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Biochemistry Block 1 > TCA CYCLE > Flashcards

TCA CYCLE Flashcards

1
Q

What are anaplerotic(building up) reactions?

A

byosynthetic reactions proceeding from the TCA cycle require the input of carbons from intermediates othar than acetyl-coa.

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2
Q

what are the two major functions of the TCA cycle

A

production of energy and byosynthesis

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3
Q

T/F does the TCA cycle provides a common ground for interconversion of fuels and metabolites?

A

TRUE

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4
Q

succinyl coa serves as precursor to?

A

porphyrins(heme) in all cells , but especially in bone marrow and liver

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5
Q

the TCA cycle is a source of non essential aminocids such as ?

A

ASPARTATE AND GLUTAMATE

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6
Q

What was the first version of the TCA cycle , proposed by Krebs in 1937 ?

A

began with pyruvic acid , not acetyl coa

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7
Q

why the TCA cycle is described as amphibolic nature?

A

because of the catabolic(top) and anabolic(bottom) nature

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8
Q

coenzyme a is what kind of nucleotide?

A

adenine, containing panthogenic acid moiety and terminates in thiol group

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9
Q

where is the TCA cycle located ?

A

mitochondrial matrix

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10
Q

what is the main fate of mitochondrial acetyl coa?

A

oxidation in the TCA cycle , but in the cytoplasm it is used for biosynthesis of fatty acids and cholesterol.

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11
Q

mention the different metabolites that pyruvate can be converted to?

A
  1. lactate(lactate dehydrogenase)
  2. alanine ( alanine aminotranferase ALT)
  3. oxaloacetate (pyruvate carboxylase)
  4. acetyl coa (pyruvate dehydrogenase complex PDH )
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12
Q

Which enzyme is tetramer of identical subunits , each of which contains an allosteric site that binds acetyl coa , a positive heterotropic modifier?

A

pyruvate carboxylase

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13
Q

what complex serves as a bridge between carbohydrates and the TCA cycle?

A

pyruvate dehydrogenase complex (PDC)

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14
Q

What complex is one of the several alfa-ketoacid dehydrogenases having analogous reaction mechanisms, including alfa-ketoglutarate dehydrogenase in the TCA cycle and alfa-ketoacid dehydrogenases associated with the catabolism of leucine, isoleucine and valine ?

A

PDC COMPLEX

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15
Q

which 5 co enzymes are required for PDC activity?

A
  1. thiamine pyrophosphate
  2. lipoamide(lipoic acid bound in amide linkage to protein)
  3. coa
  4. FAD
  5. NAD+
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16
Q

which vitamins are required for synthesis of PDC complex?

A
  1. thiamine
  2. pantothenic acid
  3. riboflavin
  4. nicotinamide
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17
Q 
deficiency of 1.thiamine
2.pantothenic acid
3. riboflavin 
4. nicotinamide
results in ?
A

beriberi due to thiamine deficiency

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18
Q

what are the symptoms of beriberi ?

A

cardiac and skeletal muscle weakness and neurologic disease.

19
Q

what kind of vitamin is common in alcoholism?

A

thiamine

20
Q

why is lactic acid measured in clinical setting?

A

because its accumulation can result in rapid death

21
Q

why is lactic acid produced?

A

produced metabolically by the reversible reduction of pyruvate with NADH by the enzyme lactate dehydrogenase(LDH)

22
Q

citrate synthase begins the TCA cycle by catalyzing the condensation of acetyl coa and oxaloacetate to form>

A

citric acid

23
Q

which protein in the TCA cycle is an iron-sulfur?

A

ACONITASE

24
Q

Aconitase is a two step reversible reaction and involves ?

A

dehydration followd by hydration

25
Q

what is IRE-BP(Iron response element binding protein)

A

is a cytosolic protein with aconitasse activity and regulates iron storage

26
Q

what is fluoroacetate?

A

potent toxin originally isolated from plants

27
Q

fluoroacetylcoa + oxaloacetate =

A

fluorocitrate

28
Q

what substance inhibits aconitase?

A

fluorocitrate

29
Q

what is an example of a suicide substance?

A

fluoroacetate

30
Q

what is a three point attachment?

A

citrate binds to the activate site of aconitase

31
Q

citrate is an ________ molecule

A

achiral

32
Q

why citrate is term a prochiral molecule?

A

because it is converted to achiral molecules , isocitrate

33
Q

which substrate is an allosteric effector inhibiting in phosphofructokinase1 and activating acetyl coa carboxylase ?

A

citrate

34
Q

T/F animals can perform net synthesis of glucose from acetyl-coa

A

FALSE

35
Q

it is a process in which ADP is converted into ATP without involving the electron transport chain or oxidative phosphorilation?

A

substrate level phosphorylation

36
Q

reactions catalyzed by phosphoglycerate kinase and pyruvate kinase in glycolysis uses also?

A

substrate level phosphorylation

37
Q

the last 3 reactions on the TCA cycle illustrates a common theme in metabolism for introducing a carbonyl group into a molecule these are?

A
  1. introduction of a double bond
  2. addition of water across the double bond to form an alcohol
  3. oxidation of the alcohol to a ketone
38
Q

which enzyme is a flavoprotein?

A

succinate dehydrogenase .. embedded in the inner mitochondrial membrane where it is a part of complex II( succinate Q reductase.

39
Q

which enzyme adds water across the trans double bond of fumarate to form alfa-hydroxy acid, L-malate?

A

fumarase

40
Q

clinical
-7 month child
-progressive neurologic deterioration characterized by loss of coordination and muscle tone
-unrelenting acidosis
tx: administration of thiamine had no effect
labs:
- elevated blood levels of lactate
-alfa-ketoglutarate
-branched-chain amino acids
postmortem
- gluconeogenic enzymes were shown to have normal activities
- pyruvate dehydrogenase and alfa-ketoglutarate dehydrogenase were deficient
-defective component show E1 , single gene component required by all of the alfa-ketoacid dehydrogenases

possible diagnosis?

A

leigh’s disease

41
Q

what is leights disease?

A

group of disorders that are all characterized by lactic acidosis

42
Q

T/F malate dehydrogenase reaction played an important role in elucidation of the cyclic nature of the TCA cycle?

A

TRUE

43
Q

__________ It is a major regulatory enzyme within the TCA cycle. it is subject to allosteric inhibition by ATP and NADH and stimulation by ADP and NAD+

A

ISOCITRATE DEHYDROGENASE

44
Q

what are the 3 TCA cycle enzymes described as tumor supressors because genetic defects in these enzymes are associated with human cancers ?

A
  1. succinate dehydrogenase
  2. fumarate hydratase
  3. isocitrate dehydrogenase

Biochemistry Block 1 (6 decks)

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