The electron transport chain occurs in the inner mitochondrial membrane and involves a series of protein complexes that pass high-energy electrons from electron carriers like NADH and FADH2 generated during glycolysis and the Krebs cycle. As electrons are passed along the chain, hydrogen ions are pumped from the mitochondrial matrix to the intermembrane space, creating an electrochemical gradient. When hydrogen ions diffuse back through ATP synthase, their movement is coupled to ATP production from ADP and inorganic phosphate. This process is called chemiosmosis and generates most of the ATP during cellular respiration. Overall, the complete breakdown of one glucose molecule yields approximately 36 ATP through glycolysis and the electron transport chain.

1. The Electron Transport
Chain

2. Overview
• Review Glycolysis
• Review Krebs Cycle
• Where does the ETC occur?
– Inner membrane of the mitochondria
• What goes to the ETC?
– Our electron carriers! NADH and FADH2
• Where do the electron carriers come
from?
– Glycolysis and the Krebs Cycle

3. A Lil’ Bit About those electron
shuttles (NADH and FADH2)
• FADH2 makes 2 ATPs
• NADH from glycolysis makes 2 ATPs
– Occurs cytoplasm
• NADH from Krebs cycle make 3 ATPs
– Occurs in matrix
• Why the difference in #s?
– The NADH made in glycolysis has to use a
little bit of energy to get into the mitochondria

4. A Lil’ Bit About the ETC
• What is the inner mitochondrial membrane like?
– Phospholipid bilayer
• What makes up the ETC?
– A series of protein complexes that pass these high E electrons
along
• Why do we need to pass the electrons along?
– To pump those hydrogen ions (that tagged along) across the
inner membrane to make a GRADIENT
– Every time an electron is passed down the chain, one H+ ionis
pumped across the membrane
– What is a gradient?
• When there is a high concentration of something on one side of a
membrane and a low concentration on the other side, THEREFORE
diffusion occurs
vcell.ndsu.nodak.edu/animations/etc/first.htm

6. So who are these guys that make
up the ETC?
• #1 Big Protein NADH dehydrogenase
• #2 Big Protein Cytochrome b-c1
• #3 Big Protein Cytochrome Oxidase
• #4 Big Protein (most important!) ATP Synthase
• We have 2 smaller protein shuttles that are
involved as well:
– Ubiquinone (You-bic-win-own)
• Carries two electrons from #1 big protein to #2 big protein
– Cytochrome c
• Carries one electron at a time from #2 big protein to #3 big
protein

9. The Job of the #3 Big Protein: Cytochrome
Oxidase (the matchmaker)
• Look at the name…what do you think is
involved here? (remember, we are almost to
the end of the ETC)
– OXYGEN!!
• #3 big protein waits for 4 electrons to enter
• When that happens, 8 H+ ions come into with
O2 (2 atoms of oxygen)…
• Time to mix and mingle!
– 2 e-, 2 H+, and an oxygen join together to
make H2O
– This happens again with the other oxygen
– These 2 water molecules are released as
products (of cellular respiration)
– But who is left by themselves in the #3 Big
Protein?
• 4 H+ ion…the party is over, no more e-
or oxygen to pick up, they leave :o(
(get pumped across membrane)

10. Uh Oh…its getting a little
crowded…
• By this time, we have way too many
H+ ions on one side (there is a
gradient=lots of pot. E)
• The ions will diffuse and get pumped
back to the less crowded side
• Who allows these ions to cross
back?
– ATP Synthase
• Every time an H+ goes thru, ATP
synthase turns, attaching an ADP to
an inorganic phosphate making…
• ATP!!! vcell.ndsu.nodak.edu/animations/etc/first.htm

11. Chemiosmosis
• Diffusion of ions • Proton Gradient
across a – Flow of High
membrane concentration of
protons to low
• Ex. H+ ions flowing
concentration of
through ATP protons
synthase in the
ETC

12. • Now the Cell has energy
to do work! What types?
– Mechanical
– Chemical
– Transport
• If there is no H+ ion
concentration gradient,
ATP synthase will NOT
turn, and if it does not
turn, no ATP is made=
NO ENERGY!! (very
BAD)

13. Cellular Respiration Totals For 1
Glucose Molecule
• Glycolysis
– 2 NADH to the ETC to make 4 ATP (2x2)
– 4 ATP – 2 ATPs used= 2ATP
– 2 pyruvates coverted to 2 acetyl CoA 2
NADH to go to the ETC to make 6 ATPs (2x3)
• Krebs cycle
– 2 ATPs
– 6 NADH x 3 atp per NADH= 18 ATPs
– 2 FADH2 x 2 atp per FADH2= 4 ATPs
• Net Total: 36 ATPs

14. Tid Bits
• 36 ATPs is 38% of the total energy contained in glucose
• What about the other 62%?
– It’s is released as heat
– Imagine all use cells working hard giving off
heat…that is why you are hot after exercising!
• Each molecule of ATP/ADP travels between the
mitochondria and the cytoplasm approximately once a
minute
• Each day, 2 x 1016 molecules of ADP are
phosphorylated in our bodies: 160kg/day.
• Each ATP Synthase complex can phosphorylate up to
100 molecules of ADP per second.

17. vcell.ndsu.nodak.edu/animations/etc/first.htm
http://vcell.ndsu.nodak.edu/animations/etc/first.htm