Biochemistry 3380G Lecture Notes - Pyruvate Dehydrogenase, Citric Acid Cycle, Decarboxylation

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6 Dec 2012

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The outer mitochondrial membrane has many pores to allow small molecules to cross. The inner mitochondrial membrane (im membrane) prevents small molecules from crossing, unless a special pathway exists. The cristae are folds of the im membrane that provide high surface area. The mitochondrial matrix is the space enclosed by the im membrane. The origins of mitochondria involve the endosymbiosis of symbiotic aerobic bacteria into eukaryotic cells billions of years ago. Pyruvate oxidation occurs in two stages: the decarboxylation of pyruvate to form acetyl coenzyme a (acetyl coa) and the oxidation of the acetyl group in acetyl coa in the citric acid (kreb s) cycle. Coenzyme a (or coa) is a carrier molecule that contains a thiol group (sh) on its end. When attached to an acetyl group, a high energy bond is formed between the acetyl and the thiol group of coa. The pyruvate dehydrogenase complex is the enzyme responsible for the conversion of pyruvate to acetyl coa.

Related Questions

5. Almost all of the oxygen (O2) one consumes in breathing is converted to: a. acetyl-CoA. b. carbon dioxide (CO2). c. carbon monoxide and then to carbon dioxide. d. none of the above. e. water.

6. A new compound isolated from mitochondria is claimed to represent a previously unrecognized carrier in the electron transfer chain. It is given the name coenzyme Z. Which line of evidence do you feel is the least conclusive in assigning this compound a position in the electron transfer chain? a. Alternate oxidation and reduction of the mitochondrion-bound coenzyme Z can be readily demonstrated. b. Removal of coenzyme Z from the mitochondria results in a decreased rate of oxygen consumption. c. The rate of oxidation and reduction of mitochondrion-bound coenzyme is of the same order of magnitude as the overall rate of electron transfer in mitochondria as measured by oxygen consumption. d. The reduction potential of Z is between that of two compounds known to participate in the electron transport chain e. When added to a mitochondrial suspension, coenzyme Z is taken up very rapidly and specifically by the mitochondria.

7. Which of the following is not true of the citric acid cycle? a. All enzymes of the cycle are located in the cytoplasm, except succinate dehydrogenase, which is bound to the inner mitochondrial membrane. b. In the presence of malonate, one would expect succinate to accumulate. c. Oxaloacetate is used as a substrate but is not consumed in the cycle. d. Succinate dehydrogenase channels electrons directly into the electron transfer chain. e. The condensing enzyme is subject to allosteric regulation by ATP and NADH.

8. Conversion of 1 mol of acetyl-CoA to 2 mol of CO2 and CoA via the citric acid cycle results in the net production of: a. 1 mol of citrate. b. 1 mol of FADH2. c. 1 mol of NADH. d. 1 mol of oxaloacetate. e. 7 mol of ATP.

force times distance

Question 48

Soccer (assuming field player) is a sport which is 90% aerobic.

True

False

Question 50

Glucose is necessary for fatty acid oxidation because...

		its derivative, pyruvate, is condensated with carbonic acid to form oxaloacetate, which in turn is a necessary carbon compound in the citric acid cycle
		it is needed to convert fatty acids to fatty acyl-CoA which in turn is oxidized to acetyl CoA
		glucose is decarboxylated into cytochrome oxidase which is a necessary intermediate in the citric acid cycle
		its derivative, acetyl CoA, is condensated with carbonic acid to form lactase, which in turn is a necessary carbon compound in the citric acid cycle

Question 51

In aerobic ATP production, the role of oxygen is to...

		to keep the electron transport chain operational
		to accept electrons from the 3rd cytochrome and thereby oxidizing it so it can accept new electrons
		act as a oxidizing agent by accepting electrons from the electron transport chain and combining with hydrogen ions (protons)
		all of the above

Question 52

The primary purpose of the citric acid cycle is...

aerobic glycolysis

gluconeogenesis using lactate

the decarboxylation of carbon compounds to produce NADH.

the shuttling of hydrogen ions through the inner mitochondrial membrane

Question 55

Which of the following is the best predictor of marathon running performance?

	A.	Maximal rate of pyruvate oxidation
	B.	Maximal rate of lactate formation
	C.	Amount of adipose tissue triglycerides
	D.	Pre-race blood glucose concentration

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Why does an electron have lower potential energy in an H-O bondthan in an O=O bond?

H has a higher electronegativity than O.

O=O is not stable.

O=O contains a double bond.

The electrons are closer to the oxygen atom in the H-O bond.

None of the answers are correct.

How is the energy from the electron transport chain used mostdirectly?

to form the bonds of a water molecule

to pump hydrogen ions across the mitochondrial inner membraneinto the mitochondrial intermembrane space

to join ADP with a phosphate

to decompose glucose into pyruvate

to rotate ATP synthase

Which process provides the energy needed to pump protons acrossthe mitochondrial membrane during oxidative phosphorylation?

the transfer of electrons in redox reactions

the breakdown of ATP to ADP

the rotation of the ATP synthase rotor

oxidation of isocitrate

None of the answers are correct.

What causes the ATP synthase rotor to spin?

the passing of electrons through ATP synthase

the movement of protons across the mitochondrial membrane

the movement of electrons across the mitochondrial membrane

the synthesis of ATP from ADP and a phosphate group

None of the answers are correct.

What of the following generates the proton-motive force duringoxidative phosphorylation?

buildup of NADH molecules at protein complex I

movement of H⁺ ions across the mitochondrial membraneduring electron transport

rotation of the ATP synthase rotor

joining of H⁺ ions with oxygen to form water

None of the answers are correct.

Suppose a microorganism invades a cell, causing damage to ATPsynthase. How would cellular respiration be affected?

Electrons could not be passed down the electron transportchain.

ADP could not be joined with a phosphate to form ATP.

Hydrogen ions could not be pumped into the mitochondrialintermembrane space.

The cell could not release any energy from the glucosemolecule.

Glucose could not be broken down into pyruvate.

Which molecules transport electrons from the citric acid cycleto the electron transport chain?

NADH and FADH₂

ATP and ADP

GTP and GDP

oxaloacetate and citric acid

None of the answers are correct.

Which type of reactions control the energy release from glucoseduring the citric acid cycle?

acid-base reactions

redox reactions

random reactions

All answers are correct.

None of the answers are correct.

What is the role of NAD⁺ in cellular respiration?

to receive electrons from the citric acid cycle and deliver themto the electron transport chain

to catalyze the synthesis of ATP from ADP

to accumulate in the mitochondrial intermembrane space tofacilitate ATP synthesis

to serve as a substrate to bind to acetyl-CoA at the beginningof the citric acid cycle

None of the answers are correct.

10.

Which molecule enters the citric acid cycle?

glucose

pyruvate

ATP

acetyl-CoA

None of the answers are correct.

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Biochemistry 3380G Lecture Notes - Pyruvate Dehydrogenase, Citric Acid Cycle, Decarboxylation

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