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PBL > Biochem 20 HY > Flashcards

Biochem 20 HY Flashcards

1
Q

confirmation of a thyamine deficency can be done by testing what enzyme that uses thyamine pyrophosphate for its activity

A

transketolase

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2
Q

most important pathway for life that you must give respect to

A

TCA cycle

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3
Q

pyruvate gets converted to Acetyl CoA by what enzyme

A

pyruvate dehydrogenase

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4
Q

each glucose generates who many acetyl CoAs?

A

2 acetyl CoA

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5
Q

at the beginning of the TCA cycle acetyl CoA combines with what other molecule to form citrate? what type of rxn is this? how many carbons does citrate have?

A

oxaloacetate; condensation rxn; 6 Cs

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6
Q

citrate–>isocitrate—> alpha ketoglutarate in the presence of what enzyme? what 2 things are released here and what type of rxns are they

A

isocitrate dehydrogenase; oxidation-reduction rxns–>removes e given them to NAd to form NADH; decarboxylation removes C resulting in CO2 release

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7
Q

alpha keotglutarate is now a 5 carbon substrate —>succinyl CoA in the presence of what enzyme? what occurs here?

A

alpha ketoglutarate dehydrogenase; NADH and CO2 released resulting in 4 C succinyl CoA

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8
Q

NADH produced by the oxidation reduction reactions of the enzymes isocitrate dehydrogenase and alpha keotglutarate go where?

A

electron transport chain! this makes the TCA cycle oxygen dependent!

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9
Q

which enzymes of the TCA cycle release CO2 that we then breath out ? how many moles of oxaloacetate are consumed in the TCA cycle for each mole of CO2 produced

A

alpha ketoglutarate dehydrogenase and isocitrate dehydrogenase; there is no net consumption of oxaloacetate because it is used in the first step and regenerated in the last step

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10
Q

pyruvate dehydrogenase and alpha keotglutarate dehydrogenase are 2 of 3 enzymes in the body that require tender loving care for nancy to do their reactions what do they require

A

thyamine pyrophosphate, lipoic acid, coenzyme A, FAD, and NAD

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11
Q

Succinyl CoA(high energy!)–> Succinate causes the release of what? what is this an example of?

A

GTP! substrate level phosphorylation! substrate used to make an ATP equivalent

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12
Q

Succinate–>Fumarate in the presence of the enzyme succinate dehydrogenase what is released? where does this go? what is succinate dehydrogenase called in the alternative pathway

A

FADH2 goes to electron transport chain is complex II and enters ETC at CoQ

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13
Q

Fumarate–>Malate-malate dehydrogenase–> oxaloacetate what is released in the generation of oxaloacetate?

A

NADH goes to ETC

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14
Q

how many ATP equiv are generated in the TCA cycle and what are they generated by?

A

12, 3 generated per NADH released, 2 genereated for FADH2 and 1 from GTP

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15
Q

coenzymes FAD and FMN are generated by waht vitamin

A

riboflavin

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16
Q

FAD is able to accept single electrons and can be very reactive as a consequence how must it be attached to its enzyme? use the example of succinate dehydrogenase

A

covalently bound FAD; succinate dehydrogenase is bound in the inner mitochondrial membrane and so allows FAD to transfer electrons to an Fe-S complex and then to CoQ of the electron ttransport chain

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17
Q

otto shapes tennispaterner told him of a health food containing succinate. the food claimed that succinate would provide an excellent source of energy during exercise bc it could be metabolized directly without oxygen what is the problem with this statement

A

succinate when oxidized produces FADH2 which donates its electrons to the ETC-oxygen dependent pathway!!!

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18
Q

the vitamin pantothenic acid is the precursor for what in the TCA cycle? Vitamin B1 is a precursor of what used in the TCA cycle

A

coenzyme A; thiamine pyrophosphate

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19
Q

thiamine defiency causes what 2 enzymes to not work? this dec ATP production especially in heart CNS and skeltal mm and can cause heart failure. thiamine def is assoc with alcoholism

A

pyruvate dehydrogenase and alphaketoglutarate

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20
Q

Eo of FAD -.2 and for NAd is -.32 therefore the transfer of electrons from FADH2 to NAD is energetically unfavorable how do alpha ketoacid dehydrogenase complexes allow the electron transfer to occur?

A

FAD is covalently bound of dehydrogenases and the dehydrogenases amino acid side chains alterFAD Eo value making it energetically favorable

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21
Q

in the alphaketoglutarate dehydrogenase complex(or potentially PDH) dihydrolipoyldehydrogenase transfers electrons from reduced lipoate to

A

FAD forms FADH2 which then donates e- to NADH

22
Q

arsenic binds dihydrolipoate in alpha ketoglutarate dehydrogenase and also inhibitis glyceraldehyde 3-dehydrogenase(??should be pyruvate dehydrogenase?) what does this result in

A

aerobic (TCA cycle) and anaerobic(glycolysis) generation of ATP is inhibited!!!

