Biochemistry : Electron Transport Chain Proteins and Complexes

Study concepts, example questions & explanations for Biochemistry

varsity tutors app store varsity tutors android store

Example Questions

← Previous 1

Example Question #1 : Electron Transport Chain Proteins And Complexes

Which electron transport chain complexes would be impaired by an iron deficiency?

Possible Answers:

Complex II and IV

Complex I and IV

Complex III and IV

Complex I and II

Correct answer:

Complex I and II

Explanation:

Complex I (NADH-CoQ reductase) contains iron-sulfur proteins, and complex II (succinate-CoQ reductase) contains both heme and iron-sulfur proteins. Thus, iron deficiency would compromise the function of complex I and II. The other enzyme complexes do not have iron-containing proteins, thus, they would not be impaired by an iron deficiency.

Example Question #2 : Electron Transport Chain Proteins And Complexes

Which electron transport chain complex would be impaired by a deficiency of copper?

Possible Answers:

Complex II

Complex III

Complex I

Complex IV

Correct answer:

Complex IV

Explanation:

Complex IV (cytochrome oxidase) contains two copper centers,  and , thus a copper deficiency would result in loss of function of enzyme complex IV. The other enzyme complexes do not contain copper, thus, they would not be impaired by a copper deficiency.

Example Question #3 : Electron Transport Chain Proteins And Complexes

What would be the most immediate result if complex II of the electron transport chain suddenly stopped working? 

Possible Answers:

Buildup of succinate in the mitochondrial matrix

Increase in glycolysis

Glycogen breakdown 

Increase in the hydrogen ion concentration in the mitochondrial intermembrane space

Correct answer:

Buildup of succinate in the mitochondrial matrix

Explanation:

Complex II of the electron transport chain catalyzes the following reaction:

It uses the enzyme succinate dehydrogenaseThe immediate result of this complex's loss of function would be a buildup of succinate, since that molecule can no longer be oxidized to fumarate. The multitude of problems that can arise come from this crucial step of the citric acid cycle not being able to move forward.

Example Question #4 : Electron Transport Chain Proteins And Complexes

Which reaction of the Krebs cycle is carried out at the electron transport chain?

Possible Answers:

Fumarate to malate

Citrate to isocitrate

Succinate to fumarate

Succinyl-CoA to succinate

Correct answer:

Succinate to fumarate

Explanation:

The conversion of succinate to fumarate is the only reaction that occurs outside of the normal Krebs cycle. Complex II of the electron transport chain has an enzyme known as succinate dehydrogenase. This enzyme is responsible for the conversion of succinate to fumarate. Fumarate is return to the cycle where it is then oxidized to malate continuing the cycle. Each of the other reactions of the Krebs cycle listed all occur in the inner mitochondrial matrix; whereas the conversion of succinate to fumarate occurs at the inner mitochondrial membrane.

Example Question #5 : Electron Transport Chain Proteins And Complexes

ATP synthase works by means of __________.

Possible Answers:

a proton gradient across the outer mitochondrial membrane

an acetyl-CoA gradient across the outer mitochondrial membrane

an acetyl-CoA gradient across the inner mitochondrial membrane

a proton gradient across the inner mitochondrial membrane

Correct answer:

a proton gradient across the inner mitochondrial membrane

Explanation:

ATP synthase uses the proton gradient across the inner membrane to generate ATP. The ATP synthase is essentially like a rotary motor. The proton gradient serves as the priming of the ATP synthase. As proton are moved from the outer mitochondrial matrix back into the mitochondrial matrix they are providing mechanical energy to turn the pump. As the pump is being turned ATP synthase utilizes a unit of ADP and inorganic phosphate to generate one molecule of ATP. This is done for every three turns of the ATP synthase.

Example Question #6 : Electron Transport Chain Proteins And Complexes

Complex IV of the electron transport chain __________.

