4.4.1 The Electron Transport Chain

Question 1

note

Answer 1

• The energy stored in reduced coenzymes is used to set up a proton gradient by way of the electron transport chain. This gradient sets up the equivalent of a battery within the mitochondria. As charges move, the work that is done can be used to make ATP.
• Energy released from the electrons of reduced coenzymes is used to set up a proton gradient. Proteins embedded in the inner mitochondrial membrane can accept electrons from the NADH + H+ and FADH2
  to make NAD+ and FAD and use the energy lost from those electrons to pump protons into the intermembrane space.
• Electrons are transferred from protein to protein in the
  electron transport chain. Each successive protein in the
  transport chain can accept a lower-energy electron. As
  electrons travel from a high-energy state to a low-energy
  state, energy is released. This energy is used to pump protons across the membrane to set up a gradient. The final electron acceptor is oxygen (O2). Oxygen has a
  high electronegativity; thus, oxygen’s high affinity for
  electrons makes it an ideal acceptor for low-energy electrons. With the electrons, hydrogen is added to oxygen forming water as the final product.

Question 2

In a hypothetical electron transport system, electrons are passed from protein A to B and then from B to C and then from C to D. The energy released from the transport of the electrons from A to D is used to create a proton gradient. Which molecule has the highest electronegativity?

Answer 2

• D

Question 3

The _____ can generate a proton motive force by oxidation of NADH + H + and FADH2.

Answer 3

• electron transport chain

Question 4

Assume that a eukaryotic cell has a full supply of glucose and oxygen, but needs ATP. In the mitochondria of this eukaryotic cell, a proton gradient will be geneated by ____________ and this gradient will be used for ____________ .

Answer 4

• the electron transport chain; ATP synthesis

Question 5

As electrons are passed in the electron transport chain, hydrogen ions (protons) are pumped from _____ to _____.

Answer 5

• mitochondrial matrix ; mitochondrial intermembrane space

Question 6

Which statement about the electron transport chain is false?

Answer 6

• It operates at the same time in the cell as fermentation

Question 7

What molecule is the final electron acceptor in the electron transport chain in cellular respiration?

Answer 7

• oxygen