Enzymes

Question 1

How do enzymes catalyze the biochemical reactions?

Answer 1

By lowering the activation energy needed for the reaction.

Question 2

How do cofactors, coenzymes and inhibitors regulate the chemical reactions?

Answer 2

Competitively binding to the active site of the enzymes or non-competitively binding to the allosteric side of the enzyme.

Question 3

What is allosteric site of an enzyme?

Answer 3

Alternate part of the enzyme that non-substrate molecules bind

Question 4

Does enzymes change G of the reaction

Answer 4

No, bcuz they don’t change the free energy of the reactants or products, they only change the activation energy required to reach the transition state

Question 5

Which parts of the enzymes are very specific to substrates and why ?

Answer 5

Active sites of the enzymes, bcuz the R groups in amino acid chains of active sites have their specific properties, polar non polar acidic or basic…., the specificity of the enz to the substrates depend on the interaction of R groups and the substrates

Question 6

Why is optimal environmental ranges require for the enzyme catalyzed reactions.

Answer 6

Bcuz outside the optimal range, enzymes can reduce its capacity to bind to the substrates. And in extreme temp and pH enzymes can denature and lose their function

Question 7

What is the induced fit model of the enzyme catalyzed reactions?

Answer 7

Enzymes and substrates do not bind together instantly once they come together, there will be mild changes in enzyme’s active sites so that active sites of the enz and substrates will be fitted to each other perfectly.

Question 8

What is competitive inhibition?

Answer 8

Inhibitor molecules are very similar to substrate and competitively bind to the substrate binding site on the enzyme. So, substrate cant bind to the active site, the reaction is inhibited.

Question 9

What is allosteric inhibition?

Answer 9

Also called the non competitive inhibition. Inhibitor binds to the non active site of the enzyme, but change the configuration of the active site, thus reducing enzyme binding capacity to the substrate.

Question 10

How does competitive and non competitive inhibition differ?

Answer 10

Competitive inhibition affect the initial rate of reaction but does not affect the maximal rate whereas non competitive inhibitor affect the rate.

Question 11

What’s the mechanism of permacutical drugs?

Answer 11

Pharmaceutical drugs are inhibitors of certain enzymes in the body.
Statins drug group- inhibitors of HMG CoA reductase which synthesize cholesterol from the body lipids.

Question 12

What are cofactors?

Answer 12

Inorganic molecules such as iron, magnesium and zinc.

Question 13

What cofactors DNA polymerase needs in DNA replication?

Answer 13

Bound ZInc.

Question 14

What are coenzymes?

Answer 14

Organic molecules, made up oof carbon and hydrogen.

Question 15

What’s the common source of coenzyme?

Answer 15

Dietary vitamins. Vitamins can be precursors of coenzymes or function as coenzyme itself

Question 16

What are the names of cofactor and coenzymes that help in the catalysis of pyruvate dehydrogenase?

Answer 16

Cofactor—magnesium(Mg++)
Coenzymes-5 different kinds of coenzymes for the specific chemical reaction.

Question 17

How are substrates held to the active site of the enzymes?

Answer 17

By weak interactions such as hydrogen bonds and ionic bonds.

Question 18

Can enzymes catalyze in reversible reactions?

Answer 18

Yes, depending on which direction G is

Question 19

How can you overcome competitive inhibition?

Answer 19

By increasing the amount of substrates so that more conc of substrates can increase the chance of substrates binding to the active site.

Question 20

At the end of the reaction, enzymes concentration lowered. T or F

Answer 20

False. Enzyme are not consumed in a reaction

Question 21

What is the activation energy and transition state?

Answer 21

Activation energy- amount of energy required to reach the transition states,

Transition state- the state where the reactants can break the bonds and form the new bonds to produce products.

