Electron Transport Chain (ETC)

Question 1

What happens in the ETC? Where does it occur

Answer 1

• NADH gives up its electrons in oxidation reactions to reduce with O2 to make H2O
• between mitochondrial matrix and intermembrane space
• complexes located in the cristae

Question 2

What happens in complex I?

Answer 2

• NADH oxidizes into NAD+ and and H+ ion is pumped through complex I from the matrix to the the intermembrane space
• then the electron from the newly oxidized NAD+ reduces ubiquinone

Question 3

What is ubiquinone?

Answer 3

• lipophillic molecule that recieves all electrons from redox reactions

Question 4

What happens at complex II?

Answer 4

• FADH2 is oxidized to FAD

- the electron is used to reduce ubiquinone

Question 5

What happens at complex III?

Answer 5

• once ubiquinone has enough energy, it travels through the cristae and ends up next to complex III. It gets oxidized and and the electrons are transferred to cytochrome c
• ubiquinone also pumps protons across the cristae intro the inner membrane space

Question 6

What happens in complex IV?

Answer 6

• the carrier molecule, which is next to complex IV, transfer the electrons it was reduced with to the mitochondrial matrix where 2H+ ions and 1/2 of an O2 molecule is reduced into water
• more protons are pumped into the inner membrane space through complex IV

Question 7

What is ATP synthase and how does it work?

Answer 7

• ATP synthase is an enzyme that rotates in order to covert ADP + P into ATP
• Since there is a surplus of H+ molecules in the inner membrane space (called the H+ gradient), a “proton motive force” is generated
• This force rotates every time a proton is pushed through the enzyme which gives it enough energy to make ATP (known as oxidative phosphorylation

Question 8

How is proton motive force generates

Answer 8

• (delta)V and (delta)pH

Question 9

How is ETC regulated?

Answer 9

• regulated through the H+ gradient; low electrochemical gradient results in faster electron transport