significantly lower

Front 22

Why is the deltaG for a spontaneous reaction negative?

Back 22

When the free energy decreases, it lowers below the starting free energy, resulting in a negative deltaG

Front 23

Describe the free energy of a non-spontaneous reaction

Back 23

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

Front 24

How do enzymes work?

Back 24

By lowering the activation energy of a reaction

Front 25

How do enzymes lower the activation energy?

Back 25

By stabilizing and lowering the energy of the transition state

Front 26

What cofactors do enzymes use to aid in catalysis?

Back 26

Metal ions

Coenzymes

Cosubstrates

Prosthetic groups

Front 27

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

Back 27

Tru

Front 28

What happens in acid-base catalysis?

Back 28

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

Front 29

What is another named for a covalent catalysis?=

Back 29

Nucleophilic catalysis

Front 30

What happens in metal ion catalysis?

Back 30

Mediate redox catalysis

Front 31

What occurs in general acid catalysis?

Back 31

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

Front 32

What occurs in general base catalysis?

Back 32

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

Front 33

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

Back 33

False, only som

Front 34

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

Back 34

1. Asp

2. Glu

3. His

4. Lys

5. Cys

6. Tyr

Front 35

What occurs in covalent catalysis?

Back 35

Covalent E-S intermediate is formed

Front 36

What do covalent catalysts do?

Back 36

Accelerate reactions by forming a covalent bong between E and S

Front 37

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

Back 37

1. His

2. Ser

3. Asp

Front 38

What stabilizes the transition state?

Back 38

Enzyme

Front 39

What is the proximity and orientation effect?

Back 39

When enzymes bind substrates, the substrates are brought into proximity and in the correct orientation to make a chemical reaction favorable

Front 40

What is induced fit?

Back 40

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