Week 11: Gluconeogenesis, Pyruvate Dehydrogenase Complex, Citric Acid Cycle

Question 1

The reduced form of _____ is an indirect source of high-energy compounds.

Answer 1

NADH

Question 2

Lipoic acid is associated with dihydrolipoyl transacetylase. It accepts a _______ from hydroxyethyl TPP, oxidizing the group to an _____. It delivers this _____ to coenzyme A. It then is oxidized by NAD+, so it acts as a _____ agent.

Answer 2

hydroxyethyl group, acetyl

acetyl group

reducing

Question 3

A condensation reaction is one in which a new ______ is formed. The reaction of ______ and ______ to form citrate involves the formation of such a ______.

Answer 3

carbon-carbon bond

acetyl-CoA, oxaloacetate

C-C bond

Question 4

What type of reaction is catalyzed by isocitrate dehydrogenase and α-ketoglutarate dehydrogenase?

Answer 4

An oxidative decarboxylation

Both dehydrogenases are involved in redox reactions in which a CO2 is abstracted from a substrate. In both cases NAD+ is reduced while the other substrate is oxidized. Thus, both of these enzymes catalyze oxidative decarboxylations.

Question 5

The reactions that act as control points in the citric acid cycle are those that have the most ______ in the cycle, i.e. these are the most ____ reactions. These control points are allosterically regulated by ATP and NADH. Other regulators also allosterically regulate each of the enzymes catalyzing these reactions.

_______ and ________ are some examples of enzymes that catalyze control point reactions in the citric acid cycle.

Answer 5

negative free energy changes, favorable

Isocitrate dehydrogenase, α-ketoglutarate dehydrogenase

Question 6

______ and _____ inhibit all four of the enzymes that are the ________ in the citric acid cycle. Succinyl-CoA inhibits two of the control points, citrate synthase and α-ketoglutarate dehydrogenase.

Acetyl-CoA inhibits pyruvate dehydrogenase. Citrate inhibits citrate synthase. ADP and NAD+ stimulate isocitrate dehydrogenase.

Answer 6

ATP and NADH, control points

Question 7

The reactions of glycolysis occur in the ______ of the cell. The citric acid cycle, which is found only in _____, occurs in the _______.

Answer 7

cytoplasm

eukaryotes, mitochondrial matrix

Question 8

How can the synthesis and breakdown of fructose-2,6-bisphosphate be controlled independently?

The concentration of fructose-2,6-bisphosphate synthesis depends on the balance between its synthesis and its breakdown. Its synthesis is catalyzed by _________ , while its breakdown is catalyzed by _________. Both of these enzymes are regulated by __________ mediated by kinases and phosphatases.

Answer 8

phosphofructokinase, fructose-1,6-bisphosphatase

phosphorylation and dephosphorylation

Question 9

Fructose-2,6-bisphosphate is an allosteric effector in glycolysis and in gluconeogenesis.

In glycolysis, it activates ______ and is a ______ allosteric effector in the glycolysis pathway.

In gluconeogenesis, it inhibits _____.

Answer 9

phosphofructokinase

positive

fructose bisphosphate phosphatase

Question 10

Most gluconeogenesis reactions take place in the _____, but there are some reactions that occur in the ______.

Answer 10

cytoplasm, mitochondria

Question 11

When the body ______, carbohydrates are broken down via _____. When ______, glucose can be synthesized from the intermediates of the glycolytic and citric acid pathways by ______.

Answer 11

needs energy, glycolysis

energy is not needed, gluconeogenesis

Question 12

Gluconeogenesis proceeds in reverse order from glycolysis, and many of the glycolysis enzymes also catalyze gluconeogenesis. However, at _____ points there are unique enzymes that catalyze only gluconeogenesis, making it a distinct pathway.

Answer 12

four points

Question 13

Gluconeogenesis is NOT the only carbohydrate biosynthetic pathway.

Carbohydrates are synthesized by ______ in plants, by the gluconeogenesis process, and when glucose is used to synthesize other hexoses and hexose derivatives.

Answer 13

photosynthesis

Question 14

If one were to introduce a pulse of acetyl CoA with the two carbons in acetyl CoA labeled with a radioactive tag, followed by unlabeled acetyl CoA, what would be the ultimate fate of the two carbons?

Answer 14

The carbonyl carbon from the acetyl CoA will be lost as CO2 during the second round, while the methyl carbon becomes incorporated in the core of the circulating compounds (e.g., the 2,3 positions of succinate and fumarate) and are only lost through dilution.

