Biochem Exam 4

The glycolytic enzymes are located in the:

• ER

• Mitochondrial Matrix

• Inner Mitochondrial Membrane

• Nucleus

• Cytosol

Cytosol

What is the initial investment of ATP in the glycolytic pathway per molecule of glucose?

2 ATP

What is the net equation of glycolysis?

Glucose + 2 ADP + 2 Pi + 2 NAD⁺ --> 2 pyruvate + 2 ATP + 2 NADH + 4 H⁺

The enzyme phosphoglucomutase catalyzes the isomerization of glucose-6-phosphate to:

Glucose-1-Phosphate

Complete the analogy:

 Glycogen synthase is to the branching enzyme as glycogen phosphorylase is to the ________ enzyme.

debranching

What is the net energetic cost of converting two pyruvate to one glucose by gluconeogenesis, in ATP equivalents?

6 (4 ATP and 2 GTP)

The anaerobic conversion of 1 mol of glucose to 2 mol of ethanol by fermentation is accompanied by the net gain of:

2 mol ATP

Compare and contrast Glycolysis and Gluconeogenesis 

Starting Substrates:

• Glycolysis —> Glucose

• Gluconeogenesis —> Pyruvate

Energy Requirements:

• Glycolysis —> 2

• Gluconeogenesis —> 6

Use of NAD⁺ and NADH:

• Glycolysis —> 2 NAD⁺

• Gluconeogenesis —> 2 NADH

Indicate which pathways each of the following enzymes are involved in:

1. Phosphoenolpyruvate (PEP) Carboxykinase

2. Aldolase

3. Hexokinase

4. Glucose-6-Phosphatase

1. Used only in gluconeogenesis

2. Used in glycolysis and gluconeogenesis

3. Used only in glycolysis

4. Used only in gluconeogenesis

I. The molecule shown above is _______    

II. In glycolysis, the substrates used to produce the molecule above are _______ and ______      

III. The metabolic pathway/cycle that the molecule above participates in is _________

IV. The glycolytic enzyme that produces the molecule above is ________

1. Fructose-1,6-Bisphosphate

2. Fructose-6-Phosphate and ATP

3. Glycolysis

4. PFK-1

One of the most important products of the pentose phosphate pathway is:

NADPH

A major allosteric regulator of both glycolysis and gluconeogenesis is:

Fructose-2,6-Bisphosphate

Both glycogen synthesis and glycogen breakdown share the metabolite:

Glucose-1-Phosphate

The steps in glycolysis that differ from those of gluconeogenesis are catalyzed by:

Pyruvate kinase, phosphofructokinase, hexokinase

The first reaction of gluconeogenesis is:

A carboxylation

Which of the following enzymes catalyzes the transfer of a phosphoryl group from ATP to glucose?

Hexokinase

What are the potential control points in glycolysis?  What is the actual control point (commitment step)?

• Possible

  • Steps 1, 3, and 10

• Actual

  • Step 3

Glucose is converted to _____ in skeletal muscle under anaerobic conditions.

Lactate

From first to last, select the intermediates as they appear in glycogen synthesis. 

1. Glucose

2. Glucose-6-Phosphate

3. Glucose-1-Phosphate

4. UDP-Glucose

5. Glycogen

The aldolase reaction is spontaneous in vivo because:

A) It is metabolically irreversible under standard biochemical conditions.

B) Aldolase uses ATP hydrolysis to make the reaction irreversible.

C) The rapid consumption of products pulls the reaction forward.

D) The reaction occurs very slowly.

C) The rapid consumption of products pulls the reaction forward

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

• Step 3

• Step 4

• Both

Both

Which reactions in the TCA cycle use a thioester substrate (a substrate with a CoA attached)?

• Steps 1 and 5

• Steps 1 and 3

• Steps 2 and 3

Steps 1 and 5

Which reaction in the TCA cycle gives electrons to ubiquinone (Q)?

• Step 6

• Step 4

• Step 2

Step 6

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

• near-equilibrium

• irreversible
  

Irreversible

Which of the following terms describes the TCA cycle as both catabolic and anabolic?

• Amphipathic

• Anaplerotic

Anaplerotic

The regulated enzymes of the TCA cycle include:

• Fumarase

• Malate dehydrogenase

• Citrate lyase

• ⍺-ketoglutarate dehydrogenase

⍺-ketoglutarate dehydrogenase

Which reactions in the TCA cycle release CO₂?

• Steps 5 and 6

• Steps 1 and 2

• Steps 3 and 4

Steps 3 and 4

Which of the enzymes listed below require NAD⁺?

Hint: The enzymes may not just be those involved in the Citric Acid Cycle

• Succinate dehydrogenase

• Malate dehydrogenase

• Isocitrate dehydrogenase

• Glyceraldehyde-3-phosphate dehydrogenase

• Malate Dehydrogenase

• Isocitrate dehydrogenase

• Glyceraldehyde-3-phosphate dehydrogenase

Which of the following answers complete the sentence correctly?

Succinate dehydrogenase...

A.) is an integral membrane protein, unlike the other enzymes of the citric acid cycle.

B.) contains FAD and NAD⁺ cofactors like pyruvate dehydrogenase.

