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Biology 2 > Lecture 11- Pathways that harvest chemical energy II > Flashcards

Lecture 11- Pathways that harvest chemical energy II Flashcards

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1
Q

What is oxidative phosphorylation?

A

Process of ATP synthesis resulting from the reoxidation of electron carriers in the presence of O2

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2
Q

What are the two stages of oxidative phosphorylation?

A

The electron transport chain

Chemiosmosis

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3
Q

Why doesn’t the cell use one step to oxidize NADH + H+?

A

The reaction is untameable- it is too exergonic, energy cannot be harvested

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4
Q

Why does the cell use the electron transport chain?

A

It releases energy in smaller, more manageable amounts

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5
Q

What is the electron transport chain?

A

Electrons from NADH and FADH2 pass through a series of membrane associated electron carriers to actively transport protons to make a concentration gradient

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6
Q

What is chemiosmosis?

A

ATP synthase couples proton diffusion to ATP synthesis

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7
Q

What is the name of the four large protein complexes involved in the electron transport chain?

A

I, II, III and IV

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8
Q

What do the four large protein complexes, I, II, III and IV contain?

A

Electron carriers and associated enzymes

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9
Q

What are the 4 large protein complexes I, II, III and IV?

A

Integral proteins on the inner mitochondrial membrane in eukaryotes- three are transmembrane

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10
Q

What is a small peripheral protein in the intermembrane space of the mitochondria involved in the electron transport chain?

A

Cytochrome c

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11
Q

What is the nonprotein associated with the electron transport chain called?

A

Ubiquinone (Q)

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12
Q

What is ubiquinone (Q)?

A

Small, nonpolar molecule that floats within the hydrophobic interior of the phospholipid bilayer of the inner mitochondrial membrane

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13
Q

What is the first step in the electron transport chain?

A

NADH + H+ passes electrons to the first large protein complex (I) called NADH-Q reductase

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14
Q

Where does NADH-Q reductase transfer this electron to?

A

Q

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15
Q

What protein passes Q electrons from the oxidation of FADH2?

A

The second complex (II) succinate dehydrogenase

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16
Q

What is the name of the third complex of the electron transport chain?

A

cytochrome c reductase

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17
Q

What does cytochrome c reductase do?

A

Receives electrons from Q

Passes them to cytochrome c

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18
Q

What does the fourth complex do?

A

cytochrome c oxidase recieves electrons from cytochrome c

passes them to oxygen

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19
Q

What happens when oxygen (1/2O2) receives electrons?

A

It picks up two hydrogen ions to form H2O

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20
Q

What happens to the protons left over from the electron transport chain?

A

They are pumped across the mitochondrial membrane

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21
Q

Theoretically, how many molecules of ATP are formed from each pair of electrons passed along the electron transport chain?

A

3

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22
Q

What is the result of the electron transport chain?

A

The active transport of protons against their concentration gradient out of the matrix across the inner membrane to the intermembrane space

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23
Q

Why does proton transport occur?

A

Electron carriers in protein complex I, III and IV are arranged so that protons are taken up on one side of the membrane and transported, along with electrons, to the other side

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24
Q

How do the transmembrane protein complexes act?

A

As proton pumps

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25
Q

What does pumping of protons cause?

A

A proton concentration gradient

A difference in electric charge

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26
Q

What is the proton concentration gradient and the charge difference potential energy called?

A

Proton-motive force

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27
Q

What does proton motive force do?

A

Drive proteins back across the membrane

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28
Q

How do protons diffuse back across the inner mitochondrial membrane?

A

though a specific mitochondrial membrane called ATP synthase

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29
Q

What does ATP synthase do?

A

Couples proton movement with ATP synthesis

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30
Q

What is the coupling of proton movement with ATP synthesis called?

A

Chemiosmosis

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31
Q

What do the exergonic reactions that occur when electrons move along the electron transport chain drive?

A

The pumping of H+ out of the mitochondrial matrix to establish a H+ gradient

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32
Q

Where are H+ ions actively transported to?

A

The intermembrane space

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33
Q

What potential energy is harnessed by ATP synthase?

A

Proton motive force

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34
Q

What is proton motive force?

A

The potential energy of the proton gradient

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35
Q

What are the two roles of ATP synthase?

A
  1. Channel that allows protons to diffuse back in

2. Uses that energy to make ATP from ADP + Pi

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36
Q

What else can ATP synthase act as?

