Electron Transport Chain POWER POINT

 The Electron Transport Chain

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

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

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 i nner 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 s ide of a membrane and a low concentration on the other side, THEREFORE diffusion occurs

vcell.ndsu.nodak.edu/animations/etc/first.htm

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 Ubiquinone (You-bic-win-own) (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

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 into with O2 (2 atoms of oxygen)… Time to mix and mingle!  – 2 e-, 2 H+, and an oxygen join together to make H 2O  – 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)

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

• Now the Cell has energy to do work! What types?  – Mechanical  – Molecular   – 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)

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

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.

vcell.ndsu.nodak.edu/animations/etc/first.htm

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