In exergonic reaction, heat is required to reach this transition state, where the reactants are most unstable and energy is released as heat after the products are formed

Question 22

Enzyme can catalyze both reversible reactions depending on the direction of ———

Answer 22

Delta G, free energy ———> exergonic reaction

Question 23

When the concentration of enzyme is full, addition of another substrate molecules is ——-

Answer 23

Uneffective, the only way to increase the rate of reaction is the addition of the enzymes

Question 24

The rate of reaction depends on ———-

Answer 24

The amount of the products released from the reactants

Question 25

The rate of reaction increases when the ——— increases.

Answer 25

Temperature, bcuz substrates collide more Temperature but the temp must be within optimal range. Extreme====> enzymes denaturation

Question 26

Enzyme inhibition are irreversible, t or f

Answer 26

Sometimes reversible, sometimes irreversible Reversible ——-> bond to enxyme with the weak interactions Irreversible- bond with covalent bonding

Question 27

Competitive inhibition can be overcome by ——-

Answer 27

Increasing the amount of substrate

Question 28

Penicillin block the enzyme that ———

Answer 28

Bacteria use to make cell walls

Question 29

Enzyme inhibition are always harmful

Answer 29

False. Drugs are enzyme inhibitors Statin- inhibitor of cholesterol synthesis

Question 30

Enzyme mutations are always harmful.

Answer 30

False, some enzymes mutate in their active sites,———> bind to different substrate and catalyze a new reaction. If the new func benefits the organism, natural selection favor that process—-> enzymes persist in the population

Question 31

What is cooperativity

Answer 31

One substrate binds to the enzyme——> change the shape of other active sites in an enzyme——> stimulating other substrates to bind to that site Cooperativity is considered to be allosteric activation bcuz substrate binding in its active site, is not the active site of other substrates. Eg HB- one O2 binds to one subunit- the other subunits activity increases and vice versa

Question 32

Can RNA act as enzymes

Answer 32

Yes. Ribozymes

Question 33

An enzyme can only bind one reactant at a time . T or F

Answer 33

False . But typically binds to one substrate at a time only,

Question 34

Enzymes are specific to ————

Answer 34

Specific molecules only

Question 35

How do enzymes catalyze the biochemical reactions?

Answer 35

By lowering the activation energy needed for the reaction.

Question 36

How do cofactors, coenzymes and inhibitors regulate the chemical reactions?

Answer 36

Competitively binding to the active site of the enzymes or non-competitively binding to the allosteric site of the enzyme.

Question 37

What is allosteric site of an enzyme?

Answer 37

Alternate part of the enzyme that non-substrate molecules bind.

Question 38

Does enzymes change ΔG of the reaction?

Answer 38

No, because they don’t change the free energy of the reactants or products, they only change the activation energy required to reach the transition state.

Question 39

Which parts of the enzymes are very specific to substrates and why?

Answer 39

Active sites of the enzymes, because the R groups in amino acid chains of active sites have their specific properties, polar, non-polar, acidic, or basic. The specificity of the enzyme to the substrates depends on the interaction of R groups and the substrates.

Question 40

Why is optimal environmental ranges required for enzyme-catalyzed reactions?

Answer 40

Because outside the optimal range, enzymes can reduce their capacity to bind to the substrates. In extreme temperature and pH, enzymes can denature and lose their function.

Question 41

What is the induced fit model of enzyme-catalyzed reactions?

Answer 41

Enzymes and substrates do not bind together instantly once they come together; there will be mild changes in enzyme’s active sites so that active sites of the enzyme and substrates will fit perfectly.

Question 42

What is competitive inhibition?

Answer 42

Inhibitor molecules are very similar to substrates and competitively bind to the substrate binding site on the enzyme. So, substrate can't bind to the active site, and the reaction is inhibited.

Question 43

What is allosteric inhibition?

Answer 43

Also called non-competitive inhibition. The inhibitor binds to the non-active site of the enzyme but changes the configuration of the active site, thus reducing enzyme binding capacity to the substrate.

Question 44

How does competitive and non-competitive inhibition differ?

Answer 44

Competitive inhibition affects the initial rate of reaction but does not affect the maximal rate, whereas non-competitive inhibition affects the maximal rate.