Question 15

How many oxidation-reduction steps are found in one turn of the cycle?

Answer 15

Four

There are four steps: the isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, succinate dehydrogenase, and malate dehydrogenase steps.

Question 16

If one NADH generates 3 ATPs through oxidative phosphorylation and 1 FADH2 generates 2 ATPs through oxidative phosphorylation, how many ATPs can be generated from the products of one cycle through the TCA pathway?

Answer 16

Twelve ATPs can be generated: 9 from the 3 NADHs, 2 from the FADH2, and 1 directly generated by the combination of succinyl-CoA synthetase and nucleoside diphosphate kinase (reaction 5).

Question 17

Gluconeogenesis:

• The synthesis of ____ from _____.
• The major site of gluconeogenesis is the ____,
  although gluconeogenesis can occur in the ____.
• Gluconeogenesis is especially important during
  _____, as glucose is the primary fuel
  for the brain and the only fuel for red blood cells.

Answer 17

glucose, pyruvate

liver, kidney

fasting or starvation

Question 18

The beginning: The Conversion of Pyruvate into Phosphoenolpyruvate
* Requires two enzymes,
* First: ______ (in _____)
catalyzes formation of ______.
* Second: _____________ (in ______)

Answer 18

pyruvate carboxylase, mitochondria

oxaloacetate

phosphoenolpyruvate carboxykinase, cytoplasm

Question 19

Pyruvate carboxylase requires the ______ as a cofactor.
* The formation of oxaloacetate by pyruvate carboxylase occurs in ____ stages.

Answer 19

vitamin biotin

three

Question 20

The formation of oxaloacetate by pyruvate carboxylase occurs in the ______. (Step 1)

• Oxaloacetate is reduced to ____ and transported into the cytoplasm, where it is _____ to oxaloacetate with the generation of _______.
• PEP is then synthesized from oxaloacetate by
  phosphoenolpyruvate carboxykinase. (Step 2)

Answer 20

mitochondria

malate, reoxidized

cytoplasmic NADH

Question 21

Step 11: Glucose-6-Phosphatase
* Glucose 6-phosphate is transported into the lumen of the endoplasmic reticulum.
* Glucose 6-phosphatase, an ______ on the inner surface of the endoplasmic reticulum, catalyzes the formation of ______ from ______.

Answer 21

integral membrane

glucose, glucose 6-phosphate

Question 22

What barrier prevents glycolysis from simply running in reverse to synthesize glucose?

How is this barrier overcome in gluconeogenesis?

Answer 22

3 irreversible steps of glycolysis (Steps 1, 3, 10)

4 new enzymes of gluconeogenesis.

Question 23

Since G6P is a ______ effector for Hexokinase since…

G6P is a ____ effector for Glucose-6-phosphatase in glucogenesis

Answer 23

negative, build-up of G6P would stop hexokinase and halter glycolysis

positive

Question 24

Lots of glucose, ATP needed –>

Glucose scarce and needed –>

Answer 24

Glycolysis

Gluconeogenesis

Question 25

If cell needs energy, [AMP] ______, therefore AMP is a ______ effector of phosphofructokinase (PFK) AMP is a _____ effector of fructose-1,6-biphosphate in gluconeogenesis

Answer 25

increases, positive negative

Question 26

If you have plenty of energy [ATP] ______, therefore ATP is a _____ effector of phosphofructokinase (PFK)

Answer 26

increases, negative

Question 27

Higher [H+] means ____ pH. H+ is a ____ effector of glycolysis to..

Answer 27

lower negative, to keep enzymes from being damaged

Question 28

Citrate is a ______ effector of glycolysis and a ______ effector of gluconeogenesis

Answer 28

negative, positive

Question 29

In the liver, the rates of glycolysis and gluconeogenesis are adjusted to maintain _______ levels. * The key regulator of glucose metabolism in the liver is _______. Fructose 2,6-bisphosphate _____ phosphofructokinase and ____ fructose 1,6-bisphosphatase. * The kinase that synthesizes fructose 2,6-bisphosphate (phosphofructokinase 2) and the phosphatase that hydrolyzes this molecule (fructose bisphosphatase 2) are located on the same polypeptide chain. Such an arrangement is called a ________.

