Final: Chapter 11 Oxidative Phosphorylation

Question 1

What is the chemiosmotic theory?

Answer 1

Theory proposed by Peter Mitchell that describes energy conversion in essentially all organisms

Question 2

Where in the cell is does the chemiosmotic theory take place?

Answer 2

The mitochondria

Question 3

How is the proton gradient in the chemiosmotic theory established across the mitochondrial inner membrane?

Answer 3

With chemiosmosis (the movement of protons down a concentration gradient). The gradients moves from high concentrations of protons to low concentrations.

ALSO ATP is produced :)

Question 4

What initiates a proton gradient?

Answer 4

Outward pumping of H+ from the mitochondrial matrix by three large protein complexes

Question 5

What does inward flow of H+ through the membrane bound ATP synthase protein accomplish?

Answer 5

ATP synthesis

Question 6

What is the electron transport chain ?

Answer 6

The combined redox reactions that occur in a set of protein complexes embedded in the inner mitochondrial membranes. NADH is oxidized to form NAD+ and O2 (the final electron acceptor) is reduced to H2O

Question 7

The proton circuit behaves like an electrical circuit. What molecules act as the resistor, capacitor, and battery?

Answer 7

ATP synthase is the resistor, the proton gradient is the capacitor, and the battery is the electron transport system

Question 8

How does proton uncoupling stop ATP synthesis?

Answer 8

Proton uncoupling is when a fraction of the proton gradient generated by the electron transport chain is not used to drive ATP synthesis. It causes a proton “leakage” and produces heat

Question 9

What are the main structural features of the mitochondria?

Answer 9

Outer mitochondrial membrane, intermembrane space, inner mitochondrial membrane, cristae (folds within the inner mitochondrial membrane), and the mitochondrial matrix

Question 10

Referring to protein components of the electron transport chain: What protein is in Complex I?

Answer 10

NADH-ubiquinone oxidoreductase

Question 11

Referring to protein components of the electron transport chain: What protein is in Complex II?

Answer 11

Succinate dehydrogenase

Question 12

Referring to protein components of the electron transport chain: What protein is in Complex III?

Answer 12

Ubiquinone-cytochrome c oxidoreductase

Question 13

Referring to protein components of the electron transport chain: What protein is in Complex IV?

Answer 13

Cytochrome oxidase

Question 14

Referring to protein components of the electron transport chain: What protein is in Complex V?

Answer 14

ATP synthase complex

Question 15

Which complexes in the electron transport system contain transmembrane regions that are embedded in the inner mitochondrial membrane as well as functional domains that face toward the mitochondrial matrix?

Answer 15

Complexes I - IV

Question 16

In which complex does NADH oxidation occur?

Answer 16

Complex I which can pump four hydrogen ions across the membrane from the matrix into the intermembrane space, thereby establishing a proton gradient

Question 17

Where does the ETC take place?

Answer 17

On the matrix side of the inner mitochondrial membrane

Question 18

What are the main inhibitors of the ETC?

Answer 18

Rotenone, hydrogen cyanide, carbon monoxide, and antimycin A

Question 19

What are redox loops?

Answer 19

A type of arrangement where protons and electrons are separated on opposite sides of the membrane.

Question 20

Which complex is a redox loop?

Answer 20

Complex III (Q cycle)

Question 21

Proton pumps for the ETC are dependent on what?

Answer 21

The conformational changes of Complexes I and IV

Question 22

What happens in Complex I and what important protein is involved?

Answer 22

• This complex includes flavin mononucleotide (FMN) and NADH-ubiquinone oxidoreductase
• NADH is oxidized while Coenzyme Q is reduced
• FMN accepts 2 electrons from NADH

Question 23

How is semiquinone and reduced flavin mononucleotide formed from flavin mononucleotides?

Answer 23

Flavin mononucleotides are reduced one electron at a time

Question 24

What does Coenzyme Q do?

Answer 24

Acts as mobile electron carrier and transports electrons from Complex I to Complex III

Question 25

Coenzyme Q’s activity serves as an entry point for what other molecules/pathways?

Answer 25

Citrate cycle, fatty acid oxidation, and glycerol-3-phosphate dehydrogenase

Question 26

What happens when Coenzyme Q is reduced?

Answer 26

Ubiquinol (QH2) forms and 4H+ are translocated from the matrix side of the membrane to the intermembrane space

Question 27

What happens in Complex II and what important protein is involved?

Answer 27

• With succinate dehydrogenase, this complex catalyzes the oxidation-reduction reaction of succinate to fumarate.
• Coupled redox reaction using FAD and reduction of coenzyme Q to QH2

Question 28

What happens in Complex III and what important protein is involved?

Answer 28

• With Ubiquinone-cytochrome C oxidoreductase, cytochrome C is reduced while translocating 4H+
• This complex is a docking site for QH2 and cytochrome c

Question 29

What does the Q cycle convert?

Answer 29

Converts a 2 electron transport process into two 1 electron transfers

Question 30

Where do electrons come from in the Q cycle?

Answer 30

Coenzyme Q

Question 31

Where does Q cycle occur and what happens during it?

Answer 31

Occurs in Complex III. Cytochrome c is reduced and transports 1 electron from Complex III to Complex IV

Question 32

What are cytochrome proteins?

Answer 32

Membrane associated, heme-containing proteins involved in electron transport-redox reactions

Question 33

What happens in Complex IV and what important protein involved?

Answer 33

Cytochrome c oxidase accepts electrons one at a time. While cytochrome c is oxidized, oxygen is reduced to water. ALSO, 2H+ are translocated across the membrane

Question 34

What two large structural components comprise the ATP synthase complex?

Answer 34

F1 (encodes catalytic activity) and F0 (acts as a proton channel crossing the inner mitochondrial membrane)

Question 35

Where do protein flow through in ATP synthase and what happens?

Answer 35

They flow through the F0 component which induces the F1 subunit to undergo a conformation change (loose to tight and then open). ATP is released only in the open position

Question 36

What two shuttles are used to shuttle biomolecules required for the ETC and oxidative phosphorylation?

Answer 36

Malate-aspartate shuttle (liver) and glycerol-3-phosphate (muscle) which transport electrons from cystolic NADH to the mitochondria

Question 37

How is the import of ADP and P into the mitochondrial matrix accomplished?

Answer 37

By using two translocase proteins located in the inner mitrochondrial matrix: ATP/ADP translocase (exports one ATP for every ADP imported) and phosphate translocase (translocates one P and one H+ into the matrix)

Question 38

What is ATP-ADP translocase?

Answer 38

An antiporter membrane transport protein

Question 39

What is phosphate translocase?

Answer 39

Protein similar to a channel that can act as a symporter (two molecules moved in the same direction) or antiporter (two molecules moved in opposite directions). It is also electrically neutral

Question 40

What is the malate-aspartate shuttle and what’s important about it?

Answer 40

It is the primary shuttle in liver cells whose reactions are all reversible. It maintains the supply of NAD+

Question 41

What is the glycerol-3-phosphate shuttle and what’s important about it?

Answer 41

Shuttle that consists of two isozymes of glycerol-3-phosphate dehydrogenase. It delivers electrons from NADH to the mitochondrial matrix using FAD. Electrons from NADH got into the ETC through coenzyme Q