Question 45

What’s the mechanism of pharmaceutical drugs?

Answer 45

Pharmaceutical drugs are inhibitors of certain enzymes in the body. Statins drug group - inhibitors of HMG CoA reductase which synthesizes cholesterol from body lipids.

Question 46

What are cofactors?

Answer 46

Inorganic molecules such as iron, magnesium, and zinc.

Question 47

What cofactors does DNA polymerase need in DNA replication?

Answer 47

Bound Zinc.

Question 48

What are coenzymes?

Answer 48

Organic molecules made up of carbon and hydrogen.

Question 49

What’s the common source of coenzymes?

Answer 49

Dietary vitamins. Vitamins can be precursors of coenzymes or function as coenzymes themselves.

Question 50

What are the names of cofactor and coenzymes that help in the catalysis of pyruvate dehydrogenase?

Answer 50

Cofactor—magnesium (Mg++), Coenzymes—5 different kinds for specific chemical reactions.

Question 51

How are substrates held to the active site of enzymes?

Answer 51

By weak interactions such as hydrogen bonds and ionic bonds.

Question 52

Can enzymes catalyze reversible reactions?

Answer 52

Yes, depending on the direction of ΔG.

Question 53

How can you overcome competitive inhibition?

Answer 53

By increasing the amount of substrate so that a higher concentration of substrate increases the chance of binding to the active site.

Question 54

At the end of the reaction, is enzyme concentration lowered? (T/F)

Answer 54

False. Enzymes are not consumed in a reaction.

Question 55

What is activation energy and transition state?

Answer 55

Activation energy—amount of energy required to reach the transition state. Transition state—the state where reactants can break bonds and form new bonds to produce products.

Question 56

When the concentration of enzyme is full, addition of another substrate molecule is ———

Answer 56

Ineffective, the only way to increase the rate of reaction is the addition of enzymes.

Question 57

The rate of reaction depends on ———-

Answer 57

The amount of product released from reactants.

Question 58

The rate of reaction increases when ——— increases.

Answer 58

Temperature, but it must be within the optimal range. Extreme temperature leads to enzyme denaturation.

Question 59

Are enzyme inhibitions always irreversible? (T/F)

Answer 59

Sometimes reversible, sometimes irreversible. Reversible—inhibitor bonds with weak interactions, Irreversible—bonds with covalent bonding.

Question 60

How can competitive inhibition be overcome?

Answer 60

By increasing the amount of substrate.

Question 61

Penicillin blocks the enzyme that ———

Answer 61

Bacteria use to make cell walls.

Question 62

Are enzyme inhibitions always harmful? (T/F)

Answer 62

False. Drugs are enzyme inhibitors. Example: Statins inhibit cholesterol synthesis.

Question 63

Are enzyme mutations always harmful? (T/F)

Answer 63

False. Some enzymes mutate in their active sites, allowing them to bind to different substrates and catalyze new reactions. If beneficial, natural selection favors them.

Question 64

What is cooperativity?

Answer 64

One substrate binds to the enzyme → changes the shape of other active sites → stimulates other substrates to bind. Cooperativity is considered allosteric activation. Example: Hemoglobin—one O₂ binds to one subunit, increasing the activity of other subunits.

Question 65

Can RNA act as an enzyme?

Answer 65

Yes. Ribozymes.

Question 66

Can an enzyme only bind one reactant at a time? (T/F)

Answer 66

False. But typically binds to one substrate at a time.

Question 67

Enzymes are specific to ———

Answer 67

Specific molecules only.

Question 68

What is the Michaelis-Menten equation?

Answer 68

Vmax—maximum velocity of the enzyme, Km—Michaelis constant, substrate concentration at half Vmax. Low Km = high affinity, High Km = low affinity.

Question 69

Competitive inhibition vs. Non-competitive inhibition?

Answer 69

Competitive: Vmax unaltered, Km increases. Non-competitive: Vmax decreases, Km remains the same.