23
Q

3 irreversible reactions of TCA cycle are catalyzed by what 3 enzymes

A

citrate synthase, isocitrate dehydrogenase and alpha ketoglutarate dehydrogenase

24
Q

citrate synthase catalyzes the rxn of acetyl CoA to citrate what inhibits citrate synthase?

A

citrate (high levels)

25
Q

rate limiting step of TCA cycle

A

isocitrate dehydrogenase

26
Q

isocitrate dehydrogenase(converts isocitrate–>alphaketoglutarate) is shut off by high concentrations of what two things? low concentrations of what 2 things turn it on

A

ATP and NADH say too much need to stop cycle!; ADP and NAD+ say turn on need to generate more ATP!!

27
Q

Ca in muscles of tissue is released from the sarcoplasmic reticulum during muscle contraction and may activate what enzymes to signal to them that ATP is being used

A

isocitrate synthase and alpha ketoglutarate

28
Q

alphaketoglutarate is inhibited by high concentrations of what 2 things

A

NADH and succinyl CoA

29
Q

when TCA cycle shuts down at isocitrate dehydrogenase enzyme this causes citrate to build up into the cell. citrate then diffuses back into the cytosol to inhibit what pathway and at what location

A

glycolysis! at PFK-1! say no need for more ATP generation!!

30
Q

the last step in all major fuel pathways is what conversion?

A

acetyl CoA–>CO2 we breath it off!

31
Q

pyruvate dehydrogenase is regulated. its activity is increased by an inc in Ca saying make more ATP! what enzyme contained in its complex dephosphorylates it to its active form

A

pyruvate dehydrogenase phosphatase

32
Q

pyruvate dehydrogenase is phosphorylated by what enzyme in its complex to stop it

A

pyruvate dehydrogenase kinase

33
Q

what 2 things inhibit pyruvate dehydrogenase KINASE to prevent it from inhibiting pyruvate dehydrogenase activity

A

inhibited by ADP and pyruvate–>say need more ATP let the pathway move on!

34
Q

2 things activate pyruvate dehydrogenase kinase to tell it the cell doesn’t need anymore ATP generation

A

acetyl CoA and NADH high levels say stop

35
Q

when TCA cycle is shut off citrate builds up enters cytoplasm in the liver which inhibits PFK1. this stimulates PFK2 to form fructose 2,3Bis p which over rides PFK1(glcolysis) inhibition but only at this location thereforein the liver the citrate produced is used for?

A

Fa synthesis

36
Q

alphakeotglutarate is a precursor for what

A

AA synthesis and GABA in brain

37
Q

succinyl CoA is a precursor for what synthesis

A

heme

38
Q

malate is used as a precursor for

A

gluconeogenesis

39
Q

oxaloacetate is a precursor for

A

AA synthesis

40
Q

removal of TCA cycle intermediates to be used as precursors causes the depletion of oxaloacetate the 4 C precursor of the cycle therefore other reactions need to replenish the intermediates so the cycle can proceeed what are these pathways called

A

anaplerotic ‘filling up’

41
Q

major anaplerotic enzyme of cells that adds Co2 to pyruvate to form oxaloacetate? it requires Mg and ATP as well as biotin

A

pyruvate carboxylase

42
Q

the concentration of what activates pyruvate carboxylase to make more oxaloacetate

A

acetyl CoA

43
Q

aspartate, glutamate, valine, isoleucine are all amino acids that can do what

A

be degraded to form TCA cycle intermediates

44
Q

in the brain pyruvate carboxylase is present in astrocytes which uses the TCA cycle intermediates to synthesize?

A

glutamine essential for neuronal survival

45
Q

in ppl with pyruvate carboxylase def what will occur in regards to pyruvate if oxaloacetate concentrations are low

A

pyruvate–>lactic acid–>lactic acidosis!

46
Q

what is the name of the disease caused by thiamine def

A

beriberi

47
Q

coenzyme unique to the alpha ketoacid dehydrogenase complexes?

A

lipoic aicd

48
Q

pt diagnosed with thiamine def exhibited fatigue and mm cramps related to accumulation of metabolic acids. which metabolic acid is likely to accumulate in thiamine def?

A

pyruvic acid

49
Q

succinate dehydrogenase differs from all other enzymes of the TCA cycle in that it is the only enzyme that displays what characteristic

A

it is embedded in the inner mitochondrial membrane

50
Q

during exercise stimulation of the TCa cycle results prinicpally from what

A

stimulation through a number of enzymes by a decreased NADH/NAD ratio

51
Q

Coenzyme A is synthesized from what vitamin

A

pantothenate

PBL (19 decks)

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