session 12-13 practice problems

The TCA (tricarboxylic acid) cycle is also known as

1) The ATP cycle

2) The citric acid cycle

3) The Jacobson cycle

4) The Krebs cycle

Answers 2) and 4) are true

Answers 1), 2) and 3) are true

All of them are true

Answers 1) and 3) are true

None of them is true

Answers 2) and 4) are true

The total amount of energy stored in acetyl CoA is 228 kcal/mol; each mole acetyl CoA can generate 3 moles of NADH (energy content = 53 kcal/mol), 1 mole of FAD(2H) (energy content = 41 kcal/mol), and 1 mole of GTP (= ATP; energy content = 7.3 kcal/mol) during a TCA cycle. What is the approximate energy transformation efficiency from oxidation of acetyl CoA through the TCA cycle?

90%

80%

20%

40%

100%

90%

The TCA cycle requires which of the following cofactors?

1) Coenzyme A

2) FAD

3) Lipoate

4) NAD+

5) Thiamine pyrophosphate

Answers 2) and 4) are true

All of them are true

Answers 1), 2) and 3) are true

Answers 1) and 3) are true

None of them is true

All of them are true

Vitamin thiamine pyrophosphate (TPP) is a coenzyme of several enzymes including pyruvate dehydrogenase and α-ketoglutarate dehydrogenase. Thiamine deficiency can result in Beriberi symptom, lactate acidosis and cardiomyopathy (congestive heart failure). Which of the following is a major cause of thiamine deficiency BESIDES inherited genetic mutation?

Vegetarianism

Obesity

Excessive exercise

Nicotine addiction

Alcoholism

Alcoholism

Which of the following statements about metabolic pathway regulation is true?

1) Feedback regulation is common

2) Regulation may occur by compartmentation

3) Regulation may occur at rate of gene expression

4) Regulation often occurs at the last step of a pathway

5) Regulation often occurs at the fastest step of a pathway

None of them is true

Answers 1), 2) and 3) are true

Answers 1) and 3) are true

Answers 2) and 4) are true

All of them are true

Answers 1), 2) and 3) are true

The TCA cycle is regulated mainly by which of the following factors to achieve an ATP homeostasis? 1)The ratio of [ADP]/[ATP] 2)The ratio of [NADH]/[NAD+] 3)[Ca2+] 4)The ratio of [ATP]/[NAD+] 5)The ratio of [ADP]/[NADH]

None of them is true

Answers 1) and 3) are true

All of them are true

Answers 2) and 4) are true

Answers 1), 2) and 3) are true

Answers 1), 2) and 3) are true

Which of the following statements about the TCA cycle is NOT true?

TCA cycle, followed by electron transport chain and oxidative phosphorylation, accounts for more than 2/3 of the ATP generated from fuel oxidation.

All enzymes required for the TCA cycle are located freely in the mitochondrial matrix.

Acetyl CoA is the direct substrate of the TCA cycle.

TCA cycle has dynamic efflux and influx of intermediates.

All enzymes required for the TCA cycle are located freely in the mitochondrial matrix.

A distance runner is training for her half marathon, which allows her muscles to use fatty acids as a fuel source. Fatty acids are converted to acetyl-CoA in the mitochondria, at which point the acetyl-CoA can be oxidized in the TCA cycle to generate GTP and reduced electron carriers. Which one of the followings correctly describes how the acetyl-CoA is metabolized in the mitochondria?

Substrate-level phosphorylation generates one high-energy phosphate bond during the TCA cycle.

NAD+ is the sole electron acceptor in the cycle.

One molecule of acetyl-CoA produces two molecules of CO2, three molecules of NADH, one molecule of FAD(2H) and one molecule of ATP.

All of the energy for high-energy phosphate bonds is derived from oxidative phosphorylation.

Substrate-level phosphorylation generates one high-energy phosphate bond during the TCA cycle.

Which of the followings is NOT a source of fuel from which acetyl CoA can be derived to enter the TCA cycle?

Sugars

Ketone bodies

Vitamins

Fatty acids

Vitamins

For a healthy individual with adequate food intake, intensive exercise usually results in the INCREASE of which of the followings?

Water content in the body

Number and size of cells in the body

Fatty acid/adipose tissue in the body

Number and size of mitochondria in muscle cells

Number and size of mitochondria in muscle cells

A patient diagnosed with thiamine deficiency exhibited fatigue and muscle cramps. The muscle cramps have been related to an accumulation of metabolic acids. Which of the following metabolic acids is most likely to accumulate in the body of a thiamine-deficiency patient?

Succinate

Isocitrate

Pyruvate

Oxaloacetate

Pyruvate

Which of the following descriptions of human metabolism is NOT an attribute of glycolysis?

 

Generation of energy

 

Contribution to ATP homeostasis in all cells

 

Storage of excessive glucose in the form of glycogen

 

Providing intermediates for other biosynthetic processes

Storage of excessive glucose in the form of glycogen

Which of the following statements about glycolysis is TRUE?

 

ATP is formed by oxidative phosphorylation during glycolysis.

 

Anaerobic glycolysis can occur in the red blood cells which carry oxygen.

 

Glycolysis takes place in the mitochondrial matrix.

 

The end-product of aerobic glycolysis is lactate

Anaerobic glycolysis can occur in the red blood cells which carry oxygen

The major fate of lactate generated from anaerobic glycolysis in extraneously exercising muscle cells is which of the followings?

 

Stored forever in muscle cells

 

Excreted through urine and sweat

 

Oxidized directly to acetyl CoA in mitochondria

 

Circulated back to liver and converted to pyruvate and then to glucose

Circulated back to liver and converted to pyruvate and then to glucose

A 4-week old baby is being seen by the pediatrician because of frequent vomiting after meals and tenderness in the abdomen. Upon examination, the physician noted an enlarged liver and a hint of cataract formation in both of the child’s eyes. A urine dipstick test for a reducing sugar gave a positive result. Blood glucose levels were slightly below normal. The compound that reacted with the urine dipstick test is most likely which of the followings?

 

Fructose

 

Galactose

 

Glucose

 

Sucrose

Galactose

The red blood cells require ATP in order to maintain ion gradients across their membrane. In the absence of these gradients, the red blood cells will swell and burst, bring about a hemolytic anemia. Red blood cells generate the energy they needed mainly via which of the following processes?

 

Complete oxidation of pyruvate to CO2 and H2O

 

Substrate-level phosphorylation

 

Oxidative phosphorylation

Substrate-level phosphorylation

What is the fundamental biochemical reason for us to breathe?

• To inflate our lungs

• To oxidize fuels with O2 to produce ATP

• To buffer our blood to maintain a pH homeostasis

• To purge CO2

• To oxidize fuels with O2 to produce ATP

Which of the following disease conditions are associated with inadequate bioenergetics? (Multi-answer question)

 

1) Anorexia

2) Hyperthyroidism

3) Myocardial infarction

4) Malnutrition

5) Abdominal obesity

6) Type 2 diabetes mellitus

7) High blood triglyceride levels (often due to excessive alcohol consumption)

 

• Only answer 6) is true

• All of them are true

• Answers 1) , 3), 5) and 7) are true

• Answers 2) , 4) and 6) are true

• None of them are true

• All of them are true

All cells require energy to survive and the laws of thermodynamics need to be followed within biological systems. Which one of the following bioenergetic terms or statements is True?
 

• ΔG0’ of a reaction is the standard free-energy change measured at 37°C and a pH at 7.4

• The change in enthalpy (ΔH) of a reaction is a measure of the total amount of heat that can be released from changes in the chemical bonds

• The first law of thermodynamics states that the universe tends toward an increased disorder

• The second law of thermodynamics states that the total energy of a system remains constant

• A high-energy bond is a bond that releases >3 kcal/mol of heat when it is hydrolyzed

• The change in enthalpy (ΔH) of a reaction is a measure of the total amount of heat that can be released from changes in the chemical bonds

True or False? For a hypothetical reaction aA + bB <=> cC + dD, the forward reaction has a ΔG0’ of +2.4 kcal/mol, therefore it is thermodynamically favorable.

True

False

False

For the reaction in Figure 20.3 at 25°C and a pH at 7.0, if the starting concentration of G6P and G1P is 1 M, what is the ratio of [G1P]/[G6P] at equilibrium? (Note: R, universal gas constant: 1.99 cal/mol-K; T, absolute temperature: K, Kelvin = 273 + °C)

• 15:1

• 1:30

• 1:1

• 1:15

• 30:1

• 1:15

For the reaction in Figure 20.3 at 25°C and a pH at 7.0, if the ratio of [G6P]/[G1P] increases to 60:1 by adding more G6P, which direction of the reaction will proceed?

• a. G6P --> G1P

• b. G6P <-- G1P

• G6P --> G1P

A calculator may be needed for this question. It is estimated that the daily hydrolysis of ATP by our heart is about 16 g of ATP per g of tissue. An average human heart weighs about 350 g that contains about 4 g of ATP at ATP homeostasis, approximately how many turnovers of ATP occur daily in the heart?

• 1400

• 1000

• 10

• 800

• 100

• 1400

Which of the following descriptions of human metabolism is NOT an attribute of glycolysis?

 

Generation of energy

 

Contribution to ATP homeostasis in all cells

 

Storage of excessive glucose in the form of glycogen

 

Providing intermediates for other biosynthetic processes

Storage of excessive glucose in the form of glycogen

Which of the following statements about glycolysis is TRUE?

 

ATP is formed by oxidative phosphorylation during glycolysis.

 

Anaerobic glycolysis can occur in the red blood cells which carry oxygen.

 

Glycolysis takes place in the mitochondrial matrix.

 

The end-product of aerobic glycolysis is lactate

Anaerobic glycolysis can occur in the red blood cells which carry oxygen.

The major fate of lactate generated from anaerobic glycolysis in extraneously exercising muscle cells is which of the followings?

 

Stored forever in muscle cells

 

Excreted through urine and sweat

 

Oxidized directly to acetyl CoA in mitochondria

 

Circulated back to liver and converted to pyruvate and then to glucose

Circulated back to liver and converted to pyruvate and then to glucose

A 4-week old baby is being seen by the pediatrician because of frequent vomiting after meals and tenderness in the abdomen. Upon examination, the physician noted an enlarged liver and a hint of cataract formation in both of the child’s eyes. A urine dipstick test for a reducing sugar gave a positive result. Blood glucose levels were slightly below normal. The compound that reacted with the urine dipstick test is most likely which of the followings?

 

Fructose

 

Galactose

 

Glucose

 

Sucrose

Galactose

The red blood cells require ATP in order to maintain ion gradients across their membrane. In the absence of these gradients, the red blood cells will swell and burst, bring about a hemolytic anemia. Red blood cells generate the energy they needed mainly via which of the following processes?

 

Complete oxidation of pyruvate to CO2 and H2O

 

Substrate-level phosphorylation

 

Oxidative phosphorylation

Substrate-level phosphorylation