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SFM Exam 2 > Bioenergetics > Flashcards

Bioenergetics Flashcards

1
Q

Acetyl CoA is the activated form of ___

A

Acetate

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2
Q

What are the 3 energy sources Acetyl CoA can be generated from?

A 
(1) Carbs
Glucose -> 2 Pyruvate -> 2 Acetyl CoA
(2) Lipids
TAG -> FAs -> Acetyl CoA (via B oxidation)
Oxidation of ketone bodies -> Acetyl CoA
(3) Proteins
Breakdown into AAs -> Acetyl CoA
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3
Q

___ form of PDC is active

A

Dephosphorylated

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4
Q

___ form of PDC is inactive

A

Phosphorylated

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5
Q

Where does phosphorylation occur in PDC?

A

Coenzyme TTP of E1 complex

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6
Q

What are the 5 coenzymes of the PDC?

A
  • Thiamine Pyrophosphate (TPP)
  • Coenzyme A (CoA)
  • Lipoic Acid
  • Flavin Adenine Dinucleotide (FAD)
  • NAD
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7
Q

What vitamin is TPP derived from?

A

B1 (thiamine)

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8
Q

What vitamin is CoA derived from?

A

B5 (panthothenic acid)

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9
Q

What vitamin is Lipoic Acid derived from?

A

None

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10
Q

What vitamin is FAD derived from?

A

B2 (riboflavin)

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11
Q

What vitamin is NAD derived from?

A

B3 (niacin)

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12
Q

What does the enzyme Pyruvate Dehydrogenase Kinase (PDK) do to PDC?

A

Phosphorylates it = inactive

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13
Q

What does the enzyme Pyruvate Dehydrogenase Phosphatase (PDP) do to PDC?

A

Dephosphorylates it = active

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14
Q

What are the 3 activators of PDK?

A
  • Acetyl CoA
  • NADH
  • ATP
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15
Q

What are the 4 inhibitors of PDK?

A
  • Pyruvate
  • CoA
  • NAD
  • ADP
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16
Q

What are the 2 activators of PDP?

A
  • Ca2+

- Mg2+

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17
Q

What are the 2 direct inhibitors of the E1 complex of PDC?

A
  • Acetyl CoA

- NADH

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18
Q

In a phosphatase deficiency…

(1) PDC is always in ___ form
(2) Glucose -> ___ rather than Acetyl CoA
(3) Results in constant ___ acidosis

A

(1) phosphorylated (inactive!)
(2) Lactate
(3) Lactic Acidosis (high blood levels of lactic acid)

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19
Q

What system is affected the most by a phosphatase deficiency?

A

Central Nervous System

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20
Q

Intake of what AA should be restricted in a phosphatase deficiency?

A

Alanine

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21
Q

What happens if there is insufficient oxygen in muscle cells for further oxidation of pyruvate?

A

NAD is regenerated from NADH by reduction of pyruvate to lactic acid via Lactate Dehydrogenase Enzyme

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22
Q

What type of diet is recommended in a phosphatase deficiency?

A

Ketogenic

helps minimize pyruvate formation

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23
Q

What are the 3 rate irreversible steps/enzymes of the CAC?

A

(1) Citrate Synthase
(2) Isocitrate Dehydrogenase
(3) α-Ketoglutarate Dehydrogenase

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24
Q

What enzyme results in the formation of GTP in the CAC?

A

Succinate Thiokinase

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25
Q

What is the rate limiting step of CAC?

A

Isocitrate -> α-Ketoglutarate

Isocitrate Dehydrogenase

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26
Q

Which enzyme in the CAC requires the same 5 coenzymes as the PDC to function?

A

α-Ketoglutarate Dehydrogenase

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27
Q

When cellular ATP levels are low, the activity of TCA cycle is ____

A

Increased

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28
Q

When cellular ATP levels are high, the activity of TCA cycle is ___

A

Decreased / Inhibited

mitochondrial ETC inhibition

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29
Q

Anaplerotic Reacations

A
  • “fill up” reactions

- provide intermediates to replenish the TCA cycle

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30
Q

What are the two major anaplerotic reactions?