Answer 29

blood-glucose fructose 2,6-bisphosphate stimulates, inhibits (positive affector for glycolysis, negative affector for gluconeogenesis) bifunctional enzyme

Question 30

Fructose 2,6-Biphosphate different names depending on the direction it is catalyzing. _________ when adding a phosphate (glycolysis) _________ when removing a phosphate (gluconeogenesis)

Answer 30

PFK-2, phosphofructokinase-2 FBPase2, Fructose biphosphatase

Question 31

How does the enzyme know which domain should be active? Synethesis and Degradation of Fructose 2,6-biphosphate is controlled by _________ Low blood glucose levels trigger pancreas to release the hormone ______. Glucagon acts as a _____ in signal transduction pathway: - Glucagon binds to a G-protein receptor * The G-protein receptor activates adenylate cyclase * Adenylate cyclase catalyzes formation of cyclic AMP * CMP binds to protein kinase A and activates it

Answer 31

blood glucose sensitive hormones glucagon primary messenger

Question 32

Alanine is a _____ effector of glycolysis Acetyl CoA is a _____ effector of glucogeonegensis

Answer 32

negative postive

Question 33

What would be the effect on an organism’s ability to produce glucose if there was an inability to produce adequate quantities of pyruvate carboxylase?

Answer 33

Lack of pyruvate carboxylase would cause hypoglycemia. Lactic acid could build up in the blood.

Question 34

What would be the effect on an organism’s ability to use glucose as an energy source if a mutation inactivated glucose 6-phosphatase in the liver?

Answer 34

During the night, while fasting glucose levels would drop to dangerously low levels.

Question 35

The formation of acetyl CoA from pyruvate is ______ in animal cells. * Acetyl CoA has two possible fates:

Answer 35

irreversible metabolism by the citric acid cycle or incorporation into fatty acids.

Question 36

The synthesis of acetyl CoA from pyruvate consists of three chemical steps:

Answer 36

a decarboxylation, an oxidation, and the transfer to CoA.

Question 37

Lipoamide, a coenzyme, is formed by the attachment of the _______ to a ______ residue in another enzyme in the complex, dihydrolipoyl transacetylase (E2). * The _____ linkages allow lipoamide to move between different sites. * The three enzymes of the pyruvate dehydrogenase complex are structurally integrated, and the lipoamide arm allows rapid movement of ________ from one active site of the complex to another.

Answer 37

vitamin lipoic acid, lysine flexible substrates and products

Question 38

The Pyruvate Dehydrogenase Is Regulated by Two Mechanisms 1. ________ of Enzyme E1. (deactivated when ______, activated when ______) * There is a kinase associated with the E2 and E3 parts of the complex * This kinase phosphorylates E1 at one of serine residues and inactivates E1 . * This kinase is activated by glucagon when glucose is low. Want to save pyruvate to make glucose * A phosphatase is also associated with the E2 and E3 parts of the complex * This phosphatase removes the phosphate and thereby activates the enzyme * The phosphatase is activated by different activators depending on cell type. * Insulin, Ca 2+

Answer 38

Covalent modification phosphorylated, not phosphorylated

Question 39

2. Allosteric regulation based on the ______ charge. * _______ inhibit the complex. * ______ stimulate the complex.

Answer 39

energy ATP, acetyl CoA, and NADH ADP and pyruvate

Question 40

List some of the advantages of organizing the enzymes that catalyze the formation of acetyl CoA from pyruvate into a single large complex.

Answer 40

Reaction facilitated by close proximity (don't have to wait for intermediate to diffuse out or float to another enzyme) Lipoamide swinging arm (speeds up process, don't have to wait for something to diffuse from one ACTIVE SITE to another) Reactants don't leave complex (reduces side reactions) Enzymes are in correct ratio from the start Regulatory enzymes part of complex

Question 40

The CAC Consists of Two Stages: * In the first stage of the citric acid cycle, ______ are introduced into the cycle by ______ of an ______ with a four-carbon compound, _______. * The six-carbon compound formed (______) undergoes two ________, generating two molecules of ______ . * In the second stage, _______ is regenerated. * Both stages generate ______ that are used to power the synthesis of _____ in __________.

Answer 40

two carbons, condensation, acetyl group, oxaloacetate citrate, oxidative decarboxylation, CO 2 oxaloacetate high-energy electrons, ATP in oxidative phosphorylation

Question 41

In step 2 of the CAC, Aconitase is a _____ because it adds ____ to break the C-C double bond.

Answer 41

lyase, H2O

Question 42

In step 4, _________ complex is structurally and mechanistically similar to the ________ complex. E3 same in both: regenerates _____ and _______

Answer 42

a-Ketoglutarate dehydrogenase, pyruvate dehydrogenase FAD, lipoamide

Question 43

Step 5. Succinyl CoA synthetase Cleavage of the _____ of succinyl CoA powers the formation of ______. * Example of a ______ because succinyl phosphate, a _________ compound, donates a phosphate to ADP.

Answer 43

thioester, ATP substrate-level phosphorylation high-phosphoryl-transfer-potential

Question 44

Oxaloacetate Is Regenerated by the _______ of Succinate

Answer 44

Oxidation

Question 45

The two carbons released as CO2 in the 1st round of the citric acid cycle did NOT come from ________.

Answer 45

acetyl-CoA

Question 46

The Citric Acid Cycle Produces: * ______ Electrons * an ______ (sometimes ______) * _______

Answer 46

High-Transfer-Potential ATP, GTP Carbon Dioxide

Question 47

Even though _____ is not a reactant in the CAC, it has to be present for the cycle to keep going

Answer 47

oxygen

Question 48

Positive effectors of CAC: Negative effectors of CAC:

Answer 48

ADP and Pyruvate ATP, acetyl CoA, succinyl CoA NADH

Question 49

Biosynthetic roles of the CAC Citrate --> a-Ketoglutarate --> Succinyl CoA --> Oxaloacetate -->

Answer 49

Citrate --> Fatty acids, sterols a-Ketoglutarate --> amino acids, purines Succinyl CoA --> heme Oxaloacetate --> Aspartate, glucose

Question 50

Which steps of glycolysis are irreversible? What bearing does this observation have on the reactions in which gluconeogenesis differs from glycolysis? These reactions are _______ in gluconeogenesis; the reactions of gluconeogenesis differ from those of glycolysis at these points and are catalyzed by ______ enzymes.

Answer 50

bypassed, different

Question 51

What is the role of biotin in gluconeogenesis? Biotin is the molecule to which _______ is attached to the process of being transferred to ______. The reaction produces ______, which then undergoes further reactions of gluconeogenesis.

Answer 51

carbon dioxide pyruvate oxaloacetate

Question 52

Fructose-2,6-bisphosphate is an allosteric _____ of phosphofructokinase (a glycolytic enzyme) and an allosteric _______ of fructose-1,6-bisphosphatase (an enzyme in the pathway of gluconeogenesis).

Answer 52

activator inhibitor

Question 53

Hexokinase can add a phosphate group to any of several _______, whereas glucokinase is specific for _____. Glucokinase has a lower affinity for glucose than does hexokinase. Consequently, glucokinase tends to deal with an excess of glucose, particularly in the liver. Hexokinase is the usual enzyme for phosphorylating six-carbon sugars.

Answer 53

six-carbon sugars glucose

Question 54

How does pyruvate from glycolysis get to the pyruvate dehydrogenase complex? There is a ______ on the inner mitochondrial matrix that allows pyruvate from the ______ to pass into the ______.

Answer 54

transporter cytosol mitochondria

Question 55

_____ and _____ are the primary electron acceptors of the citric acid cycle.

Answer 55

NAD+, FAD

Question 56

What is the advantage to the organization of the PDH complex? Five enzymes are all in close proximity for efficient shuttling of the ______ between molecules and efficient control of the complex by _______.

Answer 56

acetyl unit phosphorylation

Question 57

What are the similarities and differences between the reactions catalyzed by pyruvate dehydrogenase and a-ketoglutarate dehydrogenase? The reactions proceed by the _____ mechanism and use the same ______. The difference is the initial ______, which is pyruvate or a-ketoglutarate. During the course of the reaction, pyruvate dehydrogenase shuttles an _______ through the reaction while a-ketoglutarate dehydrogenase shuttles a _______.

Answer 57

same , cofactors substrate acetyl unit , succinyl unit

Question 58

In substrate-level phosphorylation, the energy of ______ of some compound provides sufficient energy to allow the ______ phosphorylation of ______ to take place.

Answer 58

hydrolysis endergonic ADP to ATP

Question 59

Which steps of aerobic metabolism of pyruvate through the citric acid cycle are control points?

Answer 59

The reactions are catalyzed by pyruvate dehydrogenase, citrate synthase, isocitrate dehydrogenase, and a-ketoglutarate dehydrogenase.

Question 60

PDH is controlled allosterically. It is inhibited by ______. In addition, it is subject to control by _______. When PDH kinase phosphorylates PDH, it becomes _____. Removing the phosphate with the PDH phosphatase ______.

