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Bio 131 > Exam 2: Energy and Enzymes > Flashcards

Exam 2: Energy and Enzymes Flashcards

(63 cards)

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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
Reduced molecules have higher or lower potential energy?
Higher, gains a proton
26
oxidized molecules have higher or lower potential energy?
Lower, loses a proton
27
What is NADH
Electron carrier; has reducing power (can give its electrons)
28
Why does ATP have high potential energy
The 3 negatively charged phosphate groups are very close together
29
What is phosphorylation
Transferring a phosphate group
30
What does the hydrolysis of ATP result in
ADP and inorganic phosphate
31
Is hydrolysis endergonic or exergonic
Exergonic, the entropy (disorder) of the products is higher
32
What happens to the energy released during ATP hydrolysis?
It is transferred to a protein during phosphorylation and usually causes a change in the protein’s shape
33
3 factors affecting reaction rates
1. concentration of reactants 2. temperature 3. catalysts
34
How does concentration of reactants affect reaction rates?
Higher reactant concentration => higher opportunity for interaction
35
How does temperature affect reaction rates?
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
How do catalysts affect reaction rates?
They help to trigger reactions (important biological catalysts are enzymes)
37
What is induced fit?
Enzyme undergoing a conformational change when substrates bind to active site
38
What 2 functions do enzymes perform?
1. Bring substrates together in precise orientation so electrons involved in the reactions can interact 2. Lower activation energy
39
What is activation energy?
Amount of free energy required to reach transition state i.e. start a reaction
40
Enzymes can catalyze in 3 different ways:
1. bring substrates closer and in proper orientation 2. strain the substrate 3. control the chemistry of the active site
41
While enzymes can speed up reactions,
they cannot make reactions spontaneous i.e. they only act on exergonic reactions
42
Steps of enzyme catalysis
1. Initiation 2. Transition state facilitation 3. Termination
43
Initiation
Reactants bind to active site in specific orientation => enzyme-substrate complex
44
Transition state facilitation
interactions between enzyme and substrates lowers activation energy
45
Termination
Products released, enzyme unchanged
46
What 2 things limit rate of catalysis? What does this mean?
1. Substrate present 2. Enzyme available => enzymes are saturable
47
What does it mean for an enzyme to be saturated?
The max # of substrates are present/all active sites are occupied by the substrate
48
What is velocity on an enzyme graph?
Moles of product formed per second
49
Vmax
Max rate of moles of product formed per second in reaction When enzyme is saturated, reaction can't proceed any quicker (horizontal asymptote)
50
Km
Substrate concentration at half of Vmax
51
What does a lower Km indicate?
More efficient enzyme b/c it achieves half of its Vmax consuming less substrate concentration
52
2 types of enzyme inhibitors
Competitive, Non-competitive
53
Which enzyme inhibitor binds to the active site? What does this do?
Competitive, interferes with active site so substrate cannot bind
54
Which enzyme inhibitor doesn't bind to the active site? What does this do?
Non-competitive, changes shape of enzyme so substrate cannot bind
55
Vmax and Km of enzyme when competitive inhibitor is present
Same and higher
56
Vmax and Km of enzyme when non-competitive inhibitor is present
Lower and same
57
Allosteric regulation
When a noncompetitive inhibitor activates or deactivates the enzyme
58
Cofactor
Inorganic ions that temporarily bind to enzyme for proper function
59
Coenzyme
Hold onto certain things for an enzyme to make catalysis smoother, example is NADH
60
Prosthetic group
Small molecule permanently attached to the enzyme
61
How are enzymes affected by the environment?
Most enzymes function maximally in a narrow range of temp and pH => may denature outside of that range
62
Metabolic pathway
Series of reactions, each step catalyzed by a different enzyme; sum of catabolic and anabolic pathways
63
Feedback inhibition
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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