BSCI170: Cellular Respiration - ETC

Where does the ETC take place?

eukaryotes: inner mitochondrial membrane

prokaryotes: plasma membrane

What are the 2 steps of the ETC?

• Oxidative phosphorylation

• Chemiosmosis

What does complex 1 do?

• oxidizes NADH to NAD+

• pumps H+ ions against their concentration gradient into the intermembrane space

What does complex 2 do?

• oxidizes FADH to FAD

What does complex 3 do?

• pumps H+ ions against their concentration gradient into the intermembrane space

What does complex 4 do?

• pumps H+ ions into intermembrane space against their concentration gradient

• reduces 2 H+ and 1/2 O₂ into H₂O using 2 electrons

What does ubiquinone do?

transports electrons from complex 1 and 2 and puts them into complex 3

What does cytochrome C do?

moves electrons fromn complex 3 to complex 4

What membrane spaces are used in the ETC

• intermembrane space

• inner mitochondrial membrane

• mitochondrial matrix

Which space has a higher H+ concentration?

intermembrane space

Which space has a lower H+ concentration?

Mitochondrial matrix

What makes up oxidative phosphorylation

the complexes, cytochrome C, and ubiquinone

what makes up chemiosmosis?

ATP synthase

Chemiosmosis definition

the movement of ions across a semipermeable membrane down their electrochemical gradient to generate ATP

Oxidative phosphorylation (you don’t need to know the exact definition)

he process where electrons are passed through a series of carriers in the electron transport chain, ultimately transferring them to oxygen (O2) and generating ATP by using the energy released to pump protons across a membrane, creating a proton gradient that then drives ATP synthesis through ATP synthase. 

What happens to the electrons in NADH and FADH₂?

It gets transferred to O₂, which is why oxygen is the final electron acceptor  (this forms water)

Which part of ATP synthase is F₀ and F₁?

Top part: F₀ proton channel

Bottom part: F₁ ATP synthase enzyme

What does ATP synthase do?

moves H+ ions down concentration gradient from intermembrane space to mitochondrial matrix

• exergonic reaction

How many ATP is made through an oxidized NADH?

2.5 ATP

How many ATP is made per oxidized FADH₂

1.5 ATP

How does ATP synthase work?

H+ ions are diffused down F₀ and F₁ begins to spin and exposes the active site for ATP synthesis

How much ATP is made by ETC?

26-28 because it depends on whether the electrons made 2 FADH₂ or 2 NADH. 

26: 8 NADH and 4 FADH₂

28: 10 NADH and 2 FADH₂

How are the amount of H+ ions and the amount of ATP produced related?

the less H+ ions diffused through ATP synthase, the less ATP produced

Net product of ETC

• 26-28 ATP

• 8-10 NAD+ (can go back into glycolysis/citric acid cycle)

• 2-4 FAD (can go back to citric acid cycle)

• 12 H₂O

How many H+ ions to create 1 ATP?

~4 H+ ions