TCA CYCLE

Question 1

What are anaplerotic(building up) reactions?

Answer 1

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

Question 2

what are the two major functions of the TCA cycle

Answer 2

production of energy and byosynthesis

Question 3

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

Answer 3

TRUE

Question 4

succinyl coa serves as precursor to?

Answer 4

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

Question 5

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

Answer 5

ASPARTATE AND GLUTAMATE

Question 6

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

Answer 6

began with pyruvic acid , not acetyl coa

Question 7

why the TCA cycle is described as amphibolic nature?

Answer 7

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

Question 8

coenzyme a is what kind of nucleotide?

Answer 8

adenine, containing panthogenic acid moiety and terminates in thiol group

Question 9

where is the TCA cycle located ?

Answer 9

mitochondrial matrix

Question 10

what is the main fate of mitochondrial acetyl coa?

Answer 10

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

Question 11

mention the different metabolites that pyruvate can be converted to?

Answer 11

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

Question 12

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

Answer 12

pyruvate carboxylase

Question 13

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

Answer 13

pyruvate dehydrogenase complex (PDC)

Question 14

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 ?

Answer 14

PDC COMPLEX

Question 15

which 5 co enzymes are required for PDC activity?

Answer 15

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

Question 16

which vitamins are required for synthesis of PDC complex?

Answer 16

1. thiamine
2. pantothenic acid
3. riboflavin
4. nicotinamide

Question 17

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

Answer 17

beriberi due to thiamine deficiency

Question 18

what are the symptoms of beriberi ?

Answer 18

cardiac and skeletal muscle weakness and neurologic disease.

Question 19

what kind of vitamin is common in alcoholism?

Answer 19

thiamine

Question 20

why is lactic acid measured in clinical setting?

Answer 20

because its accumulation can result in rapid death

Question 21

why is lactic acid produced?

Answer 21

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

Question 22

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

Answer 22

citric acid

Question 23

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

Answer 23

ACONITASE

Question 24

Aconitase is a two step reversible reaction and involves ?

Answer 24

dehydration followd by hydration

Question 25

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

Answer 25

is a cytosolic protein with aconitasse activity and regulates iron storage

Question 26

what is fluoroacetate?

Answer 26

potent toxin originally isolated from plants

Question 27

fluoroacetylcoa + oxaloacetate =

Answer 27

fluorocitrate

Question 28

what substance inhibits aconitase?

Answer 28

fluorocitrate

Question 29

what is an example of a suicide substance?

Answer 29

fluoroacetate

Question 30

what is a three point attachment?

Answer 30

citrate binds to the activate site of aconitase

Question 31

citrate is an ________ molecule

Answer 31

achiral

Question 32

why citrate is term a prochiral molecule?

Answer 32

because it is converted to achiral molecules , isocitrate

Question 33

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

Answer 33

citrate

Question 34

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

Answer 34

FALSE

Question 35

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

Answer 35

substrate level phosphorylation

Question 36

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

Answer 36

substrate level phosphorylation

Question 37

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

Answer 37

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

Question 38

which enzyme is a flavoprotein?

Answer 38

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

Question 39

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

Answer 39

fumarase

Question 40

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?

Answer 40

leigh's disease

Question 41

what is leights disease?

Answer 41

group of disorders that are all characterized by lactic acidosis

Question 42

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

Answer 42

TRUE

Question 43

__________ 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+

Answer 43

ISOCITRATE DEHYDROGENASE

Question 44

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

Answer 44

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