Answer 60

ATP, acetyl-CoA, and NADH phosphorylation inactive reactivates

Question 61

What are the two most common inhibitors of steps of the citric acid cycle and the reaction catalyzed by pyruvate dehydrogenase?

Answer 61

ATP and NADH are the two most common inhibitors.

Question 62

How does an increase in the ADP/ATP ratio affect the activity of isocitrate dehydrogenase?

Answer 62

If the amount of ADP in a cell increases relative to the amount of ATP, the cell needs energy (ATP). This situation not only favors the reactions of the citric acid cycle, which release energy, activating isocitrate dehydrogenase, but also stimulates the formation of NADH and FADH2 for ATP production by electron transport and oxidative phosphorylation.

Question 63

How does an increase in the NADH/NAD+ ratio affect the activity of pyruvate dehydrogenase?

Answer 63

If the amount of NADH in a cell increases relative to the amount of NAD+, the cell has completed a number of energy-releasing reactions. There is less need for the citric acid cycle to be active; as a result, the activity of pyruvate dehydrogenase is decreased.

Question 64

The citric acid cycle is less active when a cell has a high ______ ratio and a high ______ ratio. Both ratios indicate a high “energy charge” in the cell, indicating less of a need for the energy-releasing reactions of the citric acid cycle.

Answer 64

ATP/ADP , NADH/NAD+

Question 65

Thioesters are “high-energy” compounds that play a role in group-transfer reactions; consequently, their ∆G of hydrolysis is ______ to provide energy for the reaction.

Answer 65

large and negative

Question 66

The citric acid cycle is the ______ metabolic pathway and indirect producer of _____. It receives fuels from the other pathways at many points and generates reduced ______ that go into the electron transport chain. It is also involved in ______, as many of its intermediates can be drawn off to synthesize other compounds.

Answer 66

central, energy electron carriers anabolism

Question 67

In oxidative decarboxylation, the molecule that is oxidized loses a _____ group as _____. Examples of oxidative decarboxylation include the conversion of pyruvate to acetyl-CoA, isocitrate to -aketoglutarate, and a-ketoglutarate to succinyl-CoA.

Answer 67

carboxyl, carbon dioxide

Question 68

PDH Complex Subunits Cofactors E1: E2: E3:

Answer 68

E1: TPP --> oxidation decarboxylation of Pyruvate E2: Lipoamide --> transfer acetyl group to CoA E3: FAD --> regenerates oxidized form of Lipoamide

Question 69

What primarily drives the formation of citrate from oxaloacetate and acetyl-CoA?

Answer 69

Cleavage of a thioester bond

Question 70

What are the regulatory enzymes in the citric acid cycle?

Answer 70

α-ketoglutarate dehydrogenase Isocitrate dehydrogenase

Question 71

What is a potent activator of phosphofructokinase in mammalian liver cells?

Answer 71

Fructose-2,6-bisphopsphate

Question 72

describe why two steps are needed to convert pyruvate to phosphoenolpyruvate in gluconeogenesis, compared to the single step that converts the phosphoenolpyruvate in glycolysis?

Answer 72

The glycolytic conversion of phosphoenolpyruvate to pyruvate is highly exergonic and cannot be easily reversed.

Question 73

Sequence of events for gluconeogenesis:

Answer 73

Pyruvate Carboxylation of pyruvate Phosphorylation of 3-phosphoglycerate Hydrolysis of fructose-1,6-bisphoshate Hydrolysis of glucose 6-phosphate Glucose

Question 74

Glycolysis: _______ is the key regulatory enzyme Stimulated in response to _____ Acts to _____ blood glucose levels

Answer 74

Phosphofructokinase-1 insulin decrease

Question 75

Gluconeogenesis: _________ key regulatory enzyme Stimulated in response to _____ Acts to _____ blood glucose levels

Answer 75

Fructose-1,6-bisphosphatase glucagon increase

Question 76

Which of the following statements best describes the concept of reciprocal regulation?

Answer 76

When one pathway is active, the other pathway is inhibited

Question 77

Positive effectors of the pyruvate dehydrogenase complex:

Answer 77

Pyruvate, ADP

Question 78

What is ∆G for most regulatory reactions in metabolic pathways?

