Cellular Respiration: (Electron Transport Chain)

Question 1

Electron transport chain uses what kind of respiration?

Answer 1

Aerobic cellular respiration.

Question 2

So far… we’ve got the following energy:

Answer 2

FOR 1 GLUCOSE:
-glycolysis (cytoplasm):
•2 ATP (net).
•2 NADH.
-pyruvate oxidation (cytosol mitochondrial matrix):
•2 NADH.
•(2 CO2).
-Kreb’s cycle (mitochondrial matrix):
•2 ATP.
•6 NADH.
•2 FADH2.
•(4 CO2).

Question 3

Stage 3: the electron transport chain

Answer 3

•NADH and FADH2 from the Kreb’s cycle donate their electrons to the electron carriers in the electron transport chain.
•as electrons are passed from one carrier to the next, the energy that is released is used to pump hydrogen ions across the mitochondrial inner membrane into the membrane space, creating a concentration gradient.
•the energy stored in the gradient is used to generate ATP by chemiosmosis.
•O2 is the final electron acceptor.

Question 4

NADH and FADH2 oxidation:

Answer 4

•NADH and FADH2 are oxidized (lose electrons) by the first protein complex of the electron transport chain.
•The electrons are progressively passed along a series of electron carrier proteins (reduced).

Question 5

Oxygen:

Answer 5

•oxygen is the final electron acceptor.
•once oxygen has received the electrons, they combine with H+ and forms H2O (product of cellular respiration).

Question 6

Proton gradient:

Answer 6

•as electrons move down the ETC the protein complexes use energy released (photons) from the electrons to actively transport H+ ions from the matrix to the inter-membrane space creating a proton gradient.

Question 7

Chemiosmosis:

Answer 7

•The build-up of H+ outside the matrix results in 2 things:
-1. Hydrogen gradient: more H+ in the inter-membrane space than in the mitochondrial matrix.
-2. Electrochemical gradient: due to the excess H+ in the inter-membrane space it becomes more positively charged, and the matrix becomes more negatively charged.
•••
•Therefore, the H+ need to return to the mitochondrial matrix to restore the balance.
•the only way for the H+ to get out of the inter-membrane space and back into the matrix, is through the enzyme “ATP synthase”.
•The H+ moving through the ATP synthase drives the synthesis of ATP.
•thus, by chemiosmosis:
-ADP + Pi —> ATP.

Question 8

ETC inputs and outputs:

Answer 8

••inputs:
•10 NADH:
-2 glycolysis.
-2 pyruvate oxidation.
-6 Kreb’s cycle.
•2 FADH2:
-2 Kreb’s cycle.
••outputs:
•10 NAD+.
•2 FAD.
•6 H2O.
•32-34 ATP.
••Note:
-for each NADH molecule that enters the ETC —> 3 ATP produced.
-for each FADH2 molecule that enters the ETC —> 2 ATP produced.

Question 9

Cellular Respiration: Total Energy Count for 1 GLUCOSE:

Answer 9

-glycolysis (cytosol):
•2 ATP (net).
•2 NADH (go to ETC) *NADH may be converted to FADH2.
-pyruvate oxidation (cytoplasm—> matrix)
•2 NADH (go to ETC).
-Kreb’s cycle (matrix):
•2 ATP.
•6 NADH (go to stage 4: ETC).
•2 FADH2 (go to stage 4: ETC).
-ETC and chemiosmosis (inner mitochondrial membrane— cristae):
•10 NADH—> 30 ATP (may be 8 NADH if NADH—> FADH2 after glycolysis = 24 ATP).
•2 FADH2—> 4 ATP (may be 4 FADH2 if NADH—> FADH2 after glycolysis = 8 ATP).
•••
TOTAL = 2 ATP + 2 ATP + 30 ATP (24 ATP) + 4 ATP (8 ATP) = 36-38 ATP.
-remember: 1 NADH = 3 ATP, 1 FADH2 = 2 ATP.