A
  • Degradation of AAs (produces either TCA cycle intermediates or pyruvate)
  • Carboxylation of pyruvate (ie synthesis of OAA by decarbox of pyruvate)
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31
Q

(1) Degradation of what 4 AAs replenish α-Ketoglutarate? (2) What molecule are the 4 AAs turned in to before they can replenish α-Ketoglutarate?

A

(1) Glutamine, Histidine, Arginine, Proline (GHAP) (Go Poke His Arse)
(2) Glutamate

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32
Q

(1) Degradation of what 4 AAs replenish Succinyl CoA? (2) What molecule are the 4 AAs turned in to before they can replenish Succinyl CoA?

A

(1) Threonine, Isoleucine, Methionine, Valine (TIM V)
(2) Propionyl CoA
(Thor Met Val Inside College Pub)

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33
Q

(1) Degradation of what 3 AAs replenish Fumarate?

A

(1) Phenylalanine, Aspartate, Tyrosine (PAT)

Try Phucking ASaP

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34
Q

(1) Degradation of what AA replenishes OAA?

(2) What molecule is the AA turned in to before it can replenish OAA?

A

(1) Asparagine

(2) Aspartate

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35
Q

What is the path taken by Pyruvate through the CAC when it feeds into lipid synthesis?

A

Pyruvate -> Acetyl CoA -> Citrate -> Citrate -> Acetyl CoA -> FAs, Isoprenoids

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36
Q

What is the path taken by Pyruvate through the CAC when it feeds into glucose synthesis (gluconeogenesis)?

A

Pyruvate -> OAA -> Malate -> Malate -> OAA -> PEP —> Glucose

37
Q

What inhibits pyruvate carboxylase in PDC?

38
Q

What can succinyl CoA be used in?

A

Formation of Porphyrins —-> Heme

39
Q

What can TCA intermediates be used in?

A
  • Nucleotide bases
  • Proteins
  • Fatty acids
  • Isoprenoids
  • Heme groups
40
Q

2-Oxoglutaric Aciduria (α-ketoglutaric acid)

A
  • disorder of TCA cycle
  • involves α-Ketoglutarate
  • rare disorder with global developmental delay and severe neurological problems in infants
  • characterized by metabolic acidosis, severe microcephaly, intellectual disability
  • variable urine excretion of 2-oxoglutarate
41
Q

Fumarase Deficiency

A
  • disorder of TCA cycle
  • characterized by severe neurological impairment, encephalomyopathy, dystonia, increased urinary excretion of fumarate/succinate/α-Ketoglutarate/citrate
  • fatal outcome within first two years of life
  • autosomal recessive disorder
  • mutation in fumarase gene contains Q319E
42
Q

Succinyl CoA Synthetase (SCS) Deficiency

A
  • disorder of TCA cycle
  • associated with mutations in two out of three subunits making up the enzyme
  • mutations occur on genes SUCLA2 and SUCLG1
  • unique disorder b/c it involves both the CAC (due to abnormal succinate metabolism) and the mitochondrial DNA (mtDNA) maintenance
  • increased amount of TCA cycle intermediates in the urine of patients
43
Q

What do the SUCLA2 and SUCLG1 genes encode?

A

The β subunit of the ADP forming SCS and the α subunit of SCS

44
Q

What are Oncometabolites?

A

small molecules of normal metabolism; excessive accumulation of them leads to metabolic dysregulatioon

45
Q

What are the two oncometabolites of the TCA cycle? Also are major oncometabolites in cancer pathogenesis.

