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GI > TCA Cycle > Flashcards

TCA Cycle Flashcards

1
Q

Hematopoietic stem cell transplantation has been successfully used in a small number of extremely compromised pediatric patients with

A

Pyruvate kinase deficiency

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2
Q

Shows the signs of muscle weakness, hyperuricemia, and hemolytic anemia

A

PFK-1 deficiency

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3
Q

Increased serum creatine from muscle breakdown is also a sign of

A

PFK-1 deficiency

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4
Q

Developmental delay in the newborn and microcephaly. Neurologically these infants will present with repeated seizures and may also exhibit muscle spasticity and hypotonia

A

GLUT 1 deficiency

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5
Q

How can we treat a GLUT-1 deficiency?

A

Ketogenic diet

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6
Q

An autosomal dominant mutation, which results in an increased blood glucose, needed to trigger insulin secretion

A

Glucokinase Deficiency

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7
Q

This condition of glucokinase deficiency is termed

A

Maturity Onset Diabetes of the Young (MODY)

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8
Q

Signs/Symptoms: Usually minimal. Heterozygotes typically exhibit increased blood glucose levels

A

MODY

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9
Q

MODY homozygotes can present with

A

Neonatal diabetes

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10
Q

Pyruvate and lactate are the formal end points for

A

Aerobic and anaerobic glycolysis respectively

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11
Q

In the liver, Pyruvate can be converted to one of which two things?

A
  1. ) Oxaloacetate (gluconeogenesis)

2. ) Acetyl CoA (TCA)

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12
Q

Aerobic glycolysis formally ends with the production of pyruvate. With the linker reaction converting pyruvate to

A

Acetyl CoA

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13
Q

Pyruvate is converted to Acetyl CoA by

A

Pyruvate Dehydrogenase

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14
Q

Under conditions of immediate need

for ATP, acetyl CoA is directed into the

A

TCA Cycle

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15
Q

Pyruvate in the cytoplasm is transported into the mitochondria and is converted to the two-carbon acetyl CoA by the pyruvate dehydrogenase complex. This is an

A

Irreversible reaction

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16
Q

The irreversible conversion of pyruvate to acetyl CoA produces

A

NADH and releases the first free CO2

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17
Q

The pyruvate dehydrogenase complex is made up of

A

3 enzymatic activities and 5 co-factors

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18
Q

What are the 3 enymatic activities of the pyruvate dehydrogenase complex?

A
  1. ) Pyruvate decarboxylase,
  2. ) Lipoamid reductase transacetylase
  3. ) Dihydrolipoyl dehydrogenase
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19
Q

What are the 5 cofactors of the pyruvate dehydrogenase complex?

A

Thyamine pyrophosphate, FAD, NAD, CoA, and lipoic acid

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20
Q

One of three regulatory steps in the TCA cycle, pyruvate dehydrogenase is a regulated enzyme, one of three that has a strong influence on flux through the

A

TCA cycle

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21
Q

While the pyruvate –> acetyl CoA step does not commit acetyl CoA to the TCA cycle, it does decide the fate of

A

Pyruvate

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22
Q

Pyruvate dehydrogenase is negatively regulated by

A

Acetyl CoA and high levels of NADH

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23
Q

ATP, Acetyl CoA and NADH collaborate on inhibition of

A

Pyruvate Dehydrogenase

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24
Q

Stimulation of a kinase, which phosphorylates the dehydrogenase by these small molecules, inhibits

A

Pyruvate dehydrogenase complex

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25
Q

This novel kinase is inhibited by high levels of

-allows a competing phosphatase to dephosphorylate and thus activate the pyruvate dehydrogenase complex

A

CoA, NAD+, or Pyruvate

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26
Q

This phosphatase is stimulated by

A

Calcium

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27
Q

The TCA cycle is best thought to begin with the conversion of acetyl CoA and oxaloacetate (another TCA intermediate) to

A

Citrate and free CoA

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28
Q

Therefore, the pyruvate dehydrogenase complex reactions are considered a link between glycolysis and the TCA cycle, and the next-in-line reaction, catalyzed by the enzyme

A

Citrate synthase

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29
Q

Citrate is then isomerized to isocitrate by the enzyme

-an irreversible reaction

A

Aconitase

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30
Q

This sets the stage for two successive

A

Oxidative decarboxylations

31
Q

First, isocitrate dehydrogenase converts isocitrate to a-ketoglutarate with the production of

A

1 CO2 and the reduction of NAD to NADH

32
Q

Alpha-ketoglutarate is then converted into

-catalyzed by a-ketoglutarate dehydrogenase complex

A

Succinyl CoA

33
Q

his reaction releases the second

-also reduces one NAD to NADH

A

CO2

34
Q

Both of these dehydrogenases are subject to regulation, and join with citrate synthase to be the major sites for regulation of flux through the

A

TCA Cycle

35
Q

The conversion of succinyl CoA to succinate is the site for another substrate level phosphorylation, this time with the production of

