Chapter 14 - The Citric Acid Cycle

Front 1

What is the formula for the pyruvate dehydrogenase reaction?

Back 1

pyruvate + CoA + NAD+ ---> acetyl-CoA + CO2 + NADH

Front 2

How many enzymes are used to form the pyruvate dehydrogenase complex?

Back 2

Three: E1, E2, and E3

Front 3

How is acetyl-CoA generated?

Back 3

From the catabolism of other biomolecules

Front 4

What three other ways can the catabolism of other biomolecules generate acetyl-CoA?

Back 4

1. Proteins --> amino acids --> acetyl-CoA

2. Polysaccharides --> monosaccharides --> acetyl-CoA

3. Fats --> fatty acids --> acetyl-CoA

Front 5

How many reactions can be associated with the citric acid cycle?

Back 5

Eight

Front 6

What is the first reaction of the citric acid cycle?

Back 6

Citrate synthase adds an acetyl group to oxaloacetate

Front 7

What occurs in the first reaction of the citric acid cycle?

Back 7

Oxaloacetate and acetyl-CoA undergo citrate synthase to form citrate

Front 8

What goes into and comes out of citrate synthase in the first step of the citric acid cycle?

Back 8

H2O ---> HSCoA

Front 9

When does citrate synthase undergo a conformational change?

Back 9

Upon binding to oxaloacetate, allowing the binding of acetyl-CoA

Front 10

What is the second reaction of the citric acid cycle?

Back 10

Aconitase isomerizes citrate to isocitrate

Front 11

What formations occur in the second reaction of the citric acid cycle?

Back 11

Citrate <---> Aconitate <---> Isocitrate

Front 12

What is put into the reactions for the second reaction of the citric acid cycle?

Back 12

H2O for either reaction

Front 13

What is the third reaction of the citric acid cycle?

Back 13

Isocitrate dehydrogenase releases the first CO2

Front 14

What occurs during the third reaction of the citric acid cycle?

Back 14

Isocitrate reacts to form alpha - ketogluterate

Front 15

What goes into and comes out of the third reaction of the citric acid cycle?

Back 15

NAD+ goes in and H+ and NADH come out

then the first CO2 comes out

then H+ is put in

Front 16

What is the forth reaction of the citric acid cycle?

Back 16

Alpha - ketogluterate dehydrogenase releases the second CO2

Front 17

What occurs in the forth reaction of the citric acid cycle?

Back 17

Alpha - ketogluterate reacts to form succinyl CoA

Front 18

What goes into and comes out of the forth reaction of the citric acid cycle?

Back 18

CoASH goes in and CO2 comes out

NAD+ goes in and NADH comes out

Front 19

Where did the two carbons released in the 1st round of the citric acid cycle not come from?

Back 19

Acetyl-CoA

Front 20

In what reactions are the two carbons released in the citric acid cycle?

Back 20

Reactions 3 and 4

Front 21

In what form are the carbons in the citric acid cycled released?

Back 21

CO2

Front 22

What is the fifth reaction of the citric acid cycle?

Back 22

Succinyl-CoA synthetase catalyzes substrate level phosphorylation

Front 23

What occurs during the fifth reaction of the citric acid cycle?

Back 23

Succinyl-CoA undergoes succinyl-CoA synthetase to form succinate

Front 24

What goes into and comes out of the fifth reaction of the citric acid cycle?

Back 24

GDP and Pi go in and GTP and CoA-SH come out

Front 25

What is the sixth reaction of the citric acid cycle?

Back 25

Succinate dehydrogenase generates ubiquinol

Front 26

What occurs during the sixth reaction of the citric acid cycle?

Back 26

Succinate undergoes succinate dehydrogenase to form fumarate

Front 27

What goes into and comes out of the sixth reaction of the citric acid cycle?

Back 27

Enz-FAD goes in and Enz-FADH2 comes out

Front 28

What occurs in the sixth reaction of the citric acid cycle in order for Enzyme-FAD to go in and Enzyme-FADH2 to come out?

Back 28

Q must go in and QH2 comes out

Front 29

T or F: The transformation of Enz-FAD to Enzy-FADH2 is a one way path.

Back 29

False

Front 30

What is the seventh reaction of the citric acid cycle?

Back 30

Fumerase catalyzes a hydration reaction

Front 31

What occurs during the seventh reaction of the citric acid cycle?