Answer 78

∆G < 0

Question 79

Regulatory steps of gluconeogenesis & associated enzymes:

Answer 79

Step 1: Pyruvate --> Oxaloacetate (Pyruvate Carboxylase) Step 2: Oxaloacetate --> Phosphoenolpyruvate (Phosphoenolpyruvate carboxykinase) Step 9: Fructose 1,6-biphosphate --> Fructose-6-phosphate (F-1,6-BPase) Step 11: Glucose-6-Phosphate --> Glucose (Glucose-6-phosphatase)

Question 80

Positive effectors for gluconeogenesis: Negative:

Answer 80

Citrate, acetyl CoA AMP, F-2,6-BP, ADP

Question 81

The structure of the pyruvate dehydrogenase complex is fascinating. The complex is composed of 3 different enzymes (E1, E2 and E3) and _____ coenzymes, 2 of which function as co-substrates.

Answer 81

5

Question 82

When your body is low on glucose, the body will release the hormone ______.

Answer 82

glucagon

Question 83

Glucagon activates a signaling cascade that _______ the PFK2/FBPase-2 enzyme. This results in the kinase domain being ______ and the phosphatase domain being ______, ultimately lowering the amount of ______ in the cell.

Answer 83

phosphorylates inactive, active F-2,6-BP

Question 84

When body is low on glucose, ______ would slow down and ______ would speed up due to the decreased amount of ______.

Answer 84

Glycolysis gluconeogenesis F-2,6-BP

Question 85

When your body has high glucose, insulin will be released. Insulin starts a signaling cascade that will ultimately result in the _______ of the bifunctional enzyme. This will activate the kinase domain and deactivate the phosphatase domain, increasing the amount of _______ in the cell. This will activate ______ and inhibit _______.

Answer 85

dephosphorylation F-2,6-BP glycolysis gluconeogenesis

Question 86

Step 1: Citrate Synthase forms a bond between ______ and ______ to form _____. Step 2: Aconitase performs an _______ on citrate to form _____. **Step 3: Isocitrate dehydrogenase performs an ________ on isocitrate to form _______. +NADH **Step 4: alpha-ketoglutarate dehydrogenase performs an ______ to form _______ +NADH Step 5: succinyl-CoA synthetase cleaves a ______ bond to form ______ +GTP Step 6: succinate dehydrogenase performs an _______ on succinate to form _____ (formation of C=C bond) +FADH2 Step 7: Fumarase ______ fumarate to form malate Step 8: Malate dehydrogenase _____ malate to form oxaloacetate (formation of C=O bond) +NADH

Answer 86

oxaloacetate acetyl-CoA citrate isomerization isocitrate oxidative decarboxylation alpha-ketoglutarate oxidative decarboxylation succinyl-CoA high-energy thioester succinate oxidation fumarate hydrates oxidizes

Question 87

Step 1: ______ forms a bond between oxaloacetate and acetyl-CoA to form citrate. Step 2: ______ performs an isomerization on citrate to form isocitrate **Step 3: _______ performs an oxidative decarboxylation on isocitrate to form alpha-ketoglutarate +NADH **Step 4: _________ performs an oxidative decarboxylation to form succinyl-CoA +NADH Step 5: _______ cleaves a high-energy thioester bond to form succinate +GTP Step 6: _______ performs an oxidation on succinate to form fumarate (formation of C=C bond) +FADH2 Step 7: ______ hydrates fumarate to form malate Step 8: ________ oxidizes malate to form oxaloacetate (formation of C=O bond) +NADH

Answer 87

Citrate Synthase Aconitase Isocitrate dehydrogenase alpha-ketoglutarate dehydrogenase succinyl-CoA synthetase succinate dehydrogenase Fumarase Malate dehydrogenase

Question 88

FAD ___ Oxidize _______ to sulfhydryl form so it can begin another cycle. CoA E2 This coenzyme is attached to the acyl group and is important because the thioester bond it will form carries a lot of free energy. Thus, acetyl- CoA can go on to enter the citric acid cycle.

Answer 88

E3, lipoamide

Question 89

NAD+ _____ Oxidize _____ to return it to _____ so that it can perform its function in E3. Additionally, forms ______ to be used in ETC.

Answer 89

E3 FADH2 FAD NADH

Question 90

TPP ____ Involved in the _______ reaction of pyruvate and will become the first carrier of the ______

Answer 90

E1 decarboxylation acyl group

Question 91

Lipoamide _____ AKA lipoic acid, functions as an ‘arm’ that swings into E1 site to accept the _____ from TPP. Swings back into E2 to then _____ the acyl

Answer 91

E2 acyl group attach

Question 92

CoA ____ This coenzyme is _____ to the acyl group and is important because the ______ bond it will form carries a lot of free energy. Thus, acetyl- CoA can go on to enter the citric acid cycle.

Answer 92

E2 attached thioester