Lecture 9- Introduction To Enzymes And Catalysis Flashcards

1
Q

Delta G is positive means what?

A

Needs an input of energy

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2
Q

Delta G is negative means what?

A

Reaction can take place spontaneously.

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3
Q

Delta G provides info on the rate of a reaction. True or false?

A

False; Delta G provides no info on the rate of a reaction.

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4
Q

What is dependent upon Delta G?

A

The position of a reaction at equilibrium (the extent at which it will go in a certain direction).

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5
Q

What is activation energy? 2 answers

A

The minimum energy required to convert reactants to products during a collision between molecules.
Also, the energy required to position atoms for a reaction.

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6
Q

“The minimum energy required to convert reactants to products during a collision between molecules” is what?

A

Activation energy

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7
Q

As an overall concept, enzymes do what?

A

Enzymes lower the activation energy for reactions

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8
Q

What lowers the activation energy for reactions?

A

Enzymes

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9
Q

For delta G, when can a reaction take place spontaneously? When does it need an input of energy?

A

Negative; positive.

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10
Q

How does an enzyme lower the activation energy?

A

The enzymes binds tightly to one or more molecules and holds them in a precise configuration.

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11
Q

In addition to lowering the AE, enzymes do what?

A

They lower the energy barrier.

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12
Q

Enzymes are typically used to make or break what type of bonds?

A

Covalent bonds.

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13
Q

What is a catalyst?

A

A molecule or substance that can lower the AE for a reaction.

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14
Q

In terms of equilibrium, what CANT enzymes do?

A

They cannot change the equilibrium point for a reaction.

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15
Q

Why won’t the equilibrium position for the reaction be changed for enzymes?

A

They lower the AE for both the forward and backward reaction equally.

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16
Q

True or false: Enzymes choose to lower the AE for an unspecific type of reaction.

A

False; enzymes are selective and precise

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17
Q

For the enzyme, where do substrates bind and undergo catalysis?

A

At the active site?

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18
Q

What is the active site in the enzyme responsible for?

A

It is where the substrate binds and undergoes catalysis.

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19
Q

What is the first step in catalysis?

A

Substrate binding.

20
Q

When is the reaction NOT limited by the binding event?

A

When the substrate is present at very high concentrations.

21
Q

When the substrate is present at very high concentrations, what is the rate of reaction limited to?

A

The rate is dependent only upon how fast the enzymes can convert substrates to product (the enzyme is said to be “saturated” with substrate).

22
Q

Why can enzymes find their substrates?

A

The molecular motions cause by heat energy within the cell are rapid.

23
Q

What are the three kinds of molecular motions caused by heat energy?

A

Translational energy, vibrational energy, and rotation.

24
Q

What is translational energy?

A

Movement from one place to another

25
Q

“Movement from one place to another” is what?

A

Translational energy.

26
Q

What is vibrational energy?

A

Rapid back and forth movement of covalently bonded atoms with respect to each other.

27
Q

“Rapid back and forth movement of covalently bonded atoms with respect to each other” is what?

A

Vibrational energy.

28
Q

Another name for translational energy?

A

Diffusion.

29
Q

True or false: small molecule substrates of enzymes move much more rapidly than the relatively huge enzymes themselves.

A

True

30
Q

Structurally, what is the active site for an enzyme?

A

A 3-D cleft or crevice formed by groups that come from different parts of the amino acid sequence.

31
Q

Dose the active site take a small or large part of the total volume of an enzyme?

A

Small part.

32
Q

What is the amino acid sequence of an enzyme responsible for?

A

The amino acid sequence of an enzyme is responsible for creating a “scaffold” that precisely positions the amino acids in the active site.

33
Q

Is water often included in active sites.

A

No.

34
Q

How are substrates bound to enzyme active sites?

A

By multiple weak interactions.

35
Q

What is an induced fit?

A

When the active site assumes a shape that is complementary to the substrate only after the substrate is bound.

36
Q

“When the active site assumes a shape that is complementary to the substrate only after the substrate is bound” is called what?

A

An induced fit.

37
Q

Conceptually, how do enzymes accelerate reactions?

A

By stabilizing the transition state.

38
Q

What is a transition state?

A

The transition state is a configuration of atoms in which they are positioned for a reaction.

39
Q

In terms of free energy, does the transition state have high or low? Is is stable or not? Does it occur often?

A

High free energy; it is the least stable in the reaction pathway; it is seldom occurring in the reaction pathway.

40
Q

Another name for the transition state?

A

Transient state

41
Q

What is the “essence of catalysis?”

A

The stabilization of the transition state structure

42
Q

Do enzymes have a higher affinity for the unstable transition structure or that most stable and common structure?

A

Enzymes have a much higher affinity for the unstable transition structure.

43
Q

What happens when an enzyme bonds to the transition state structure?

A

When an enzyme binds to the transition state structure, this releases energy. As a consequence, it lowers the energy required to reach the transition state, and thereby lowers the AE for the reaction.

44
Q

True or false: the energy of binding is used to lower the AE of the reaction.

A

True.

45
Q

What is a coenzyme?

A

Small organic molecules that are found in active sites that aid catalysis.

46
Q

“Small organic molecules that are found in active sites that aid catalysis” are called what?

A

Co-Enzymes.