Lab 3 - Enzyme Kinetics

Question 1

Activation Energy

Answer 1

additional energy that molecules must acquire in order to react; the difference between the energy of the transition state and the energy of the reactants or products
- the rate of a reaction increases as the height of the barrier decreases because, at any given temperature, only a fraction of the collisions between molecules have sufficient energy to surmount the barrier and produce a reaction

Question 2

Active sites on an enzyme

Answer 2

The closeness of fit between a substrate molecule and the enzyme’s active site enables binding and the formation of an enzyme-substrate complex
- The closeness of fit between substrate molecule and the enzyme’s active site enables binding and the formation of an enzyme-substrate complex

Question 3

Enzyme-Substrate Complexes

Question 4

Lock and Key Mechanism

Answer 4

the substrate matches the active site just as a key matches a lock
- does not explain the reversibility of enzyme-catalyzed reactions
- if the enzyme fits the substrate, then it cannot also fit the product for the reverse reaction

Question 5

Induced Fit Mechanism

Answer 5

the substrate fits active site more like foot fits a sock than lock fits a key (shapes are similar but not precisely complementary)
- when the substrate binds to an enzyme, it induces a conformational change in the enzyme to produce a better fit (like a sock fits a foot)
- both the substrate and the product can bind to the active site, allowing the reaction to proceed in reverse

Question 6

Naming of Enzymes

Question 7

Effects of pH and temperature on rates on enzyme-catalyzed reactions

Answer 7

Changes in temperature and pH alter the structure of all proteins; thus such changes alter the shape, and therefore the activity, of enzymes
- enzyme activities decline if the temperature of pH becomes significantly higher/lower than normal

Question 8

Cofactors and coenzymes

Answer 8

Cofactors: nonprotein components of some enzymes necessary for them to hold normal conformation during metabolic reactions
Coenzymes: molecules that do not themselves have catalytic activity but that are necessary for proper enzyme function and participate directly in reactions catalyzed by enzymes; often serve to transfer certain chemical groups from one reactant to another

Question 9

End-product Inhibition

Answer 9

when the allosteric inhibitor in feedback inhibition is the end-product of the metabolic pathway

Question 10

Allosteric and Covalent Regulation of Enzyme Activity

Answer 10

Allosteric Regulation: regulatory mechanism in which a modulator binds reversibly to the regulatory site (binding site) on an enzyme, inducing a change in its conformation and activity (catalytic rate and/or affinity for substrate)
- weak

Covalent Regulation: regulatory mechanisms in which changes in an enzyme’s activity are brought about by the covalent bonding of a specific chemical group to a site on the enzyme molecule; usually involves bonding of a phosphate group
- strong

Question 11

Describe the factors which influence reaction rates

Question 12

Explain the role of enzymes with regard to chemical reactions

Question 13

Describe the factors which influence enzymatic rates

Question 14

Explain the factors which influence enzyme regulation

Question 15

Describe how and why temperature and PH influence lactate dehydrogenase