A
  • Citrate

- 2-Hydroxyl Glutarate

46
Q

Mitochondrial depletion syndrome is associated with:

A
  • Profound hypotonia (decreased muscle tone)
  • Progressive dystonia (involuntary muscle contractions)
  • Muscular atrophy
  • Severe sensory neural hearing impairment
47
Q

(CITRATE ONCOMETABOLITES)

Excess citrate reduces activity of the mitochondrial isoform of ____ and results in a shift of the cells metabolism towards ____

A
  • Pyruvate Dehydrogenase

- Glycolysis

48
Q

(CITRATE ONCOMETABOLITES)

Increased accumulation of citrate activates _____ which increases the production of acetyl CoA and malonyl CoA

A

Acetyl CoA Carboxylase (ACC)

49
Q

(CITRATE ONCOMETABOLITES)

Increased Acetyl CoA and Malonyl CoA is directed towards increased synthesis of __ and ___

A

Lipids & Sterol

50
Q

Citrate Oncometabolites

A
  • citrate accumulation in the cell
  • favors non-oxidative breakdown of glucose in the cells and promotes cancer growth
  • gylcolysis favored
  • increased accumulation of pyruvate so cells convert it to lactate in order to regenerate NAD for use in glycolysis
51
Q

2-Hydroxy Glutarate Oncometabolites

A
  • mutations of IDH1 and IDH2 (cystolic and mitochondrial forms of IDH)
  • leads to accumulation of 2HG
  • mutation occurs in conversion of α-KG to 2-HGs
  • accumulation of 2-HGs leads to the malignant progression of gliomas
52
Q

Role of Phosphoenolpyruvate Carboxykinase in Cancer

A
  • promotes cancer cell growth and proliferation (esp in colorectal cancer)
  • increases glucose and glutamine uptake in cancer cells and favors anabolic metabolism
53
Q

Successful OxPhos must accomplish the following 3 key goals:

A
  • Transfer electrons from NADH and FADH2 to O2
  • Establish a proton gradient across the inner mitochondrial membrane and in intermembrane space (proton motive force)
  • Synthesize ATP
54
Q

Electrons flow from ___ standard redox potential (Eo) to ___ standard redox potential. (measure of electron affinity)

A

Low to high

55
Q

Standard redox potential and standard free energy (G) are ___ related

56
Q

In the ETC, electrons are pumped from the __ to the ___

A
  • Matrix

- Inner-mitochondrial space

57
Q

Inner-mitochondrial membrane is ___ to H ions, protons, and hydroxyl ions.

A

Impermeable

58
Q

What two factors constitute a proton-motive force to drive ATP synthesis by Complex V?

A

(1) pH gradient in intermembrane space

2) membrane potential (“membrane intactness”

59
Q

What membrane bound protein in OxPhos catalyzes ATP synthesis?

60
Q

1 mole of ATP requires passage of __ H through complex V

A

4

3 protons going thru channel, 1 proton used by adenine nucleotide translocator

61
Q

What portion of Complex V contains the proton channel? Fo or F1?

62
Q

What portion of Complex V contains subunits that provide catalytic activity for the complex?

63
Q

What inhibits Complex V?

A

Oligomycin - disrupts the proton transport thru the channel by inhibiting Fo region

64
Q

What are 3 consequences of inhibiting the transfer of electrons across the ETC?

A
  • decrease in the pumping of protons (b/c less protons in intermemb space)
  • decrease in the proton (H+) gradient
  • inhibition of ATP synthesis
65
Q

What are the 4 inhibitors of Complex 1 of the ETC?

A
  • Rotenone
  • Amytal
  • Myxothiazol
  • Piericidin A
66
Q

What inhibits Complex 2 of the ETC?

67
Q

What happens in ETC/TCA when there is a high ATP/ADP ration?

A

inhibits ATP synthase -> increases H+ gradient -> decreases electron transport and H+ pumping -> slows down TCA cycle -> decreases glycolysis -> decreases ATP concerntration

68
Q

What happens in ETC/TCA when there is a low ATP/ADP ration?

A

activation of ATP synthase -> decreases H+ gradient -> increases electron transport and H+ pumping -> accelerates TCA cycle -> increases glycolysis -> increases ATP concentration

69
Q

What are the two things OxPhos regulation is sensitive to?