B.) is a copper-sulfur protein.

D.) carries out an oxidative decarboxylation like isocitrate dehydrogenase.

A.) Is an integral membrane protein, unlike the other enzymes of the citric acid cycle.

What cellular location contains pyruvate dehydrogenase and most of the citric acid cycle enzymes?

Mitochondral Matrix

Which of the following pyruvate dehydrogenase enzymes is correctly paired with the coenzyme that is associated with it?

• E3: lipoamide

• E3: FAD

• E2: thiamine pyrophosphate

• E1: coenzyme A

E3: FAD

What makes the reaction catalyzed by citrate synthase highly exergonic?

• Conversion from keto to enol tautomer

• Hydrolysis of thioester

• Decarboxylation reaction

• Hydrolysis of ATP

Hydrolysis of Thioester

Which of the following condenses with oxaloacetate to form citrate?

• Succinyl-phosphate

• Carboxybiotin

• Cis-aconitate

• Acetyl-CoA

Acetyl-CoA

The reaction catalyzed by fumarase is _____.

• a hydroxylation of an alkene

• a hydration of an alkene

• a dehydration of an alcohol

• an isomerization of an alcohol

A hydration of an alkene

Which of the following is activated by ADP?

• Isocitrate dehydrogenase

• Succinyl-CoA synthetase

• Malate dehydrogenase

• Aconitase

Isocitrate dehydrogenase

Put the TCA cycle enzymes in the correct order:

1. Citrate synthase 

2. Aconitase

3. Isocitrate dehydrogenase

4. α-Ketoglutarate dehydrogenase

5. Succinyl-CoA synthetase 

6. Succinate dehydrogenase  

7. Fumarase 

8. Malate dehydrogenase             

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

3

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

• Succinate

• Malate

• α-ketoglutarate

• Succinyl-CoA

• Fumarate

• Succinate

• α-ketoglutarate

• Succinyl-CoA

Which component of ATP synthase functions as a transmembrane proton channel?

F0

How many electrons can be carried by the prosthetic group in cytochrome c?

1

When 2 electrons are passed through Complex I, ____ protons are transferred to the intermembrane space.

4

Identify if the following statement is true or false:

NADH accepts electrons during respiratory electron transport.

False

• Select the answers below as they pertain to the indicated pathway.

• Note: for the NET ATP yield include any and all ATP equivalents generated in a particular pathway (i.e. ATP, GTP). This should include the oxidation of reducing equivalents that may be generated in the pathway.

  • Assume that NADH=2.5 ATP and FADH₂=1.5 ATP

  • Assume the carbon reactants are each going through the pathway once. 

40, 140

Complex IV of the electron transport chain oxidizes_____, reduces ______ , and _______  protons in the process.

• Cytochrome C

• O₂

• Pumps

If the reduction potential for NAD⁺ is -0.315 V and the reduction potential for oxygen is 0.815 V, what is the potential for the oxidation of NADH by oxygen?

1.13 V

What is the ∆Gº' for the reduction of pyruvate to lactate by NADH given the following half reactions?

pyruvate + 2H⁺ + 2e^- -> lactate      ∆εº' = -0.185

NAD⁺ + H⁺ + 2e^- -> NADH             ∆εº' = -0.315

-25.1 kJ/mol

A man presents in the emergency room after ingesting an insecticide.  The Poison Control Center indicates that the insecticide contains cyanide (CN^-), which binds to and completely inhibits cytochrome c oxidase.  Would ATP synthesis in this man’s mitochondria be stopped?

Yes

What is the terminal (final) electron acceptor in aerobic organisms?

O₂ (Oxygen)

In the malate-aspartate shuttle, _____ is reduced to _____ in the cytosol.

• malate; aspartate

• oxaloacetate; malate

• aspartate; malate

• aspartate; oxaloacetate

Oxaloacetate; malate

What does the reduction potential of 0.815 V for the reduction of oxygen to water indicate?

• Oxygen is a very strong oxidizing agent.

• Water is a very strong reducing agent and oxygen is a very strong oxidizing agent.

• Water is a very strong reducing agent.

• Water will be spontaneously reduced to oxygen.

Oxygen is a very strong oxidizing agent

Which of the following is the location of the Q cycle?

• Complex I

• succinate dehydrogenase

• Acyl-CoA dehydrogenase

• Complex III

• NADPH

Complex III

Complex II accepts electrons from _____ and transfers them to _____.

• ubiquinol; fumarate

• cytochrome c; cytochrome a

• ubiquinone; cytochrome c

• succinate; ubiquinone

Succinate; ubiquinone

Complex IV uses _____ and _____ ions to reduce oxygen to water.

• manganese; iron

• copper; iron

• zinc; lead

• manganese; copper

Copper; iron

How many cytochrome c molecules are oxidized by Complex IV for each molecule of oxygen (O₂) that is reduced?

4

Which subunit of ATP synthase is responsible for the catalysis of ATP formation?

• Gamma

• Alpha

• Beta

• c

Beta

Which of the following occurs when the catalytic subunit of ATP synthase is in the loose state?

• ATP is hydrolyzed

• ADP and P_i bind

• ATP is released

• ADP and P_i are converted to ATP

ADP and P_i bind