A

ATPase

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37
Q

Why does ATP synthase prefer synthesis as opposed to acting as ATPase?

A
  • ATP concentration is low in matrix because ATP moves elsewhere in the cell
  • H+ gradient is maintained by electron transport chain
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38
Q

What method can be used to test the hypothesis that a H+ gradient drives ATP synthesis by isolated mitochondria?

A
  1. isolate mitochondria, place in pH8 (low H+ concentration outside and inside organelles)
  2. Move to acidic medium (pH4, high [H+])
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39
Q

What are the results of moving isolated mitochondria from a high pH solution to a low pH solution?

A

H+ movement into mitochondria drives ATP synthesis in the absence of continuous electron transport.

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40
Q

What can be concluded by H+ movement into the mitochondria driving ATP synthesis in the absence of a continuous electron transport chain?

A

In the absence of electron transport, an artificial H+ gradient is sufficient for ATP synthesis by mitochondria

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41
Q

What method can be used to test the hypothesis that ATP synthase is needed for ATP synthesis?

A
  1. extract proton pump from bacteria, add to lipid vesicle
  2. H+ is pumped into vesicle, creates gradient
  3. ATP synthase from a mammal is inserted into the vesicle membrane
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42
Q

What is the result of the experiment to see if ATP synthase is needed for ATP synthesis?

A

The H+ diffuses out of the vesicle, driving synthesis of ATP by ATP synthase

43
Q

In the experiment to test if a proton gradient drives ATP synthesis, how was changing the pH of the solution able to change [H+] in the mitochondria?

A

In outer membrane of mitochondria is freely permeable to protons so they rapidly diffused into the intermembrane space

44
Q

What is another way to demonstrate the chemiosmotic mechanism?

A

Show that diffusion of protons and formation of ATP must be tightly coupled

45
Q

What happens if another type of H+ channel (not ATP synthase) is inserted into mitochondrial membrane?

A

Energy of H+ gradient is released as heat (not coupled to ATP synthesis)

46
Q

When might H+ and ATP synthesis be deliberately uncoupled?

A

To generate heat instead of ATP

47
Q

What protein uncouples ATP synthesis and H+ gradient energy?

A

Thermogenin

48
Q

What is the function of uncoupling ATP synthesis and the H+ gradient energy using thermogenin?

A

To regulate temperature

49
Q

In what organisms does thermogenin play an important role?

A

Newborn human infants (no hair to keep warm)

Hibernating animals

50
Q

What two parts is ATP synthase composed of?

A

F0 unit

F1 unit

51
Q

What is the F0 unit of ATP synthase?

A

A transmembrane region that is the H+ channel

52
Q

What is the F1 unit of ATP synthase?

A

The lollipop of interacting subunits that constitute the active site for ATP synthesis

53
Q

What type of energy does ATP synthase turn the potential energy from the H+ gradient into?

A

Kinetic energy of movement

54
Q

How does ATP synthase use the kinetic energy of movement to produce ATP?

A

The subunits of F1 rotate, exposing the active site for ATP synthesis

55
Q

What is the maximum yield of ATP through glycolysis followed by cellular respiration?

A

32 gross 30 net

56
Q

Why is the net yield only 30?

A

Inner membrane of some animal cells is inpermeable to NADH, one ATP is paid for each NADH to enter the mitochondrial matrix

57
Q

How many molecules of ATP are produced in the electron transport chain per glucose molecule?

A

28

58
Q

How do carbon skeletons enter the metabolic pathway?

A

Catabolic interconversions- other molecules are broken down to release their energy

59
Q

what catabolic interconversions occurs for polysaccharides?

A

They are hydrolyzed into glucose which passes through glycolysis and cellular respiration- energy is captured as NADH and ATP

60
Q

What catabolic interconversions occurs for lipids?

A

Broken down into glycerol and fatty acids

61
Q

What is glycerol converted into?

A

dihydroxyacetone phosphate (DAP)

62
Q

What is dihydroxyacetone phosphate?

A

An intermediate in glycolysis

63
Q

What are fatty acids converted into?

A

acetyl CoA in the mitochondria

64
Q

How do proteins enter the metabolic pathway?

A

They are hydrolyzed into amino acids

20 different amino acids feed into glycolysis and citric acid cycle at different points

65
Q

How does the amino acid glutamate enter the metabolic pathway?

A

converted into alpha-ketoglutarate- an intermediate in the citric acid cycle

66
Q

What are anabolic interconversions?