Back 31

Fumarate undergoes fumarase to form malate

Front 32

What goes into the seventh reaction of the citric acid cycle?

Back 32

H2O

Front 33

What is the eighth reaction of the citric acid cycle?

Back 33

Malate dehydrogenase regenerates oxaloacetate

Front 34

What occurs during the eighth reaction of the citric acid cycle?

Back 34

Malate undergoes malate dehydrogenate to form oxaloacetate

Front 35

What goes into and comes out of the eighth reaction of the citric acid cycle?

Back 35

NAD+ goes in and NADH+ and H+ comes out

Front 36

Where does regulation occur in the citric acid cycle?

Back 36

At the three irreversible steps

Front 37

What are the three irreversible reactions of the citric acid cycle?

Back 37

Reaction 1, reaction 3, and reaction 4

Front 38

What type of cycle is the citric acid cycle?

Back 38

An Energy-Generating cycle

Front 39

What comes out of the reaction of glucose to pyruvate?

Back 39

2 NADH = 5 ATP

2 ATP

Total: 7 ATP

Front 40

What comes out of the reaction of pyruvate to acetyl-CoA?

Back 40

2 NADH = 5 ATP

Total: 5 ATP

Front 41

What comes out of the citric acid cycle?

Back 41

6 NADH = 15 ATP

2 QH2 = 3 ATP

2 GTP

2 CO2

Total: 18 ATP + 2 GTP + 2 CO2

Front 42

T or F: The intermediates of the citric acid cycles are precursors of other molecules

Back 42

True

Front 43

What is an example of an amino acid formation from a citric acid cycle intermediate?

Back 43

Alpha-ketogluterate and NH4+ undergoes glutamate dehydrogenase to form glutamate

Front 44

T or F: Intermediates that are diverted to other pathways cannot by replenished

Back 44

False

Front 45

What can replenish citric acid cycle intermediates?

Back 45

Anaplerotic reactions

Front 46

What can occur to some pyruvate during exercise?

Back 46

Some pyruvate can be converted to an alpha-ketoglutarate to boost the activity of the citric acid cycle

Front 47

Which TCA cycle intermediate is found at both the beginning and end of the citric acid cycle?

Back 47

Oxaloacetate

Front 48

How many NADH are produced when one acetyl group is oxidized in the TCA cycle?

Back 48

Three

Front 49

Citrate synthase binds which substrate first?

Back 49

Oxaloacetate

Front 50

T or F: The two carbon atoms that enter the TCA cycle as acetyl-CoA are released as two CO2 molecules in the same round of the citric acid cycle

Back 50

False

Front 51

What can dispose of carbon atoms through the TCA cycle?

Back 51

Carbohydrates, fatty acids, and amino acids

Front 52

Flux through the TCA cycle is regulated at the __________ steps.

Back 52

Irrevirsible

Front 53

During oxidation of acetyl-CoA through the TCA cycle, which steps involve oxidative decarboxylations?

Back 53

Steps three and four of TCA cycle

Front 54

Which enzymes of the TCA cycle contain an FAD cofactor?

Back 54

Succinate dehydrogenase

Front 55

How many NADH are oxidized in one turn of the TCA cycle?

Back 55

Zero

Front 56

Which reactions in the TCA cycle release CO2?

Back 56

Steps three and four

Front 57

Which reaction in the TCA cycle directly generates a GTP?

Back 57

Step 5

Front 58

Which reaction in the TCA cycle gives electrons too ubiquinone?

Back 58

Step six

Front 59

Malonate is a competitive inhibitor of succinate dehydrogenase. What TCA intermediates accumulate if malonate is present in the preparation of isolated mitochondria?

Back 59

Succinate, succinyl-CoA, and alpha-ketoglutarate

Front 60

Oxaloacetate is labeled with 14C at the C4 carbon. In which step of the TCA cycle will the label be lost as 14CO2?

Back 60

Alpha-ketoglutarate dehydrogenase reaction

Front 61

Acetyl-CoA is labeled with 14C at the C1 carbon and enters the TCA cycle. In which round of the cycle will the label be lost as 14CO2?

Back 61

The second round

Front 62

Citrate, the produce of step one of the TCA cycle, is an allosteric effector of phosphofructokinase. Would it be likely to activate or inhibit this enzyme?

Back 62

Inhibit