Enzyme Catalysts

Question 1

Enzyme complications in cystic fibrosis

-treatment

Answer 1

-a neutrophil mediated inflammatory response releases elastase which contributes to lung destruction -blockage of the pancreatic ducts leads to insufficient digestive pancreatic enzymes which leads to malabsorption of fat
and proteins
-treatment: nebulized antibiotics and supplemental enzymes

Question 2

oxidoreductases

Answer 2

oxidation-reduction reactions

Question 3

transferases

Answer 3

transfer of a chemical group

Question 4

hydrolases

Answer 4

lysis by water

Question 5

lyases

Answer 5

a cleavage reaction not using water

Question 6

isomerases

Answer 6

change of molecular confirmation

Question 7

ligases

Answer 7

joining of two compounds

Question 8

serine proteases

Answer 8

• proteolytic enzymes that catalyze peptide bond hydroplysis

- include pancreatic enzymes: chymotrypsin, trypsin, elastase, adn neutrophil elastase

Question 9

Specificity of serine proteases

Answer 9

-not only specific for binding peptides, but also have specificity pockets for preferantially binding certain amino acids

Question 10

active site

Answer 10

• usually a crevice on the surface of the enzyme

- comprises amino acids that bind the substrate and those that catalyze the reaction

Question 11

summary of mechanism for serine protease

Answer 11

• correct substrate is bound in the correct orientation (serine is made unusually reactive)
• attack by a serine
• oxyanion formed in the transition state is stabilized by the enzyme
• product release

Question 12

Gibbs Free Energy (delta G)

Answer 12

• intrinsic energy to certain compounds.
• a drop indicates that a more stable form has been achieved
• spontaneous reactions have a negative delta G, reactions that flow in the opposite direction have a positive
• sensitive to concentration of reactants and products
• standard conditions: certain temp, 1M concentrations except for H+ (ph=7)

Question 13

at equilibrium, Q=
When Q>Keq
When Q

Answer 13

Keq
the reaction goes in reverse
the reaction moves forward

Question 14

when delta G =0

Answer 14

the reaction is in equilibrium

Question 15

differences between biochemical and chemical reactions

Answer 15

• reactions in the body are not in equilibrium, we are burning fuel to keep it this way
• removing product can shift equilibrium
• reactions in the bod proceed under very non-standard conditions

Question 16

the free energy of activation

-enzymes role

Answer 16

• the amount of energy necessary to put into a reaction toget it to go a certain way
• this is the change in energy between the reactant (substrate) and the transition state
• enzymes act to reduce the energy of the transition state,

Question 17

stabilization of the transition state by a catalyst

Answer 17

• lowers the activation barrier, increasing the attainment of equilibrium
• catalyst does not change the free energy of the substrate of product
• does not alter the equilibrium ratio

Question 18

catabolism vs anabolism

Answer 18

• catabolism burns fuel to generate ATP

- anabolic: burning ATP for biosynthetic processes, active transport, or mechanical work

Question 19

coupled reactions

Answer 19

• enzymes will couple the hydrolysis of ATP with another, less favorbale reaction
• this uses the energy produced from ATP hydrolysis to drive the other reaction

Question 20

example of a coupled reaction

Answer 20

• hexokinase uses hydrolysis of ATP to add a phosphate to glucose, creating glucose-6-phosphate
• if you sum the delta G’s, it comes up negative, suggesting the forward reaction is favored overall.

Question 21

enzyme velocity

Answer 21

-the amount of product formed per unit time

Question 22

Km

Answer 22

• the concentration of substrate that it takes to reach half of Vmax
• this does not change with the addition of more substrate
• larger Km’s reflect a lower enzyme to substrate affinity

Question 23

Vmax

Answer 23

• this is the maximum amount of product per unit time that a certain amount of enzyme can pump out.
• Vmax is directly proportional to the amount of enzyme present

Question 24

Lineweaver Burk plot

-y and x intercepts

Answer 24

• this is a linear plot
• also known as the double reciprocal plot
• 1/v=(Km/Vmax) 1/[S]+1/Vmax
• y intercept = 1/Vmax
• x intercept = -1/Km

Question 25

active site of chymotrypsin

Answer 25

is hydrophobic and open therefore it binds buly hydrophobic residues

Question 26

trypsin active site

Answer 26

has a negatively charged Asp, therefore it binds positively charged molecules

Question 27

Elastase active site

Answer 27

has a Val and Thr which narrow the crevice of the active site, only allowing small amino acids such as Gly, Ala, and Val to bind

Question 28

Energy stored in ATP

Answer 28

There are two possible high energy bond cleavages in ATP

• ATP to ADP and ADP to AMP
• this releases about 13 kcal/mol