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Biocheem > Lecture 28 > Flashcards

Lecture 28 Flashcards

1
Q

what is Phosphate Transfer Potential?

A

Free energies of hydrolysis for phosphate-containing compounds

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2
Q

What is the order from highest to lowest free energy change of phosphate transfer potentials?

A
  • Glycolysis intermediates
  • Phosphocreatine
  • thioester
  • ATP
  • Glucose 6-phosphate (glucose intermediate
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3
Q

Why can one phosphate transfer be used to create a phosphate bond?

A

Because it takes less energy to make the phosphate bond in one process than the energy released when a phosphate bond is broken in another process

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4
Q

If a reaction is coupled, what must the free energy chnage of the combined reactions add up to?

A

A negative number

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5
Q

When coupling two reactions with separate free energy changes what must be done?

A

One reaction will have a negative free energy change and the other will have a positive one (if not flip the reactions and the sign of the reaction). Then cancel out what is the same in both reactions and add the free energy changes

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6
Q

What are the reactants and products of the hydrolysis of phosphocreatine?

A

Reactants: Phosphocreatine, H2O
Products: Creatine, Pi

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7
Q

What is the free energy change of the hydrolysis of phosphocreatine?

A

-43kj/mol

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8
Q

What can phosphocreatine be used to make?

A

ATP

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9
Q

Why can phosphocreatine be used to create ATP?

A

Because the energy of hydrolysis is greater than the energy required to phosphorylate ADP

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10
Q

What does the product of the dephosphorylation of phosphocreatine resemble?

A

Arginine

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11
Q

What is phosphocreatine used for?

A

A transient source of ATP

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12
Q

What is the free energy required for the synthesis of ATP?

A

32kJ/mol

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13
Q

What is AcetylCoA produced from?

A

Fat, protein, and carbohydrate metabolism

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14
Q

What is AcetylCoA a central molecule in?

A

Aerobic catabolic processes

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15
Q

What cycle does AcetylCoA go into?

A

The citric acid cycle

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16
Q

What does the Citric acid cycle produce?

A

Lots of reduced cofactors (NADH/FADH2)

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17
Q

What are reduced cofactors?

A

High energy structures that are reduced

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18
Q

What reduced cofactors can the citric acid cycle produce?

A

NADH and FADH2

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19
Q

What occurs in oxidative phosphorylation?

A

The reduced cofactors are converted into ATP and oxidized back to their oxidized forms

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20
Q

What are the two puposes of Catabolic pathways?

A
  • Breakdown of larger molecules into smaller building units

* Release and (temporary) storage of energy in high-energy molecules

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21
Q

What are some high energy molecules used to store energy after catabolism?

A
  • ATP/NTP

* Reduced cofactors (NADH/FADH2)

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22
Q

What can the reduced cofactors produced in catabolism be used for?

A

Oxidative phosphorylation to generate ATP

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23
Q

What are the two processes that occur in oxidative phosphorylation?

A
  • Oxidation of reduced cofactors (NADH, FADH2)

* Phosphorylation of ADP to ATP

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24
Q

What is the reaction of the oxidation of NADH?

A

NADH ➡️ NAD+ + H+ + 2e

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25
Q

What is the reaction for the oxidation of FADH2?

A

FADH2 ➡️ FAD + 2H+ + 2e

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26
Q

What does the oxidation of the NADH and FADH2 go on to do?

A

Reduce O2 to H2O

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27
Q

For how many what does the reduction of O2 molecules in oxidative phosphorylation produce?

A

Two water molecules

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28
Q

What is the reaction for the reduction of O2 in oxidative phosphorylation?

A

4H+ + 4e + O2 ➡️ 2H2O

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29
Q

How is the oxidation of reduced cofactors and the phosphorylation of ADP to ATP in oxidative phosphorylation connected?

A

Through a proton gradient across the mitochondrial membrane that is created by one process and used by another

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30
Q

What generates the proton gradient in oxidative phosphorylation?

A

Electron transport in the oxidation of NADH and FADH2

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31
Q

What consumes the energy gradient produced in oxidative phosphorylation?

A

ADP to create ATP and synthesize phosphoanhydride bonds

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32
Q

What are reduced cofactors (NADH, FADH2) generated from?

A

Glycolysis and the citric acid cycle (oxidative processes)

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33
Q

Where do the reduced cofactors in oxidative phosphorylation feed their electrons?

A

To the electron transport chain

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34
Q

What occurs once reduce cofactors feed their electrons to the electron transport chain?

A

They become oxidized and O2 becomes reduced to water

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35
Q

What occurs in oxidative phosphorylation once NADH and FADH2 are oxidized and O2 is reduced to H2O?

A

A proton gradient is produced and used for ATP synthesis

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36
Q

Where does oxidative phosphorylation occur?

A

Across the inner mitochondrial membrane

37
Q

How many membranes do mitochondria have?

A

Two membranes

38
Q

What are the characteristics of the outer mitochondrial membrane?

A
  • Very porous

* Has porins

39
Q

What are the characteristics of the inner mitochondrial membrane?

A

Doesn’t let things pass through easily

40
Q

What are the components to the electron transport chain?

A
  • Complex I
  • Complex II
  • Complex III
  • Complex IV
  • Coenzyme Q
  • Cytochrome C
41
Q

What kind of enzyme is Coenzyme Q?

A

A lipid soluble coenzyme

42
Q

What kind of protein in Cytochrome C?

