Chapter 2: Enzymes

Question 1

Enzymes:

Answer 1

Is a molecule with catalytic activity; that includes many proteins and some RNA molecules. • Are very important as biological catalysts. • Molecules that enzymes act upon are called substrates.

Question 2

Enzyme Specificity:

Answer 2

This is when a given enzyme will only catalyze a given reaction or a type of reaction.

Question 3

Catalysts:

Answer 3

This is a substance or enzyme that increases the rate of reaction by lowering activation energy. • Does not impact the thermodynamics of a biological reaction and the equilibrium position nor does the (ΔHrxn) change. • This makes the reaction proceed at a much faster rate.

Question 4

Enzymes can be classified into 6 categories which are:

Answer 4

Enzyme Classification: Oxidoreductases, Transferases, Hydrolases, Lyases, Isomerases, and Ligases: An enzyme that catalyzes the synthesis of a large polymeric biomolecules, most commonly nucleic acids.

Question 5

Oxidoreductases:

Answer 5

This is an enzyme that catalyzes an oxidation-reduction reaction, often using an electron carrier as a cofactor. ○ Examples of cofactors are: NAD+ or NADP+. ○ In reactions that are catalyzed by this, the electron donor is known as the reductant and the electron acceptor is known as the oxidant. ○ Enzymes with dehydrogenase or reductase in their names are usually oxidoreductase. ○ Enzymes with oxygen as the final electron acceptors will have oxidase in their name.

Question 6

Transferases:

Answer 6

This is an enzyme that catalyzes the transfer of a functional group. Kinase is an example. It catalyzes the transfer of a phosphate group generally from ATP, to another molecule.

Question 7

Hydrolases:

Answer 7

This is an enzyme that catalyzes the cleavage of a molecule with the addition of water. ○ It breaks the compound into two molecules. ○ Most hydrolases are named only for their substrate. ○ Example: phosphatase: which cleaves a phosphate group from another molecule. ○ Other examples: peptidases - breaks down proteins, nucleases - breaks down nucleic acids, and lipases - breaks down lipids.

Question 8

Lyases:

Answer 8

This is an enzyme that catalyzes the cleavage or synthesis of a molecule without the addition or loss of water. ○ Cleavage of a single molecule into two products.

Question 9

Isomerases:

Answer 9

This is an enzyme that catalyzes the constitutional or stereochemical rearrangement of a molecule.

Question 10

Ligases:

Answer 10

An enzyme that catalyzes the synthesis of a large polymeric biomolecules, most commonly nucleic acids. ○ These often require ATP.

Question 11

Exergonic + Endergonic Reactions:

Answer 11

Endergonic Reactions: This is a reaction that is one that requires energy input. (ΔG>0) Exergonic Reactions: This is a reaction that is one in which energy is given off. (ΔG<0)

Question 12

How do enzymes act:

Answer 12

Enzymes can act to provide a favorable microenvironment in terms of charge or pH, stabilize the transition state, or bring reactive groups nearer to one another in the active site.

Question 13

Substrate:

Answer 13

This is a molecule which an enzymes act upon. • The interaction between the enzymes and substrates is referred to as enzyme-substrate complex. These have active sites.

Question 14

Active Sites:

Answer 14

Part of substrates. This is the location within the enzyme where the substrate is held during the chemical reaction. § Site of catalysts.

Question 15

Two theories that explain how enzymes and substrates interact.

Answer 15

Two theories are lock and key theory, and the induced fit theory.

Question 16

Lock and key theory:

Answer 16

Talks about how the enzyme and substrate are exactly complementary. a. Basically, the enzymes active site (lock) is in an appropriate conformation for the substrate (key) to bind. b. It is like a puzzle.

Question 17

Induced Fit Theory:

Answer 17

Enzymes and substrates will undergo conformation changes to interact fully. a. Example is a stress ball. The substrate can be the student who has squeeze the ball and basically has induced a change in the shape of the enzyme (stress ball). The reaction requires energy to squeeze the ball and is endergonic. The ball is released in its original shape.

Question 18

Cofactor and Coenzyme act as what?

Answer 18

These act as activators of enzymes. These regulators induce conformational changes in the enzyme that promotes its activity.

Question 19

Cofactors: Coenzyme:

Answer 19

Coenzymes: An organic (vitamins) molecule that helps an enzyme carry out its function. Cofactors: An inorganic (minerals) molecule or ion that helps an enzyme carry out its function.

Question 20

How does temperature affect enzyme activity?

Answer 20

As the temperature increases, the enzyme activity increases. • If it is above body temperature, the enzyme activity will quickly drop and the enzyme will be denatured. • Ideal Temperature: 37 C, 98.6 F, and 310 K

Question 21

How does salinty affect enzyme activity?

Answer 21

Saltinty changes in this will disrupt bonds within the enzyme, causing disruption of tertiary and quaternary structure, which leads to loss of enzyme function.

Question 22

How are enzymes activated?

Answer 22

They are regulated by feedback Inhibition, reversible Inhibition, and irreversible Inhibition.

Question 23

Feedback Inhibition:

Answer 23

This is a regulatory mechanism where the catalytic activity of an enzyme is inhibited by the presence of high levels of a product later in the same pathway.

Question 24

Reversible Inhibition:

Answer 24

This is the ability to replace the inhibitory with a compound of greater affinity or to remove it using mild laboratory treatment. There are four types: Competitive Inhibition, Noncompetitive Inhibition, Mixed Inhibition, and Uncompetitive Inhibition.

Question 25

Competitive Inhibition:

Answer 25

This results when the inhibitor is similar to the substrate and binds at the active site. This can be overcome by adding more substrate. a. The Vmax is unchanged, as Km increases.

Question 26

Noncompetitive Inhibition:

Answer 26

This results when the inhibitor binds with equal affinity to the enzyme and the enzyme-substrate complex. a. Vmax is decreased, and Km is unchanged.

Question 27

Mixed Inhibition:

Answer 27

This results when the inhibitory binds with unequal affinity to the enzyme and the enzyme-substrate complex. a. The Vmax is decreased, the Km is either it just depends on whether the inhibitor has higher affinity for the enzyme or enzyme-substrate complex.

Question 28

Uncompetitive Inhibition:

Answer 28

This results when the inhibitor binds only with the enzyme-substrate complex. a. Km and Vmax both decrease.

Question 29

Irreversible Inhibition:

Answer 29

This refers to the prolonged or permanent inactivation of an enzyme, such that it cannot be easily renatured to gain function.