A

GTP

36
Q

This step in the TCA cycle is catalyzed by

-releases free CoA

A

Succinyl CoA Thiokinase

37
Q

The GTP formed by the reaction catalyzed by succinyl CoA thiokinase can later be used to convert ADP to ATP via the enzyme

A

Nucleotide diphosphate kinase

38
Q

Succinate is then converted to fumarate via

A

Succinate dehydrogenase

39
Q

The conversion of succinate ot fumarate produces

A

FADH2

40
Q

Adds a water molecule across the double bond of fumarate to produce L-malate

A

Fumarase

41
Q

Finally, L-malate is oxidized to

-Produces NADH

A

Oxaloacetate

42
Q

L-malate is converted to oxaloacetate by the enzyme

A

Malate dehydrogenase

43
Q

We have thus replenished the oxaloacetate that was recruited, with acetyl CoA, at the beginning of our cycle, by

A

Citrate Synthase

44
Q

When all is said and done, the TCA cycle produces

A

2 CO2, 3 NADH, 3 H+, FADH2, GTP, and CoA

45
Q

In oxidative phosphorylation, how many ATP molecules are produced from the following?

  1. ) NADH
  2. ) FADH2
A
  1. ) 3 ATP per NADH

2. ) 2 ATP per FADH2

46
Q

How many total ATP are produced as a result of the TCA cycle?

A

12

47
Q

The three enzymes that regulate flux through the TCA cycle are?

A

Citrate synthase, isocitrate dehydrogenase, and a-ketoglutarate dehydrogenase

48
Q

Both glycolysis and the TCA cycle will halt if we can not recycle?

A

NAD and FAD

49
Q

The principal players of NAD and FAD recycling are O2, Pi and the ratio of ADP (and Pi) to ATP, in a process called

A

Respiratory Control

50
Q

A TCA intermediate that functions as an allosteric regulator of glycolysis

A

Citrate

51
Q

In an effort to conserve glucose for other tissues unable to metabolize fats such as the brain and red blood cells, high concentrations of citrate will shut down

A

Glycolysis

52
Q

This doesn’t mean the cell is inert; it could still rapidly metabolize fatty acids via

A

B-oxidation and the TCA cycle

53
Q

Is Citrate able to shut down glycolysis in the liver?

A

No

54
Q

In the liver, the allosteric inhibition by citrate is trumped by the allosteric activation of

A

PFK-1

55
Q

Insulin and glucagon play no direct regulatory roles in the steps of the

A

TCA cycle

56
Q

In fact, neither glucagon nor insulin directly regulate any events in the

A

Mitochondria

57
Q

There are several mechanisms for pyruvate dehydrogenase complex deficiency. One of them is X linked mutation of the E1 subunit of the

A

Pyruvate Dehydrogenase Complex (PDC)

58
Q

Binds to E1 subunit of PDC, therefore in some cases, its affinity to the enzyme is reduced

A

Thiamin

59
Q

Patients with this kind of mutation may benefit from high dose of

A

Thiamin supplementation

60
Q

Lactic acidosis and neurological symptoms are signs of

A

PDC deficiency

61
Q

The lactic acidosis in PDC deficiency is due to the shunting of

A

Pyruvate to lactate

62
Q

Can increase activity of the remaining functional PDCs in patients with PDC deficiency and has been shown to improve patient symptoms

A

Thiamine supplementation

63
Q

Disorders of the TCA cycle enzymes are

A

Rare

64
Q

The various deficiencies in enzymes of the TCA cycle have been grouped as variants of

A

Leigh Disease

65
Q

Patients typically begin showing symptoms shortly after birth with few surviving childhood

A

Leigh disease

66
Q

LActic acidosis and neurological problems are frequently observed with

A

Leigh disease

67
Q

Compared to inborn errors of the TCA cycle nutritional deficiencies or toxin exposure is a much more common presentation of

A

TCA cycle dysfunction

68
Q

Interferes with the E2 subunit of dehydrogenase enzymes resulting in a clinical picture similar PDC deficiency with patients showing signs of lactic acidosis and neurological impairment

A

Arsenic Poisoning

69
Q

The classic indication of arsenic poisoning is

-from oxidized arsenic

A

Garlic Breath

70
Q

Essential for dehydrogenase enzymes e.g. PDC, alpha ketoglutarate dehydrogenase complex and branched-chain alpha keto acid dehydrogenase

A

Vitamin B1 (Thiamin)

71
Q

Its deficiency leads to impaired carbohydrate, lipid and amino acid metabolism

A

Thiamin

72
Q

Progressive heart failure resulting in edema, dyspnea, increased JVP and fatigue are signs of

A

Wet Beriberi

73
Q

Constellation of neurological symptoms following peripheral nerve damage: Decreased Reflexes, paresthesia, loss of coordination, confusion etc are signs of?

A

Dry Beriberi

GI (59 decks)

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