A

A peripheral membrane protein

43
Q

What are type of protein are complexes I - IV?

A

They are integral, transmembrane membrane proteins

44
Q

What are complexes I - IV in the electron transport chain involved in?

A

Proton translocation

45
Q

What does Coenzyme Q do?

A

Takes electrons from proteins I and II and takes them to protein III

46
Q

Which surface does Cytochrome C sit on?

A

The outer surface of the inner mitochondrial membrane (the intermembrane space)

47
Q

What happens to cofactors during electron transport in oxidative phosphorylation?

A

They are reversibly oxidized and reduced

48
Q

What are the cofactors involved in oxidative phosphorylation?

A
  • Flavin mononucleotide
  • Iron-sulfur clusters
  • Copper (cu2+)
  • Cytochrome heme groups
  • Coenzyme Q
49
Q

What is the lipid soluble cofactor in oxidative phosphorylation?

A

Coenzyme Q

50
Q

What are the prosthetic group cofactors in oxidative phosphorylation?

A
  • Flavin mononucleotide
  • Iron-sulfur clusters
  • Copper (Cu2+)
  • Cytochrome heme groups
51
Q

What is the basis of reduction potentials of cofactors that electrons move through in oxidative phosphorylation?

A

Electrons move from cofactors with lower reduction potential to those with higher reduction potentials

52
Q

What is the electron transport chain?

A

A series of connected redox reactions that move electrons from one location to another

53
Q

Where are the cofactors that are prosthetic groups located?

A

They are prosthetic groups within the integral membrane proteins or cytochrome C

54
Q

What do prosthetic groups and cosubstrates have in common?

A

They are both cofactors

55
Q

What are cosubstrates?

A

A subset of cofactors

56
Q

What is the difference between prosthetic groups and cosubstrates?

A

Whether or not they are incorporated into the protein structures

57
Q

What is the difference between Flavin mononucleotide (FMN) and FAD/FADH2?

A

FMN has no Adenosine so it is just a mononucleotide

58
Q

What is the reaction for the reduction of FMN?

A

FMN +2H+ + 2e ➡️ FMNH2

59
Q

What is the reduced form of FMN?

A

FMNH2

60
Q

What are Iron-Sulfur clusters?

A

The product when iron and sulfur come together

61
Q

What is the reaction for Iron-Sulfur Clusters?

A

Fe3+ + e- ➡️ Fe2+

62
Q

What are Cytochromes?

A

Hemoproteins that carry out electron transport

63
Q

What is the difference in heme in hemoglobin and myoglobin vs cytochromes?

A

In Cytochromes the heme groups switch between oxidized and reduced states

64
Q

What is the solubility of Coenzyme Q (Q)?

A

It is lipi soluable

65
Q

What does Coenzyme Q do?

A

Transports electrons to complex III from Complexes I and II in the inner mitochondrial membrane

66
Q

What is Coenzyme Q a cosubstrate for?

A

Complex I, II and III

67
Q

What is the formula for the reduction of Q?

A

Q + 2H+ + 2e ➡️ QH2

68
Q

What makes Coenzyme Q hydrophobic?

A

Its hydrocarbon structure

69
Q

What does Q being hydrophobic allow it to do?

A

Dissolve within the hydrophobic core of the inner mitochondrial membrane and interact with transmembrane portions of integral membrane proteins

70
Q

What redox reactions have a free energy change related to?

A

Reduction potential

71
Q

What is reduction potential?

A

Affinity for electrons

72
Q

What does a higher reduction potential change mean?

A

More negative 𝛥G

73
Q

Where do electrons move in regards to reduction potential?

A

Electrons move from compounds with lower reduction potentials to those with higher reduction potentials

74
Q

What is a positive change in reduction potential associated with?

A

A negative change in free energy

75
Q

What can the free energy from redox reactions be used to transport?

A

Protons across the membrane (1º active transport)

76
Q

Which complex is not involved in the oxidation of NADH?

A

Complex II

77
Q

What is the first step in the electron transport chain for NADH?

A

It is oxidized at complex I to for NAD+

78
Q

What happens once NADH is oxidized to form NAD+ in the electron transport chain?

A

Two electrons pass into complex one (reducing it) and then passing the electrons to coenzyme Q

79
Q

What happens once coenzyme Q takes the electrons from NADH from Complex I?

A

It becomes reduced to QH2 and diffuses through the membrane to complex III

80
Q

What happens once Complex III takes the electrons from Coenzyme Q?

A

Coenzyme III becomes reduced and passes electrons to Cytochrome C which passes electrons to complex IV which passes the two electrons to O2 to form H2O

81
Q

Why is oxygen the terminal electron acceptor?

A

Because it has a very high reduction potential

82
Q

What happens in the electron transport chain when NADH is oxidized?

A

2e go to complex I. Complex I gives them to Q. Q gives them to complex III. III give them to Cyt C. Cyt C gives them to IV. IV gives them to O2

83
Q

How many protons can be move out of the matrix once NADH is Oxidized?

A

10 Protons

84
Q

How many protons are moved at each complex with NADH?

A

I: 4H+
III: 4H+
IV: 2H+

85
Q

What cofactors does complex I have?

A

FMN and Fe-S

86
Q

What cofactors does complex III have?

A

Fe-S and Cyt b (heme groups)

87
Q

What cofactors does complex IV have?

A

Heme groups

88
Q

What are the cofactors in Complex II?

A

FAD as a prosthetic group and Fe-S

Biocheem (38 decks)

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