Chapter 7.5: The Electron Transport Chain and Chemiosmosis

Question 1

After A carrier called ubiquinone then passes the electrons to a protein-cytochrome complex called the bc₁ complex what is the last step of the electron transport chain?

Answer 1

• The electrons are then carried by another carrier. Cytochrome c, to the cytochrome oxidase complex
  
  • Uses four electrons to reduce a molecule of oxygen
  • Each oxygen then combine with two protons to form water

O₂ + 4H⁺ + 4e^- –> 2H₂O

Question 2

How is the proton gradient in the electron transport chain formed?

Answer 2

• Three transmembrane complexes of the electron transport chain accomplish the proton transport
  
  • The flow of electrons induces a change in the shape of pump proteins, which causes them to transport protons across the membrane
    
    • The electrons contributed by NADH activate all 3 of these proton pumps
    • Electrons from FADH₂ activate only two because of where they enter the chain
  • A proton gradient is formed between the intermembrane space and the matrix

Question 3

What is an enzyme located on the inner mitochondrial membrane that catalyzes the oxidation by NAD⁺ of pyruvate to acetyl-CoA?

Answer 3

NADH dehydrogenase

Question 4

How does FADH₂ differ from NADH in the electron transport chain?

Answer 4

• FADH₂ feeds its electrons to ubiquinone thus “skipping” the first step in the electron transport chain

Question 5

What is the first step of the electron transport chain?

Answer 5

The first of the proteins to receive electrons is NADH dehydrogenase

Question 6

What is the purpose of the F₀ complex of ATP synthase?

Answer 6

• F₀ membrane-bound complex
  
  • Contains a channel through which protons move across the membrane down their concentration gradient
    
    • This movement causes part of the F₀ complex and the stalk to rotate relative to the knob

Question 7

Define NADH dehydrogenase

Answer 7

an enzyme located on the inner mitochondrial membrane that catalyzes the oxidation by NAD+ of pyruvate to acetyl-CoA.

Question 8

What is the formula for the electron transport chain?

Answer 8

O₂ + 4H⁺ + 4e^- –> 2H₂O

Question 9

What is the purpose of the F₁ complex of ATP synthase?

Answer 9

• F₁ complex composed of the stalk and a knob, or head domain
  
  • Has enzymatic activity

Question 10

Where is the proton gradient in the electron transport chain and chemisomosis?

Answer 10

between the intermembrane space and the matrix

Question 11

Why are protons attracted to the mitochondrial matrix?

Answer 11

o Protons are attracted to the mitochondrial matrix because it is more negative compared to the intermembrane space

Question 12

After The first of the proteins to receive electrons is NADH dehydrogenase what is the next step of the electron transport chain?

Answer 12

• A carrier called ubiquinone then passes the electrons to a protein-cytochrome complex called the bc₁ complex
  
  • Each complex in the chain operates as a proton pump, driving a proton out across the membrane into the intermembrane space