Possible Answers:

Includes an  dehydrogenase

Directs electron to oxygen to form water

Is responsible directly for the production of ATP from ADP and inorganic phosphate

Includes a succinate dehydrogenase

Correct answer:

Directs electron to oxygen to form water

Explanation:

Complex IV is also known as cytochrome c oxidase because it accepts the electrons from cytochrome c and directs them towards the four electron reduction of oxygen to form two molecules of water. ATP synthase is directly responsible for the generation of ATP by utilizing one unit of ADP and one unit of inorganic phosphate along with the proton motive force (PMF). Complex II is also known as succinate dehydrogenase which is responsible for one of the reaction of the Krebs cycle: succinate to fumarate. This reaction generates one molecule of . Complex I is also known as  dehydrogenase in that it oxidizes the coenzyme .

Example Question #7 : Electron Transport Chain Proteins And Complexes

Complex I of the electron transport chain __________.

Possible Answers:

includes succinate dehydrogenase

is responsible directly for the formation of water

is responsible for accepting electrons from NADH

carries electrons to oxygen

Correct answer:

is responsible for accepting electrons from NADH

Explanation:

Complex I is also called NADH-Coenzyme Q (CoQ) reductase because it transfers 2 electrons from NADH to CoQ. Complex I was formerly known as NADH dehydrogenase. This complex binds NADH and takes up two electrons.The last step of this complex is the transfer of two electrons one at a time to CoQ. The process of transferring electrons from NADH to CoQ by complex I results in the overall transport of protons from the matrix side of the inner mitochondrial membrane to the inter membrane space where the hydrogen ion concentration increases generating a proton motive force which is utilized by ATP synthase.

Example Question #8 : Electron Transport Chain Proteins And Complexes

Complex II of the electron transport chain __________.

Possible Answers:

includes a succinate dehydrogenase

has a cytochrome c binding site

is responsible for accepting electrons from 

includes an  dehydrogenase

Correct answer:

includes a succinate dehydrogenase

Explanation:

Complex II of the electron transport chain is generally apart of both the electron transport chain as well as the Krebs cycle. It is the the succinate dehydrogenase that carried out the conversion of succinate to fumarate in the Krebs cycle. The only enzyme of the citric acid cycle that is an integral membrane protein. The conversion of succinate to fumarate generates an .  then transfers its electrons one at a time through complex II. The final step of this complex is the transfer of two electrons one at a time to coenzyme Q.

Example Question #9 : Electron Transport Chain Proteins And Complexes

In complex II of the electron transport chain which is/are the coenzyme(s) mainly oxidized?

Possible Answers:

 only

 only

 and 

 only

Correct answer:

 only

Explanation:

Complex II of the electron transport chain is generally apart of both the electron transport chain as well as the Krebs cycle. It is the the succinate dehydrogenase that carried out the conversion of succinate to fumarate in the Krebs cycle. The only enzyme of the citric acid cycle that is an integral membrane protein. The conversion of succinate to fumarate generates an .  then transfers its electrons one at a time through complex II. The final step of this complex is the transfer of two electrons one at a time to coenzyme Q.

Example Question #10 : Electron Transport Chain Proteins And Complexes

What is the role of ubiquinone in the electron transport chain?

Possible Answers:

Ubiquinone accepts electrons directly from 

Ubiquinone carries electrons from the first enzyme complex to the second enzyme complex

Ubiquinone accepts electrons directly from 

Ubiquinone is the final step in which oxygen is reduced to water

Ubiquinone carries electrons from the third enzyme complex to the fourth enzyme complex

Correct answer:

Ubiquinone carries electrons from the first enzyme complex to the second enzyme complex

Explanation:

Ubiquinone functions to carry electrons in oxidative phosphorylation from the first enzyme complex to the second enzyme complex.  It does not receive electrons from  nor  directly. 

← Previous 1
Learning Tools by Varsity Tutors

Incompatible Browser

Please upgrade or download one of the following browsers to use Instant Tutoring: