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Bio 131 > Exam 2: Energy and Enzymes > Flashcards

Exam 2: Energy and Enzymes Flashcards

1
Q

In what 2 circumstances do reactions take place?

A
  1. Reactants collide in precise orientation
  2. Reactants have enough kinetic energy to overcome repulsion b/t the electrons that come in contact during bond formation (activation energy)
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2
Q

What is energy?

A

The ability to promote change or do work

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3
Q

2 forms of energy

A

kinetic and potential

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4
Q

Kinetic energy is associated with…

A

Movement

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5
Q

Potential energy is associated with…

A

Structure/location

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6
Q

Chemical energy

A

energy in molecular bonds, form of potential energy
=> structure of a molecule determines potential energy

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7
Q

First Law of Thermodynamics

A

Energy cannot be created or destroyed, but can be transformed

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8
Q

Second Law of Thermodynamics

A

Transfer of energy from one form to another INCREASES THE ENTROPY of a system => as entropy increases, there is less energy available for organisms to use

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9
Q

Where do electrons have high potential energy

A

In outer electron shells

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10
Q

Formula for free energy change

A

ΔG=ΔH-TΔS

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11
Q

ΔG

A

Change in free energy

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12
Q

ΔH

A

Change in total energy (enthalpy)

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13
Q

T

A

Temperature in Kelvin

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14
Q

ΔS

A

Change in entropy

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15
Q

ΔG > 0

A

endergonic

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16
Q

ΔG < 0

A

exergonic

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17
Q

Which type of reaction occurs spontaneously?

A

exergonic

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18
Q

Which type of reaction is thermodynamically favored?

A

Exergonic

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19
Q

How can you conduct an endergonic reaction?

A

Couple it with an exergonic reaction

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20
Q

What are 2 ways in which energetic coupling occurs?

A
  1. Transfer of high energy electrons
  2. Transfer of a phosphate group
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21
Q

What are 3 examples of coupled reactions?

A
  1. Redox reactions: electron transfer
  2. Electron carriers: NADH and FADH2 both receive high energy electrons to deliver to the right places
  3. ATP driven reactions: include high energy electrons
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22
Q

What are redox reactions?

A

Reactions that involve transfer of electrons

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23
Q

The more CH bonds…

A

The more reduced it is

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24
Q

The less CH bonds…

A

The more oxidized it is

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25
Q

Reduced molecules have higher or lower potential energy?

A

Higher, gains a proton

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26
Q

oxidized molecules have higher or lower potential energy?

A

Lower, loses a proton

27
Q

What is NADH

A

Electron carrier; has reducing power (can give its electrons)

28
Q

Why does ATP have high potential energy

A

The 3 negatively charged phosphate groups are very close together

29
Q

What is phosphorylation

A

Transferring a phosphate group

30
Q

What does the hydrolysis of ATP result in

A

ADP and inorganic phosphate

31
Q

Is hydrolysis endergonic or exergonic

A

Exergonic, the entropy (disorder) of the products is higher

32
Q

What happens to the energy released during ATP hydrolysis?

A

It is transferred to a protein during phosphorylation and usually causes a change in the protein’s shape

33
Q

3 factors affecting reaction rates

A
  1. concentration of reactants
  2. temperature
  3. catalysts
34
Q

How does concentration of reactants affect reaction rates?

A

Higher reactant concentration => higher opportunity for interaction

35
Q

How does temperature affect reaction rates?

A

Heat causes molecules to move more rapidly and collide => speeds up reaction times
Cold causes molecules to move more slowly and collide less => slows reaction times

36
Q

How do catalysts affect reaction rates?

A

They help to trigger reactions (important biological catalysts are enzymes)

37
Q

What is induced fit?

A

Enzyme undergoing a conformational change when substrates bind to active site

38
Q

What 2 functions do enzymes perform?

A
  1. Bring substrates together in precise orientation so electrons involved in the reactions can interact
  2. Lower activation energy
39
Q

What is activation energy?

A

Amount of free energy required to reach transition state i.e. start a reaction

40
Q

Enzymes can catalyze in 3 different ways:

A
  1. bring substrates closer and in proper orientation
  2. strain the substrate
  3. control the chemistry of the active site
41
Q

While enzymes can speed up reactions,

A

they cannot make reactions spontaneous i.e. they only act on exergonic reactions

42
Q

Steps of enzyme catalysis

A
  1. Initiation
  2. Transition state facilitation
  3. Termination
43
Q

Initiation

A

Reactants bind to active site in specific orientation => enzyme-substrate complex

44
Q

Transition state facilitation

A

interactions between enzyme and substrates lowers activation energy

45
Q

Termination

A

Products released, enzyme unchanged

46
Q

What 2 things limit rate of catalysis? What does this mean?

A
  1. Substrate present
  2. Enzyme available

=> enzymes are saturable

47
Q

What does it mean for an enzyme to be saturated?

A

The max # of substrates are present/all active sites are occupied by the substrate

48
Q

What is velocity on an enzyme graph?

A

Moles of product formed per second

49
Q

Vmax

A

Max rate of moles of product formed per second in reaction
When enzyme is saturated, reaction can’t proceed any quicker (horizontal asymptote)

50
Q

Km

A

Substrate concentration at half of Vmax

51
Q

What does a lower Km indicate?

A

More efficient enzyme b/c it achieves half of its Vmax consuming less substrate concentration

52
Q

2 types of enzyme inhibitors

A

Competitive, Non-competitive

53
Q

Which enzyme inhibitor binds to the active site? What does this do?

A

Competitive, interferes with active site so substrate cannot bind

54
Q

Which enzyme inhibitor doesn’t bind to the active site? What does this do?

A

Non-competitive, changes shape of enzyme so substrate cannot bind

55
Q

Vmax and Km of enzyme when competitive inhibitor is present

A

Same and higher

56
Q

Vmax and Km of enzyme when non-competitive inhibitor is present

A

Lower and same

57
Q

Allosteric regulation

A

When a noncompetitive inhibitor activates or deactivates the enzyme

58
Q

Cofactor

A

Inorganic ions that temporarily bind to enzyme for proper function

59
Q

Coenzyme

A

Hold onto certain things for an enzyme to make catalysis smoother, example is NADH

60
Q

Prosthetic group

A

Small molecule permanently attached to the enzyme

61
Q

How are enzymes affected by the environment?

A

Most enzymes function maximally in a narrow range of temp and pH => may denature outside of that range

62
Q

Metabolic pathway

A

Series of reactions, each step catalyzed by a different enzyme; sum of catabolic and anabolic pathways

63
Q

Feedback inhibition

A

When an enzyme in a pathway is inhibited by the product of the reaction sequence, feedback inhibition occurs; how your cell knows when to stop

Bio 131 (25 decks)

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