A
  • Oxygen

- ATP/ADP ratio

70
Q

___ production is the result of uncoupling Ox Phos from ATP synthesis

71
Q

Brown Adipose Tissue

A
  • very rich in mitochondria
  • high expression of uncoupling protein (UPC1) which is found in inner mitochondrial membrane
  • involved in thermogenesis
  • uncoupling of Ox Phos from ATP synthesis occurs here
72
Q

How does UCP1 generate heat?

A

It short-circuits the mitochondrial proton gradient which results in the energy from the proton gradient being released as heat as protons fall thru UCP1 to mitochondrial matrix

73
Q

What binds to/activates UCP1?

A

Long Chain FAs
(bind to UCP1 which causes structural change in enzyme and forms UCP channels so protons can flow from intermemb space to matrix)

74
Q

What happens when the proton gradient is disrupted?

A
  • P ~ ADP uncouples from ETC
  • protons reenter mitochondrial matrix from intermemb space
  • TCA cycle and electron transfer to O2 are accelerated
  • ATP synthase is inhibited (no ATP synthesis)
  • heat generation
75
Q

Free ___ mainly generated in the mitochondria

76
Q

What two enzymes play a role in neutralizing free radicals?

A
  • Superoxide Dismutase (SOD)

- Catalase

77
Q

List 3 anti-oxidants

A
  • Glutathione Peroxidase
  • Vitamin E
  • Vitamin C
78
Q

What powers the mitochondrial membrane transport system?

A

Membrane Potential or Proton Gradient

79
Q

Phosphate/OH- Antiport

A
  • pumps OH- into intermembrane space
  • pumps H2P04- into mitochondrial matrix
  • driving force is pH gradient
80
Q

Phosphate/Malate Antiport

A
  • pumps malate into intermembrane space

- pumps HP04 into mitochondrial matrix

81
Q

ADP/ATP Antiport

A
  • pumps ATP into intermembrane space
  • pumps ADP into mitochondrial matrix
  • driving force is pH gradient and membrane potential
82
Q

Pyruvate/OH- Antiport

A
  • pumps OH- into intermembrane space

- pumps Pyruvate into mitochondrial matrix

83
Q

Malate-Aspartate Shuttle

A
  • reversible
  • operates in the heart, liver and kidneys
  • generates NADH into mito-matrix
  • NADH enters ETC at Complex 1
  • can form max of 3 ATP
84
Q

Glycerophosphate-Shuttle

A
  • irreversible
  • operates in skeletal muscle and brain
  • generates FADH2 in the inner mitochondrial membrane
  • FADH2 enters ETC at CoQ
  • can form max of 2 ATP
85
Q

(MITOCHONDRIAL DISEASE)

Luft’s Disease

A
  • dominant sxs: perspiration, increased fluid intake with normal urine volume, high daily caloric intake, stable body weight, asthenic (loss of strength), progressive weakness
  • lab findings: increased BMR (signifies heat production)
  • mitochondria from striated muscle: uncoupling of OxPhos, high levels cytochrome c oxidase, low levels of CoQ
  • other findings: large accumulations of mitochondria with highly variable size
86
Q

Two primary causes of Mitochondrial Disease

A

(1) defect in nuclear DNA (nDNA) encoding the mitochondrial proteins
(2) defect in mitochondrial DNA (mDNA)

87
Q

Clinical Features of Mitochondrial Disease

A
  • nervous system: seizures, ataxia, dementia, deafness, blindness
  • eyes: ptosis, retinis pigmentosa with vision loss
  • heart: cardiomyopathy
  • skeletal muscle: weakness, fatigue, myopathy, exercise intolerance, loss of coordination and balance
  • others: liver failure, pancreatic disease, DM
88
Q

Metabolic Features of Mitochondrial Disease

A
  • low energy production
  • increased free radical production
  • lactic acidosis

SFM Exam 2 (10 decks)

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