A

When catabolic pathways operate in reverse

67
Q

What process forms glucose?

A

Gluconeogenesis

68
Q

What molecules are reduced to form glucose?

A

glycolytic and citric acid intermediates

69
Q

What can be used to form fatty acids?

A

Acetyl CoA

70
Q

What are the most common number of carbon atoms in fatty acids?

A

14,16,18

71
Q

How are the most common fatty acids formed?

A

By adding two carbon acetyl CoA units one at a time until correct length is reached

72
Q

What molecule can be used as the starting point for purines?

A

alpha-ketoglutarate

73
Q

What molecule can be used as the starting point for pyrimidines?

A

oxaloacetate

74
Q

What is alpha-ketoglutarate the starting point for?

A

purines

chlorophyll synthesis

75
Q

What molecule is oxaloacetate the starting point for?

A

Pyrimidines

76
Q

What is acetyl CoA a building block for?

A 
fatty acids
various pigments
plant growth substances
rubber
steroid hormones of animals
77
Q

What are all of these substances called?

A

The metabolic pool

78
Q

How does the level of substances in the metabolic pool vary?

A

They don’t- they are constant

79
Q

What is metabolic homeostasis?

A

The cell regulates anabolism and catabolism to maintain balance

80
Q

Give an example of the metabolic homeostasis being upset.

A

Undernutrition

81
Q

Why are proteins not preferentially broken down?

A

They have essential roles as enzymes and structural elements- using as energy deprives these vital roles

82
Q

Why do fats weigh less in water than polysaccharides?

A

Fats are nonpolar, they do not bind as much water

83
Q

Why do fats store more energy in their bonds?

A

They are more reduced than carbohydrates (C-H vs C-OH)

84
Q

The level of what molecule in the blood rises as fatty acids are broken down?

A

Acetyl CoA

85
Q

Why can fatty acid not be the bodies only source of energy?

A

Fatty acids cannot cross the blood-brain barrier

The brain must use glucose as its energy source

86
Q

How does the body, depleted of glucose, convert something else to make glucose for the brain?

A

Gluconeogenesis from amino acids from the break down of proteins

87
Q

What happens after several weeks of starvation?

A 
Proteins and fats are used up
Essential proteins (such as muscle and antibodies) are broken down
88
Q

What happens when essential proteins are broken down?

A

can lead to illness and eventual death

89
Q

How is glycolysis, the citric acid cycle and the electron transport chain regulated?

A

Allosteric control of enzymes involved

90
Q

How can excess product effect a metabolic pathway?

A
  1. suppress action of enzymes that catalyze earlier reaction

2. speed up reactions in another pathway

91
Q

How does speeding up reactions in another pathway control the amount of product being formed?

A

Diverts raw materials away from synthesis of the first product

92
Q

What type of mechanisms control metabolic pathways?

A

Positive and negative control mechanims

93
Q

What is the main control point in glycolysis?

A

Phosphofructokinase

94
Q

What reaction does phosphofructokinase catalyze?

A

The third reaction of glycolysis from fructose-6-phosphate to fructose-6-bisphosphate

95
Q

How is phosphofructokinase controlled?

A

Inhibited by ATP

Activated by ADP or AMP

96
Q

What is the main control point of the citric acid cycle?

A

The enzyme isocitrate dehydrogenase

97
Q

What does isocitrate dehydrogenase do?

A

Interconverts isocitrate into alpha ketoglutarate (reaction 3)

98
Q

What are the feed back inhibitors and activators of isocitrate dehydrogenase?

A

NADH + H+ and ATP are inhibitors

NAD+ and ADP are activators

99
Q

What builds up when isocitrate dehydrogenase is inhibited?

A

isocitrate and citric acid

100
Q

What stops the build up of isocitrate and citric acid when isocitrate dehydrogenase is inhibited?

A

Acetyl CoA conversion to citrate is inhibited by ATP and NADH + H+

101
Q

What else does a build up of citrate do to the metabolic pathway?

A

feedback inhibitor to slow fructose-6-phosphate reaction early in glycolysis

102
Q

How does Acetyl CoA act as a control point?

A

When too much ATP is made the accumulation of citrate diverts acetyl CoA to fatty acid synthesis for storage

103
Q

What is the final control point for metabolic pathways?

A

Cell differentiation- for example, PPARδ which controls proliferation of slow twitch muscle fibers

Biology 2 (14 decks)

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